How to Order Gate Valves
Gate valves are the most common isolation valves in process piping, and their specification varies significantly depending on whether the valve is cast or forged, the pressure class, and the service conditions. An incomplete gate valve specification, missing the bonnet type, trim, or stem configuration, forces the supplier to select defaults that may not match your piping class or process requirements.
This checklist covers the mandatory and optional parameters for ordering gate valves per API 600 (cast, flanged), API 602 (forged, compact), and API 603 (corrosion-resistant stainless/alloy).
Core Attributes
These parameters must appear in every gate valve line item on your RFQ or purchase order.
| Parameter | What to Specify | Example |
|---|---|---|
| Design standard | API 600 (cast, flanged/BW, NPS 1 and larger), API 602 (forged, compact, NPS 1/2 through NPS 4), API 603 (corrosion-resistant cast stainless/alloy) | API 600 |
| Nominal size | NPS (1/2” through 60” depending on standard) or DN | NPS 6 |
| Pressure class | Class 150, 300, 600, 900, 1500, or 2500 per ASME B16.34 | Class 300 |
| Body-bonnet connection | Bolted bonnet (BB) for Class 150–300 typical; pressure seal (PS) for Class 600 and above | BB |
| Gate type | Solid wedge, flexible wedge, or slab (through-conduit) | Flexible wedge |
| End connection | Flanged (FL) with face type: raised face (RF) or ring-type joint (RTJ). Butt-weld (BW). Threaded (NPT). Socket weld (SW). | FL-RF |
| Body material | Cast CS: ASTM A216 WCB/WCC. Low-temp cast: ASTM A352 LCB/LCC. Cast SS: ASTM A351 CF8/CF8M. Forged CS: ASTM A105. Forged SS: ASTM A182 F316. | ASTM A216 WCB |
| Trim | Seat, wedge face, and stem materials. Specify by material name or refer to API 600 Table 1 trim numbers: Trim 1 (CS/13Cr), Trim 5 (13Cr/13Cr), Trim 8 (Stellite 6 HF), etc. | Trim 5 (13Cr) |
| Stem type | Rising stem, outside screw & yoke (OS&Y) or non-rising stem (NRS) | OS&Y |
| Actuation | Handwheel, gear operator (bevel/spur), pneumatic actuator, electric actuator, hydraulic actuator | Handwheel |
Optional / Special Attributes
Include these when the service, project specification, or client requirements demand it.
| Parameter | What to Specify | When Required |
|---|---|---|
| Bypass and drain connections | Bypass valve size and class; drain connection size, type (NPT/SW), and plugged or valved | Large valves (NPS 10+), high-pressure classes where pressure equalization is needed before opening |
| Locking device | Padlock lugs, chain lock, lockable gear operator | Safety isolation, lockout/tagout (LOTO) procedures |
| Stem extension | Specify extension length in mm or inches | Buried valves, insulated valves, underground installations |
| Cryogenic extension | Extended bonnet per BS 6364 or MSS SP-134 with specified cold box distance | Cryogenic service (LNG, ethylene, liquid nitrogen) |
| Fire-safe certification | API 6FA or API 607 fire-test certification | Hydrocarbon service, offshore, fire-risk areas |
| NACE MR0175 / ISO 15156 | Sour service compliance with hardness and chemistry restrictions | H2S-containing environments |
| Fugitive emission testing | API 624 or ISO 15848-1 with leakage class specified | Environmental compliance, volatile organic compounds, toxic service |
| Certificates | EN 10204 Type 3.1 (MTR) or Type 3.2 (third-party witnessed). Pressure test certificate per API 598. | Always specify; 3.2 for critical and sour service |
Example Line Item
Correct:
5 pcs - Gate valve, API 600, NPS 6, Class 300, FL-RF, BB, OS&Y, flexible wedge, ASTM A216 WCB body, Trim 5 (13Cr), handwheel, MTR EN 10204 3.1
This line item defines: quantity and UOM, design standard, size, pressure class, end connection and face type, bonnet type, stem configuration, gate type, body material, trim, actuation, and certification.
Incorrect:
5 - Gate valve 6 inch 300#
This is missing the design standard, end connection type, face type, bonnet connection, stem type, gate type, body material specification, trim, actuation, and certification. The supplier cannot determine whether this is a cast or forged valve, what material is required, or how it should be operated.
Common Pitfalls
- Omitting the body-bonnet connection type. Bolted bonnet and pressure seal are not interchangeable. Pressure seal bonnets are standard for Class 600 and above in many project specifications. If your piping class calls for BB at Class 600, state it explicitly; otherwise the manufacturer may supply PS, which changes the valve dimensions and weight.
- Not specifying the trim number or materials. API 600 Table 1 defines standard trim combinations by number. “Trim 1” means a different seat/wedge material combination than “Trim 5” or “Trim 8.” If you simply write “standard trim,” the manufacturer will select Trim 1 (the lowest cost), which may not be suitable for your temperature range or erosion conditions.
- Confusing rising stem (OS&Y) with non-rising stem (NRS). OS&Y is the standard for above-ground process piping because the exposed stem thread indicates valve position. NRS is used for buried or space-restricted applications. Specifying the wrong type affects headroom requirements, handwheel accessibility, and visual position indication.
- Forgetting to specify the gate type for pipeline service. Slab (through-conduit) gates are required for pipeline applications where the bore must be scraped or pigged. Wedge-type gates are standard for process plant isolation. Ordering a wedge gate for a pipeline application means the valve cannot be pigged.
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