Hydraulic Reducing Valve Symbols
Like pressure-relief valve symbols, reducing valve symbols can represent
either direct or pilot operated valves. You will notice that symbols
for reducing valves are similar to those of relief valves, except
for two major changes.
First, since the reducing valve is normally open, the flow arrow
is in line with the inlet and outlet ports to the square box. This
shows that the valve passes fluid freely until pilot pressure overcomes
the spring force. At this point, the flow arrow is pushed out of
alignment with the inlet and outlet, which closes off the flow.
Second, since the reducing valve is sensing pressure at its outlet,
the pilot line differs from that of the relief. In the reducing valve
symbol, the pilot line works against its control spool by sensing outlet
pressure. Also, since a reducing valve must always have a drain connection
to its spring chamber, the “Y” port external drain is always shown.
Various reducing valve symbols are shown below:
Above: Hydraulic Reducing Valve Symbols. If you can't read the text,
hover your cursor over each symbol for a pop-up text caption to appear.
Sunday, September 16, 2007 2:23