The spring rate is equal to the spring rate of both flow bellows plus the spring rate of the balancing bellows.
What’s the typical spring rate for a 20″ pressure balanced expansion joint?
August 6, 1990
Tag: faq
For a higher pressure system, how do you absorb pipe axial displacement without pressure thrust going to equipment with use of the expansion joint?
By using an in-line pressure balanced expansion joint.
What is axial deflection?
August 5, 1990
Axial deflection refers to the movement of the expansion joint in regards to changes in the dimensional length of the bellows parallel to the centerline of the expansion joint.
 Axial Deflection |
Do hinged and gimbal expansion joints serve the same purpose?
August 2, 1990
Hinged expansion joints take angular rotation in only one place. Gimbal expansion joints take angular rotation in two planes.
On a lateral tied expansion joint, is there space allowed in between the nut and the retainer to functionally avoid tilt of the tie-rod when at the operating temperature?
We do not put slots on our expansion joints, but we leave a minimum gap between the nuts and the lug depending on the lateral movement.
Why are loads on tied universal bellows not transferred?
Loads on a tied universal bellows are not transferred because pressure thrust is contained within the tie rods and is not transferred to the piping system equipment.
How do you achieve lateral movement in a tied universal expansion joint?
The lateral movement in a tied universal expansion joint is achieved by having the bellows work together in angular rotation in order to obtain the correct lateral deflection.
Where should I use a universal expansion joint in piping?
Universal expansion joints are typically used in z-bend or l-shape pipe arrangements where the expansion joint allows for lateral motion
How long should a universal expansion joint be?
The length of a universal expansion joint is dependent upon the amount of lateral motion to be absorbed by the expansion joint. This is determined on a case by case basis.
Can you use a tied expansion joint in the exhaust of a gas turbine application?
Yes, a tied expansion joint is a correct application for tied expansion joints to eliminate pressure thrust on the turbine exhaust nozzle.
How do you decide on the number of tie-rods in a universal expansion joint?
The number of tie-rods on a universal expansion joint is calculated according to the amount of pressure thrust that the particular expansion joint will absorb. Low-pressure expansion joints may have two rods, for example, while high-pressure expansion joints may have four or more.
Do hinged expansion joints have to be designed for pressure thrust?
Yes, hinged expansion joints do need to be designed to accommodate for pressure thrust.
Why do expansion joints have one loose flange?
Expansion joints have one loose flange when specified to facilitate the alignment of flanges on the piping system during installation.
When should you replace metal bellows expansion joints?
Metallic expansion joints should be replaced if they are leaking or can simply be replaced on a scheduled maintenance program in order to avoid leaks that may occur in the future.
How common is it to use steel expansion joint in and out of centrifugal pump?
We get inquiries for steel and rubber expansion joints for pump suction and discharge.
Where can I find a metal expansion joint slide show?
You can find a slide show on an introduction to U.S. Bellows that covers a wide variety of metallic expansion joints at the following link:
Read More
How does a toroidal expansion joint work?
A toroidal convolution consists of a circular tube (or totus) wrapped around weld ends or pipe ends having a gap at the I.D. to permit axial stroke. A toroidal expansion joint may consist of one convolution or multiple convolutions. This joint is also known as an Omega bellows expansion joint for it resembles the Greek letter Omega. Most toroidal bellows are hydraulically formed which requires high pressure. Others are free formed, similar to blowing up a balloon. More accurate convolution shapes may be formed into toroidal dye cavities. Since this forming pressure is high, pressure resistance is also high. “U” shaped bellows cause a bending stress due to the pressure load on the convolution side wall. This generally determines the maximum pressure, however, the toroid contains only membrane stress thus determining the maximum pressure. Due to the toroidal shape, deflection is limited. With “U” shaped convolutions, more deflection can be achieved but allowable pressures are lower.
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