What are Multi Ply Metal Bellows and where are they used?

Multi-ply bellows are made up of a multiple telescoping tube (or plys) of sheet metal. The telescoping tubes are formed (Expanded mandrel or hydraulic) together to form each convolution.

Multi ply Layer in the Metal bellow
Why are they better than single-ply bellows?
  • They offer redundance in the event of inner ply failure.
  • The offer much lower stiffness.
  • Leak detection measures can be incorporated to detect ply failure hence providing time to change out the existing expansion joint.
  • Much higher cycle life per corrugation.
  • Corrugated length can be much shorter to achieve similar movement and cycle life performance to that of a single ply bellows.
What are the drawbacks?
  • They have higher meridional bending stress.
  • They have less resilience to corrosion due to the individual wall thickness.
  • Higher ply count can result in slightly higher manufacturing cost.
  • Increased in-plane and column instability compared to a similar single ply construction.
  • Difficult to repair in the field due to the much thinner ply thickness.
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Single Ply Bellow Banner

What are Single Ply Metal Bellows and where are they used?

Single ply bellows are made up of a single tube (or ply) of sheet metal of a defined thickness.

Single Ply Bellow
Why are they better than multi-ply bellows?
  • The Expansion joint offers a simple construction and lower manufacturing.
  • They offer a higher pressure capacity compared to multi-ply expansion joints of a similar combined thickness
  • They more stable and less susceptible to in-plane and column squirm.
  • They are more resilient to corrosion due to their thicker wall.
What are the drawbacks?
  • They are generally stiffer than multi-ply bellows, which means they need more axial force per unit compression.
  • They have lower cycle life compared to a multi-ply bellows of similar wall thickness.
  • Preventive leak detection is not possible in many cases.
  • Longer convoluted lengths / taller convolutions are required compared to multi-ply bellows to provide similar movement compared to multi-ply bellows.
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High Temperature piping Expansion Joints

Hinged and Gimbaled piping Expansion Joints for a Natural Gas Fired Heater

High-Pressure High-Temperature piping Expansion Joints for a Natural Fired Heater at a US AFB.

  • Design pressure of 1,300 Psi and design temperature of 1,250 F.

  • Hydrotest at 1,900 Psi

Bellows Systems designed and manufactured one hinged and two gimbal expansion joints for a recent project. The gimbal type expansion joints included one with an external cover and removable insulation.
The bellows materials included Inconel 718 alloy construction with integral root rings and collars. Hinge and Gimbal structural components included 304 SS and 347H SS.

Hinged bellows were designed to be capable of 7 degrees of angular rotation at design temperature and pressure.

Bellows Systems is your go-to source for the standard to the most challenging bellows and expansion joint applications.

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High Pressure Universal Tied Expansion Joint

High Pressure Universal Tied Expansion Joint

Bellows Systems shipped another High Pressure Universal Tied Expansion Joint for a process plant piping application. The Expansion Joint had full Stainless Steel 316/ 316L construction & was designed per EJMA 10th Edition & ASME B31.3.

Our expansion joints are used in both the pulp line and chemical recovery process. Check our expansion joints for our complete line up of products or chat with one of our experienced sales and engineering staff to find the right solution for you.

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Exhaust compensator for a LPG Tanker

Exhaust compensator for a LPG Tanker

Recently we received an urgent request for replacement of the main engine (MAN B&W 8S35MC) exhaust compensator (bellows expansion joint) for a LPG Tanker en-route to Houston. Bellows Systems designed, fabricated and delivered the replacement 4-ply exhaust expansion joint within 5 days. Drop-off and pick-up was successfully completed during the vessel’s Houston port call.

We also provide quick turn around repair services on exhaust bellows and expansion joints to vessels calling into port of Houston or Galveston.

Make Bellows Systems your go to source for emergency repairs or rebuilds of exhaust bellows and expansion joints. Call us today to find more about our repair services.

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