Bellows Design

Most engineered structures are designed to inhibit deflection when acted upon by outside forces. Since the bellows must accept deflections repetitively, and deflections result in stresses, these stresses must be kept as low as possible so that the repeated deflections will not result in premature fatigue failures.

Bellows, are a flexible element of the expansion joints that absorb the thermal pressure. It must be strong enough to endure the pressure and should be quite flexible to accept the deflections for which it is specifically designed. These metal bellows and expansion joints are used in numerous industry mainly in piping systems.

Reducing bending stress resulting from a given deflection is easily achieved by simply reducing the thickness of the bending member, which in the case of the bellows, is the convolution. However, in order to withstand the pressure, the convolution, which is also a pressure vessel, must have a thickness great enough that the pressure induced membrane stresses are equal to or less than the allowable stress levels of the materials at the design temperatures.

We ensure, that the metallic bellows and the expansion joints that we produce are designed as per the guidelines and design data sheet of Expansion Joint Manufacturers Association (EJMA) 9th edition guidelines be provided.

Basic Steps Involved in Bellow Designing:

  • Making of bellow tubes.
  • Formation of Bellows
  • Re-polling process
  • The Roll Seam welding process ROLL SEAM WELDING
  • Trimming of bellow necks
  • Providing size to bellow necks.

Bellows are not springs, in that most of their deflections produce bending stresses in excess of the materials' yield strength. Understanding how various materials perform and their capabilities in this "plastic" deformation region require years of experience and design equations based upon this empirical understanding.

Before delivering the products, all the product go under the testing phase. We at Pliant Bellows use various testing methods like:-

  • Hydrostatic Pressure and Leak Test
  • Pneumatic Bubble Soap Leak Test
  • Vacuum Test
  • Dye Penetrant Test
  • Visual Test
  • Fatigue Test
  • Squirm Test
  • Spring Rate Test
  • Radiography Test (Through third party approved vendors)
  • X-Ray Test (Through third party approved vendors)
  • Ultrasonic Test (Through third party approved vendors)
  • Helium Leak Detection Test (Through third party approved vendors )

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