May — 2012 — The Expansion Joints Blog


Archive for May, 2012

Pressure Balancing Expansion Joints are Ideal for Absorbing Thermal Expansion of Equipment

May 30th, 2012 Comments off

The pressure thrust produced by low pressures can be tremendous in large diameter systems, just as it can be at normal pressure ratings in small pipes. To avoid expensive anchors, to keep long pipe runs in tension, to prevent buckling, or reduce reaction forces on equipment, the pressure in the pipe can be used to generate balancing forces within the expansion joint. These combinations of bellows and thrust restraining structural components can accept almost any combination of movements, as shown in the following examples.

Example of how the pressure in the pipe can be used to generate balancing forces within a pressure balanced elbow expansion joint.The pressure balanced elbow is ideal for absorbing the thermal expansion of equipment, such as turbines, pumps and compressors, which rely upon low reaction forces on their inlet and exhaust flanges. In this example, only an intermediate anchor is provided at the elbow, to isolate the equipment from any forces produced in the remaining piping.

The pressure thrust force produces tension on the equipment flange, but the only forces produced by the deflection, are the spring resistance of the bellows within the expansion joint. The spring rate of these units is the sum of the spring rates of the bellows on each side of the elbow, and care must be taken to provide a unit which produces spring forces low enough to satisfy the equipment maximums as stated by the equipment manufacturer. Bellows may also be cold sprung to reduce these forces even lower.

Example of how the flange is subjected to an axial force equal to the pressure thrust.Example of how the flange is subjected to an axial force equal to the pressure thrust. In this example, which may be typical for a turbine exhaust application, the force on the machine’s flange is the spring reaction of the bellows in lateral deflection, as described in the above example. Again, the flange is also subjected to an axial force equal to the pressure thrust, as if it were capped, but the turbine’s mounts are not. The pipe guide between the expansion joint and the equipment flange absorbs the forces produced by the thermal expansion of the pipe, along its axis.

View all the examples in the full article on, Pressure Balancing Expansion Joints.

Neoprene Fabric Expansion Joints for a Ventilation Fan Intake Duct

May 21st, 2012 Comments off

Neoprene Fabric Expansion Joints for a Ventilation Fan Intake Duct

Neoprene fabric expansion joints were custom designed for a ventilation fan intake duct in a power plant. They are 42″ in diameter and are 65″ in overall length. They were designed for 1/4″ axial movement, 1/8″ lateral deflection and a 100″ water column at 200°F. The expansion joints are fabricated with a neoprene reinforced belt with stainless steel clamps, carbon steel spool pipe and angle flange ends. Each joint was dye penetrant examined prior to shipping.

View our past expansion joint and duct work projects in the Featured Product Archives

May 14th, 2012 Comments off

Check out some of our past projects in the Featured Product Archives section of our website.

  • View images of metallic and fabric expansion joints, duct work, and combination assemblies.
  • Also read the details on the project itself, including design specifications and testing requirements.
  • The projects are conveniently grouped by the type of expansion joint and then listed descending by the release date.

Here are a few examples:

36″ Tied Universal Expansion Joint for a Petrochemical Plant in Kuwait
36" Tied Universal Expansion Joint
U.S. Bellows Inc. designed and fabricated a 36″ tied universal expansion joint for a petrochemical plant in Kuwait. The expansion joint measures 36″ in diameter x 318″ from center of elbow to face of flange. It is fabricated from 316H stainless steel with Inconel® 800 bellows. The design pressure of the expansion joint is 65 PSIG, and the design temperature is 1076°F. It is designed for axial compression within the tie rods and lateral movement of 3.02″. Hydro-testing was performed at 98 PSIG to assure the integrity of the tie rods and also to assure quality. The pictures show the expansion joint leaving the shop on its way to the customer. The stainless steel flange faces are protected with 3/4″ plywood during delivery.
44″ Double Gimbal Universal Expansion Joint for an Oil Refinery in Wyoming
44" Double Gimbal Universal Expansion Joint
This gimbal expansion joint is designed for angular rotation in two planes of up to 4° in each plane. It has an overall length of 140″ with a total assembly weight of 11,000 lb. It is fabricated with 316 stainless steel bellows and carbon steel piping. This expansion joint was 100% dye-penetrant examined and hydro-tested prior to shipment. U.S. Bellows, Inc. and Piping Technology & Products, Inc. also furnished the spring supports and pipe attachments for this project.
128″ x 229″ Rectangular Fabric Expansion Joints for an Exhaust Duct
128" x 229" Rectangular Fabric Expansion Joints
The fabric expansion joints shown above are fabricated with a three layer fabric belt. The three layers consist of an inner layer of silica cloth, a middle layer of mineral wool and an outer layer of PTFE/coated fiber glass. The frame includes an insulation blanket of mineral wool and stainless steel wire mesh. The frame and liner are fabricated from 3/8″ thick 304 stainless steel and each expansion joint’s frame and liner welds were dye-penetrant tested before shipping. 

- Pressure: 1 PSIG
- Temperature: 1010°F

Design Movements:
- 2″ Axial Displacement
- 3/4″ Lateral Displacement

Universal Tied Expansion Joint, 48″ Dia. and 141″ OAL, for Service in an Acid Regeneration Plant

May 7th, 2012 Comments off

Universal Tied Expansion Joint, 48" Dia. and 141" OAL, for Service in an Acid Regeneration Plant

A tied universal expansion joint was custom designed for service in an acid regeneration plant in Louisiana. It is 48″ in diameter, 141″ in overall length and designed for 1″ axial movement, 2-1/2″ lateral movement and .33° angular rotation. The expansion joint is fabricated with 310 stainless steel bellows, and 301 SS liner, duct, flanges, transition duct and covers. It was designed for 10 psig at 1150°F, and was dye penetrant examined, hydro-tested at 15 psig, and the bellows and pipe longitudinal weld seams were 100% x-rayed.


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