When the media is toxic, volatile, radioactive, or because it is extremely expensive does not allow reciprocating movement of the stem to bring external leakage, often with bellows seal valve cover. This special bonnet construction protects the valve stem and valve packing against contact with process fluids, and uses a standard or environmentally friendly stuffing structure on the bellows seal element to avoid any catastrophic failure in the event of a bellows failure Sexual consequences. Therefore, usually observe the valve stem packing is leaked, if the filler is involved, the bellows valve may be a problem.
First, the bellows structure
Bellows for regulating valves are usually two kinds, one is machined forming, the other is welded sheet-type corrugated pipe. The overall height of welded corrugated bellows is relatively low, but its service life may be limited due to its manufacturing method and internal structure defects. The corrugated pipe formed by machining is higher than the overall height, but the reliability is higher and the service life is higher. long.
Second, the application should pay attention to the problem
The pressure rating of the bellows seal decreases as the temperature increases. The bellows seal form should be carefully considered and proper attention should be paid to proper use and maintenance after installation to achieve the longest cycle life.
Third, the typical bellows products
Using a straight valve body structure with bellows seal on the valve cover and consider the appropriate factors can become bellows sealing valve.
(1) bellows seal small-caliber single-seat control valve
Valve body parts HV3000 series of small-caliber single-seat control valve is a high-performance upper-oriented structural control valve, Cv value of 0.01 to 1.4, in addition to the overall height of a slight increase in weight, the other body data are basically the same.
(2) bellows seal single seat control valve
Valve parts HV3000 series single-seat control valve, is an upper-oriented structure control valve, DN: 40 ~ 200, in addition to the overall height, weight slightly increased, the other body data are basically the same.
(3) bellows sealed cage type two-seat control valve
Valve body parts HV3000 series cage type two-seat control valve, is a pressure balance control valve, DN: 40 ~ 200, in addition to the overall height, a slight increase in weight, the other body data are basically the same.