The Model 730 Pressure Relief/Sustaining Valve is a hydraulically operated, diaphragm actuated control valve that can fulfil either of two separate functions. When installed in-line, it sustains minimum pre-set, upstream (back) pressure regardless of fluctuating flow or varying downstream pressure. When installed as a circulation valve, it relieves excessive line pressure when above maximum pre-set.
The Model 730 is a pilot controlled valve equipped with an adjustable, 2-Way pressure sustaining pilot. The restriction  continuously allows flow from the main valve inlet into the upper control chamber . The pilot  senses upstream pressure and should be set to minimum system pressure allowed. Should upstream pressure tend to fall below pilot setting, the pilot throttles, enabling pressure to accumulate in the upper control chamber, causing the main valve to throttle, sustaining upstream (back) pressure at pilot setting. Should upstream pressure be below pilot setting, the pilot closes, causing the main valve to close drip tight. Should upstream pressure tend to rise above pilot setting, the pilot releases accumulated pressure causing the main valve to modulate open. The downstream cock valve  enables manual closing.
The Model 730 sustains pump discharge pressure, preventing pump overload and cavitation damage caused by excessive demand.
By connecting the pilot sensing line to pump suction, the Model 730 becomes Model 730R which sustains pump suction pressure.
Where suction pressure regimes vary, the Model 736 is needed to limit pump flow by sustaining pump differential pressure.
This application is usually found in gravity fed systems. The Model 730 enables prioritizing the higher elevation zone over downhill consumers when they create excessive total demand. By adding a pressure reducing feature to the primary pressure sustaining function, the Model 730 becomes a Model 723 that also protects downhill consumers from over pressure during low demand.
Line emptying presents a serious problem in water distribution networks. Preventing it in downhill networks requires setting the pilot slightly above the elevation differential between the highest point of the line and the valve. Where a pump provides pressure A , the relatively high pressure causes the Model 730 to open wide. When the pump stops, pressure drops below pilot setting and the valve closes drip-tight preventing line emptying. Where a reservoir provides pressure B , there is only a small potential for variation in pressure (the difference in high and low reservoir levels). The problem is made worse by having a significant part of that potential pressure lost on line friction.
The standard Model 730 might not be enough. The solution is to install a valve with very low head loss, super sensitivity, accuracy and repeatability. Install the Model 730-85 pressure sustaining with high sensitivity hydraulic positioning.
Body: Stainless Steel 316 or Bronze
Elastomers: Synthetic Rubber
Spring: Galvanized Steel or Stainless Steel
Tubing & Fittings: Stainless Steel 316 or Copper & Brass
Accessories: Stainless Steel 316, Brass and Synthetic Rubber Elastomers
Pilot Adjustment Range:
0.5 to 3.0 bar ; 7 to 40 psi
0.8 to 6.5 bar ; 11 to 95 psi
1 to 16 bar ; 15 to 230 psi
5 to 25 bar ; 70 to 360 psi
The Model 730 is a pilot controlled valve equipped with an adjustable, 2-Way pressure sustaining pilot. The restriction  continuously allows flow from the main valve inlet into the upper control chamber . The pilot  senses upstream pressure and should be set slightly above system working pressure. Should upstream pressure rise above pilot setting, the pilot releases pressure from the upper control chamber, causing the main valve to modulate open, relieving excessive upstream pressure. Should upstream pressure fall, the pilot throttles, enabling pressure to accumulate in the upper control chamber, causing the main valve to throttle closed, sustaining upstream (back) pressure at the pilot setting. Should upstream pressure be below pilot setting, the pilot closes, causing the main valve to close drip tight. The downstream cock valve  enables manual closing.
The Model 730 relieves over pressure caused by excessive pump discharge during low demand. To keep a constant discharge pressure, the difference between pumped flow and consumer demand can be circulated back to pump suction.
Circulation valves are often exposed to severe cavitation because valve ΔP and velocity are usually high while downstream pressure is very low. On the other hand, the valves operate under these conditions for relatively short periods. Increased valve durability for applications requiring long operating periods will be achieved by using cavitation resistant materials, adding a downstream orifice, installing an upstream pressure reducing valve, increasing valve size, or any combination of these choices.
Size Range: DN40-900 ; 11/2–36”
End Connections (Pressure Ratings):
Flanged: ISO PN16, PN25 (ANSI Class 150, 300)
Threaded: BSP or NPT
Others: Available on request
Valve Patterns: “Y” (globe) & angle, globe (DN600-900 ; 24”-36”)
Working Temperature: Water up to 80°C ; 180°F
Body & Actuator: Ductile Iron
Internals: Stainless Steel, Bronze & coated Steel
Diaphragm: Synthetic Rubber Nylon fabric-reinforced
Seals: Synthetic Rubber
Coating: Fusion Bonded Epoxy, RAL 5005 (Blue) approved for drinking water or Electrostatic Polyester Powder
Please specify the requested valve in the following sequence: (for more options please contact us)