Selection of shut-off valve

In terms of the cut-off effect, the quarter-turn valve has a simpler structure, more reliable sealing effect, and more superiority than straight-stroke valves (such as single-seat valves, sleeve valves, gate valves, etc.). The more representative ones are triple eccentric hard seal butterfly valve, ball valve and so on.

Sealing surface

Face-to-face sealing

The common plunger valve core has a small cone surface with a sealing surface of 60°. The width of this small cone surface is usually between 0.5 mm and 2 mm. To seal well, it is necessary to ensure that the two cone surfaces are in good contact. But in fact, it is always affected by machining errors (such as concentricity, out-of-roundness, inclination, etc.), and its sealing effect is not very satisfactory. The leakage rate of this kind of valve is usually 10-4, and can reach 10-6 after precision grinding, which can reach a higher sealing level.

Spherical seal

The spherical rotation of the spherical surface is tangent to the fixed small taper surface, and there is a line contact between them, which is better than the above face-to-face sealing effect. Ball valves, spherical seal butterfly valves, etc. are made using this idea, and the leakage rate can reach 10-6~10-8, and the high-performance triple-eccentric butterfly valve can reach 10-8, or even zero leakage.

Seal type

Soft seal

In addition to corrosion-resistant lined valves, general soft-sealed valves refer to valves with a non-metallic material (mainly polytetrafluoroethylene, rubber, etc.) in the valve core or seat. The soft sealing valve has a good sealing effect, but more or less unclean debris (such as welding slag, iron filings, etc.) may be left in the pipeline installation and system cleaning. The sealing valve seat or valve core is scratched, which increases the leakage and poor sealing reliability. Therefore, the choice of soft sealing structure must consider the cleanliness of the medium and strictly flush the pipeline before putting it into operation.

Hard seal

Hard seal and surfacing welded ground alloy is a good choice for shut-off valves . This method takes into account the service life and reliability while considering the tightness. Although the factory index is only 10-4~10-5, it cannot achieve the effect of soft sealing and zero leakage, but it is enough to meet the requirements of strict shut-off. Durable and durable, it is more cost-effective from an economic point of view.