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Featured Product Archives

Protecting Hospital Medical Gas Lines with Precision Expansion Joints
February 20, 2026

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Ensuring Uninterrupted Care: The Critical Role of Expansion Joints in Medical Gas Delivery

In a healthcare facility, the medical gas distribution system is the literal lifeline of the building. At any given time, it could be delivering oxygen to an ICU or maintaining the high-flow vacuum required in a surgical suite, and these systems must operate with zero margin for error.

For hospital facility managers, the challenge isn’t just maintaining the gas supply: it’s protecting the rigid piping network from the invisible forces of thermal expansion, mechanical vibration, and seismic activity. This is where precision-engineered expansion joints become critical safeguards.

Engineering for NFPA 99: Material Standards and Pressure Tolerances

Medical gas systems are unique in their material requirements and pressure sensitivities. To maintain gas purity and system integrity, most hospitals utilize ASTM B819 Level L or K degreased copper tubing.

  • Oxygen and Nitrous Oxide Lines: Typically range from 1/2″ to 4″ in diameter, depending on the distance from the bulk source and the number of terminal units served. These lines must remain free of oils and contaminants to prevent spontaneous combustion.
  • MRI Equipment: Hospital MRI systems require two kinds of piping systems. Quench Venting systems are safety components in the MRI system. Designed to vent helium gas out of the system during a “quench” event, where the magnet’s cooling system fails and rapidly boils off liquid helium. These lines are 8”-10” NPS Range and made out of stainless steel due to the extreme operating temperature of -270 deg.C.  
  • Medical Vacuum and WAGD (Waste Anesthetic Gas Disposal): Often use larger diameters, often 6″ to 8″ in main headers, to maintain consistent flow rates without pressure drops.
  • Media Types: These systems transport high-purity oxygen (O2), medical air, nitrous oxide (N2O), nitrogen (N2), and carbon dioxide (CO2). Each has specific pressure profiles and temperature sensitivities that exert stress on the piping joints.

Why Rigid Piping Needs Flexible Solutions

While stainless steel or copper are often the choice for durability in healthcare environments, their thermal expansion coefficient means that long runs of piping will expand and contract as the building’s internal climate or gas temperature fluctuates. Without an expansion joint to absorb this movement, the stress is transferred directly to the brazed joints, leading to hairline fractures and catastrophic leaks.

The  NFPA 99 (Health Care Facilities Code) mandates that medical gas systems be protected against physical damage and seismic events. In seismic-prone zones, a rigid pipe can snap during a tremor; a customized metallic expansion joint for seismic activity from US Bellows allows for multi-axial movement, keeping the “lifeline” intact when the building moves.

Stainless steel metallic bellows expansion joint for industrial piping systems

Selecting the Right Guard: Expansion Joint Types for Healthcare

1. Metallic Expansion Joints: The Standard for Medical Gas

For oxygen, nitrous oxide, and high-pressure steam, metallic expansion joints are the gold standard.

  • The Value: They are non-permeable and can be factory-certified as oxygen-cleaned.
  • Application: Ideal for sterilization lines where temperatures often reach 121 °C to 134 °C

2. Universal Gimbal Expansion Joints: The Seismic Lifeline

Hospitals are “Category 1” structures, meaning they must remain functional during and after an earthquake. Universal Gimbal expansion joints use a specialized “ring” harness to allow for angular rotation in any plane.

  • The Value: They absorb multi-axial movement while resisting pressure thrust, eliminating the need for massive, costly concrete anchors in tight ceiling cavities.
  • Application: Critical for main headers crossing building expansion joints, to absorb a substantial amount of lateral movement

3. Fabric Expansion Joints: Quiet Comfort for Patient Care

A hospital’s HVAC system is its lungs. Fabric expansion joints are used in low-pressure air handling units (AHUs).

  • The Value: They act as vibration breakers, preventing mechanical hum and fan noise from traveling through the ductwork into patient recovery zones.
  • Application: Large-diameter air intake and exhaust systems.

Hospital Medical Piping: Expansion Joint Selection & Pressure Rating Guide

 

Application

Recommended Type

Primary Value
Medical Gas / O2 Metallic Gas purity & high burst pressure (1,000 psi)
MRI Pipelines Metallic Chilled water & Helium venting/quenching
Seismic Protection Universal Gimbal Multi-axial movement & anchor load reduction
HVAC / Air Ducting Fabric Noise reduction & vibration dampening
Sterilization Steam Metallic Thermal expansion at 121 °C to 134 °C

The US Bellows Value: Engineering for Zero-Failure Environments

At US Bellows, we understand that hospital infrastructure demands more customization. Our expansion joints for medical gas service are:

  • Oxygen-Cleaned: Every joint is factory-cleaned and certified for oxygen service, ensuring no hydrocarbons or oils enter your high-purity lines.
  • Compliance-First: We design in accordance with EJMA standards and facilitate compliance with NFPA 99 requirements for metallic flexible connectors.
  • Material Integrity: We utilize high-grade stainless steel bellows and bronze or copper end fittings to match the metallurgy of your existing system, preventing galvanic corrosion.

FAQ: Expansion Joints in Healthcare Facilities

What are the NFPA 99 requirements for flexible connectors in medical gas systems? 

NFPA 99 requires that flexible connectors be used only where necessary for expansion or vibration control, and that they have a minimum burst pressure of 1,000 psi. They must be made of materials like stainless steel, bronze, or copper that are compatible with the gas being served.

Can rubber expansion joints be used for medical oxygen lines? 

Generally, no. For high-purity medical gases, metal bellows (typically stainless steel) are preferred because they are non-permeable and can be easily degreased and cleaned for oxygen service, whereas certain elastomers may degrade or pose a fire risk in high-oxygen environments.

How do expansion joints help with hospital MRI and imaging equipment? 

Expansion joints act as vibration isolators. By installing them on the HVAC and chilled water lines serving imaging suites, you prevent mechanical vibrations from the plant room from reaching sensitive diagnostic equipment, which could otherwise cause “noise” in imaging results.

What is the typical lifespan of a metal expansion joint in a hospital setting? 

When properly engineered and installed, a high-quality metal expansion joint can last 20 years or more. However, regular inspections every 3–5 years are recommended to detect signs of fatigue or corrosion, especially in steam-intensive environments such as sterilization centers.

Why are chiller water lines in imaging suites typically constructed from non-ferrous materials like copper or stainless steel?

Precision medical imaging equipment, such as MRI machines, relies on powerful and highly sensitive magnetic fields. To ensure the accuracy of these diagnostics, the surrounding infrastructure must not create magnetic interference.

We use non-ferrous metals (typically in the 2” NPS range) for chiller water piping because they are non-magnetic. Using stainless steel or copper prevents the piping from “tugging” on or distorting the machine’s magnetic field. Because these metals have different thermal expansion rates than standard carbon steel, integrating precision expansion joints is critical to absorb thermal movement without risking leaks or mechanical stress near the sensitive equipment.

Secure Your Hospital’s Infrastructure Today

Don’t wait for a “Code Red” leak to evaluate your system’s flexibility. If you are upgrading an existing wing or designing a new surgical center, our engineers can provide a custom assessment of your medical gas piping needs.

Contact a US Bellows engineer for a consultation on your next project.

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How Expansion Joints Prevent Expensive Delays in Airport Operations
February 13, 2026

US Bellows expansion joints help control the massive forces and temperature fluctuations in utility tunnels in airports.

In aviation, the most expensive asset is an aircraft that isn’t moving. While “Aircraft on Ground” (AOG) usually refers to mechanical issues with the plane itself, a failure in airport infrastructure can be just as paralyzing. If a main steam line in a utility tunnel ruptures or a chilled water pipe fails due to thermal expansion, the impact ripples through the entire terminal. Expansion joints can provide the solution.

The High Stakes of Utility Tunnel Failures

Airports are essentially small cities connected by miles of either underground piping or piping going through the roofs of buildings. These utility tunnels carry the facility’s primary media: steam for de-icing, chilled water for HVAC, and pressurized lines for fire suppression. Because these lines span such vast distances, they are hyper-sensitive to thermal expansion and contraction.

Preventing Catastrophic Pipe Stress

Without properly engineered expansion joints, pipes that expand under heat will exert forces on anchors and equipment. This leads to cracked welds, warped flanges, and, eventually, equipment damage or a catastrophic breach. In an airport environment, a single pipe failure can lead to terminal evacuations, canceled flights, and millions of dollars in lost revenue. Expansion joints act as the lungs of the system, absorbing this movement and keeping the utility grid stable.

Maximizing Infrastructure Lifespan and Reliability

Investing in high-quality expansion joints is a strategic move for airport asset owners. These components are designed to handle thousands of cycles, ensuring that the infrastructure can withstand decades of seasonal temperature shifts without requiring emergency repairs. The expansion joints can also be pressure-tested at 1.5x the design pressure to enhance reliability. 

Reducing Unscheduled Maintenance

When an expansion joint is designed correctly, it protects expensive pumps and turbines from vibration, thermal stress, and line pressure thrust. This shifts the facility’s profile from reactive to proactive, allowing maintenance teams to perform scheduled inspections rather than scrambling to fix a burst pipe under a busy taxiway. By ensuring the reliability of these systems, airports can focus on their primary goal: keeping passengers moving and planes in the air.

Airport Infrastructure FAQ

How do expansion joints handle seismic activity at airports? Modern expansion joints are engineered for multi-axis movement. In the event of an earthquake, these joints allow the piping system to flex and shift without leaking or buckling, thereby preventing pipeline compromise and maintaining fire suppression and emergency utilities during a disaster.

Can expansion joints be customized for space-constrained airport tunnels? Yes. Because many older airports have congested utility tunnels, manufacturers such as PT&P design custom-engineered bellows and gimbal expansion joints. These are specifically tailored to fit into tight footprints while still providing the necessary movement compensation.

Why is “Big Ton” technology relevant for airport utilities? For large-scale airport power plants or massive HVAC hubs, piping loads can be substantial. Using heavy-duty spring supports and large-diameter expansion joints helps control these massive forces, protecting the structural integrity of the entire utility building.

Fortify Your Airport Infrastructure with US Bellows

Don’t let a preventable piping failure ground your operations. Contact the engineering experts at US Bellows to schedule a pipe stress analysis and speak to an engineer to ensure your airport’s utility tunnels are equipped for long-term reliability.

 

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Why Modern Airport Architecture Relies on Expansion Joint Technology
February 4, 2026

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

 

Modern airport terminals are breathtaking examples of engineering, often featuring expansive glass curtain walls and soaring steel skeletons. However, these massive structures are constantly in motion. As the sun beats down on a terminal’s exterior, the materials expand; as temperatures drop overnight, they contract. Without a sophisticated system of expansion joints, these natural movements would result in shattered glass, cracked components, and compromised structural integrity.

Designing for Aesthetics and Mechanical Stability

In a large-scale terminal, the architectural beauty must be matched by mechanical resilience. The HVAC and plumbing systems running through these buildings are often rigid, yet they are anchored to a frame that is designed to flex. Expansion joints serve as the essential interface between these two worlds, allowing the building to breathe without putting undue stress on the life-safety and comfort systems that passengers rely on.

Protecting Fragile Glass and Facade Systems

When a terminal spans hundreds of thousands of square feet, the cumulative effect of thermal expansion can extend a pipeline by several inches. Expansion joints integrated into the piping and ductwork ensure that this movement isn’t transferred to the building’s facade. By absorbing these shifts, expansion joints prevent the massive thermal forces from damaging the building’s facade.

Ensuring Uninterrupted Passenger Comfort

Passenger comfort is a top priority for airport operators, and this depends entirely on the health of the HVAC system. Expansion joints installed at key intervals and equipment headers act as shock absorbers, helping with flexibility and isolating mechanical equipment from piping movement. This means passengers can enjoy their time in the terminal, whether cooling or heating is needed.

Managing Extreme Temperature Differentials

Airports are unique because they maintain a strict climate-controlled interior while being exposed to extreme outdoor runway temperatures. This creates a significant thermal gradient across the building’s envelope. Engineered expansion joints are designed to accommodate these differentials, ensuring that even when the tarmac is radiating heat, the internal piping remains stable and leak-free, keeping the terminal cool and the passengers comfortable.

To help airport facility managers and MEP engineers select the right components, the following table outlines the technical differences between metallic and fabric expansion joints. Each material serves a specific purpose based on the terminal location and the media being transported.

Comparison of Expansion Joint Materials for Airport Infrastructure

Feature Metallic Bellows Fabric Expansion Joints
Primary Use Case High-pressure steam, fuel lines (Jet A-1), and chilled water loops. Low-pressure HVAC ducting, air handling units, and ventilation.
Movement Capability Good for axial, lateral, and angular movement in high-pressure systems. Superior for large amounts of concurrent movement in multiple directions.
Pressure Rating Can handle extreme pressures (from vacuum up to 1,000+ PSI). Strictly for low-pressure or atmospheric systems (typically < 5 PSI).
Vibration Isolation Good, but often requires specific engineering to dampen high-frequency noise. Exceptional; the non-rigid material naturally absorbs almost all mechanical vibration.
Space Constraints Compact design; Single EJs are ideal for tight utility tunnels and ceiling plenums.   Compact. Design must allow the fabric to flex without tearing. Can accomplish larger movements than metal in the same face-to-face length.
Durability Highly resistant to external corrosion when coated, galvanized, or made of stainless steel. Vulnerable to sharp objects or high-velocity particulate if not lined.

Which One Does Your Terminal Need?

Protect modern airport infrastructure with expansion joints from US Bellows.

Choosing the wrong material can lead to premature failure and expensive terminal repairs. US Bellows can perform a system-wide review to ensure your specifications match the unique demands of your airport’s mechanical design.

Selecting the right expansion joint depends on the specific zone of the airport:

  • The Utility Tunnel: These areas almost exclusively require metallic bellows. Because they carry high-pressure steam for heating or de-icing, the material must withstand significant forces and accommodate the large thermal expansion over long distances.
  • The Concourse HVAC: For the air distribution systems that keep passengers comfortable, fabric expansion joints are often the better choice. They are cost-effective, easy to install in ductwork, and eliminate the “rattle” that can occur when heavy air-handling units cycle on and off.
  • The Tarmac Fueling System: This is a mission-critical environment; only metallic joints that have undergone rigorous testing (e.g., those provided by US Bellows) should be used. These joints must withstand the chemical properties of aviation fuel and the physical loads imposed by overhead ground support equipment.

Airport Expansion Joint Engineering FAQ

How do expansion joints contribute to the acoustics of an airport terminal? Expansion joints do more than just manage movement; they also act as vibration isolators. By breaking the metal-to-metal contact in piping and ductwork, they prevent the “hum” of mechanical rooms from traveling through the terminal walls, contributing to a quieter, more pleasant environment for travelers.

Are expansion joints required for airport fire sprinkler systems? Absolutely. Because fire protection lines run the entire length of the terminal, they are subject to the same thermal and seismic stresses as any other pipe. Expansion joints ensure these lines remain intact and pressurized, even if the building shifts during a seismic event or extreme weather.

How often should expansion joints in terminal ceilings be inspected? While many joints are designed for a long service life, we recommend a visual inspection every 2 to 5 years. This is especially important in terminals located in regions with high seasonal temperature swings, as the bellows undergo more frequent cycles of expansion and contraction.

Build for Longevity in Terminal Design, Not Just Aesthetics

Don’t let thermal stress compromise your architectural vision or passenger experience. Book a meeting with our engineering team at US Bellows to see how our custom-engineered expansion joints can add decades of reliability to your next terminal project.

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The Engineering Guide to Selecting Expansion Joints for Dielectric Fluid Loops
January 28, 2026

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.

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Hinged Expansion Joints Custom-Designed for a Process that Produces High-Density Polyethylene (HDPE)
January 20, 2026

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.

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Preventing Unplanned Coke Drum Outages: An Integrated Approach to Piping Flexibility
January 13, 2026

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.

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Custom Single Ply X-Flex Bellows Designed for a Manufacturing Company of Flooring Products
December 31, 2025

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.

 

 

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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.

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Protecting Industrial Ductwork: Fabric vs. Rubber Expansion Joints
December 22, 2025

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 ApplicationRubber 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.

 

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The Single Expansion Joint Advantage in Steam Piping
December 9, 2025

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:

  1. 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.
  2. 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.
  3. 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.
  4. 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.

 

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