Bellows Sealed Design
Bellows sealed construction is the optimal solution when the valves handle process fluids which are very toxic, polluting, highly hazardous or radioactive, or when the valves are used in inaccessible locations where periodic inspection and maintenance of the valve packing is not possible. It also conserves expensive process fluids.

A valve with standard gland packing construction requires frequent monitoring, maintenance and replacement as any leakage of toxic or hazardous fluids will lead to the creation of high risk zones. When the process fluid is to be completely sealed off from the atmosphere, Bellows sealed construction is the only option. This design incorporates formed metallic bellows that makes a barrier between the stem and the body cavity. Normally standard backup packing is provided as secondary packing.
The lower bushing of the bellows sub assembly is welded to the stem and the upper bushing is either welded to the bonnet or seat tightness is ensured with a Helicoflex gasket. A Helicoflex gasket (a spring energised gasket) or any suitable equivalent is used between the body and the bonnet to ensure leak tightness of 1 x 10-6 std cc/sec.

An existing control valve can be retrofitted with a Bellows sealed construction by changing the bonnet sub assembly and the stem sub assembly.

Bellows are available in a range of exotic materials that are compatible with any service fluid or temperature of application.
For pressure ratings up to 600#ANSI, single ply bellows can be used, and for high pressure ratings multi¨C ply bellows are used.

MIL has experience in supplying Bellows sealed valves for various applications ranging from 150#ANSI to high pressure bellows (up to 420 kg/cm2 ) for The Liquid Propulsion System Centre (Indian Space Research Organisation.)

Bellows sealed construction is the right solution for arresting stem leakage when the service fluids are highly toxic or hazardous such as in the cases of Hydrogen, Chlorine, Ammonia, Cyanide, Natural gas, radio active fluids etc. With high quality bellows available in the import market at reasonable prices, this is also an economical choice.

 

Technical Documentation
(PDF 290KB)