Expansion Joints and Metal Bellows Products

Expansion Joints

Beyond our line of signature metal hose and braid products, Penflex designs and manufactures expansion joints to offer a broader range of flexible piping solutions to customers across industries.

What is an Expansion Joint

Expansion joints accommodate movement and absorb vibration in a piping system and, in doing so, they protect adjacent piping and equipment from damage.

To make an expansion joint, we weld various end fittings on to a flexible bellows component. Relatively thin-walled tubing is used to form a single or multi-ply corrugated cylinder. In the expansion joint industry, these corrugations are called convolutions. This is the bellows component. Selecting the right alloy, wall thickness and convolution geometry allows for the design of a bellows that can meet or exceed the pressure and temperature requirements of adjacent piping.

The interplay between alloy, wall thickness and convolution geometry also determine how much movement an expansion joint can absorb.

When to Use an Expansion Joint

Some applications lend themselves to either a metal hose or to an expansion joint, but more often than not, there is a preferred option. A few key application criteria let us know when to use an expansion joint instead of a hose. These criteria are listed below, but for further reading, please see this engineering bulletin.

Axial Movement
Vibration Damping
Exotic Material Requirements
Space Limitations
Size Requirements

Sometimes the answer may not be so clear, and rather than deciding between an expansion joint and hose, the ideal solution may be a combination of the two.

Key Features of Penflex Expansion Joints

Multi-ply bellows for maximum cycle life under stringent conditions
Bellow material: 304, 316L, 321, Inconel® 625, 600 & 825, Hastelloy® C-22 & C-276, Monel® 400
Pipe sizes of 2-1/2” through 30,” with tooling up to 120” available
Designed per EJMA, B31.3 or B31.1 specifications
Various attachments available: Fixed Flanges, Floating Flanges (Vanstone), RF Flanges, Weld Nipples
Universal and Pressure Balanced Joints are available
Pump Connectors 3”ND to 12”ND in stock
Various materials in stock for a quick response and lead time
Structural welding is in accordance to ASME Section IX
Markets served: Steel Mills, Power Generation, Engine Exhaust, Heat Exchangers, Petrochemical, Pulp & Paper, Ship Building, Fuel Cells, Chemical Processing and Waste Water
NDE available: Pressure Testing, Liquid Penetrant Testing, Fluorescent Penetrant Testing and Radiography

Exhaust Expansion Joints

Penflex EX Series Expansion Joints are used to damp vibration and absorb thermal movements in exhaust applications thereby preventing damage to hard pipe and surrounding equipment. They have received Product Design Assessment certification from the American Bureau of Shipping.

The three-ply stainless steel and high nickel alloy components, available in sizes 4” – 24”, are designed in accordance with the latest Expansion Joint Manufacturers Association (EJMA) standards, with movements based on 30,000 non-concurrent EJMA fatigue cycles.

For more information, please click here.

Externally Pressurized Expansion Joints

As media flows through an externally pressurized expansion joint, it comes into contact with the outside, rather than the inside, of the bellows. This external pressurization removes pressure instability as a design limitation, allowing for a longer construction and bigger stroke.

With their ability to absorb large amounts of axial movement, externally pressurized expansion joints are often used in lieu of multiple expansion joints or a pipe loop. Heating and cooling systems as well as applications involving water, steam, and steam condensate commonly call for these kinds of components.

For more information, please click here.

Safety Relief Valve Vent Connectors

Vent connectors play a critical role in helping piping systems absorb the movements and vibrations associated with the quick opening and closing of safety relief valves. Penflex manufactures vent connectors using metal bellows or its unique fully-packed and pressure-tight M-100 interlocked hose.

For more information, please click here.