Technical Articles
Common Breakdowns of Valves (Part Two)
Posted: 08/26/2017 17:31:20  Hits: 6
4. Adopting the lens gasket
For the sealing of the upper and lower bonnets, the valve seat and the upper and lower valve bodies, if the seal is the flat seal, the sealing performance will be poor under high temperature and high pressure, resulting in outer leakages of valves; we can use the lens gasket to achieve the satisfactory result.

5. Replacing the gasket
So far, most of the gaskets still adopt asbestos gaskets; the sealing performance of the asbestos gasket is poor at high temperatures; the asbestos gasket has the short service life and can cause outer leakages. In this case, we can replace asbestos gaskets with spiral wound gaskets and "O" rings which are adopted by many factories.

6. Symmetrically screwing the bolt and using the thin gasket
For regulating valves with "O" ring sealing structures, when we use thick gaskets with larger deformation, asymmetrically pressing the thick gaskets will easily make the sealing damaged, tilt and deform, which will seriously affect the sealing performance.

Therefore, when we maintain or assemble regulating valves, we must symmetrically crew and press bolts; it should be noted that bolts can not be crewed only once. We had better replace the thick gasket with the thin gasket to reduce the tilt and ensure the sealing.

7. Increasing the width of the sealing surface
There are no guiding and drive surfaces for flat-plate valve spools; when valves are working, valve spools are affected by side force and tend to be close to the outflow side. The greater the fit clearance of valve spools is, the more serious this unilateral phenomenon will be. Coupled with deformation or small chamfer of valve spools' sealing surfaces, end faces of chamfer of valve spools' sealing surfaces will be placed on sealing surfaces of valve seats when the valves are almost closed, which will make valve spools bounce or even not to be closed properly, resulting in the increasing of the leakage.

The simplest and the most effective solution is to increase sizes of valve spools' sealing surfaces and to make minimum diameters of valve spools' ends 1 to 5mm smaller than the diameters of the valve seats so as to ensure valve spools getting into valve seats and good sealing surface contact.