Pressure Relief Valve for Dosing Pumps: Why You Need One and How to Set It
Closed valves, blocked injection points and choked strainers happen on every plant. With a centrifugal pump that just means low flow. With a metering pump it means bursting pipes, broken diaphragms or a damaged gearbox. A relief valve is the cheapest protection you can buy.
Need help choosing? Send chemical, flow and pressure.
Why metering pumps need relief protection
Metering pumps are positive displacement pumps. Each stroke moves a fixed volume, whatever the pressure. If the discharge is closed, the pump keeps building pressure until the weakest part fails: tubing, fittings, the diaphragm, the pump head or the drive.
Where to install it
- On the discharge line, between the pump and the first isolation valve.
- With the outlet piped back to the chemical tank, not to the floor or a drain.
- Close to the pump, so no valve can isolate the pump from the PRV.
How to set it
- Find the normal maximum discharge pressure at the injection point.
- Set the PRV 10–20% above that, but below the pump’s rated pressure.
- Close the discharge valve slowly during commissioning and watch the gauge to confirm the valve lifts at the set point.
- Record the setting and check it at every service.
Choosing the material
| Chemical | Valve body | Spring |
|---|---|---|
| Water, caustic, solvents | SS316 | SS316 or PTFE-coated |
| Hypochlorite, HCl | PP or PVDF | PTFE-coated or Hastelloy |
| Sulphuric acid (strong) | Alloy 20 or PTFE-lined | PTFE-coated |
JEW makes pressure relief valves in SS316 with PTFE-coated springs. Check your chemical in our compatibility chart.
PRV vs back pressure valve
A relief valve protects against too much pressure. A back pressure valve creates a minimum pressure so the pump does not siphon or over-dose. Many lines need both.
Related
Frequently asked questions
Is a relief valve built into the pump enough?
Some pumps have an internal relief valve, but an external PRV piped back to the tank is easier to inspect, adjust and service. Most plant specs ask for an external one.
What happens if the PRV is set too low?
It will open during normal operation and send chemical back to the tank, so the process gets less chemical than you think.
Can I use the same PRV for different chemicals?
Only if the body, spring and seals suit every chemical. Otherwise use a separate valve per line.
Get a pump sized and quoted by our engineers.
Jagdish Engineering Works, Mumbai – manufacturer of plunger and diaphragm metering pumps and pressure relief valves since 1969. Our engineers design, test and repair dosing pumps for water treatment, chemical, refinery, fertilizer, sugar and paper plants.
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