several common problems in the valve

Why can't the double sealing valve be used as the cut-off valve?

The advantage of the double seat valve spool is the force balance structure, which allows the pressure difference to be large, and its outstanding drawback is that the two sealing surfaces cannot be in good contact at the same time, resulting in large leakage. If it is artificially, forcibly used in cutting-off situations, it is clearly not effective, even if many improvements have been made for it (such as double-sealed sleeve valves) are not desirable.

Why is the control valve easy to oscillate when the small opening of the two-seat valve is working?

For single core, the stability of the valve is good when the medium is flow open, and the stability of the valve is poor when the medium is flow closed. The two-seat valve has two spools, the lower spool is in the flow closed, and the upper spool is in the flow open, so that, when working on the small opening, the flow closed type spool can easily cause the vibration of the valve, which is the reason why the double-seat valve cannot be used for small opening work.

What straight stroke regulating valve anti-blocking performance is poor, angle stroke valve anti-blocking performance is good?

The straight-stroke valve spool is vertically throttled and the medium flows horizontally into the outflow, and the flow path in the valve chamber must turn and turn the valve so that the flow path of the valve becomes quite complex (shape such as inverted S-type). In this way, there are many dead zones, which provide a space for the precipitation of the medium, which, in the past, causes a blockage. The direction of the throttle of the angle stroke valve is the horizontal direction, the medium level flows into, the horizontal flow is out, the non-clean medium is easy to take away, the flow path is simple, and the space of the medium precipitation is small, so the anti-blocking performance of the angle stroke valve is good.