Safety Valves - Progressive opening type 368-371 | Valfonta

Valfonta 368–371 Progressive Opening Relief Valves

The Valfonta 368 and 371 are progressive opening relief/safety valves designed for overpressure protection of vessels, small boilers, and pipelines. Operation is purely mechanical: the process medium acts against a spring, with no auxiliary energy required. The valve recloses automatically once pressure drops below the setpoint.

Difference Between Types 368 and 371

• Fig. 368: Discharges freely to atmosphere; male BSP thread at inlet.
• Fig. 371: Discharge is piped; male BSP inlet, female BSP outlet for connection to a discharge line.

Type 371 is selected when discharge must be routed to a safe location, collector, or drain line. Type 368 is used where local atmospheric discharge is permissible.

Technical Specifications

• Series: 368–371
• Opening: Progressive (modulating)
• Connections: BSP standard, NPT available
• Materials: Brass / bronze
• Sealing: Metal seat or Viton
• Pressure rating (PN): 16 bar (metal seat), 12 bar (Viton)
• Set pressure ranges: 0–1 bar, 1–11 bar, 11–16 bar (per configuration)
• Max temperature: 180°C
• Certification: PED 2014/68/EU
• Testing: Factory tested with air at ambient temperature

Suitable Media and Applications

Compatible with liquids, compressed air, inert gases, and steam. Typical uses include small boilers, tanks, auxiliary air lines, water piping, and applications requiring gradual pressure relief rather than instantaneous full opening.

Selection Criteria

Selection is based on set pressure, medium, temperature, thread size, discharge type (free or piped), and sealing material. For steam or hot liquids, verify Viton compatibility and ensure discharge piping allows condensate drainage to prevent seat accumulation.

FAQ

Are these full-lift valves?
No. They are progressive opening; relief flow increases proportionally with overpressure.

When is type 371 used?
When discharge must be piped to a safe area.

Is an actuator required?
No. Operation is by spring force and process pressure only.