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It is the force generated by the expansion joint due to the pressure inside. As shown in the picture, we have seen several incorrect ways to calculate the thrust force of an expansion joint. Per the EJMA  Standards, as well as ASME Section VIII B&PV Codes, the Pressure thrust is calculated by multiplying the Bellows Effective Area, corresponding to the mean diameter of the convolutions of the Bellows by the Pressure of the line.

Yes, an externally pressurized expansion joint requires that the piping system be anchored.

Externally pressurized expansion joints
Externally pressurized expansion joints

We can allow for a total of 16″ of axial compression with a double x-flex expansion joint with an intermediate anchor base that will allow 8 inches of axial compression on either side of the anchor base.

40 externally pressurized expansion joints
Externally Pressurized (X-Flex) Expansion Joint

You can use externally pressurized expansion joints in this application provided that the piping is anchored, supported, and guided correctly.

Externally pressurized expansion joints
Externally pressurized expansion joints

The spring rate is equal to the spring rate of both flow bellows plus the spring rate of the balancing bellows.

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Elbow Pressure Balanced Pipe Expansion Joint

In general, there are fabric, metallic, and rubber expansion joints. At U.S. Bellows, we manufacture:

Metallic Expansion Joints

  • Single Expansion Joints
  • Hinged Expansion Joints
  • Gimbal Expansion Joints
  • Universal Expansion Joints
  • Elbow Pressure Balanced Expansion Joints
  • In-line Pressure Balanced Expansion Joints
  • Externally Pressurized Expansion Joints
  • Toroidal Expansion Joints
  • Thick Wall Expansion Joints
  • Slip-type Expansion Joints
  • Rectangular Metallic Expansion Joints
  • Refractory Lined Expansion Joints

Fabric Expansion Joints

* Rubber (Neoprene) Expansion Joints

Single tied metallic expansion joint
Metallic Expansion Joint
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Fabric Expansion Joint
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59″ Neoprene Expansion Joint

It is the force generated due to the pressure inside the expansion joint. Pressure thrust is calculated by multiplying the area of the mean bellows diameter by the pressure.

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Bellows “PA” (pressure x area) load

No, it is the total of the spring rates of all three bellows.

36 pressure balanced elbow expansion joints
36″ Pressure Balanced Elbow Pipe Expansion Joint