U.S. Bellows offers many accessories to protect the bellows and extend the life of your expansion joint. This article briefly describes a few of them including protective covers, internal liners, limit rods, hinges and purge connections.
Protective Covers
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External covers protect the bellows element from mechanical damage, during shipping, maintenance activities, and plant construction |
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Cover may be used for the application of insulation when the ductwork is insulated |
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Protective covers are provided in removable and non-removable configurations |
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The picture shows the installation of a protective cover on a 30″ diameter spent catalyst standpipe metallic expansion joint with pantographic linkage |
Internal Liners
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Internal liners, also known as “Internal Sleeves” and “Telescoping Sleeves,” extend the life of a metallic expansion joint |
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Protects the convolutions from direct flow impingement, which can cause flow-induced vibration |
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Standard liners are fabricated from 300 series stainless steel (optional materials include Inconel 625 and Inconel 600) |
Limit Rods
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Limit rods are used to limit axial expansion or compression to prevent the bellows from over-compression. Limit rods are designed to absorb the pressure thrust of the expansion joint in case of anchor failure. |
Hinges
| Hinges permit angular rotation in one plane only by the use of a pair of pins through hinge plates attached to expansion joint ends. Hinges and hinge pins are designed to restrain the thrust of the expansion joint due to internal pressure. Hinges can also be designed to carry piping loads. |
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Angular rotation in one plane |
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Eliminates pressure thrust forces |
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Transmits external loads |
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Prevents torsion on bellows |
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No main anchors required |
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Minimum guiding required |
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Low forces on piping system |
Purge Connections
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Used in systems where sediments can collect between the outside of the internal liner and the inside of the bellows element |
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Purge connectors can be added to the upstream end of the liner |
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Inert gas or air can be injected to periodically blow collected material out or can be continuously supplied during system operation |
This rectangular metallic expansion joint is fabricated with 321 stainless steel bellows and Cor-ten flanges. The inside of this unit is lined with both vibra cast and abrasion resistance refractory. The dimensions are 65″ x 81″ x 41-1/2″ overall length and the assembly weighs 3,900 lb. All welds are 100% dye penetrant examined and the design conditions are 1400°F with 5 PSIG.
This inline pressure balanced expansion joint is fabricated from ASTM A-240 321 SS bellows and ASTM A-105 carbon steel flanges. Due to its highly corrosive application, all of the internal surfaces are coated with a PTFE lining to resist corrosion. The expansion joint is designed for 51 PSIG at 167°F. and was hydro-tested at 77 PSIG prior to shipping.
