Pressure Reducing Valves protect pipes and other downstream equipment from overpressure by regulating the higher upstream pressure to a lower, controlled pressure. This reduced pressure is known as the set pressure and is easily adjusted by turning the adjusting bolt, thus compressing the spring (clockwise increases the set pressure, anti-clockwise reduces the set pressure).
There are some general rules to help select the best regulator and the best control for each application:-
• Unlike other valves where the valve size matches the pipe size, these pressure control valves must be “sized”, using the pressure drop (P1- P2) and the flow range required. In many cases, a valve at least one size smaller than pipe diameter is selected. This reduces overall cost, guarantees better pressure control and avoids hunting and poor regulation associated with oversizing.
• Self acting valves are the simplest design and represent the lowest cost but they are not as accurate as pilot operated valves.
• Always use the lightest spring as this will reduce “droop” (if the set pressure is 7 bar and there are two ranges, spring #1 5 bar-7 bar, spring #2 range 4 bar-10 bar, spring #1 is the best choice). Spring ranges are generally mid compression ranges, not spring limits, so further adjustment outside of the published ranges is always possible.
The following range is extensive, mainly because every regulator has limitations on sizes, materials of construction, suitability to various media, inlet pressures and reduced pressure ranges. In addition to the metal bodied valves offered below, a good quality Thermoplastic reducing valve (DMV755) can be found on this website.