Safety valve · Progressive opening
368 – 371 progressive-opening safety valve
Progressive opening
Progressive-opening safety valve in brass/bronze that detects overpressure in tanks, boilers, or pipes and discharges the excess fluid without auxiliary power. It is made in two figures: 368, with open discharge, and 371, with piped discharge.
- Sizes3/8″ to 3″
- OpeningProgressive
- DischargeOpen (368) · piped (371)
- Set pressure ranges0–1 · 1–11 · 11–16 bar
- Pressure ratingPN16 bronze seat · PN12 Viton
- Max. temperature180 °C
Questions about the set pressure? Call 933 720 888 or email valfonta@valfonta.com.
- PED 2014/68/EU certificate
- Bench-tested with compressed air
- Supplied set to the pressure you specify
- Numbered main components
What the 368–371 valve is used for
It is a progressive-opening safety valve: when the pressure exceeds the set pressure, it starts to open and discharges the excess fluid; once the pressure returns to normal, it closes again. It works with liquids, compressed air, inert gases, and steam. If you are unsure whether you need a safety valve or a relief valve, read the difference between a safety valve and a relief valve.
368–371 valve technical specifications
| Type | Progressive-opening safety valve (relief) |
|---|---|
| Figures | 368: open discharge · 371: piped discharge |
| Sizes | 368: ½″ to 3″ · 371: 3/8″ to 3″, with an outlet the same size as the inlet |
| Connections | Inlet: BSP male thread · Outlet (371): BSP female thread |
| Material | Brass / bronze |
| Seat and pressure rating | Bronze seat: PN16, 0–1 and 11–16 bar ranges · Viton seat: PN12, 1–11 bar range |
| Fluids | Liquids, compressed air, inert gases, and steam |
| Maximum temperature | 180 °C |
| Test | On a test bench with compressed air at ambient temperature; supplied set to the requested pressure |
| Certification | PED 2014/68/EU. Material, heat, and output certificates if requested in advance |
| Other options | AISI 302/316 stainless steel spring · NPT thread |
How it works
- Closed in service. The spring, set to the requested pressure, holds the plug on the seat.
- Progressive opening. If the pressure exceeds the set pressure, the valve opens progressively, not all at once like a full, instantaneous-opening valve.
- Closing. When the pressure returns to normal, the valve closes again.
368–371 valve technical documentation
Frequently asked questions about the 368–371 valve
What is the difference between figure 368 and figure 371?
The 368 discharges directly to atmosphere (open discharge) and has only an inlet, with a BSP male thread. The 371 adds an outlet with a BSP female thread to pipe away the discharge.
What set pressure does it accept?
It depends on the seat: with a bronze seat, ranges from 0 to 1 bar and from 11 to 16 bar (PN16); with a Viton seat, from 1 to 11 bar (PN12). The valve is supplied set to the pressure you specify.
Can it be used with steam?
Yes, up to 180 °C. It also handles liquids, compressed air, and inert gases.
Other Valfonta safety valves
ALPER safety valveFull, instantaneous opening, bronze or stainless, up to PN25 and 280 °C.
JAS safety valveFull, instantaneous opening in brass, ¼″ to ¾″, PN16.
ALPER atmospheric valvesTank protection against vacuum and overpressure.
Pressure relief valvesS1–S4 and PRV53–55 range, from DN15 to DN150 and set pressure up to 20 barg.
Request a quote for the 368–371 valve
Give us your installation details and we will recommend the right figure, size, and seat.
- Fluid and temperature
- Set pressure
- Figure: open discharge (368) or piped discharge (371)
- Connection size and seat type
You can also call 933 720 888.
