The Engineering Guide to Selecting Expansion Joints for Dielectric Fluid Loops

Discover how material selection in expansion joints is an important procurement detail and a strategy for long-term reliability.

As data centers pivot toward direct-to-chip (DTC) and immersion cooling to handle the heat of next-gen GPUs, the data center “plumbing” is being pushed to its physical limits. Data center operators are moving away from simple chilled-water systems toward specialized dielectric-fluid and treated-water loops.

In this environment, the choice of expansion joint material is both an important procurement detail and a strategy for long-term viability. While rubber expansion joints may survive a standard office HVAC system, critical high-performance computing (HPC) loops require the chemical resistance of 300-series stainless steel or Inconel.

Navigating the Chemistry of Modern Cooling Fluids

The shift to liquid cooling introduces a complex variable: chemical compatibility. Whether you use propylene glycol blends or specialized immersion oils, the elastomers in traditional gaskets and rubber joints can degrade, leach, or become brittle over time.

The Case for 300-Series Stainless and Inconel

Metallic bellows, specifically those engineered from Type 304 or 316L stainless steel, provide an inert surface that won’t react with modern coolants. In ultra-aggressive environments or systems where chloride-induced stress-corrosion cracking is a risk, Inconel 625 provides even greater protection. These materials ensure that no particulates enter the loop stream due to corrosion or degradation—a necessity when the cooling channels on a cold plate are measured in microns.

Engineering for the Infinite Loop: Fatigue and Cycle Life

In an HPC environment, thermal loads are non-stationary. As workloads spike during AI training runs and drop during idle periods, the piping system undergoes constant thermal expansion and contraction. This is where cycle life becomes the most important metric you’ve never heard of.

Mastering the Thermal Pulse

Unlike rigid piping, a metallic expansion joint is engineered as a flexible pressure vessel. Each convolution in the bellows is designed to evenly distribute stress, while containing the pressure of the line. By using the design temperature to estimate the line’s movements and the frequency of power cycles, our engineers can design a bellows with a rated cycle life in the tens of thousands. This prevents fatigue cracking: the microscopic failure of the metal grain structure, and ensures that the joint lasts as long as the data center itself, not just the current server generation.

FAQ: Critical Insights for Liquid Cooling Infrastructure

How does dielectric fluid creep affect expansion joint seal selection?

A: Dielectric fluids have lower surface tension than water, making them prone to creep through standard gaskets. Effective designs use convoluted metallic bellows with welded ends rather than flanged mechanical joints to ensure a zero-leakage environment.

Can metallic expansion joints be used in two-phase immersion cooling?

A: Yes. Because metallic bellows are hermetically sealed and are resistant to the high pressures and vapor phases of dielectric fluids (especially 316L), they are the preferred choice for sealing the integrity of two-phase cooling loops.

What is the typical lifespan of an Inconel-625 bellows in an HPC loop?

A: When properly engineered for the system’s thermal movements, an Inconel-625 bellows is often rated for a design life of 20+ years, far outlasting the 3–5 year refresh cycle of the IT equipment it cools.

Make sure your cooling infrastructure is ready for the next generation of power density.

Transitioning to direct-to-chip or immersion cooling is a complex leap, but your piping doesn’t have to be a source of stress. We help engineers bridge the gap between traditional HVAC and modern HPC reliability.

Let’s discuss your project’s unique requirements and find the exact bellows solution to keep your uptime at 100%. Contact our engineering team for a comprehensive review of your piping stress analysis and material compatibility requirements.

Root Cause Analysis of Expansion Joint Internal Sleeve Failure Under Reverse Flow Conditions

Front view liner

Overview and Background

Expansion joints are crucial piping components designed to accommodate the flexibility requirements imposed by thermal expansion, vibration, and mechanical movement. In systems with high flow velocities, expansion joints often incorporate internal sleeves (flow liners) to protect the bellows convolutions by separating them from direct fluid flow and reducing the risk of flow-induced vibration (FIV).

The design of bellows expansion joints is generally governed by the guidelines set by the Expansion Joint Manufacturers Association (EJMA). However, current EJMA standards do not provide detailed guidance or design requirements for internal sleeves operating under reverse flow conditions.

Longitudinal slots in the sleeve are sometimes incorporated to equalize pressure between the inner and outer surfaces of the liner. However, care must be taken when designing these liners for reverse-flow conditions, as the slots act as a weak point in the design.

US Bellows was engaged by the end-user and conducted this case study after being asked to investigate several failures seen in the plant where the expansion joints were subjected to bidirectional flow conditions. Although an overseas company supplied the expansion joints, US Bellows agreed to conduct the analysis.

Problem Description and Field Observations

Lng 1

The failure incident occurred at a Liquefied Natural Gas (LNG) facility with vacuum-jacketed lines. During transient operations, such as process upsets or startup/shutdown, the piping systems experience bidirectional.

Extent of Failure: Over 80 internal sleeves in the expansion joints showed some sort of deformation or buckling, and 10 liners had collapsed entirely.

The challenge that USB Faced was that the end-user did not want to change the design or replace all 80 expansion joints, as that would require extraordinary effort due to the expansion joints being installed in a double-walled system (vacuum jacket). The customer wanted to replace only the units that had collapsed entirely, and for us to determine a ‘safe-operating’ reverse-flow velocity to prevent further failures.

Failure Condition: Reverse flow speeds reached up to 40 ft/s when the field failures occurred.
Mechanism Suspected: The core issue stemmed from the longitudinal pressure equalization slots. Under reverse flow, these slots can deform or close, preventing effective pressure equalization and, in turn, generating damaging forces that can accelerate liner deformation or collapse.

The liner design studied had an outer diameter of 8-¼”, a length of 25”, and 22 individual slots with an opening of 1/32.”

Methodology: Fluid Structure Interaction (FSI) Analysis

Liner no 2

To determine the root cause and a safe operating limit, the investigation employed a combination of Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) using a one-way coupled Fluid Structure Interaction (FSI) methodology.

CFD forces (fluid pressures) were generated and then mapped onto the FEA mesh to calculate resulting deformations. The analysis considered the non-linear relationship between large deformations, applied fluid pressures, and the subsequent closure of the pressure equalization slots.

The study analyzed three primary geometries reflecting different operational states and tolerances:

“Gaps Open”: The as-manufactured, undeformed geometry.
“Gaps Closed”: A deformed geometry reflecting the start of closure of the original slot open area.
“Angled Liner”: A geometry simulating installation offset with a 1° angulation forced on the expansion joint.

Acceptance Criteria: Results were evaluated against ASME Section VIII Division 2 criteria for plastic collapse and local failure.

Key Findings and Root Cause Determination

The FSI analysis confirmed the failure mechanism and established a safe operating limit:

A. Pressure Differential and Plastic Collapse

The study found that the limiting criterion was plastic collapse.

The pressure differential between the inner and outer sleeve surfaces significantly increased with flow speed, which was because this accelerated the closure of the slots in the liner. Pressure will not equalize effectively as the slots close. This pressure imbalance produced inward radial deformation.
Crucially, the “gaps closed” model generated a significantly larger pressure differential compared to the “gaps open” model at the same speeds. This result demonstrates that slot closure directly causes increased stress and deformation. In fact, it was found that an already deformed liner increases the pressure differential by a factor of 2.
The root cause of failure was pressure-differential-induced plastic collapse triggered by the closure of the equalization slots during reverse flow. The deformation increases the differential pressure as the slots close, which in turn increases the force, which further increases deformation, potentially leading to an unstable cycle.

B. Determining the Failure Speed

The initial (“gaps open”) geometry passed the plastic collapse criterion until approximately 65 ft/s.
However, when iterating on the deformation (i.e., using the “gaps closed” model), the plastic collapse failure speed dropped sharply to approximately 38 ft/s.
This calculated failure speed of 38 ft/s aligned closely with the field observations, where complete collapse occurred near 40 ft/s.

C. Influence of Geometry and Turbulence

Asymmetry/Angulation: Geometric imperfections and installation tolerances were highly influential. The angled liner (1° angulation) case showed drastically higher resulting pressure differentials, suggesting that even small amounts of bellow angulation significantly increase generated forces.

Transient Effects: Simulations involving turbulent flow conditions (deadleg and mixing flow cases) showed that while forces varied over time, the variations were not at a resonant frequency or high enough magnitude to cause significant deflections. The study concluded that transient effects and turbulence were insignificant as the primary failure mechanism; the collapse was static in nature.
Field Validation: X-ray inspections of damaged liners in the facility confirmed deformation patterns and extreme plastic deformation consistent with the shapes and locations predicted by the simulation model.

Resolution and Recommendations

Top view liner

The study demonstrated a reliable methodology for qualifying expansion joint liners against reverse flow instability, providing guidance where EJMA standards currently lack detail. A one-way CFD–FEA coupling can effectively predict instability in expansion joint liners under reverse flow, especially when large deflections are involved, provided stability is proven through iterative deformation analysis. The design is considered acceptable if the radially inward deformation does not increase with subsequent iterations, indicating that stability is achieved at that flow speed.

Conclusion: The expansion joint liners failed due to plastic collapse driven by an excessive pressure differential resulting from the closure of pressure equalization slots at high reverse flow speeds (near 40 ft/s).

Our final report established a safe reverse-flow limit for the existing expansion joint design, allowing our client to operate safely as long as the flow velocity is not exceeded.

Finally, this study, its methodology, and its results were submitted and published for the ASME Pressure Vessels and Piping Conference.

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An expansion joint internal sleeve is like a dam with controlled overflow gates. If the water flow suddenly reverses (reverse flow), the equalization gates (slots) might get pushed shut by the new pressure direction. If the gates close, the pressure differential across the dam wall (the sleeve) spikes dramatically, causing the entire structure to collapse or buckle because the pressure is no longer balanced.

Hinged Expansion Joints Custom-Designed for a Process that Produces High-Density Polyethylene (HDPE)

U.S. Bellows custom designed these hinged expansion joints for a Polyolefin process which produces High-Density Polyethylene (HDPE) resin at a chemical plant. Polyolefins are a family of polyethylene and polypropylene thermoplastics. The job included expansion joints ranging from 12″ to 32″ NPS. The units pictured above have a nominal pipe size of 16″. The bellows and liner were fabricated from 304 stainless steel and the flanges, cover, and hardware from carbon steel. They are designed for an operating temperature of 176°F at 145 psig and 1° of angular movement. The expansion joints were 100% dye penetrant tested, the bellows longitudinal seam welds were 100% X-rayed, PMI examined, and hydro-tested prior to shipment.

Preventing Unplanned Coke Drum Outages: An Integrated Approach to Piping Flexibility

Top view male worker inspection at steel long pipes and pipe elbow in station oil factory during refinery valve of visual check record pipeline oil and gas

In this environment, the greatest threat to uptime isn’t just the heat; it’s the mechanical stress it causes. Without a sophisticated approach to piping flexibility, the assets that drive refinery margins become the greatest liabilities.

The Danger of Stiff Piping on Critical Assets

When piping is too rigid, thermal expansion has nowhere to go. This force is transferred directly to the unit’s most expensive equipment: the coke drums.

Excessive nozzle loads caused by stiff piping lead to:

Drum Shell Cracking: Repeated stress at the nozzle-to-shell interface can lead to fatigue and catastrophic failure.
Leakage: Thermal growth can pry open bolted connections, leading to hazardous leaks and fire risks.
Support Failure: Rigid systems can buckle steel structures or crush pipe shoes as they try to expand.

To protect the drum, engineers must design a system that “breathes.”

The Solution: Engineered Flexibility and PSA Validation

Managing these loads requires a strategic combination of pipe stress analysis (PSA) and custom-engineered expansion joints. Using advanced software such as CAESAR II, engineers can model the exact displacement of the piping system at every phase of the coking cycle.

The Role of Specialized Expansion Joints

In the tight footprints of a Coker unit, there often isn’t enough room for large pipe loops. This is where specialized hardware becomes essential:

Gimbal and Hinged Expansion Joints: These units allow for angular rotation in any plane while containing pressure thrust. They are ideal for absorbing multi-planar movement in overhead vapor lines.
Refractory-Lined Joints: Specifically designed for the feed lines, these joints handle abrasive catalyst fines and extreme temperatures simultaneously.

By integrating PSA data into the hardware design, US Bellows can manufacture joints with convolution profiles specifically calculated to survive the predicted cycle life of the Coker unit.

Although refineries are not limited to delayed coking units, they may use fluid coking and flexicoking processes, but the end result is the same: producing petroleum coke.

The Power of One: The Piping Technology and US Bellows Combined Value Proposition

In critical midstream and refining projects, failures occur at the interface between a pipe hanger and a bellows. The combined expertise of Piping Technology & Products (PT&P) and US Bellows eliminates this gap.

We provide a single-source solution where the pipe supports (PT&P) and the expansion joints (US Bellows) are engineered in tandem. This ensures that every variable, from variable spring hanger settings to bellows spring rates, is synchronized within your stress model. The result is a unified system that reduces nozzle loads, extends equipment life, and simplifies project management.

Strategic Engineering FAQ: Coker Units & Thermal Stress

Q: Why is pipe stress analysis (PSA) critical for coker expansion joint design?

A: PSA determines the cold spring requirements and the hot position of the piping. Without this data, an expansion joint might be installed in a way that exhausts its movement capacity before the unit even reaches operating temperature, leading to immediate bellows failure.

Q: How does quenching affect expansion joint metallurgy?

A: Quenching is the rapid-cooling of metal. It normally uses water or air as the medium to alter the metal’s structure, locking in a hard, strong microstructure and increasing hardness. However, during plant operation, rapid cooling during the quench cycle can cause thermal shock and brittleness. We utilize high-nickel alloys and specific heat-treatment processes to ensure the bellows material can withstand the “fatigue cycles” inherent to the coking process without stress-corrosion cracking.

Q: Can expansion joints reduce the frequency of coke drum inspections?

A: Yes. By using expansion joints to keep nozzle loads well within ASME B31.3 or Section VIII limits, you reduce mechanical fatigue on the drum shell, enabling optimized inspection intervals and lower maintenance costs.

De-Risk Your Next Turnaround with PT&P and US Bellows

Don’t leave your coker drum integrity to chance. We can help you troubleshoot a chronic leak or design a new transfer line. Our team of stress analysts and bellows engineers is ready to help.

Contact the US Bellows Engineering Team to explore our expansion joint solutions for coker units.

Custom Single Ply X-Flex Bellows Designed for a Manufacturing Company of Flooring Products

U.S. Bellows designed and manufactured customized single-ply X-Flex® bellows for the world’s largest manufacturer and supplier of flooring products, with facilities located throughout the United States. Flooring products—including carpet, ceramic tile, natural stone, laminate, vinyl, and hardwood—require many of the same piping systems found in traditional industrial plants such as automotive, food processing, semiconductor, textile, and pulp and paper facilities.

Flooring manufacturing plants are typically very large, often spanning extensive tracts of land. As a result, pipe runs can extend hundreds of feet, necessitating the use of expansion joints to accommodate thermal movement and relieve stresses within the piping systems.

Externally pressurized expansion joints are particularly well suited for applications requiring large amounts of axial compression or extension. In these designs, the bellows elements are configured so that the process media flows along the external surface of the bellows. This external pressurization eliminates pressure instability as a design limitation and allows for the absorption of significant axial movement.

For this application, the expansion joints were fabricated with 304 stainless steel bellows, flanges, and pipe. The units were designed for operating temperatures up to 300°F at ±14.7 psig (full vacuum) and were capable of accommodating up to 8 inches of axial movement. The assemblies included 3-inch pipe by 40-inch-long units and 4-inch pipe by 40-inch-long units.

All expansion joints were hydrostatically tested and subjected to non-destructive examination (NDE) quality control inspections, including liquid penetrant examination (LPE), prior to shipment to ensure compliance with performance and quality requirements.

Refinery Reliability: The Critical Role of Expansion Joints in FCCU

Petroleum oil and gas industry

In a modern oil refinery, the fluid catalytic cracking unit (FCCU) serves as the primary engine of production. These units convert heavy crude into high-value products like gasoline and diesel, but they operate under punishing mechanical conditions. With process temperatures frequently reaching 1400∘F (760∘C) and the constant movement of abrasive catalysts, the piping system is under a heavy strain.

The essential components that manage this volatility are high-temperature refractory-lined metal expansion joints. Without these precision-engineered parts, the thermal expansion of massive steel piping would generate forces powerful enough to buckle structural supports, crush turbine nozzles, and trigger catastrophic system breaches.

Engineering for Extreme Heat: Why FCCUs Demand Specialized Joints

US Bellows offers custom-engineered expansion joints for FCCU Refinery piping is a dynamic system. In an FCCU, the transition from ambient temperature to whole operation can cause a 100-foot-long pipe to expand by nearly 12 inches. If rigid connections constrain this movement, the resulting stress will concentrate at the weakest point—typically a weld or a critical component of rotating equipment.

The largest and most critical expansion joints, often refractory-lined, manage significant thermal growth between the massive vessels, between the reactor and the separator/regenerator, and are primarily installed in the overhead line of the FCC Unit.

Expansion joints are also used on the Power Recovery Train (PRT) Connections to handle thermal and dynamic movements, as well as the transfer Lines between equipment and flue gas lines.

The flue gas lines are among the most punishing service environments a component can encounter. These lines transport abrasive catalyst fines and scorching exhaust at high velocities, creating a constant battle against thermal expansion and vibration. Because FCCU flue gas lines operate at extreme temperatures, often exceeding 1200°F, the expansion joints must be engineered with specialized refractory linings and multi-ply bellows to withstand both internal erosion and external stress.

A failure here doesn’t just mean a leak—it can lead to a complete unit shutdown, making the precision of US Bellows engineering and historical design insights essential for maintaining continuous operation in these critical paths.

The Challenge of Catalyst Abrasion

In FCC units, expansion joints must withstand not only heat but also “fluidized” catalysts that act as abrasive media. To combat this internal wear, engineers utilize refractory-lined expansion joints. These “Cold Wall” designs employ internal insulation to keep the outer shell temperature below 650∘F (343∘C). This allows the use of carbon steel for the main piping while isolating the bellows from erosion and extreme thermal degradation.

Managing Pressure Thrust in FCC Units

FCC units undergo cyclic temperature swings, leading to “pipe walking” and intense pressure thrust. Tied Universals, or a hinge/gimbal arrangement, are vital in these configurations. They use constraints to constrain the pressure forces, ensuring that the refinery’s anchors and equipment nozzles are not overloaded by internal system pressure during cycles.

Refinery Engineering Insights: FCCU Expansion Joint FAQ

Q.Why do the FCCU industry (designers/owners) prefer a “Cold Wall” design for both piping and expansion joints?

A. FCCU systems often transport catalysts at temperatures that exceed the allowable stress limits of standard piping materials. A “Cold Wall” design uses an internal refractory lining to lower the shell’s skin temperature, protecting the structural integrity of the pipe. In contrast, the internal flow remains at extreme process temperatures.

FCC units use cold wall designs over hot wall designs primarily for better reliability, easier maintenance, lower metallurgy costs, and reduced thermal stress on components like expansion joints, as cold walls use internal refractory to keep the outer shell cooler (e.g., below 650°F), preventing high-temperature issues like creep and sulfidation seen in hot wall designs where the shell operates near media temperatures. Hot walls are simpler but suffer from significant expansion issues and costly, time-consuming repairs, while cold walls offer better control and a longer lifespan for high-temperature transfer lines.

Q. How does a 2-ply testable bellows prevent refinery downtime?

A. In a 2-ply design, each layer is engineered to handle the full pressure of the system. By installing a pressure gauge or “sniffer” between the plies, operators can detect a leak in the inner layer immediately. This provides a safety buffer, allowing the unit to continue running safely until the next scheduled turnaround.

Q. What materials are best for high-temperature refinery expansion joints?

A. Standard stainless steels often fail due to creep or corrosion at refinery temperatures. We typically use high-nickel alloys such as Inconel 625LCF for its superior fatigue resistance and high-temperature strength, or Incoloy 800/H/HT for its excellent resistance to high temperatures, carburization, and chloride-stress cracking, and 304H/321H stainless steel for applications requiring high-carbon stability.

The US Bellows Advantage: Engineering for 24/7 Refinery Performance

Off-the-shelf components cannot survive the specific “hot wall” or “cold wall” requirements of a modern refinery. At US Bellows, we specialize in custom-engineered solutions that prioritize mechanical safety and long-term cycle life.

Our Value Proposition:

US Bellows delivers refinery-grade expansion joints engineered with advanced alloys (Inconel 625LCF, 304H/321H) and specialized refractory systems that eliminate thermal fatigue and catalyst erosion, backed by 24/7 emergency field services to ensure your FCCU maintains peak uptime.

Key Features of Our Refinery Solutions:

Multi-Ply Testable Bellows: We offer redundant-ply designs featuring active monitoring ports. If the inner ply reaches its wear limit, the outer ply maintains the pressure boundary, allowing for a planned maintenance window rather than an unscheduled shutdown.
Custom Refractory Integration: Our designs account for the added stiffness of refractory linings, ensuring accurate stress analysis and predictable movement absorption.
EJMA-Compliant Design: Every unit is designed according to the Expansion Joint Manufacturers Association (EJMA) standards, ensuring it can handle the specific axial, lateral, and angular movements unique to your facility.

Protect your refinery’s most critical assets by partnering with US Bellows for your next FCCU turnaround. Connect with our engineering team for a custom pipe stress analysis and project quote.

Protecting Industrial Ductwork: Fabric vs. Rubber Expansion Joints

Man wearing hard hat and safety vest inspects hvac system in industrial building. worker monitors ductwork and pipes in commercial facility. engineer oversees infrastructure in large office building.

Industrial Expansion Joints Explained: Fabric, Rubber, and Essential Accessories

Industrial ductwork in power generation and chemical processing faces three main challenges: thermal expansion, vibration, and misalignment.

The solution to preventing leaks and structural damage is the use of engineered fabric and rubber expansion joints. Think of expansion joints as the shock absorbers of your industrial piping; without them, every bump in temperature or pressure rattles the entire frame until something breaks.

This guide explores the differences between fabric and rubber expansion joints, as well as the essential accessories required to build a resilient system.

Fabric vs. Rubber Expansion Joints: Which Is Right for You?

Selecting the correct expansion joint depends heavily on the specific environmental factors of your operation, such as temperature, pressure, and the presence of corrosive elements.

When to Choose Fabric Expansion Joints

Fabric expansion joints are engineered for flexibility and high-heat environments. They are the best choice for:

High-Temperature Applications: They excel in environments like flue gas ducts, and fabric joints can be insulated for extreme temperatures
Low-Pressure Systems: Best suited for applications where pressure is not the primary stressor. In general, fabrics are limited to +/- 100” of water column.
Complex Movements: These joints can handle significant multi-plane movements, including axial, lateral, and angular shifts, all in a relatively short span of length in the ductwork
Minimize Reactive Forces: Fabric joints are lightweight, exerting minimal reactive forces on equipment and making them ideal for large-diameter ductwork and exhaust applications.
Maintenance: Because it is lightweight, fabric joints can be easily maintained and replaced. One can only replace the fabric, not the entire frame of the expansion joint.
Corrosive Environments: Fabric joints offer high resistance to corrosive gases and harsh chemicals, especially PTFE Fabrics

Considerations

Leak-tight Applications: While many fabrics can be leak-tight, you will see leakage at fabric attachments to your ductwork, whether via clamps, retaining bars, or bolts.

When to Choose Rubber Expansion Joints

Rubber Expansion Joints for Centrifuge Suction & Discharge of Paraxylene Application Rubber expansion joints are the industry standard for liquid handling and vibration control. They are ideal for:

Vibration-Heavy Systems: Excellent at vibration dampening and noise reduction.
Liquid Systems: specifically designed for pumping systems, chillers, and water/wastewater treatment plants.
Moderate Corrosion Resistance: Rubber offers good sealing and water resistance. Specific rubber compounds are key for common chemicals, weathering, and UV.
Longevity: In the right environment, rubber joints are long-lasting and maintenance-free.

Considerations

Extreme temperatures (High Temps or Cryogenic): Rubber joints are not meant to handle high temperatures. In these situations, consider metal or fabric. By the same token, at cryogenic temperatures, rubber is brittle and not recommended.
High Pressure: Rubber joints can withstand up to 300 psi, depending on the diameter; for larger diameters, the pressure rating decreases. Metal joints need to be considered for high pressures.

Common Questions: Essential Expansion Joint Accessories

An expansion joint is only as effective as the system it is part of. To get the best performance and safety, engineers should integrate specific accessories to protect the infrastructure from heat, erosion, and stress.

What is the function of flow liners?

Flow liners are critical components that increase gas flow efficiency in ductwork. They serve a dual purpose by protecting the expansion joint itself from abrasive media flowing through the system.

Why are Insulation pillows necessary?

Insulation pillows provide thermal protection for the joint. They are essential for maintaining system temperatures while protecting the expansion joint from heat damage.

How do flanges and backing bars improve safety?

Flanges and backing bars are mechanical components that ensure a secure, leak-proof connection to the ductwork. They improve safety and longevity by distributing the load evenly across the connection point.

Building a Resilient System with US Bellows

Pipe stress should not jeopardize your operations. By selecting the right combination of fabric or rubber expansion joints and integrating essential accessories like flow liners, you can build a more resilient ductwork system.

US Bellows engineers resilience into your operations. We provide the precise combination of fabric or rubber expansion joints and essential accessories to absorb stress, eliminate leaks, and ensure your ductwork performs efficiently for years to come.

Stop Unscheduled Downtime

Are you unsure if your current ductwork can handle the stress of thermal expansion or vibration? Book a meeting with a US Bellows engineer to conduct a system assessment and determine the right expansion joint for your piping operation.

The Single Expansion Joint Advantage in Steam Piping

US Bellows single expansion joints are engineered for high-cycle steam

In heavy industries, from power generation and chemical processing to refineries, steam is the diligent workhorse. It drives turbines, heats process fluids, and provides motive force. But the very thing that makes steam valuable, its high temperature, is also its greatest challenge to piping integrity. When a steam line heats up from ambient to 1000 °F, effectively becoming superheated steam, the pipe can expand dramatically, creating immense axial forces that threaten to damage anchors, strain pumps, and cause catastrophic failure.

This is where the single expansion joint earns its title as the steam system MVP.

The Problem: Unrestrained Thermal Growth

Steam distribution systems often feature long, straight runs of pipe. The thermal expansion along these lengths is significant and is calculated as pure axial movement: the pipe simply gets longer.

If this movement is not absorbed, it results in:

Massive Anchor Loads: Fixed points must withstand thousands of pounds of compressive force, leading to oversized, expensive support structures.
Equipment Damage: Pumps, valves, and heat exchangers connected to the pipe are subjected to stress, causing premature failure, misalignment, and increased maintenance.
Pipe Buckling: If the line is improperly guided or supported, the immense force can cause the pipe to bend or buckle.

The Solution: The Efficiency of the Single Expansion Joint

The single expansion joint, consisting of one bellows element and end fittings, is the most direct, cost-effective, and efficient component for handling this specific challenge: pure axial movement.

Here’s why single expansion joints are the go-to component for critical high-temperature steam distribution:

Direct Absorption of Axial Movement: They are explicitly designed to compress or extend along the pipe’s centerline, flawlessly absorbing thermal growth without transmitting damaging stresses to connected equipment or supports.
Compact Footprint: Unlike large, bulky pipe loops that require significant space to bend and accommodate movement, single joints fit neatly within the existing pipe run, minimizing structural engineering costs and conserving valuable plant space.
High-Pressure, High-Temperature Capability: Constructed from robust materials such as Inconel-625 or specialized stainless steel alloys, single joints can be engineered to withstand the extreme pressures and superheated temperatures typical of modern steam systems.
Cost-Effectiveness: When the required movement is strictly axial, the single-joint solution is the most economical, requiring less material and a simpler design than universal or pressure-balanced alternatives.

Secure your piping against the forces of thermal expansion, and boost operations with single expansion joints from US Bellows.

US Bellows: Engineered Reliability for High-Cycle Steam

At US Bellows, we provide engineered certainty for your most critical utility systems. We understand that a failure in a refinery’s catalytic cracking steam line or a power plant’s main steam header is not an option.

For your high-temperature, high-pressure steam systems, US Bellows delivers single expansion joints engineered for maximum cycle life, superior materials compatibility (even in corrosive service), and rapid deployment, safeguarding your critical infrastructure against thermal fatigue and minimizing the risk of expensive, unscheduled downtime.

We custom-fabricate every expansion joint with precision bellows technology to match the exact temperature, pressure, and movement requirements of your application and deliver the best performance in the toughest environments.

Don’t Let Thermal Stress Compromise Your Steam System

Whether you’re dealing with live steam, auxiliary steam, or boiler feed lines, securing your piping against the forces of thermal expansion is essential for continuous operation and safety. Rely on the engineered performance of our single expansion joint.

Contact US Bellows today for a consultation on how our single expansion joints can address your high-temperature piping needs.

The Engineer’s Guide to Refractory Selection: A Deep Dive into High-Temperature Expansion Joints

Outdoor shot of the back of an engineering manager with a helmet under his arm and a hydrogen power plant in the background.

The success of any high-temperature industrial process, from petrochemical refining to power generation, hinges on the integrity of its refractory lining. However, the aggressive thermal cycles these systems endure can subject the lining and its containment vessels to mechanical stress. This is where the workhorse of high-temperature engineering steps in: the expansion joint.

The Critical Interface: Expansion Joints and Refractory

$Refractory lined expansion joints$ Refractory materials, typically ceramic or concrete, are designed to insulate and protect steel components from extreme heat. Yet, they possess a relatively low tensile strength and are highly susceptible to cracking and spalling when subjected to differential thermal movement.

An expansion joint, integrated into the ductwork or piping system, absorbs the axial, lateral, and angular movement caused by thermal expansion and contraction of the surrounding steel structure. By managing this movement, the expansion joint prevents stresses from being transferred directly into the brittle refractory material, thereby maintaining the system’s structural integrity and keeping the piping’s internal insulation intact.

Key Considerations in Refractory Selection

Choosing the right refractory is only half the battle; ensuring the expansion joint is compatible with the refractory and the operating environment is paramount. Here are the factors an engineer must consider:

Maximum Operating Temperature: This dictates the material for both the refractory and the metallic or fabric expansion joint elements. The insulation thickness will also determine the temperature of the piping and the bellows.
Refractory thickness Trade-off: A thicker refractory lowers piping temperature, allowing the use of cheaper steels such as Carbon steel; however, the piping will be heavier, requiring larger loads and supports. A thinner refractory will yield a higher shell temperature, and the use of stainless steel or alloys for the piping will lower the pipeline’s weight.
Chemical Environment: The presence of corrosive gases (such as SOx or NOx) or particulate matter can lead to premature degradation, requiring specialized alloys or fabric coatings, as well as abrasion-resistant refractories
Thermal Expansion Coefficient: Understanding the difference in expansion rates between the steel duct, the refractory material, and the expansion joint’s liner and bellows is crucial for designing the correct gap and insulation scheme.
Vibration and Fatigue: Systems with high flow rates or cycling operations require bellows designed to withstand the resulting fatigue stress. Vibration may be an issue for refractory, potentially leading to cracking if not accounted for during design.

Protecting the Heat: Integrating Expansion Joints

Mastering Movement: How Expansion Joint Design Preserves Refractory Integrity

The biggest threat to a refractory-lined pipe is the uncontrolled force generated by the thermal expansion of the surrounding steel ductwork. A properly selected and installed expansion joint acts as a pressure-relief valve for mechanical stress, thereby directly extending the service life of the refractory and the piping system.

The Essential Role of Liners and Internal Insulation

The protection of the expansion joint itself is critical. High-temperature metal bellows are often protected internally by a flow liner and refractory insulation.

The flow liner serves a dual purpose: it smooths the flow of media past the bellows, reducing turbulence and vibration-induced fatigue, and it acts as a mechanical barrier to the internal insulation. This internal insulation, often ceramic fiber or a castable refractory material, shields the bellows material from the highest process temperatures. The liner must be designed to allow the bellows to move freely without compromising the insulation’s integrity during the line’s thermal cycling.

This reduction in thermal gradient is critical, as it allows the use of lower-temperature-rated bellows alloys, which are better suited for cyclic operation due to improved cycle life, without the creep phenomenon becoming an issue under constant stress on the bellows. Without this integrated protection, the bellows would be subjected to higher temperatures and operate in the bellows material’s creep range, leading to premature failure.

US Bellows: Your Partner in Customization

At US Bellows, we specialize in custom, refractory-lined, high-temperature expansion joints that are pre-engineered to match the thermal expansion coefficients and chemical composition of your specific refractory system. Our custom solutions minimize stress transfer, virtually eliminate refractory spalling, and drastically reduce the costly downtime associated with high-temperature system failure, providing you with predictable, sustained operational success.

Stop settling for generic solutions that fail under the heat. Contact a US Bellows high-temperature specialist today to design a refractory-matched expansion joint solution that guarantees the maximum service life for your critical assets.

Stop Over-Anchoring: Pressure-Balanced Expansion Joints Slash Installation Costs

Pressure Balanced Expansion Joints in Piping Design

The design of a piping system is crucial in industrial settings, where failure can result in damage and downtime. One of the biggest challenges engineers face is managing the immense thrust forces generated by pipeline pressure. These forces can strain anchors, damage equipment, and compromise the entire system. This is where the innovative design of pressure-balanced expansion joints (elbow and in-line) adds value, offering a scalable solution to a complex problem.

What Are Pressure Balanced Expansion Joints?

Pressure-balanced expansion joints are highly engineered components designed to absorb thermal pipe expansion and contraction, as well as lateral movements, while simultaneously neutralizing the pressure thrust force that would otherwise act on surrounding anchors, supports, and equipment.

The Mechanism of Balance

The value lies in their unique internal mechanism. This is accomplished by using a balancing bellows that is exposed to the same pressure as the main, or inline bellows. For in-line pressure-balanced expansion joints, the balancing bellows is specifically designed with an effective area twice that of the inline bellows. For elbow pressure-balanced expansion joints, the effective area remains the same for all bellows.

The core principle is simple but powerful: the pressure acts on both bellows, but the force generated by the balancing bellows acts in the exact opposite direction of the force generated by the inline bellows. Since the entire expansion joint is tied via tie-rods, this creates a state of force equilibrium, effectively containing the thrust from the pressure within the expansion joint.

The thermal movement absorption of the in-line pressure-balanced expansion joints follows that same principle. The inline bellows will compress, while the balancing bellows will actually extend by the same amount as the thermal compression. See our Inline pressure balance EJ below in action:

In-Line Pressure Balanced GIF from US Bellows

This neutralization eliminates the need for large, expensive main anchors, as the only forces the anchors must now contend with are the minor spring forces required to move the bellows themselves. This makes them ideal for systems with limited space, poor structural support, for protecting fragile components, or systems where it’d be impractical or cost-effective to install anchors.

When to Use Pressure Balanced Expansion Joints

These specialized joints are instrumental in situations where the system cannot handle the pressure thrust forces, such as:

Piping connected to sensitive equipment: They protect pumps, turbines, and compressors from axial forces that could cause damage.
Systems with limited structural anchoring: In crowded plants or offshore applications where large anchors are not feasible, these joints offer a compact, effective solution. Also, in situations where the piping is elevated, it would not be cost-effective to install an elevated anchor.
Where Low Loadings Are Needed: In specific applications, especially on large-diameter lines or when connecting to thin-walled equipment, minimizing all loads on the surrounding structure is a primary design driver.

Precision-Engineered Trust: Choose US Bellows

US Bellows is an industry-leading manufacturer of high-quality expansion joints, committed to precision engineering and reliability.

When you specify a US Bellows pressure-balanced expansion joint, you are investing in certainty and safety. Our expansion joints are custom-engineered solutions designed by experts to solve your specific piping challenges. We offer:

Custom Design & Sizing: Every joint is engineered to the precise size, pressure, temperature, and movement requirements of your application, ensuring perfect force neutralization and decades of reliable service.
Unmatched Material Quality: We utilize advanced materials and stringent welding processes, including specialized alloys for high-temperature and corrosive environments, guaranteeing optimal performance and longevity.
Code Compliance & Certification: Our manufacturing adheres to strict industry codes, including ASME Section VIII, Div. 1, and B31.3, ensuring fully certified, safe, and dependable products.
On-site Field Services: We inspect your bellows for loss of pressure, signs of leakage, and observe for specific movement due to pressure.

Stop designing systems around enormous anchors and start protecting your critical equipment with the precision of our solutions at US Bellows.

Ready to reduce pipe stress? Contact US Bellows today to discuss your elbow pressure-balanced expansion joint needs.

Super U-Loop Expansion Joint Designed for a Chilled Water Line

Super U-Loop Expansion Joint Designed for a Chilled Water Line for Paint and Body Shops in Automotive Manufacturing Plants

U.S. Bellows, a division of PT&P, has developed its Super U-Loop and Super V-Loop product line for applications requiring reliable accommodation of axial growth, especially on longer piping runs. These designs restrain pressure thrust without any system anchoring and bring the same advanced expansion joint technology used in the world’s most demanding environments to a standardized loop offering. Today, Super U-Loops are trusted across key industries, including oil and gas, chemical, power, semiconductor, food, automotive, pharmaceutical manufacturing, battery production facilities, and hyperscale data centers, where they withstand extreme temperatures of over 1000°F, pressures above 200 PSI, and highly corrosive media. This particular U-Loop, shown below, was designed, manufactured, and shipped in under nine days from our Houston-based facility.

Us bellows universal expansion joint loop 185130 b — **Super U-Loop for Automotive Plant – 14” NPS, 4” Axial Movement**

Option

Super U-Loop Advantages

Super U-Loop Disadvantages

Pipe Loop

· Super U-Loop requires far less space

· Can be designed to accommodate large amounts of axial movement

· Pipe loop is a lower cost if the space is available

Flexible Metal Hose-Based U-Loop and V-Loop

· Flow liner protects the interior of the bellows

· Cover on Bellows protects the exterior of the bellow – Flexible metal hose can be damaged easily by accidental bumping, banging, etc.

· Super U-loop can be designed with varying thickness to optimize strength versus a lower spring rate

· Super U-loop can be made with custom metals to accommodate environmental conditions – includes Hastelloy, Inconel, Monel, …

· Designed to better withstand vibration in the piping system

· Standard designs can be delivered in as little as 1 week

· Flexible metal hose offers a very low spring rate

U.S. Bellows/PT&P’s Super U-loop and Super V-loop offer a breakthrough option for accommodating large amounts of axial growth in both commercial and high-temperature industrial environments. The traditional option used when space was not available for a pipe loop was a flexible metal hose, which introduced the risk of failure into the piping system. U.S. Bellows design is built around minimizing the risk of failure by:

Flow Liner – Protects the interior of the bellows
Cover – Protects the exterior of the bellows from damage such as falling wrenches, accidental banging by a forklift, etc.
Limits Excessive Cycling – If vibration in the piping system “cycles”, a flexible metal hose may not be an adequate solution. The reason is that neither expansion joints nor flexible metal hoses are designed to support millions of cycles. The low spring rate of the flexible metal hose makes it more vulnerable to being cycled by unintended continuous vibration in the piping system. Even 1 hz of vibration rapidly leads to excessive cycling with 86,400 cycles per day. By incorporating either a Super U-loop or Super V-loop with an expansion joint, we are able to accommodate a large amount of movement with the ability to dampen vibration due to the higher spring rate of the expansion joint design.

Us bellows universal expansion joint loop 185130 c

Eliminating Thermal Stress in High-Purity Food & Beverage Processing

How Single Expansion Joints Eliminate Thermal Stress in High-Purity Food & Beverage Piping

Single expansion joints are critical, precise components that maintain system integrity and operational flow across diverse food and beverage processing lines, particularly where temperature variance, high pressure, and stringent hygiene requirements intersect.

This focused approach to piping challenges in sanitary food processing is like installing shock absorbers on a high-speed assembly line. While the piping system operates under intense thermal stress and continuous cycles, the expansion joints absorb destructive forces, ensuring that critical components maintain their precision and longevity.

Single expansion joints are essential for managing axial movement —lengthening and shortening of pipes due to temperature changes. Constructed from materials such as stainless steel, which offers superior corrosion resistance and hygiene, these components ensure the reliability of complex production infrastructure.

Engineering for Uncompromised Hygiene

In a high-purity setting, the need to eliminate thermal stress is inseparable from maintaining absolute hygienic integrity. The expansion joint itself must not introduce a point of failure or contamination.

CIP/SIP Endurance: The most significant source of thermal shock in high-purity environments comes from Clean-in-Place (CIP) and Steam-in-Place (SIP) systems. These rigorous sanitation processes involve frequent, rapid, and extreme temperature swings. Single expansion joints are specifically engineered to withstand thermal shock without permanent deformation, metal fatigue, or structural failure.
Surface Finish and Design: To meet stringent FDA and 3-A Sanitary Standards, the metal bellows and components of the expansion joint are manufactured with a smooth internal surface finish. This design is crucial for minimizing the potential for bacterial growth, product accumulation (hold-up), or micro-crevices where contaminants could harbor. By accommodating movement, the joints also prevent the pipe misalignment that could otherwise create difficult-to-clean dead legs or pockets.
Leak Prevention: By effectively managing stress, the joints prevent the forces that would otherwise cause fatigue or rupture in the pipe walls, flanges, or welds. This elimination of leaks is paramount, as a leak in a food-grade line is an immediate path for product loss and microbial contamination.

In essence, these expansion joints serve a dual, mission-critical purpose: safeguarding the physical structure from heat damage and protecting the product purity from contamination caused by system failure.

Uptime vs. Thermal Expansion: Solving the Food &Beverage Piping Dilemma

Here is how these joints align specifically with piping operations in key food and beverage industries:

Dairy Production: Piping systems must handle a vast temperature range, from high-temperature short-time (HTST) pasteurization processes to subsequent refrigeration cycles. Single expansion joints accommodate these varying milk temperatures, preventing immense stress on pipelines, pumps, and other critical equipment caused by thermal expansion and contraction.

Improve hygiene and compliance with engineered solutions from PT&P.

Breweries and Wineries: These facilities involve significant thermal cycles. Expansion joints are vital in managing the stresses associated with brewing kettles (high heat), fermenters (controlled temperature), and chilling lines (low temperature). By absorbing movement, they protect equipment and maintain the integrity necessary for precise fermentation processes.

Save valuable floor space in brewery production and keep processing flowing efficiently with expansion joints from US Bellows.

Confectionery: In systems that transfer high-viscosity products such as heated syrups and chocolate, temperature must be meticulously controlled to maintain fluidity. Single expansion joints ensure that the piping structure remains secure, accommodating the stresses generated by heat transfer lines without risking leaks or ruptures that would result in product loss.

Meet stringent hygiene standards of confectionary production with US Bellows expansion joints.

Meat Processing: Operations heavily rely on steam lines for cooking and sanitation. These steam lines experience extreme temperature spikes and are essential for maintaining food safety. The expansion joints use tie rods and robust bellows to reliably absorb the significant axial movement inherent in high-heat steam delivery, protecting the surrounding infrastructure.

Improve high-purity meat processing with expansion joints from US Bellows.

Beverage Bottling: As products move through filling and packaging lines, piping must accommodate frequent temperature changes, particularly during rapid filling operations. Expansion joints maintain alignment and accommodate thermal stresses, preventing premature equipment failure in high-speed, continuous-flow production environments.

Increase uptime and reliability in beverage processing with expansion joints from US Bellows.

CIP (Clean-in-Place) / SIP (Steam-in-Place) Systems: These rigorous cleaning processes are characterized by frequent, rapid temperature swings. CIP/SIP systems are non-negotiable for hygiene, but the thermal shock they impose can severely damage standard piping. Single expansion joints are engineered to endure these rigorous cleaning cycles, maintaining system integrity and ensuring that the smooth internal surfaces minimize the potential for bacterial growth or product accumulation.

Improve the rigorous CIP and SIP processing for hygiene, with single expansion joints from US Bellows.

Choose US Bellows to Ensure Safety and Performance in High-Purity Production

US Bellows delivers mission-critical piping solutions that safeguard your protection, uptime, and regulatory compliance. As a plant manager, you prioritize two things: uninterrupted output and unwavering hygiene standards. Our custom-engineered single expansion joints, manufactured from the highest-quality stainless steel for superior corrosion resistance, are designed to address thermal expansion.

US Bellows offers a clear return on investment by providing:

Maximum Uptime and Equipment Longevity: By reliably accommodating axial movement, our joints protect costly pumps, valves, and surrounding equipment from damaging stresses, significantly extending their lifespan and preventing the catastrophic consequences of pipe ruptures or leaks.

Uncompromised Hygiene and Compliance: Unlike traditional, bulky solutions such as pipe loops, our expansion joints are compact and feature smooth internal surfaces, meeting the stringent hygiene standards of the food and beverage sector by minimizing areas where product can accumulate. They are resilient enough to withstand frequent, rigorous CIP/SIP cleaning cycles.

Customized Engineering and Rapid Support: We provide engineered solutions tailored to your specific operational needs, customizable to various pipe sizes and movement requirements. This precision integration, coupled with rapid turnaround times, means you save valuable floor space and keep your complex production flowing efficiently.

Choose US Bellows and our parent company, Piping Technology & Products, to transform potential thermal risk into reliable, consistent performance. Talk to one of our engineering experts today.

The Dual Mandate: Designing Expansion Joints that Satisfy Both EJMA and ASME

The Foundation: Understanding the Role of Bellows Design Standards

Expansion joints are the critical, yet often most stressed, components in any piping system, designed to absorb thermal movement, vibration, and pressure changes. Ensuring their reliable performance requires strict adherence to codified design principles. In the industrial world, two organizations primarily govern the design and application of metallic bellows expansion joints: the Expansion Joint Manufacturers Association (EJMA) and the American Society of Mechanical Engineers (ASME).

While both organizations strive for safety and reliability, they approach design, particularly fatigue-life calculations, with distinct philosophies. EJMA provides the fundamental industry-specific guide, establishing the nomenclature, formulas, and best practices verified by manufacturers’ testing. ASME, on the other hand, is the overarching pressure equipment code that governs piping systems (e.g., ASME B31.3) and pressure vessels (ASME Section VIII).

EJMA vs. ASME: The Critical Difference in Cycle Life and Safety

The most significant and often confusing difference between EJMA and ASME design calculations lies in their respective fatigue curves used to predict the service life (or cycle life) of the bellows element.

Feature	EJMA Standards (The Practical Guide)	ASME Code (e.g., B31.3 Appendix X)
Design Philosophy	Focuses on practical cycle prediction based on extensive manufacturer testing.	Focuses on conservative safety margins required by pressure vessel and piping codes.
Fatigue Curve	It is a “best fit” curve representing the expected average cycle life.	A more conservative curve that results in an expansion joint design in line with ASME piping codes.
Safety Factor	No inherent safety factor is included in the cycle-life calculation itself, so designers are expected to add their own margin.	Design margins and safety factors are inherently included in the curve, resulting in a much lower calculated cycle life for the same bellows.
Calculated Cycle Life	Significantly higher. Provides the most practical estimate of bellows’ lifespan.	Significantly lower. Provides a guaranteed minimum life based on stringent code requirements.

In short, a bellows designed to EJMA standards may have an estimated cycle life of 7,000 cycles. In comparison, the same bellows, calculated using the latest ASME B31.3 Appendix X cycle-life calculation, might yield only 1,150 cycles. This difference is not a flaw in either standard, but a reflection of the margin of safety built into the ASME code to guarantee system integrity.

Compliance and Integration: Where the Standards Align

Despite differences in cycle-life calculation, the two standards are not entirely independent; they often overlap and rely on each other to complete a design. In fact, ASME B31.3 code incorporates the EJMA standard into its design but modifies it to fit within its own framework.

- Shared Foundation: Both EJMA and ASME derive their fatigue curves from the same initial set of empirical test data collected from bellows manufacturers.
- Structural Components: EJMA standards require that all external hardware (such as tie rods, hinges, and gimbals) necessary to manage pressure thrust and movement be designed using accepted methods based on elastic theory, which often means meeting the allowable stresses and design principles outlined in ASME B31.3 and BPVC.
- Material Properties: Material allowable stresses, which are foundational to any pressure design, are typically derived from ASME Boiler and Pressure Vessel Code (BPVC) Section II, Part D.
- Buckling/Squirm: Factors of safety for structural instability, such as column squirm (typically 2.25), are explicitly mandated by EJMA equations, aligning with requirements in piping codes such as ASME B31.3.
- Hydrotesting: ASME B31.3: Requires testing the expansion joint at the unit’s design temperature, which may result in a higher test pressure.

A piping system built in the US or in many global markets will require the expansion joint assembly to be designed to the EJMA standard for the bellows element while ensuring the entire joint’s construction, materials, and structural attachments comply with the applicable ASME code (e.g., B31.3, B31.1, or Section VIII).

US Bellows Delivers Bellows Performance and Safety

When navigating the differences between EJMA’s optimized design and ASME’s stringent compliance, you need a partner with genuine expertise.

At US Bellows and our parent company, Piping Technology & Products (PT&P), we engineer solutions that balance performance and compliance.

As a longstanding member of the Expansion Joint Manufacturers Association (EJMA) and a leading ASME-certified fabricator (Section VIII), our teams can interpret and apply the complexities of both code systems. PT&P is the only company globally to combine deep, proprietary pipe stress engineering expertise with in-house manufacturing of expansion joints and pipe supports. This means our experts design your bellows with the practical, proven cycle-life assurance of EJMA, while guaranteeing full compliance with mandatory ASME safety margins. Request a quote today to learn more.

Fatigue Testing or Cyclic Testing

Fatigue Testing

Fatiguetest 3 — **Fatigue Testing on a 12″ Bellow**

Fatigue Testing PDF

This is a preliminary summary report describing fatigue testing conducted by U.S. Bellows, Inc. The objective of the fatigue test was to detect fatigue crack growth generated by compressions during controlled cycling on a fatigue-testing machine.

U.S. Bellows, Inc. conducted a fatigue test on 12” diameter A240 TP 321SS bellows with 8 convolutions. The EJMA calculations for this test was based on compressing the bellows 2.3/4” 1000 times. This bellows was attached to each side of the cylinder of the fatigue test machine and pressurized to 25 PSIG for the purpose of leak detection. This bellows failed in the root of the convolutions at 1,285 cycles.


Figure 1 shows an overall view of the axial cycle fatigue test machine with bellows installed	Figure 2 shows a linear crack in the root of the convolution–about 3 inches long, which is typical of bellows low cycle fatigue)
This test has proven that U.S. Bellows Inc., EJMA cycle life calculation of 1,000 cycles is met. The actual cycle life of 1,285 cycles is higher than the EJMA Calculated cycle life.

Key reasons Cyclic Testing can be important in design and operational considerations:

Validates design life – Confirms the joint meets its rated cycle life as calculated per EJMA formulas.
Ensures structural integrity – Verifies welds, convolutions, and materials won’t crack or fail under repeated flexing.
Confirms design assumptions – Demonstrates that analytical or computer-based life predictions match real-world performance.
Enhances safety and reliability – Prevents premature failure in high-pressure or high-temperature piping systems.
Spring rate check – When coupled with a load cell, it can verify that the spring rate of the expansion joint matches or exceeds theoretical calculations. Doing this will verify the assumptions done in a Pipe Stress Analysis (PSA).

Inspection Checklist: 5 Signs a Single Expansion Joint is Approaching End-of-Life

Single expansion joints are the unsung heroes of your piping system, quietly absorbing thousands of cycles of thermal movement. Because they’re designed to flex, they endure fatigue over time. While they are built for durability, they aren’t meant to last forever. Proactive visual inspection is your best tool for preventing catastrophic failures that lead to costly unplanned downtime.

For maintenance and inspection teams, knowing what to look for is crucial. Here are five practical visual signs that a single expansion joint is nearing the end of its service life and needs to be replaced.

1. Bellows Thinning or Cracking (Fatigue Failure)

Bellows thinning

This is the most direct sign of bellows failure, resulting from the cumulative stress of cycles.

What to Look For: Examine the bellows convolutions (the curved ridges) for fine, hairline cracks, especially in the crests (tops) or roots (bottoms), as well as the weld seam of the metal folds. In high-cycle or vibration applications, you might see pitting or thinning of the metal surface due to constant stress, bending, and work-hardening. Particularly on stainless steel, look for rusty-brown streaks or spots, which can be an early sign of a pinhole leak.
Why it Matters: Cracks indicate the material has reached its fatigue limit. Once a crack starts, it will propagate more for each additional cycle under pressure, leading to an immediate, full-system leak or rupture.

2. Squirm or Localized Bulging of the Bellows

Squirm bellows

“Squirm” is a term used to describe a lateral instability or buckling of the bellows convolutions under high internal pressure.

What to Look For: Instead of the convolutions being evenly spaced and uniform, look for one or more convolutions that appear swollen, distorted, or significantly wider than the others. In severe cases, the bellows may be forced out of a straight line, resembling a snake or an “S” curve.
Why it Matters: This catastrophic deformation occurs when the bellows convolutions can no longer withstand the internal pressure. The bellows’ deformation indicates it can no longer absorb movement correctly, and imminent failure often occurs shortly before a complete rupture.

3. Missing or Damaged Hardware (Tie Rods, Limit Rods, Covers)

Damaged hardware

While a single expansion joint is primarily designed for axial movement, it may incorporate limit rods or external hardware to provide safety or protection in the event of anchor/equipment failure.

What to Look For:
- Limit Rods: Check that the rods and the nuts/washers at the ends are intact. If a nut is missing or the nuts are visibly strained against the stop plates, it may indicate the joint is being forced beyond its designed movement capacity and should be inspected.
- Hardware: Check that the lugs and hardware are not bent, and look for cracks in the attachment welds.
- External Covers: If the joint has an external cover (which protects the delicate bellows from external damage, weld splatter, or insulation material), look for dents, missing bolts, or signs that the cover has been broken: this suggests improper installation or external impact.
Why it Matters: Damaged or missing hardware is often evidence of a pre-existing problem in which the piping system has exceeded the joint’s movement limit, placing immense, unseen stress on the expansion joint.

4. Misalignment & Non-Axial Deflection

Misalignment bellows

Single expansion joints are designed mainly to absorb axial movement (lengthening and shortening along the pipe axis). They cannot handle significant lateral (sideways) or angular (bending) movement.

What to Look For: Visually inspect the joint’s ends. Does the pipe going into the joint line up perfectly with the pipe coming out? If the bellows appear to be bent, sagged, or leaning at an angle, or if the flanges are not parallel, the joint is misaligned and suffering from dangerous non-axial stress. This often occurs during installation errors or when pipe anchors or guides have been compromised or failed.
Why it Matters: Forcing a single expansion joint to absorb lateral or angular movement dramatically reduces its fatigue life, sometimes to just a fraction of its intended rating, and makes it highly vulnerable to premature failure.

5. Evidence of Corrosion on the Bellows

Corrosion bellows

Corrosion degrades the bellows material, quickly reducing its ability to handle pressure and movement.

What to Look For: Look for heavy surface rust (on carbon-steel components) or signs of stress-corrosion, cracking (delicate, mud-crack-like patterns, often near welds on stainless steel). This can be caused by exposure to moisture or chemicals (such as chlorides from cleaning agents or insulation). Internally, check for scale or media buildup, which can restrict movement and cause erosion.
Why it Matters: Corroded metal is thinner and weaker, compromising the bellows’ structural integrity. A bellows that has lost half its wall thickness due to corrosion will fail at a fraction of its original design pressure, regardless of its cycle life.

Your Next Step: Call the Experts at US Bellows

Catching these signs early allows for a scheduled, controlled replacement rather than an emergency shutdown. If your inspection reveals any of the five warning signs above, it’s time to consult with an expert.

US Bellows provides rapid assessment, custom design, and quick manufacturing of single expansion joints to replace worn or failed components. Don’t wait for a rupture: partner with us to keep your systems operating safely and efficiently.

The US Bellows Guide to Metal Expansion Joint Inspection and Turnaround Success

Safeguarding Your System: Proactive Metal Expansion Joint Maintenance & Turnaround Planning

In the interconnected environment of industrial operations, where high temperatures, extreme pressures, and corrosive media are the norm, certain components silently bear the brunt of the forces at play. Among these durable components, metal expansion joints are a notable example. These flexible elements are designed to absorb movement, vibration, and thermal expansion within piping systems, preventing stress buildup that could otherwise lead to catastrophic failures. Yet, despite their critical role, expansion joints are often overlooked until a problem arises, leading to costly emergency repairs and unscheduled downtime.

This guide explores the key strategies for proactive maintenance and meticulous turnaround planning of metal expansion joints. By understanding their function, recognizing common failure modes, and implementing an inspection and replacement program, you can significantly enhance the reliability of your entire piping infrastructure.

The Crucial Role of Metal Expansion Joints: More Than Just a Flex Point

Before we dive into maintenance, let’s understand why expansion joints are so critical. Imagine a rigid piping system subjected to extreme temperature fluctuations. As the pipe heats up, it expands; as it cools, it contracts. If the pipes are fixed at the ends and lack a flexible element to accommodate thermal movement, immense stresses would buildup, leading to buckling, cracking, and eventual failure of the pipes, flanges, or connected equipment such as pumps and turbines.

Metal expansion joints, typically fabricated from corrugated metal bellows, are specifically engineered to:

Absorb Thermal Movement: They compensate for axial (along the pipe’s axis), lateral (perpendicular to the axis), and angular (rotational) movements caused by temperature changes.
Isolate Vibration: They can prevent the transmission of mechanical vibrations from rotating equipment (pumps, compressors) to the rest of the piping system, reducing noise and fatigue.
Accommodate Misalignment: They can absorb minor misalignments in piping runs that occur during installation or due to settling.
Relieve Mechanical Stress: By providing flexibility, they protect sensitive equipment from stresses induced by pipe movement, and when coupled with tie-rods or hinges, they can also retain the pressure thrust.

Without properly functioning expansion joints, the integrity of your entire system is compromised, leading to safety incidents, environmental releases, and financial losses.

Metal expansion joint3

Understanding Expansion Joint Design and Types for Informed Maintenance

To effectively maintain expansion joints, it is essential to understand their basic design principles and the common types encountered in industrial applications.

Bellows: The heart of the expansion joint, typically made from thin-gauge stainless steel alloys (e.g., 304, 316, Inconel-625), formed into a series of convolutions (ridges and valleys). The number and depth of convolutions determine the joint’s flexibility and movement capacity.
End Fittings: Flanges, weld ends, or threaded connections that connect the bellows to the piping system.
Liners (Internal Sleeves): Used to reduce flow turbulence, prevent abrasion from solid particles, and protect the bellows from flow-induced vibration.
Covers (External): Protect the delicate bellows from external damage, weld splatter, installation damage, and mechanical impact.
Hardware (Tied Rods, Limit Rods, Gimbals, Hinges): These external components are crucial for controlling and distributing movement, restraining pressure thrust, and preventing over-extension or compression of the bellows.
- Tie Rods: Restrain pressure thrust while allowing lateral and angular movement.
- Limit Rods: Allow for axial movement (extension/compression) but prevent over-extension or over-compression beyond design limits.
- Hinged Joints: Allow angular movement in a single plane.
- Gimbal Joints: Allow angular movement in any plane.
- Universal Joints: Consist of two bellows and a central pipe section, designed to absorb large lateral movements.

Each type has specific maintenance considerations, particularly regarding the condition of its external hardware, which directly influences its ability to perform its designed function.

The Pitfalls: Common Failure Modes of Metal Expansion Joints

Understanding how expansion joints fail is the first step toward preventing them. Most failures are not sudden but rather a culmination of prolonged stress, improper installation, or environmental degradation.

Fatigue Failure: This is the most common failure mode, typically manifesting as cracking in the bellows convolutions. It results from repeated cycling of the bellows beyond its design limits or from excessive vibration. Factors contributing to fatigue include:
- Over-extension/Over-compression: Movement exceeding the specified design limits.
- Lateral Misalignment: Excessive sideways movement.
- Vibration: Low-frequency, high-amplitude vibrations are especially detrimental to metal expansion joints.
- Improper Guiding & Anchoring: Insufficient pipe guides and anchors can result in unsupported pipe sections and unguided thermal movement, leading to buckling of the expansion joint.
1. Corrosion:
  - External Corrosion: Exposure to aggressive atmospheric conditions, chemical spills, or insulation leaching can cause the bellows’ external surface to corrode.
  - Internal Corrosion: Attack by the transported media (e.g., acids, chlorides) can thin the bellows material, leading to pinholes or cracks. This is often exacerbated by stagnant flow or condensate buildup in the convolutions.
  - Stress Corrosion Cracking (SCC): A particularly insidious form of corrosion where specific environmental conditions (e.g., chlorides, sulfur compounds) combine with tensile stress to cause cracking, even in otherwise resistant alloys.
2. Mechanical Damage:
  - Puncture/Abrasion: External impact during installation, maintenance, or operation (e.g., dropped tools, weld splatter, falling debris). These can dent the bellows, acting as stress risers and a potential failure point.
  - Flow Erosion: High-velocity abrasive media (e.g., slurries) or excessive turbulence can erode the internal surface of the bellows, especially if a liner is absent or damaged.
3. Flange & Weld Failures: Less common for the bellows itself, but failures can occur at the attachment points due to poor welding, excessive stress, or improper bolting.
4. Improper Installation: This is a leading cause of premature failure. Issues include:
  - Installation Misalignment: Forcing the joint into position can lead to permanent pre-stress.
  - Lack of Proper Pre-Set: Some joints are designed with a specific pre-compression or pre-extension to achieve optimal performance at operating temperatures.
  - Inadequate Pipe Support, Guides, and Anchors: The expansion joint relies heavily on the surrounding pipe infrastructure to function correctly. Without proper guidance and anchorage, the joint can experience unexpected movements and stresses.
  - External Damage: Damaging the bellow during handling and installation.
5. Galling of Tie Rods/Hardware: If tie rods or limit rods are seized, they can restrict the intended movement, leading to over-stressing of the bellows. If the tie-rods are corroded, they can break loose and cause over-extension/compression of the bellows, as well as potential mechanical damage from the pressure thrust.
6. Upset events: System over-pressurization, pressure surges, upset conditions exceeding the expansion joint limits, or an increase in media velocity/conditions without consulting the manufacturer.

Metal expansion joint2

The Maintenance Imperative: Developing a Proactive Inspection Program

An inspection program is the cornerstone of effective maintenance for expansion joints. This isn’t just about identifying failures; it’s about predicting and preventing them.

Routine Visual Inspections (Operating Conditions)

These quick checks should be integrated into regular plant rounds and conducted by operations or maintenance personnel familiar with the system.

Tie Rod/Limit Rod Condition: Are they straight? Free to move? Signs of corrosion or seizing? Are nuts loose and out of position?
Alignment: Any obvious signs of pipe misalignment leading into or out of the joint.
Pipe Support Integrity: Are adjacent pipe supports and guides intact and functioning properly? Sagging pipes or damaged guides can transfer excessive loads to the expansion joint.
Evidence of Movement: Mark the initial position of tie rods or bellows convolutions relative to a fixed point. During inspections, verify that the actual movement falls within the expected range for the operating conditions.
Foreign Material: Accumulation of debris, insulation fibers, or chemical residue on the bellows.

In-Depth Inspections (During Shutdowns/Turnarounds)

These are more thorough inspections conducted when the system is depressurized, de-energized, and cooled down (or at ambient temperature). This is where detailed assessment and planning for replacements occur.

Frequency: Quarterly, or after any significant system upset (e.g., emergency shutdown, pressure spike).
What to Look For:
- Obvious Signs of Leakage: Staining, drips, or puddles around the bellows or end connections.
- External Damage: Dents, gouges, scratches, or corrosion on the bellows or cover.
- Distortion of Bellows: Bulging, flattening, or unusual deformation of convolutions.
- Tie Rod/Limit Rod Condition: Are they straight? Free to move? Signs of corrosion or seizing? Are nuts loose and out of position?
- Alignment: Any obvious signs of pipe misalignment leading into or out of the joint.
- Pipe Support Integrity: Are adjacent pipe supports and guides intact and functioning properly? Sagging pipes or damaged guides can transfer excessive loads to the expansion joint.
- Evidence of Movement: Mark the initial position of tie rods or bellows convolutions relative to a fixed point. During inspections, verify that the actual movement falls within the expected range for the operating conditions.
- Foreign Material: Accumulation of debris, insulation fibers, or chemical residue on the bellows.

In-Depth Inspections (During Shutdowns/Turnarounds)

Frequency: Typically during every planned shutdown or turnaround (1-5 years, depending on service severity).
What to Look For (in addition to routine checks):
- Internal Inspection (if possible): If the line is open, visually inspect the bellows’ internal surface for corrosion, erosion, or liner damage. This is particularly crucial for abrasive or highly corrosive services.
- Dye Penetrant or Magnetic Particle Testing: For suspicious cracks or surface imperfections, NDT methods can confirm the presence and extent of defects.
- Hardware Functionality: Manually attempt to move tie rods or limit rods (if safe and possible) to ensure they are not seized. Check all bolted connections for tightness.
- Insulation & Cover Removal: Carefully remove protective covers/insulation to gain full visual access to the bellows. Reinstall properly after inspection.
- Leak testing: If the expansion joint has two plies and a testable port, perform a leak test using air or nitrogen between the plies to ensure the two plies are working correctly.

Documentation: Record detailed findings, including photographs, measurements, and recommended actions. This data is invaluable for trend analysis and future planning.

Metal expansion joint

Strategic Turnaround Planning for Expansion Joint Replacement

Turnarounds are high-stakes events where meticulous planning can prevent costly overruns and delays. Expansion joint replacement should be a core component of this planning.

Pre-Turnaround Preparation: The Key to Success

Identify Critical Spares: Based on historical data, inspection reports, and failure rates for different services, identify all expansion joints that are likely candidates for replacement.
- “Run to Failure” vs. “Proactive Replacement”: For critical services, proactive replacement based on age or condition assessment is often cheaper than emergency replacement. For less critical services, a “run to failure” strategy might be acceptable if spares are readily available.
Detailed Scope Definition: For each identified joint, document:
- Full Specifications: Material, size, pressure rating, temperature, design movement, end fittings, and external hardware. Access original manufacturer drawings and data sheets.
- Installation Location: Line number, equipment tag, exact position.
- Access Requirements: Scaffolding, lifting equipment, hot-work permits, confined-space entry, and insulation removal.
Procurement Lead Times: Expansion joints are often custom-engineered, which can result in longer procurement lead times. Standard lead times can range from weeks to months for specialized materials or complex designs.
- Order Well in Advance: Place orders for critical spares months before the turnaround.
- Emergency Spares: Maintain a stock of standard sizes and types for unforeseen failures or minor projects.
Contractor Selection & Training:
- Ensure that installation contractors are experienced in handling and installing expansion joints. Improper installation is a leading cause of premature failure.
- Confirm they understand the importance of proper handling (e.g., avoiding lifting by the bellows), alignment, and torqueing of bolts.
- Emphasize the importance of removing shipping restraints only after the joint is fully installed and anchored.
Develop Detailed Work Procedures:
- Step-by-step instructions for removing old joints and installing new ones.
- Include safety precautions, required tools, bolt torque specifications, and pre-setting instructions.
- Reference applicable standards (e.g., EJMA standards for metallic bellows expansion joints).

During the Turnaround: Execution and Verification

Safe Removal: Depressurize, drain, and decontaminate the line. Support adjacent piping before removing the old joint.
Piping Alignment Check: Before installing the new joint, verify that the mating flanges/pipe ends are correctly aligned. Any misalignment must be corrected in the piping, not by forcing the expansion joint.
Careful Installation:
- Handling: Never lift or support the expansion joint by the bellows itself. Use lifting lugs, end fittings, or dedicated lifting devices.
- Pre-set (if required): Ensure the expansion joint is set to the correct length, as specified by the manufacturer’s installation instructions for the applicable temperature.
- Bolting: Torque flange bolts evenly and incrementally to the specified values, using a star pattern.
- Gasket Selection: Use appropriate gaskets for the service conditions.
Remove Shipping Restraints: CRITICALLY IMPORTANT! Shipping bars/restraints must only be removed after the expansion joint is fully installed, bolted, and the adjacent piping is properly supported and anchored. Failure to do so can lead to over-pressurization and catastrophic failure.
Post-Installation Inspection: Visually inspect the newly installed joint for proper alignment, tight connections, and removal of all shipping hardware.
Pressure Testing: After installation, the system will undergo pressure testing. Monitor expansion joints closely during this phase for any signs of leakage or deformation.

Post-Turnaround Follow-up: Ensuring Long-Term Reliability

First-Run Inspection: Conduct a visual inspection shortly after the system returns to operation and reaches stable operating temperatures. Look for any unusual movement, leaks, or deformation.
Baseline Documentation: Update plant records with installation dates, new joint specifications, and any observed conditions. This creates a new baseline for future inspections.
Lessons Learned: Conduct a post-turnaround review to identify successes, challenges, and areas for improvement in the expansion joint maintenance and planning process.

Partner with US Bellows for Turnaround Success

At US Bellows, we don’t just fabricate expansion joints; we engineer peace of mind from the ground up.

Unlike commodity suppliers, we combine decades of American manufacturing excellence with a deep bench of in-house ASME-certified engineers who understand the complex interplay of pipe stress and environmental factors.

Our value isn’t just in the superior quality of our components, but in our proactive partnership approach: from advanced finite element analysis (FEA) to custom design for extreme conditions, rapid emergency manufacturing, and expert field service consultation.

When your system demands absolute reliability and precise engineering, US Bellows delivers a solution built to outlast, outperform, and protect your most critical assets: ensuring your turnarounds are defined by certainty, not speculation.

Is your plant’s reliability hanging by a thread? Don’t let failing expansion joints dictate your next shutdown.

Take control of your system’s integrity. Contact US Bellows today for a complimentary engineering consultation on your most critical expansion joint applications. Let our experts help you identify potential failure points, optimize your turnaround strategy, and design robust solutions that guarantee uptime and peace of mind.

Schedule your consultation and secure your system’s future.

Top 5 Reasons Metal Expansion Joints Are Critical in Industrial Piping

Why Your Industrial Piping Needs Metal Expansion Joints

Metal expansion joints are indispensable components in industrial piping and duct systems, serving as flexible connectors designed to absorb movement. Often overlooked until a problem arises, these specialized components are crucial for ensuring the safety and lifespan of complex piping infrastructure. They manage the stresses and movements induced by thermal changes, equipment vibration, seismic activity, and misalignments, and their inclusion is a critical factor in pipe stress analysis (PSA), often providing the most economical solution for keeping pipe reaction loads within acceptable limits for connected equipment and supports.

5 Critical Reasons Metal Expansion Joints are Essential

Here are the top five reasons why metal expansion joints are fundamental to industrial piping systems:

1. Absorbing Thermal Movement and Expansion

Metal Expansion Joint

Industrial processes often involve significant temperature changes, causing pipes to expand and contract. This thermal movement creates immense stress on the entire piping system, anchor points, and/or equipment. Metal expansion joints, particularly the bellows section, are engineered to compress, extend, shift sideways, and angulate, effectively absorbing the thermal movement. Without them, the cumulative stress could lead to pipe warping, cracking, or failure at welds, anchors, and equipment.

2. Maintaining Intended Alignment to Avoid Unexpected Strain

Metal Expansion Joint temperature change

During installation or due to foundation settling, pipes may not align perfectly. Expansion joints can accommodate minor axial, lateral, or angular misalignment, reducing installation time and preventing “built-in” stresses that compromise the system from day one.

It is essential to address misalignment during the design phase, rather than making adjustments in the field. Using an expansion joint to compensate for large field misalignment can shorten its lifespan.

3. Protecting Equipment by Reducing Vibration & Loads

Metal Expansion Joint

Piping systems are often connected to vibrating equipment like pumps, compressors, and turbines. If this vibration is transmitted directly through the pipes, it can cause noise, fatigue, and damage to the surrounding structure and equipment. Expansion joints can act as dampers, isolating vibration and preventing its propagation, thus extending the operational life of the machinery and the piping. Note: Expansion joints cannot absorb all types of vibrations, and in some cases, other custom solutions may be more effective.

4. Absorbing Pressure Thrust and Movement

Internal pressure in a pipe exerts a thrust force on the system. When a pipe changes direction and using an anchor is not feasible or cost-effective, the pressure force created by the line must still be contained. Specialized, tied or hinged metal expansion joints are designed to withstand this pressure thrust, protecting sensitive equipment and anchors from overstress while still allowing lateral or angular displacement.

5. Enhancing System Safety and Reliability

Metal Expansion Joint

By managing movement, vibration, and pressure thrust, expansion joints significantly reduce the risk of catastrophic pipe failure, leaks, and downtime. They are a proactive safety measure that contributes to a more reliable and maintainable operation. Investing in high-quality metal expansion joints improves the overall safety and continuous operation of your facility.

Partner with the Experts at US Bellows: Protect Your Piping Infrastructure

US Bellows: Engineered for Extreme Performance. We design and manufacture custom-engineered metal expansion joints that solve your toughest thermal, pressure, and vibration challenges, helping you ensure maximum uptime and safety in your critical industrial applications.

Don’t wait for a failure to start thinking about movement control. Book a meeting with our US Bellows engineering team today to discuss custom expansion joint solutions.

Rubber Expansion Joints Designed for Water Cooling Loops at a Chemical Plant

Type:	Neoprene Expansion Joint
Size:	3×10, 6×10, 8×12, 10×14
Material:	Neoprene Twin Sphere Rubber Tubing with 304 SS Flanges & Covers
Design	Operating Temp: 225°F at 225 PSIG \| 1-3/8″ – 1-3/4″ of Lateral Offset
Testing:	Hydro-Tested \| PMI on all Rubber Joint Root-Rings

Rubber pipe expansion joints are often used to compensate for minor misalignment and offset. The design is chemical and abrasion resistant, accommodates for higher pressures than the standard metal expansion joints, and eliminates sediment buildup. They feature an integrally flanged design that eliminates the need for gaskets and are engineered to absorb noise, vibration, and shock, enhancing system reliability and performance.. This single, wide arch, spool-type rubber expansion joint is provided with either Stainless steel or hot-dipped galvanized retaining rings. View Rubber / Fabric Expansion Joints Product Section.

These neoprene expansion joints were custom-designed for water cooling loops at a chemical plant in Louisiana. They have a neoprene twin sphere rubber tubing with 304 stainless steel flanges and covers. US Bellows fabricated five of each of the following dimensions: 3×10, 6×10, 8×12, and 10×14. They were designed for an operating temperature of 225°F at 225 PSIG and 1-3/8″ – 1-3/4″ of lateral offset. The units were hydro-tested and PMI on all rubber joint root-rings prior to shipment.

Besides chemical plants, other plants that utilize rubber expansion joints are air scrubber systems, sewage treatment, wastewater treatment, and water treatment plants. Combined cycle power plants also often utilize rubber spool-type expansion joints.

No matter the application, our team of experienced engineers and designers can help to resolve your expansion joint needs. Please contact us via our 24×7 emergency service or send an email to info@pipingtech.com.

PT&P REF. ORIGINAL POST 06242020

42″ SINGLE EXPANSION JOINTS FOR AN EXHAUST DUCT APPLICATION AT A TURBINE FACILITY IN Michigan

Usbellows single expansion joint 132974

Type: Single Expansion Joints

Size: 42″ ID | 24″Face-To-Face

Material: Inconel 600 | 304 Stainless Steel | Carbon Steel

Design: 350°F Operating Temp. @ 100 PSIG | 0.75″ Lateral

Testing: Hydro-tested

These single expansion joints were custom-designed by US Bellows for an exhaust duct application in the turbines of a pressurized water nuclear power plant in Michigan. The bellows were fabricated to meet the plant’s specific operating conditions, accommodating the required axial and lateral movements, and were constructed from high-performance alloys to withstand elevated temperatures and pressures typical of turbine exhaust systems. There is a clear resurgence in upgrading and servicing turbine facilities to meet datacenter demand, as AI-driven power loads outpace grid capacity. Operators are overhauling existing turbines and deploying new high-efficiency units to provide reliable, large-scale, and dispatchable power close to datacenter campuses.

For this project, the units have a 42” ID and are 27” face-to-face. The bellows were fabricated from Inconel 600, the liners from 304 stainless steel, and the cover, limit rods, and hardware from carbon steel with red oxide primer on all exposed carbon steel. It is important to note that our manufacturing and production abilities around mixed metallurgy are unique in that we can isolate and manage different metals in our production, but also have the experience, depending on the client’s needs.

These units are designed for an operating temperature of 350°F at 100 psig, 0.625” of axial compression, and 0.75” of lateral deflection. The expansion joints were hydro-tested prior to shipment.

Over 60-65% of the expansion joints we provided replace existing units. US Bellows is not necessarily the OEM in all cases; however, we have the experience to manufacture, repair, or audit our designs and others as we are members of EJMA with deep expertise in expansion joint design and manufacturing for over 50 years, with an in-house Field service team. Our expansion joint engineers use the EJMA (Expansion Joint Manufacturers Association) latest edition to maintain a calculations-based spreadsheet and a stand-alone engineering design software program for the ASME ( American Society of Mechanical Engineers) code section VIII-based calculations to design expansion joints.

Applications for expansion joints include:

Fossil Fuel Power Plant Chemicals and Petrochemical Stationary Engine Exhaust Pulp, Paper, Wood Pellets

Power (Nuclear/Fossil Fuel/Renewables) Heat Exchangers Municipal Water Districts Space Aviation/Aerospace Engine Exhaust

District Energy FCC Units Wastewater Treatment Truck Exhausts

Gas Turbines Navy Biofuels/Solid Waste Incineration Steel Mills/Blast Furnaces/Mining

Steam Distribution Kilns Solar/Environmental Applications Marine Piping and Exhaust

Geothermal Power Plants Furnace Sealing Bags HVAC Building and Heating Systems Liquefied Natural Gas Service (LNG)

Refineries Education/Labs Food Processing Cement Manufacturing

PT&P REF. ORIGINAL POST 11252019

Expansion Joints for High-Temperature Applications

High tempature expansion joint 03

What are High-Temperature Expansion Joints?

Expansion joints for high-temperature applications are engineered to accommodate significant thermal expansion, contraction, and vibration in systems operating at temperatures often exceeding 750°F.

Their crucial role lies in accommodating the thermal expansion that pipes experience when transporting high-temperature media, thereby preventing high stresses, bent pipes, cracks, and failures.

Why are Standard Expansion Joints Insufficient for High-Temperature Applications?

Standard expansion joints are manufactured with stainless steel alloys that may rapidly degrade when exposed to continuous high temperatures or rubber, which would melt at high temperatures.

These materials lose their elasticity and become brittle, leading to premature failure.

High temperatures could also exacerbate other issues in expansion joints, such as:

Deformation (Creep): Materials deform permanently under sustained stress at high temperatures.
Oxidation & Corrosion: Chemical reactions accelerate, leading to material degradation.
Thermal Fatigue: Thermal cycles cause weakening and cracking.

High-temperature expansion joints, essential in many industrial applications, rely on refractory‑lined expansion joints and insulation materials to form a protective liner cover that resists extreme heat and prevents thermal stress.

Temperature Ratings and Applications of Expansion Joint Materials

Expansion joints for high-temperature environments are designed using a range of specialized materials, each chosen for its ability to withstand heat, maintain mechanical strength, and resist oxidation, creep, and corrosion.

The chart below illustrates the maximum temperature ratings of commonly used materials, including high-nickel alloys (Inconel 625, Incoloy 800/H/HT, and Hastelloy 276), specialized stainless steels (304, 321/347, and 310), fabric composites, and internal insulating materials, along with their typical applications.

From refineries, aerospace, and chemical plants to ducting systems, boilers, and pollution control facilities, the chart provides a clear comparison of where each material is most effective.

Notably, for environments exceeding 1800°F, internal insulating materials such as ceramic fibers, mineral wool, and refractory linings are recommended to protect components. Temperature ratings indicated are without added insulation.

Expansion joint material temperature graph

Why Choose US Bellows for Your High-Temperature Expansion Joints?

US Bellows stands as a leader in designing and manufacturing custom-engineered solutions that meet the most stringent industrial demands. With decades of experience, cutting-edge technology, and a commitment to quality, our team delivers durable, high-performance expansion joints that ensure the safety of your high-temperature systems.

Most of our expansion joints manufactured for high-temperature piping systems, can be designed, manufactured, and out the door within eight weeks.

Investing in the right materials, design, and maintenance practices for these specialized joints can significantly extend the lifespan of your valuable infrastructure.

Contact Our Experts: Do you need a high-temperature expansion joint solution tailored to your extreme conditions? Connect with our engineering team today for a personalized consultation.

Get a Quote: Request a detailed quote to optimize your high-temperature operations with our durable expansion joints.

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Click on the button below, fill out a form, and get 3D printed models mailed directly to your address!

REQUEST A 3D PIPE SUPPORT MODEL

Non Metallic Expansion Joints

Product & Application Resources

Navigating the Chemistry of Modern Cooling Fluids

The Case for 300-Series Stainless and Inconel

Engineering for the Infinite Loop: Fatigue and Cycle Life

Mastering the Thermal Pulse

FAQ: Critical Insights for Liquid Cooling Infrastructure

How does dielectric fluid creep affect expansion joint seal selection?

Can metallic expansion joints be used in two-phase immersion cooling?

What is the typical lifespan of an Inconel-625 bellows in an HPC loop?

Make sure your cooling infrastructure is ready for the next generation of power density.

Overview and Background

Problem Description and Field Observations

Methodology: Fluid Structure Interaction (FSI) Analysis

Key Findings and Root Cause Determination

A. Pressure Differential and Plastic Collapse

B. Determining the Failure Speed

C. Influence of Geometry and Turbulence

Resolution and Recommendations

The Danger of Stiff Piping on Critical Assets

The Solution: Engineered Flexibility and PSA Validation

The Role of Specialized Expansion Joints

The Power of One: The Piping Technology and US Bellows Combined Value Proposition

De-Risk Your Next Turnaround with PT&P and US Bellows

Engineering for Extreme Heat: Why FCCUs Demand Specialized Joints

The Challenge of Catalyst Abrasion

Managing Pressure Thrust in FCC Units

Refinery Engineering Insights: FCCU Expansion Joint FAQ

Q.Why do the FCCU industry (designers/owners) prefer a “Cold Wall” design for both piping and expansion joints?

The US Bellows Advantage: Engineering for 24/7 Refinery Performance

Key Features of Our Refinery Solutions:

Industrial Expansion Joints Explained: Fabric, Rubber, and Essential Accessories

Fabric vs. Rubber Expansion Joints: Which Is Right for You?

Common Questions: Essential Expansion Joint Accessories

Building a Resilient System with US Bellows

The Problem: Unrestrained Thermal Growth

The Solution: The Efficiency of the Single Expansion Joint

Don’t Let Thermal Stress Compromise Your Steam System

The Critical Interface: Expansion Joints and Refractory

Key Considerations in Refractory Selection

Protecting the Heat: Integrating Expansion Joints

Mastering Movement: How Expansion Joint Design Preserves Refractory Integrity

The Essential Role of Liners and Internal Insulation

Pressure Balanced Expansion Joints in Piping Design

What Are Pressure Balanced Expansion Joints?

The Mechanism of Balance

Super U-Loop Expansion Joint Designed for a Chilled Water Line for Paint and Body Shops in Automotive Manufacturing Plants

Engineering for Uncompromised Hygiene

The Foundation: Understanding the Role of Bellows Design Standards

EJMA vs. ASME: The Critical Difference in Cycle Life and Safety

Compliance and Integration: Where the Standards Align

US Bellows Delivers Bellows Performance and Safety

Fatigue Testing

1. Bellows Thinning or Cracking (Fatigue Failure)

2. Squirm or Localized Bulging of the Bellows

3. Missing or Damaged Hardware (Tie Rods, Limit Rods, Covers)

4. Misalignment & Non-Axial Deflection

5. Evidence of Corrosion on the Bellows

Your Next Step: Call the Experts at US Bellows

Safeguarding Your System: Proactive Metal Expansion Joint Maintenance & Turnaround Planning

The Crucial Role of Metal Expansion Joints: More Than Just a Flex Point

Understanding Expansion Joint Design and Types for Informed Maintenance

The Pitfalls: Common Failure Modes of Metal Expansion Joints

The Maintenance Imperative: Developing a Proactive Inspection Program

Routine Visual Inspections (Operating Conditions)

In-Depth Inspections (During Shutdowns/Turnarounds)

In-Depth Inspections (During Shutdowns/Turnarounds)

Strategic Turnaround Planning for Expansion Joint Replacement

Pre-Turnaround Preparation: The Key to Success

During the Turnaround: Execution and Verification

Post-Turnaround Follow-up: Ensuring Long-Term Reliability

Partner with US Bellows for Turnaround Success

Why Your Industrial Piping Needs Metal Expansion Joints

5 Critical Reasons Metal Expansion Joints are Essential

2. Maintaining Intended Alignment to Avoid Unexpected Strain

3. Protecting Equipment by Reducing Vibration & Loads

4. Absorbing Pressure Thrust and Movement

5. Enhancing System Safety and Reliability

Partner with the Experts at US Bellows: Protect Your Piping Infrastructure

What are High-Temperature Expansion Joints?