Double Seal Zero Leakage
Product Overview
Spirax Sarco PF51G is a 2-way pneumatic piston on/off angle valve with bronze body construction and PTFE soft seal plug (G type) for tight shut-off. The valve is operated by pneumatic signal driving the actuator piston, with spring return function. Standard models and those with flow regulator are equipped with position indicator.
This product is suitable for water, air, oil, gas media, and can also be used in low pressure steam systems.
Three Operating Modes
- NC (Normally Closed): Flow over seat (1-2), not recommended for applications where water hammer may occur
- NO (Normally Open): Flow under seat (2-1), suitable for liquid systems, prevents water hammer when valve closes
- BD (Bi-directional Normally Closed): Supports bi-directional flow with anti-water hammer, flow under seat (2-1), pressure should not exceed 1 bar g when flow is over seat (1-2)
Optional Accessories
- Limit Switch: Indicates valve open/close position
- Flow Regulator: Manual control of maximum flow, normally open valve can be manually closed
Technical Specifications
| Parameter | Value |
|---|---|
| Body Design Rating (½"-1½") | PN25 |
| Body Design Rating (2") | PN16 |
| Maximum Allowable Pressure (PMA) | 25 bar g |
| Maximum Allowable Temperature (TMA) | 180 ℃ |
| Minimum Allowable Temperature | -10 ℃ |
| Maximum Operating Pressure at Saturated Steam (PMO) | 9 bar @ 180 ℃ |
| Maximum Operating Temperature (TMO) | 180 ℃ |
| Ambient Temperature Range | -10 ℃ ~ 60 ℃ |
| Leakage Rate (PTFE Soft Seal) | ASME class VI |
| Flow Characteristic | Quick Opening (On/Off) |
| Pilot Media | Air or water, max 60 ℃ |
| Actuator Rotation | 360° |
Flow Direction
| Valve Type | Flow Direction | Port |
|---|---|---|
| PF51G-NC | Over seat | 1-2 |
| PF51G-NO | Under seat | 2-1 |
| PF51G-BD | Over seat | 1-2 |
| PF51G-BD | Under seat | 2-1 |
Actuator Types and Sizes
| Actuator Type | Diameter | Pilot Connection | Max Pilot Pressure |
|---|---|---|---|
| Type 1 | 45mm | ⅛" BSP | 10 bar g |
| Type 2 | 63mm | ¼" BSP | 10 bar g |
| Type 3 | 90mm | ¼" BSP | 8 bar g |
Pressure/Temperature Limits
Kvs Values
| Size | ½" | ¾" | 1" | 1¼" | 1½" | 2" |
|---|---|---|---|---|---|---|
| Kvs | 4.5 | 8 | 15.6 | 24.6 | 42 | 57 |
Conversion Formulas
- Cv (UK) = Kv x 0.963
- Cv (US) = Kv x 1.156
Pilot Media Pressure Relationship
PF51G-NC (Normally Closed)
PF51G-NO (Normally Open)
PF51G-BD (Bi-directional Normally Closed)
Dimensions and Weight
| Valve Size | Actuator Type | A1 (mm) | B1 (mm) | C (mm) | D (mm) | Weight (kg) |
|---|---|---|---|---|---|---|
| ½" | Type 1 (45mm) | 65 | 144 | 136 | 123 | 0.8 |
| ½" | Type 2 (63mm) | 65 | 192 | 184 | 171 | 1.2 |
| ¾" | Type 1 (45mm) | 75 | 149 | 142 | 126 | 0.9 |
| ¾" | Type 2 (63mm) | 75 | 198 | 192 | 176 | 1.3 |
| 1" | Type 1 (45mm) | 90 | 168 | 161 | 141 | 1.1 |
| 1" | Type 2 (63mm) | 90 | 212 | 205 | 185 | 1.5 |
| 1" | Type 3 (90mm) | 90 | 223 | 216 | 196 | 2.2 |
| 1¼" | Type 2 (63mm) | 110 | 225 | 217 | 193 | 1.9 |
| 1¼" | Type 3 (90mm) | 110 | 234 | 227 | 202 | 2.4 |
| 1½" | Type 2 (63mm) | 120 | 230 | 225 | 198 | 2.4 |
| 1½" | Type 3 (90mm) | 120 | 239 | 235 | 207 | 2.6 |
| 2" | Type 2 (63mm) | 150 | 248 | 241 | 207 | 2.9 |
| 2" | Type 3 (90mm) | 150 | 257 | 250 | 216 | 3.3 |
Additional Weight
Valves with limit switch and flow regulator add 0.2kg (except Type 1 actuator); limit switch dimension is 77mm, flow regulator dimension is 83mm.
Materials of Construction
| No. | Component | Material | Specification |
|---|---|---|---|
| 1 | Body | Bronze | EN 1982 CC491K |
| 2 | Bonnet | Bronze (½" and 1") | EN 1982 CC491K |
| 2 | Bonnet | Brass (¾", 1¼", 1½" and 2") | EN 12165 CW617N |
| 3 | Plug | Stainless Steel | AISI 316L |
| 4 | Plug Seal | PTFE | - |
| 5 | Stem | Stainless Steel | AISI 316 |
| 6 | Stem Seal | V-ring PTFE | - |
| *7 | Stem 'O' Ring | Fluorocarbon Rubber | - |
| 8 | Actuator Housing | Glass Filled Polyamide | - |
| 9 | Piston | Glass Filled Polyamide | - |
| 10 | Piston Lip Seal | Fluorocarbon Rubber | - |
| 11 | Gasket | PTFE | - |
Note
*Part 7 not shown in diagram
Selection Guide
Actuator Selection
| Actuator Type | Diameter | Compatible Valve Sizes |
|---|---|---|
| Type 1 | 45mm | ½" - 1" |
| Type 2 | 63mm | ½" - 2" |
| Type 3 | 90mm | 1" - 2" |
Selection Example
For a 1" screwed BSP connection, Type 2 actuator, Normally Closed (NC) PF51G valve, the designation is: 1" PF51G-2NC (Screwed BSP)
Installation Instructions
Installation Requirements
- Valve can be installed in any orientation, actuator supports 360° rotation for convenient solenoid valve installation
- Installation must follow detailed requirements in the Installation and Maintenance Instructions supplied with the product
- For operation below -10℃ ambient temperature, consult Spirax Sarco in advance
- During cold testing, test pressure must not exceed maximum differential pressure △PMX (with internals installed)
Ordering Information
Spirax Sarco PF51G-2NC Bronze Pneumatic Piston On/Off Angle Valve, 1" size, BSP screwed connection.
Spare Parts Ordering
Seal kits are available for all valve sizes and actuators, including: piston lip seal, actuator O-ring, plug soft seal (PTFE), body seal. When ordering spares, specify valve size, model and date code (located on actuator label).
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