Relief Valve, Back Pressure, By-Pass, Anti-Siphon Valve

Relief Valve, Back Pressure, By-Pass, Anti-Siphon Valve

The thermoplastic pressure relief valve protects equipment and systems against overpressures or sudden pressure surges. Able to handle highly corrosive or ultrapure liquids, it prevents pumps from dead-heading due to unexpected shut-offs downstream (also known as a "bypass relief valve"). It maintains backpressure in closed-loop systems to make pumps run more smoothly (also known as a back pressure valve). Valves are intended for fluid control and not as safety relief valves or rupture discs.

We offer to customers many kind of pressure relief, regulator, back pressure, by-pass, anti siphon valves from Plast-O-Matic, one of the well-known manufacturer in USA for chemical thermoplastic valves that include styles of RVD, RVDM, RVT, RVTX, RVDT, TRVDT series.

All styles are normally-closed and begin opening once the set pressure is reached. They use spring force to push down upon a shaft or diaphragm. The pressure setting is done manually by turning the adjusting bolt clockwise to raise the pressure setting, and counter-clockwise to lower it. This simply varies the compressive force of the internal spring across the valve orifice. The more it is compressed, the higher the set pressure will be.

When the inlet pressure reaches the set pressure, the force created by the inlet pressure is equal to the force exerted by the spring. Liquid then begins to trickle through the valve. As inlet pressure continues to increase, the valve opens farther, allowing more flow.

In addition to relieving excess/dangerous pressure from closed-top vessels or piping systems, these normally-closed valves provide system control benefits as shown. Depending upon the function performed, they are given different names.

Pressure relief, by-pass, back pressure regulator, anti siphon.gif

  1. "Pressure Relief Valve"- to protect a system (e.g. pump, pipe segment or tank) from excessive pressure (in excess of the set point).
  2. "Back Pressure Regulator"- to provide a means of retaining desired system pressure to points of use in upstream line(s).
  3. "Pressure By-Pass Valve"- to protect a pump from 'dead-heading' by enabling the flow to by-pass an obstruction.
  4. "Back Pressure Valve"- to provide back pressure directly on the discharge of a pump to enhance its performance.
  5. "Anti-Siphon Valve"- to prevent unwanted chemical siphoning through a pump; when negative pressure at a lower elevation could create a siphon and drain a tank. The valve is set to open at the desired pumping pressure, but seals tightly when a vacuum occurs downstream.

Applications: Chemical Processing, Aquariums, Water Treatment, Swimming Pools, Mining, Paper Mill,…

Some typical applications using pressure regulators:

Application - By-Pass Excessive Pressure.jpg

During the remediation process for ground water, the water passes through several different pieces of equipment. Relief Valves are used in the system to protect the pump from dead heading, should one of the pressure regulators close. As the pressure regulator reaches the set pressure and closes, the normally-closed relief valve senses the increase in system pressure and begins to open, diverting the flow back to the suction side of the pump. When the pressure regulator opens again, the relief valve senses the decrease in pressure and begins to close, allowing normal flow patterns to resume.

Application - Anti-Siphon & By-Pass Protection.jpg

A major clarifier manufacturer required a reliable, weather resistant mechanical method of preventing bulk tank siphoning when their clarifier system was down/off. Plast-O-Matic Series RVT Relief Valve was specified for its pressure set range of 5-100 PSI. By setting the RVT at 10 PSI, the possibility of the tank’s 16' head siphoning was eliminated when the pump was of. Additionally, the maximum pressure rating of RVT was well over the pump’s maximum of 100 PSI. The RVT’s solid PTFE shaft, standard stainless steel fasteners and Fail-Dry® system offered obvious value added benefits. To further ensure system reliability, a manual spring return or “dead man” valve by-pass method was required. Plast-O-Matic spring return palm or foot operated Series MFR was selected for its high flow and compact size. The MFR Series valve eliminated the possibility of a worker accidentally forgetting to close a manual by-pass valve (i.e. ball valve) and draining the tank. The Series RVT was also specified as an emergency by-pass valve to protect the pump from “dead heading.”

Application - Provide Proper Pressure & Flows to Dialysis Station.jpg

Dialysis center, consisting of 30 stations (beds), was having difficulty in delivering 0.014 GPM at 1 to 8 PSI thru 950 feet of 3/4" pipe to each station with a pump delivering 5 GPM at approximately 32 PSI. They were finding that front-end stations were being subjected to high pressures while those towards the end were not being provided the sufficient pressure nor flows. The installation of a 3/4" Series RVDT valve as a by-pass between the pump and the Series PR Pressure Regulator took off a lot of the excess flow, while the Series PR (set at 8 PSI) assured that the closed loop pressures would not exceed the 8 PSI maximum. Lastly, the installing of another Series RVDT as a back pressure regulator, set at 5 PSI, further assured a 5 PSI (mid-range) system (loop) pressure.

PVC with EPDM seals was found to be compatible with both solutions, as well as economical.

Application - Prevent Siphoning Through Pump in a Paper Mill.jpg

As paper stock leaves the machine it is wet and proceeds through a de-watering process. The conveyor is laid with felt to prevent the paper from becoming dirty. To keep the felt clean it is periodically sprayed with a liquid soap solution, followed by a water rinse. The Series RVDT Relief Valve was selected for use as an anti-siphon valve to prevent the soap solution from being drawn into the spray nozzles when the pump is off and the rinse water feed is in progress.

Advantages of POM Pressure regulators:

One valve design serves many functions...:

• Preventing overpressure conditions in vessels and piping systems (relief valve).

• Providing by-pass flow relief to avoid pumping problems such as deadheading (pump bypass valve).

• Maintain backpressure in a piping system (backpressure regulator).

• Enhance pump performance by maintaining backpressure on the pump outlet (pump backpressure valve).

• Prevent gravity-induced siphoning through a pump, opening only when the pump is on (anti-siphon valve).

NEW! Series TRVDT 3-port design...the features of our state-approved RVDT now in a 3-way valve!

One valve design provides many outstanding features...:

• Offer wide range of pressure settings with sensitive operation.

• Provide smooth operation with higher flow.

Fail-Dry safety feature (not available on RVD or RVTX).

• Each valve is individually tested prior to shipment.

• No wetted metals; all external fasteners are stainless steel.

• Maintenance-free designs.

• Designs for crystallizing liquids.

• Designs with no wetted elastomers for ultra-pure chemicals and water. Non-contaminating PTFE diaphragm designs.

• Factory pre-set if requested.

• Tamper-proof option.

Thông số kỹ thuật

Material: PVC, CPVC, PP, PVDF, PTFE (Teflon)      Diaphragm: EPDM, FKM (Viton), PTFE


RVD Series: ¼” – ½” (DN8 – DN15)

RVDM Series: ½” – 1” (DN15 – DN25)

RVT Series: ½” – 2” (DN15 – DN50)

RVTX Series: 3”DN80

RVDT/RVDTM Series: ¼” – 2” (DN8 – DN50)

TRVDT Series: ½” – 1” (DN15 – DN25)

Relief Pressure Setting: 5 psi – 150 psi

Connection: Socket End, Threaded

Made in: USA