What are Bellow seal Valves. Under what circumstances this requirement is called for. Is this related to the sealing requirement near the Gland packing area or it an alternative to that. Are there any International standards which specifies design method for this bellow seal valves?Multi-functional Water Pump Control Valves

Bellows seal valves are essentially valves which are less likely to have fugitive emissions problems by containing the valve stem mechanism in a bellows. Thus a valve stem packing leak will not leak to atmosphere.Ball Valves Due to the required flexibility of the bellows, the stems of these valves are LONG. Check ValvesThey can be designed in for new construction, though that can be painful. Retrofitting into existing installations can be virtually impossible due to interferences.Gate Valves

In the High Purity Gas industry, bellows seal valves (sizes from 1/4' thru 2") are preferred in applications where long cycle life, metallic body sealing, ease of operation and low particulate generation are required.Butterfly Valves For instance, the average bellows valve design would have a cycle life of 10,000 cycles or more where a metal diaphragm valve would have a cycle life of aprox. 1000 cycles. However, in the smaller sizes the simplicity and strength of the springless packless valve (designed in 1982) would be preferred in applications where there is a limited cycle requirement. The pressure rating and purity levels are similar and the installation space and product cost are usually much less.

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