Face-to-Face, Flange & Pressure Ratings for RF and BW Class 150 Gate Valves — a specification reference for engineers and procurement.
ⓘ
Quick answer: A Class 150 gate valve carries a maximum working pressure of about 19–20 bar at 20°C per ASME B16.34, uses a bolted bonnet, and is specified primarily by its face-to-face dimension (ASME B16.10), flange size (ASME B16.5), and pressure-temperature rating (ASME B16.34).
1. Why Class 150 Dimensions Matter
An Class 150 Gate Valve is the workhorse of utility, cooling-water, and low-pressure process lines. Dimension errors here are just as costly as in higher classes — an incorrect face-to-face length breaks the piping run, and an undersized flange bolts leaks.
Three standards govern the dimensions of any Class 150 flanged or butt-weld gate valve:
| Standard | What It Controls |
|---|---|
| ASME B16.10 | Face-to-face (F-F) and end-to-end dimensions of valves |
| ASME B16.5 | Flange dimensions (OD, bolt circle, bolt holes) for flanged valves |
| ASME B16.34 | Pressure–temperature ratings and general dimensional tolerances |
Note: The table below gives standard reference dimensions for short-pattern Class 150 steel gate valves (cast or forged) with raised-face flanges. Always confirm final dimensions against the manufacturer’s certified drawing and your actual end connections — RTJ faces and special patterns differ.
2. Class 150 Gate Valve – Standard Face-to-Face Dimensions (ASME B16.10)
Typical face-to-face (F-F) lengths for Class 150 gate valves (short pattern, RF ends, mm):
| NPS | DN | Face-to-Face (mm) |
|---|---|---|
| ½” | 15 | 108 |
| ¾” | 20 | 117 |
| 1″ | 25 | 127 |
| 1¼” | 32 | 140 |
| 1½” | 40 | 165 |
| 2″ | 50 | 178 |
| 2½” | 65 | 190 |
| 3″ | 80 | 203 |
| 4″ | 100 | 229 |
| 5″ | 125 | 254 |
| 6″ | 150 | 267 |
| 8″ | 200 | 292 |
| 10″ | 250 | 330 |
| 12″ | 300 | 356 |
| 14″ | 350 | 406 |
| 16″ | 400 | 457 |
| 18″ | 450 | 508 |
| 20″ | 500 | 610 |
| 24″ | 600 | 711 |
| 30″ | 750 | 864 |
| 36″ | 900 | 978 |
Values above are short-pattern Class 150 gate valve face-to-face dimensions per ASME B16.10 (reference). Butt-weld (BW) end-to-end lengths may differ from flanged F-F; always verify with the valve drawing.
3. Class 150 Flange Dimensions (ASME B16.5)
Reference flange dimensions for Class 150 raised-face (RF) flanges (mm):
| NPS | Flange OD (mm) | Bolt Circle Ø (mm) | No. of Bolts | Bolt Size |
|---|---|---|---|---|
| ½” | 89 | 60.3 | 4 | ½” |
| ¾” | 98 | 69.9 | 4 | ½” |
| 1″ | 108 | 79.4 | 4 | ½” |
| 1¼” | 117 | 88.9 | 4 | ½” |
| 1½” | 127 | 98.4 | 4 | ½” |
| 2″ | 152 | 120.7 | 4 | ¾” |
| 2½” | 178 | 139.7 | 4 | ¾” |
| 3″ | 190 | 152.4 | 4 | ¾” |
| 4″ | 229 | 190.5 | 8 | ¾” |
| 6″ | 279 | 241.3 | 8 | ¾” |
| 8″ | 343 | 298.5 | 8 | ¾” |
| 10″ | 406 | 362.0 | 12 | 1″ |
| 12″ | 483 | 431.8 | 12 | 1″ |
| 14″ | 533 | 476.3 | 12 | 1¼” |
| 16″ | 597 | 539.8 | 16 | 1¼” |
| 18″ | 635 | 577.9 | 16 | 1¼” |
| 20″ | 699 | 635.0 | 20 | 1¼” |
| 24″ | 813 | 749.3 | 20 | 1½” |
Flange data per ASME B16.5 (reference). Ring-joint (RTJ) flanges and long-pattern valves use different dimensions — request the certified drawing.
4. Class 150 Pressure–Temperature Rating (ASME B16.34)
ASME Class 150 rating is roughly 19.6 bar (284 psi) at -29°C to 38°C for carbon steel, and derates with temperature. Approximate working pressures (bar):
| Temp (°C) | Carbon Steel (A105/WCB) | Stainless (F316) |
|---|---|---|
| 20 | ~19.6 | ~19.6 |
| 100 | ~17.7 | ~15.9 |
| 200 | ~15.8 | ~13.0 |
| 300 | ~13.8 | ~10.2 |
| 400 | ~11.6 | ~8.2 |
Values are representative ASME B16.34 ratings and must be confirmed against the latest standard for your exact material and temperature.
5. Body & Trim Materials for Class 150
| Part | Common Options |
|---|---|
| Body / Bonnet | Cast WCB, forged A105; stainless CF8M / A182 F316 |
| Wedge | WCB / A105, or SS316 with Stellite overlay for erosive service |
| Stem | A182 F6a (13Cr), SS304 / SS316 |
| Seat rings | Integral or SS316; Stellite overlay optional |
| Packing | Flexible graphite / PTFE, per service |
| Gasket | Graphite (bolted bonnet compression) |
6. Testing (API 598)
A Class 150 gate valve is typically tested per API 598:
Shell test: hydrostatic
Seat test: hydrostatic, plus pneumatic where specified
Backseat test: optional per spec
Fugitive emission (optional): ISO 15848-1 if required
7. When to Move Above Class 150
If your operating pressure exceeds ~20 bar, or your line sees thermal cycling, high temperature, or sour service, Class 150 bolted-bonnet design may not hold. Step up to Class 300/600 first, and for Class 900 and above move to a Pressure Sealed Bonnet Gate Valve.
➜ Deep dive: Pressure Sealed Bonnet vs Bolted Bonnet Gate Valve · High Pressure Gate Valve Selection & Manufacturer Guide
8. Need a Certified Drawing or Quotation?
Send your datasheet (NPS, rating, end connection, material, quantity) to sales1@nswvalve.com and NSW Valve’s engineering team will return a certified drawing and factory-direct quotation.
NSW Valve · https://www.nswvalve.com
Post time: Oct-21-2026