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Safety Reccomendations

Piping Technology highly recommends that our customers thoroughly understand the uniqueness of pipe expansion joints and their application. The following safety recommendations are paraphrased from the Fifth Edition of The Standards of the Expansion Joint Manufacturers Association, 1980.


Bellows pipe expansion joints are employed in piping systems to absorb differential thermal expansion while containing the system pressure. They are being successfully used in refineries, chemical plants, fossil and nuclear power plants, shipboard applications, heating and cooling systems, pulp and paper plants, and cryogenic plants. Typical service conditions range from pressures of full vacuum to 1,000 psig (70 kg/cm3) and -420F to +1,800 F (-251C to +968 C). Thus, pipe expansion joints must be specified as a highly engineered product. They cannot and should not be purchased and used as commodity items if the pipe expansion joints are to perform their intended function safely and reliably. The system operating requirements, the pipe expansion joint design and manufacturing quality, the installation, test and operating procedures must all be considered for all pipe expansion joint installations.

Unlike most commonly used piping components, a bellows is constructed of relatively thin gauge material in order to provide the flexibility needed to absorb mechanical and thermal movements expected in service. This requires design, manufacturing quality, nondestructive examination, handling, installation and inspection procedures which recognize the unique nature of this product.

In general, the most reliable and safe bellows pipe expansion joint installations have always involved a high degree of understanding between the user and manufacturer. With this basic concept in mind, the following recommendations are given in order to better inform the user of those factors which many years of experience have shown to be essential for the successful installation and performance of piping systems containing bellows pipe expansion joints.

Would you recommend expansion joints become filled with Kao when the expansion joint is utilized in high-temp applications (e.g. reactor overhead lines)?

Yes, we would recommend that the expansion joint is filled with Kao, but it would require a special design or over-sized bellows.

With regards to materials, how do you certify the materials?

We obtain the MTR’s and additionally we perform positive material identification tests in house and if a customer requires additional the additional chemical and physical properties, we can obtain that as well.

Why should I use a double offset expansion joint?

A double offset expansion joint can be used to absorb large amounts of lateral motion with a minimum amount of deflection forces

Why do bellows have corrugations?

Bellows have corrugations (convolutions) in order to be able to absorb the thermal movement of the piping.

Which forming method is better of more quality?

We punch form our bellows. This is an industry accepted forming method.

Where is the insulation pillow located within the expansion joint?

There are a variety of places for the insulation pillow to be placed within the expansion joint. It can be inside the unit or we can fabricate the expansion joint over sized and we can fill the extra space with the insulation pillow for example to reduce the skin temperature of the fabric.

Where is the gasket installed in a fabric expansion joint?

The gasket is a non-porous deformable material that is installed between the belt attachment flange and the fabric belt. The gasket allows a gas tight seal when the back-up bar clamping action is applied.

Where do I install expansion joints in a piping system?

The location of expansion joints in a piping system depends on the design conditions and the piping system configuration. All cases must be evaluated individually.

When are center supports required on expansion joints?

Use a center spool support to support the weight of the spool between the bellows and to stabilize the center spool during operation.

What type of material is normally used in the accumulation barrier?

Kaowool is used. It is a ceramic thermal blanket.

What type of EJ do I use so that I don’t need to design for the pressure thrust force?

Pressure balance type. The major advantage of a pressure balanced joint is its ability to absorb axial movement without imposing additional pressure thrust into the piping system.

What’s the highest cycle # you can handle?

Fatigue life of any unit has to be calculated. The number of cycles varies according to the design conditions of the expansion joints.

What’s the difference between a single and multi-layer bellows?

If you use a two-ply bellows, each ply can be designed for the full temperature and pressure conditions so that if the inside ply were to fail, you would still have the outside ply to carry the design pressure and temperatures.

What other name is the toroidal pipe expansion joint known as?

This expansion joint is also known as an Omega bellows pipe expansion joint for it resembles the Greek letter Omega.

What limits the U-shaped design application?

Design condition of bellow prescribes physical dimension and shape of convolution. It also depends on a combination of size, temperature and pressure. The image of the rounded corner below is an example of an U-shaped design.

What is the smallest inner diameter you can fabricate?

1″ nom diameter.

What is the service life of expansion bellows before it needs to be serviced in steam application?

There is not a particular time period of service life, but it depends on the environmental condition of the expansion joints. Maintenance is not required on expansion joints.

What is the purpose of the hinged expansion joint on a duct expansion loop?

Hinged expansion joints are used in conjunction with piping loops in order to absorb large amounts of thermal expansion.

What is the leak “rate” acceptance criterion for the bolt to fabric connection?

There is not an acceptance criterion for bolt to fabric connection.