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Hydraulic Pressure-reducing Valves - What You Need to Know Lyndsey Nash

What You Need to Know About Pressure-reducing Valves

In a Hydraulic System, you are most likely aware that the main system pressure is maintained by the system relief valve or even another type of pressure setting device.

The purpose of pressure reducing values is to keep the secondary pressures correct in branches of hydraulic systems.

Most pressure reducing valves are open and 2 way, this allows the pressure to flow freely until they reach further downstream where there is a set pressure. They then shift to throttle the flow in the branch.

Forces from pressure downstream are what actuates pressure reducing valves. This is what will deliver the correct working pressure by enabling a pressure drop to occur in the main spool of the valve. The way that a press-reducing valve works is that it is not a device that is either on or off. In contrast, it delivers a continual adjustment to the pressure. Keep in mind that these types of valves are the most conducive to suffering from contamination when it comes to malfunctioning.

How can pressure-reducing valves go wrong?

Pressure-reducing valves can go wrong in a number of ways. Again, pressure gauges will need to be installed in order to understand what’s going wrong with one. Once this has been done, you can look for:

·         A low pressure at outlet port. If this drops below what it should be, the first action to take is to check the pilot head spool and seat. Check for wear and tear which may be affecting the drain flow. Too much drain flow through this area of the valve will result in reduced pressure and therefore affect performance.

·         If you find that the valve will not retain a reduced pressure setting, and the pressure is exceeding it, then check whether the pilot drain line is blocked or affected by contaminants. This will increase pressure which will result in flow to the branch circuit. It’s also possible that the main spool is stuck open due to contaminants blocking it. Again, there could be scoring of either the main spool or bore.

·         If you find that you cannot adjust the value to the low pressure setting, even after turning the adjustment knob, then check whether there is wear of the spool or bore. There may even be a broken spring in the pilot head, which will mean not enough force between spool to seat in the control head.

·         If there is not enough pressure at the output port, check whether the main spool is stuck in the closed position. This will result in no pressure fluid being unable to flow to the branch. Contaminants could be to blame.

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