Excess pressure valve · Direct-acting
PRV53 excess pressure valve
316L stainless
Self-regulating, direct-acting, piston-balanced excess pressure valve with body, cap, and internals in 316L stainless steel. It keeps the line pressure stable and discharges the excess when the set pressure is exceeded, on liquids, compressed air, and inert gases up to 150 °C.
- SizesDN15 to DN25
- Pressure ratingPN25
- Set pressure range0.5 to 10 barg 15 on request
- Inlet pressureup to 10 barg standard
- Temperature−30 to 150 °C depending on gaskets
- Kv2 to 3.5 m³/h
Configure your valve
Questions about set pressure or sizing? Call 933 720 888 or email valfonta@valfonta.com.
- In-house design and manufacturing in Badalona
- ATEX II 2 GD marking for zones 1 and 21
- Installation in any position
- Spare gasket kits and spring
What the PRV53 is used for
The PRV53 is a self-regulating excess pressure valve: it needs no auxiliary power or pilot line. When the upstream pressure exceeds the set value, it opens proportionally and relieves the excess, so the main line pressure is held at the set value.
The typical installation is in a bypass downstream of a pump, with the excess flow returned to the tank. Body, cap, and internals are made of AISI 316L stainless steel. More detail in our article on self-regulating excess pressure valves.
- Pump bypassRelief of the pump discharge, with the excess flow returned to the tank.
- Chemical laboratoriesStable pressure in liquid and gas circuits.
- Sanitary plantsCircuits that require stainless steel.
- Compressed airLimits network pressure to the set value.
- Fuel oil and nitrogenGroup 1 and 2 fluids, including inert gases.
- Oxygen serviceOn request, the valve is supplied fully degreased.
- Mining slurry linesRelief for abrasive concentrate and tailings pipelines: pressure relief in mining slurry lines.
PRV53 technical specifications
| Type | Self-regulating, direct-acting, piston-balanced excess pressure valve |
|---|---|
| Sizes | DN15 (½″), DN20 (¾″), and DN25 (1″) |
| Connections | BSP or NPT thread · EN PN16/25 flanges · ANSI CL150 flanges |
| Pressure rating | PN25 |
| Maximum inlet pressure | 10 barg in standard version (contact us for other ranges) |
| Set pressure ranges | 0.5 – 3 barg · 1 – 6 barg · 3 – 10 barg (depending on spring). 5 – 15 barg on request |
| Kv coefficient | 2 m³/h (DN15) · 2.5 m³/h (DN20) · 3.5 m³/h (DN25). Reduced Kv on request |
| Temperature depending on gaskets | NBR: −20 to +80 °C · EPDM: −30 to +125 °C · Viton: −10 to +150 °C |
| Fluids | Group 1 and 2 liquids and gases: water, fuel oil, compressed air, nitrogen, inert gases |
| Materials | Body and cap in A351 CF3M (AISI 316L) stainless steel. Internals in AISI 316L. NBR plug as standard (EPDM, PTFE+GR, or FKM) |
| Mounting position | Any position, following the flow direction arrow on the body |
| Pressure Equipment Directive | PED 2014/68/EU, Article 4.3: CE marking not required (Group 1 and 2 fluids) |
| ATEX | II 2 GD c IIC Tx / c IIIC TxºC · certificate LOM 14.034 U |
| On request | Body and cap in bronze or super duplex · weld ends (socket weld or butt weld) · clamp connection · degreased for oxygen service · special gaskets |
Dimensions and weight
| ½″ threaded | ¾″ threaded | 1″ threaded | DN15 EN | DN20 EN | DN25 EN | DN15 ANSI | DN20 ANSI | DN25 ANSI | |
|---|---|---|---|---|---|---|---|---|---|
| Kv (m³/h) | 2 | 2,5 | 3,5 | 2 | 2,5 | 3,5 | 2 | 2,5 | 3,5 |
| Length A / AA | 108 | 108 | 108 | 130 | 150 | 160 | 184 | 184 | 184 |
| Height H1 | 135 | 135 | 135 | 135 | 135 | 135 | 135 | 135 | 135 |
| Height H2 | 185 | 185 | 185 | 185 | 185 | 185 | 185 | 185 | 185 |
| Flange Ø D1 | – | – | – | 95 | 105 | 115 | 89 | 98 | 108 |
| Weight (kg) | 2,5 | 2,5 | 2,5 | 5 | 5 | 5 | 5 | 5 | 5 |
Dimensions in millimeters. The dimensioned drawings and the remaining flange dimensions are in the PDF datasheet.
Exploded view and materials (20 parts)
| No. | Part | Material |
|---|---|---|
| 1 | Body | Stainless steel A351 CF3M |
| 2 | Sealing screw | Stainless steel A2-70 |
| 3 | Plug | NBR (EPDM, PTFE+GR, FKM) |
| 5 | Seat | Stainless steel AISI 316L |
| 6 | Body gasket | PTFE |
| 7 | Cap | Stainless steel A351 CF3M |
| 8 | Spring washer | Galvanized steel ST-52 |
| 9 | Adjusting screw | Stainless steel |
| 10 | Adjusting spring | Steel 52SiCrNi5 with epoxy paint (60–100 microns) |
| 11 | Piston | Stainless steel AISI 316L |
| 12 | O-ring | NBR (EPDM, FKM) |
| 13 | Plunger gasket | NBR (EPDM, FKM) |
| 14 | Screws (x4) | Stainless steel A2-70 |
| 15 | O-ring | Same as no. 12 |
| 16 | O-ring | NBR (EPDM, FKM) |
| 17 | Stem | Stainless steel AISI 316L |
| 18 | Seat guide | Stainless steel AISI 316L |
| 20 | Bushing guide | Stainless steel AISI 316L |
| 21 | Bottom cover | Stainless steel AISI 316L |
| 22 | O-ring | NBR (EPDM, FKM) |
Recommended spare parts
| Reference | Description | Parts |
|---|---|---|
| PRV53.SP1 | NBR gasket kit (80 °C) | 3, 6, 12, 13, 15, 16 and 22 |
| PRV53.SP2 | EPDM gasket kit (125 °C) | 3, 6, 12, 13, 15, 16 and 22 |
| PRV53.SP3 | FKM gasket kit (150 °C) | 3, 6, 12, 13, 15, 16 and 22 |
| PRV53.SP5 | Adjusting spring | 10 |
How the PRV53 works
The PRV53 works on a balance between the adjusting spring and the inlet pressure acting on the piston. It needs no air or electricity.
- Closed without pressure. As long as the inlet pressure has not reached the set pressure, the adjusting spring keeps the valve closed.
- Internal sensing. The upstream pressure reaches the piston through the stem, with no external control line.
- Proportional opening. When the inlet pressure exceeds the set point, the plug moves and the valve opens in proportion to the excess pressure.
- Relief. As the excess flow is discharged, the line pressure is held at the set value. If it drops, the spring closes the valve again.
PRV53 installation
The typical installation of the PRV53 is on a branch line downstream of the pump, discharging the excess flow to the tank.
- Pump or equipment that generates the pressure
- Inlet pressure gauge
- PRV53 excess pressure valve, on a branch line
- Excess flow discharged to the tank
- Point of use or protected equipment
Installation and start-up
- Clean the pipe before installing the valve: any particle can damage the seat.
- Install a strainer upstream of the valve to protect the seat.
- Follow the arrow on the body. The valve can be installed in any position.
- Install the branch line with its isolation valves, connected to the main pipe downstream of the pump.
- Leave a minimum of 0.5 to 1 m between the PRV53 and the isolation valve for better regulation.
- Start up slowly: open the isolation valves gradually to avoid water hammer.
- Adjust the set pressure with an 8 mm Allen key on the adjusting screw. Compressing the spring raises the set pressure; releasing it lowers it. Check the value on the inlet pressure gauge.
The valve must be installed by qualified personnel and must never exceed the operating pressure and temperature for which it was sized. In ATEX zones, the valve must be equipotentially bonded to the installation. See also how to prevent water hammer in pipes.
PRV53 technical documentation
Do you need an order certificate or the ATEX documentation? See our quality certificates or request it from our technical team.
PRV53 vs. other excess pressure valves
The range covers DN15 to DN150 and set pressures from 0.01 to 20 barg. Check whether the PRV53 is the right model or whether another one suits you better.
| Model | DN | PN | Set pressure (barg) | Max. T (°C) | Steam | Body |
|---|---|---|---|---|---|---|
| PRV53 | 15 – 25 | 25 | 0,5 – 15 | 150 | No | CF3M stainless |
| PRV54 | 15 – 25 | 25 | 0,5 – 12 | 210 | Yes | CF3M stainless |
| PRV55 | 15 – 25 | 25 | 0,01 – 8 | 150 | Yes | CF3M stainless |
| S1 | 15 – 150 | 40 | 0,5 – 15 | 220 | Yes | WCB steel or CF3M stainless |
| S2 | 15 – 100 | 40 | 0,02 – 10 | 180 | Yes | WCB steel or CF3M stainless |
| S3 | 15 – 150 | 40 | 0,5 – 20 | 220 | Yes | WCB steel or CF3M stainless |
| S4 | 15 – 100 | 40 | 0,5 – 20 | 220 | Yes | WCB steel or CF3M stainless |
Data from the Valfonta excess pressure valve summary catalog (2025), except the S2 set pressure, which comes from its datasheet. All models accept liquids, oil, air, and non-flammable gases. If you are unsure whether you need an excess pressure valve or a safety valve, read the difference between a safety valve and a relief valve.
Frequently asked questions about the PRV53
Can the PRV53 be used with steam?
What set pressure can be adjusted?
It depends on the spring: there are three standard ranges, 0.5 to 3, 1 to 6, and 3 to 10 barg, plus a 5 to 15 barg range on request. The standard maximum inlet pressure is 10 barg.
How do you adjust the set pressure of the PRV53?
With an 8 mm Allen key on the adjusting screw. Compressing the spring raises the pressure at which the valve opens; releasing it lowers it. Check the value on the inlet pressure gauge and see our guide on relief valve set pressure.
What maintenance does it need?
It requires no periodic maintenance, but the gaskets and wear parts should be checked according to the service conditions. This can be done with the valve installed, depressurized, and isolated. Gasket kits are available in NBR, EPDM, and FKM (PRV53.SP1 to SP3), as well as the adjusting spring (PRV53.SP5).
Does the PRV53 carry CE marking?
No. Given its size (DN15 to DN25) and pressure rating (PN25), it falls under Article 4.3 of the Pressure Equipment Directive 2014/68/EU, with Group 1 and 2 fluids.
Can it be installed in an ATEX zone?
Yes. The PRV53 carries ATEX II 2 GD marking (certificate LOM 14.034 U) and can be used in zones 1 and 2 (flammable gases, vapors, and liquids) and 21 and 22 (combustible dust), according to the temperature class that corresponds to the fluid temperature. See our article on ATEX valves.
Other excess pressure valve models
- PRV54 excess pressure valveDN15–25 and PN25 like the PRV53, but suitable for steam up to 210 °C.
PRV55 excess pressure valveWith diaphragm: set pressure from 0.01 barg and steam up to 150 °C.
S1 excess pressure valveFrom DN15 to DN150 and PN40, for steam up to 220 °C.
S2 excess pressure valveFrom DN15 to DN100, PN40, and set pressure from 0.02 barg.
S3 pressure relief valveFrom DN15 to DN150, PN40, set pressure up to 20 barg and 220 °C.
Request a quote for the PRV53
Give us your installation details and we will recommend the size, the spring range for your set pressure, and the gaskets suited to the fluid and temperature.
- Fluid and operating temperature
- Set pressure and normal operating pressure
- Flow rate the valve must discharge
- Connection type (threaded or flanged)
You can also call 933 720 888.
