PF61G stainless steel piston actuated on/off valve
The Spirax Sarco PF61G is a two-port, pneumatically actuated on/off valve with a stainless-steel body and screwed BSP or NPT pipeline connections. It is intended for on/off duties on steam, water, air, oil and gases. A pneumatic signal acts on the actuator piston and spring return establishes the specified valve action.
Select the PF61G connection size, actuator and action together. Normally closed (NC) configurations are for flow over the seat; normally open (NO) configurations are for flow under the seat and can help prevent waterhammer at closure in liquid applications. Bidirectional normally closed (BD) configurations are for two-way flow; for liquid flow over the seat, the source guidance limits pressure to 1 bar g to help avoid waterhammer.
Confirm the material, pressure, temperature, pilot-pressure and flow-direction limits against the current technical information before specifying the valve. The available download documents provide the detailed limits, installation requirements and maintenance instructions.
PF61G range and construction (TI-P373-13)
The Spirax Sarco PF61G is the screwed BSP or NPT member of the PF6 stainless-steel piston actuated on/off valve range. The source identifies three actuator diameters: Type 1, 45 mm; Type 2, 63 mm; and Type 3, 90 mm. The standard configuration has a valve-position indicator; a travel switch, flow regulator and position module are optional according to the selection guide.
| Component | Material |
|---|---|
| Body, bonnet, plug and stem | AISI 316L stainless steel |
| Valve plug seal | Modified PTFE G500 |
| Standard stem seal | PTFE with FKM chevron |
| Option H stem seal | 25% carbon-graphite-filled PTFE with FKM chevron |
| Stem O-ring and body O-ring | FKM |
Operating boundary
| Condition | Published value |
|---|---|
| Maximum design temperature | 200 C |
| Minimum design temperature | -10 C |
| Standard seals, saturated-steam service | 9 bar g at 180 C |
| Option H, saturated-steam service | 14.5 bar g at 200 C |
| Ambient temperature | -10 C to 60 C |
| Leakage | ASME Class VI with TFM 1600 soft seal |
| Flow characteristic | Fast opening for on/off service |
The body design pressure depends on the connection, size and temperature. Do not operate beyond the published pressure/temperature graph or the relevant body rating. The maximum cold hydraulic test pressure is 1.5 times PMA; the technical information also requires a fully open valve for hydraulic testing.
Flow data and action selection
| Nominal size | Kvs |
|---|---|
| DN15 / 1/2 in | 4.5 |
| DN20 / 3/4 in | 8.0 |
For NC operation, flow is from port 1 to port 2 over the seat. For NO operation, flow is from port 2 to port 1 under the seat. BD operation permits either direction; the source gives special anti-waterhammer guidance for liquid systems. Instrument air or inert gas is the stated pilot medium; consult Spirax Sarco for other pilot media. The actuator may be rotated through 360 degrees in the direction shown on the product label.
Ordering and service
Specify the Spirax Sarco PF61G size, connection standard, action, actuator size and any required option when ordering. A seal kit is available and includes the piston lip seal, stem O-ring, valve-head seal, body seal and body O-ring. Specify the valve size, type and actuator date code when ordering spare seals.
Safety information (IM-P373-05)
Safe operation depends on correct installation, commissioning, use and maintenance by qualified personnel following the operating instructions. Before installation, check the intended duty, materials, pressure and temperature limits, and provide system protection where a dangerous overpressure or overtemperature could occur.
Before work, isolate pressure safely and vent it to atmosphere; do not assume a system is depressurised solely because a gauge reads zero. Allow temperature to normalise after isolation, consider hazardous pipeline contents and external stresses, and use appropriate safety equipment and genuine replacement parts.
Installation
- Check that the nameplate, technical information and installation conditions match the application. Do not exceed the valve rating or pilot-pressure limit.
- Determine the correct fluid-flow direction. For liquid applications above 2 bar g, the guide recommends a BD valve to help prevent waterhammer at closure.
- Support the pipework so that it does not impose stress on the valve body. Ensure connecting pipework is clean; debris can damage the PTFE head seal and prevent tight shut-off.
- PF61G valves can be mounted in any orientation. Rotate the actuator only in the labelled direction, up to 360 degrees, to facilitate pilot connection.
- Leave maintenance clearance for actuator removal and check for leaks during commissioning.
Maintenance
Before removing an actuator or valve stem, isolate the upstream and downstream valves, vent actuator pilot pressure and disconnect pilot pipework or the solenoid valve. For normally closed valves, relieve the internal spring force before removing the valve body. The guide warns that the spring is under compression and provides the detailed disassembly, seal-kit replacement and tightening steps.