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Categories - Frequently Asked Questions (FAQ)

Category Articles
How do you do a fatigue life cycle test for bellows?
Added on Thu, Feb 10, 2011
The bellows is placed on a test machine and allowed to cycle continually until the bellows fails. Fatigue Test Read More
What is blotting in a dye-penetrant test?
Added on Wed, Jun 29, 2011
Blotting on a dye-penetrant test typically indicates a crack in the weld. Therefore, the crack would be repaired and the test performed once again. Dye Penetrant Test Read More
How long is a burst test on an expansion joint?
Added on Sat, Apr 16, 2011
A burst test is performed under controlled conditions and pressure is applied over a period of one to two hours using the necessary safety precautions for all personnel involved. Expansion Joint Burst Testing Read More
What’s the typical spring rate for a 20" pressure balanced expansion joint?
Added on Fri, Oct 19, 2012
The spring rate is equal to the spring rate of both flow bellows plus the spring rate of the balancing bellows. Elbow Pressure Balanced Pipe Expansion Joint Read More
What is the difference between pneumatic testing and helium testing?
Added on Thu, Nov 3, 2011
For pneumatic testing, air is used as the medium for testing and for helium testing they use helium, and the cost for helium is much higher. Helium Testing Read More
How do you detect a crack in a fatigue testing machine?
Added on Sat, Apr 16, 2011
Cracks on a fatigue testing machine are detected by the loss of internal pressure that is shown pressure gauge on the machine. Fatigue Testing Machine Read More
How do you service test an expansion joint?
Added on Mon, Feb 7, 2011
Expansion joints are maintenance free. They can only be tested if the expansion joint is supplied with 2-ply testable bellows using vacuum or air pressure testing. Air Pressure Test on a Metallic Expansion Joint Read More
What are the quality tests that are conducted on expansion joints?
Added on Tue, Feb 8, 2011
At U.S. Bellows, we perform a variety of tests: Burst Testing - The objective of the burst test is to determine the ultimate pressure resistance. Primarily conducted on bellows. Normally, hydraulic pressure is slowly increased until failure occurs... Read More
For an inline pressure balanced expansion joint, overall speaking, is it equivalent to a simple expansion joint without thrust force?
Added on Fri, Oct 19, 2012
No, it is the total of the spring rates of all three bellows. 36" Pressure Balanced Elbow Pipe Expansion Joint Read More
Why should we do a dye-penetrant test?
Added on Sat, Apr 16, 2011
Dye-penetrant tests should be performed in order to check the integrity of the welds. At U.S. Bellows, all bellows undergo a dye-penetrant examination before being shipped to the customer. Dye-Penetrant Testing Read More
What acceptance criteria do you use for air testing the fabric expansion joints?
Added on Tue, Oct 16, 2012
We do not air test fabric expansion joints; all welds are liquid penetrant tested. Liquid Dye Penetration Test Read More
How do you do the fatigue analysis of the bellows in high temperature application?
Added on Fri, Oct 19, 2012
We perform EJMA calculations.   Fatigue Testing (also known as Cycle Testing) Read More
What is the maximum operating temperature range that expansion joints can be exposed to?
Added on Tue, Oct 16, 2012
Regarding the operating temperature, we design metal pipe expansion joints up to 2000° F with refractory and 1000° F to 1500° F without refractory. Metallic Expansion Joint Read More
When cycle testing an expansion joint, what was the length of the stroke?
Added on Mon, Jun 18, 2012
When cycle testing, the length of stroke is from neutral position to the compressed movement and back to neutral position of the expansion joint. Fatigue/Cycle Testing Read More

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