Why double seal valve can not be used instead of shut-off valve?

Some people may at some point use double seal valves instead of shut-off valves, but valve manufacturers do not recommend this. The reason why the valve manufacturer does not support the use of double seal valve instead of the shut-off valve is because the advantages of two-seater valve spool is its force balance structure allows a larger pressure drop, but it has two sealing surface can not be a good contact, easy to cause The big disadvantage is that if it is used artificially or forcefully to cut off the occasion, the effect is definitely not ideal and it is not desirable to make improvements halfway.

Welded Bed Plate For Flanges Of Ship Pipe

The flange welded single-sided seat plate is mainly installed on the top, side wall and bottom of the cabin or cabinet as the entrance and exit of the cabin or cabinet. Valves, accessories or pipes can be installed directly on the single-sided seat plate.

Flange welded single-sided seat plate is suitable for seawater, fresh water, oil, air and steam pipelines below 300 °C. The commonly used nominal diameter is 15~150 mm, and the nominal pressure is lower than 1.6 MPa. The shape of the single-sided seat plate is similar to the corresponding lap-welded Steel Flange.

Flange welded double-sided seat plates are generally used when pipelines pass through decks and tanks, and the two sides of the seat plate are respectively connected to valves, accessories or pipes.
Compared with the single-sided seat plate, the double-sided seat plate has an extra shoulder and double-sided mounting stud bolts. The outer diameter of the shoulder is 10~20 mm larger than that of the corresponding flange, and the thickness of the shoulder is 6~12 mm.
Its scope of application and other structural dimensions are basically the same as those of the single-sided seat plate.
The manufacturing and installation methods of the flange-welded double-sided seat plate are basically the same as the single-sided seat plate, but when the screw holes are drawn, the positions of the upper and lower screw holes of the seat plate must be staggered from each other and must not overlap; deck or bulkhead The diameter of the hole on the top is 2~3 mm larger than the diameter of the seat plate.

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