Bellows Testing and Safety Factors

Bellows materials are fully traceable.  Bellows tubes undergo mechanical and dimensional tests following manufacture.  PTFE sintering and convolution are undertaken using calibrated ovens with precise temperature control.  Independent process checks are undertaken using infra-red thermometry.  In-process visual inspection of the PTFE tubes is undertaken and this combined with a hydrostatic test and further visual inspection of the finished product completes the product verification.  Certification is available if required to reassure the customer on materials of construction, process control and product testing.

Safety Factor / Bellows Design
A key consideration in bellows performance is the temperature and pressure that the bellows will withstand for extended periods of time.

Bursting Pressure Test
A safety factor is defined as the ratio of burst pressure to allowable operating pressure.  A factor of 3 is considered acceptable by most bellows manufacturers.
CRP has adopted a safety factor of 6 for bellows up to DN150 and a safety factor of 4 for larger diameters.

Pressure Increase Test
In addition to the bursting pressure tests, innovative pressure increase tests have been undertaken successfully at 100°C and 150°C by TÜV.  These unforgiving tests slowly increase the delivered pressure to the bellows at high temperatures, encouraging the PTFE material to flow as in service.  The pressure increase test results confirm the outstanding creep resistance of the FluoroFlow Bellows based on the unique convolution process.

Lifetime Assurance
CRP Bellows are designed to have a residual safety factor of 2 after more than 10 years in operation.

International Standards
All bellows, comply with the Pressure Equipment Directive 2014/68/EU and are provided with a CE declaration of conformity.  PTFE armoured bellows for high pressure performance are designed according to the EJMA international standard.

Contact Details

Corrosion Resistant Products Ltd
Todmorden Road
OL15 9EG

Phone: +44(0)1706 756400
Fax: +44(0)1706 379567