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Why Should These Refrigeration Stop Valves Be Low in and High out?

Released on Aug. 11, 2020

The stop valve is also called the globe valve, which is a forced-sealing valve and a kind of globe valve. According to the connection mode, there are three types: flange connection, threaded connection, and welding connection.

This type of shut-off valve is very suitable for shutting off or regulating and throttling. Because the opening or closing stroke of the valve stem of this type of valve is relatively short, and it has a very reliable shut-off function, and because the change of the valve seat port is in direct proportion to the stroke of the valve disc, it is very suitable for flow adjustment.

The stop valve is designed for low inlet and high outlet, the purpose is to make the flow resistance small and save effort when opening the valve. At the same time, when the valve is closed, the gasket between the valve casing and the valve cover and the packing around the valve stem is not stressed, and will not be subjected to medium pressure and temperature for a long time, which can prolong the service life and reduce the probability of leakage. In addition, the packing can be replaced or added when the valve is closed for easy maintenance.

Stop Valve

Many people think that the stop valve is low in and high out, but it is not. In general, the shut-off valve is low inlet and high outlet, but there are some special cases where the shut-off valve is high inlet and low outlet:

1. High-pressure stop valves with a diameter greater than 100mm: Due to poor sealing performance of large-diameter valves, when the cut-off valve is closed, the medium pressure acts on the valve flap to increase the sealing performance of the valve.

2. Two stop valves in series on the bypass pipeline, the second stop valve requires "high inlet and low outlet": In order to ensure the tightness of the valve during an overhaul period, the valve that frequently opens and closes requires two series connection stop valve. For the bypass system, the installation functions of this bypass include:

①Balance the front and backpressure of the main pipeline valve to make it easy to open and save effort and reduce the wear of the main pipeline valve;

②Small flow heating pipe during startup;

③On the main feedwater pipeline, control the feedwater flow to control the boiler pressure increase speed to perform the boiler water pressure test. According to the flow direction of the medium, the bypass stop valves are respectively the primary valve and the secondary valve. The primary valve and the secondary valve are closed during normal operation of the unit, and both of them are in direct contact with the medium. In order to prevent the gasket between the valve casing and bonnet of the secondary valve and the packing around the valve stem from being affected by medium and temperature for a long time, and the packing of the valve can be replaced during operation, the installation direction of the secondary valve is "high in and low out" .

The information is provided by the stop valve factory.