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Two-ply Testable Bellows

U.S. Bellows designs two-ply bellows with 100% redundancy; therefore, if a leak occurs in the inner ply, the outer ply is designed for the full pressure and temperature. This design allows for the critical piping system to continue operating while plans for replacement can be formulated. This can prevent unexpected shut-downs saving valuable time and money.

Two-ply bellows also make it possible to pressure test and inspect for leaks during field inspections and in some cases, if conditions permit, the expansion joint can be tested while in service. Universal, hinged and gimbal are some of the common types of expansion joints that include two-ply bellows. Sometimes a wire mesh is used between the bellows to ensure flow equalization between the plies of the bellows.

Most expansion joints in oil refineries, especially FCC units use two-ply bellows, but they are also ideal for regenerated catalyst standpipe, spent catalyst standpipe, recirculation cooled catalyst flue gas piping and hot gas expanded piping. Contact our team to have your single bellows expansion joint refurbished to include two-ply bellows.

Two ply bellows 86076 44″ Hinged Expansion Joint with Refractory-lining and Two-ply Bellows

  • Designed with two-ply Inconel® 625 LCF bellows, 5″ thick refractory-lining, and 2″ thick attachment rings for part of a reactor piping system in a synfuels plant
  • Pneumatically tested between the bellows plies and the complete expansion joint
  • Thermal and structural Finite Element Analysis (FEA) was performed for the bellows operating temperature
Two ply bellows 70679 55″ Refractory-lined Universal Gimbal Expansion Joint with Two-ply Bellows

  • Designed for a spent catalyst standpipe in an FCC unit & includes slotted hinges
  • 163″ O.A.L and 60 PSIG at 1020°F, A516 GR 70 pipe and two Inconel® 625 LCF two-ply bellows
  • 100% dye penetrant tested, 100% x-ray tested, pressure tested, pneumatic and vacuum tested between the bellows plies and the complete expansion joint
Two ply bellows dec2001 44″ Universal Expansion Joint with Refractory-lining and Two-ply Bellows

  • Designed for a chemical plant in Venezuela 44″ diameter and 100 PSIG at 1000°F
  • 321 SS two-ply testable bellows, A-387 GR 11 weld ends, 5″ vibra cast and 1″ abrasion resistant refractory
  • Pneumatically tested between the bellows plies and the complete expansion joint