PTFE Expansion Bellows – Key Features

PTFE Convolutions

FluoroFlow Bellows from CRP provide stress free formed convolutions with a uniform wall thickness. The number of convolutions is key to the range of movement provided by the bellows, however both pressure and vacuum performance are reduced as the number of convolutions increases.

Root Rings

Root rings provide support for the PTFE which is a mechanically weak material especially when hot.  These sit at the base of each convolution. Our root rings come x-ray tested in high grade stainless steel (1.4571/316Ti) as standard.

Limit Sleeves

Limit sleeves are standard for CRP. They prevent damage to the convolutions by preventing the bellows from being compressed below the minimum allowable axial length..


Bellows flanges are available to all of the international piping standards including ASME Class 150 and 300 and DIN PN 6, 10 and 16.  The flange connection drillings are drilled and tapped either UNC for ASME or Metric for DIN.

Please note the internal flange profiling that assists the first convolution in minimising any stress generated by the flange. Flanges are painted in an ultra high temperature paint in a silver finish.

Tie Rods

Tie rods prevent the bellows from exceeding their maximum allowed movements. They arrive factory set at the maximum allowable extension as detailed on the data label – Ready To Install. The Tie Rods on CRP Bellows are designed & strong enough to absorb the forces from the full pressure thrust.

Data Labels

The CRP bellows give the best example of data labels in the market. There are three or four data labels present on the bellows flanges to carry as much information about the bellows as practical. More information can be found in our catalog, or by reference to CRP, quoting the part number and serial number references.

Bellows items