How to Order Globe Valves
Globe valves provide throttling and positive shutoff capability due to their disc-to-seat geometry, but this same geometry creates a higher pressure drop than gate or ball valves. Specifying a globe valve correctly requires defining the size, class, and material, and the disc type, flow direction, and, for critical applications, whether a bellows seal or Y-pattern body is needed.
This checklist covers the parameters required for ordering globe valves per API 600 (cast, flanged/BW), BS 1873 (cast, globe and check valves), and API 602 (forged, compact).
Core Attributes
These parameters must appear in every globe valve line item on your RFQ or purchase order.
| Parameter | What to Specify | Example |
|---|---|---|
| Design standard | API 600 (cast, up to NPS 24), BS 1873 (cast globe and check, widely used internationally), API 602 (forged, compact, NPS 1/2 through NPS 4) | BS 1873 |
| Nominal size | NPS or DN | NPS 4 |
| Pressure class | Class 150, 300, 600, 900, 1500, or 2500 per ASME B16.34 | Class 600 |
| Body-bonnet connection | Bolted bonnet (BB) or pressure seal (PS) for Class 600 and above | PS |
| Disc type | Plug disc (standard for throttling), conventional disc (flat or bevel), needle (for fine flow control in small sizes) | Plug disc |
| End connection | Flanged (FL) with face type: RF or RTJ. Butt-weld (BW). Threaded (NPT). Socket weld (SW). | FL-RF |
| Body material | Cast CS: ASTM A216 WCB/WCC. Cast alloy: ASTM A217 WC6 (1.25Cr-0.5Mo), WC9 (2.25Cr-1Mo), C5 (5Cr-0.5Mo). Cast SS: ASTM A351 CF8/CF8M. Forged CS: ASTM A105. Forged SS: ASTM A182 F316. | ASTM A217 WC6 |
| Trim | Disc, seat, and stem materials. Specify by name (e.g., Stellite 6 hard-faced seat and disc) or reference API 600 Table 1 trim numbers. | Stellite 6 (seat + disc) |
| Stem type | Rising stem, outside screw & yoke (OS&Y); standard for globe valves | OS&Y |
| Flow direction | Specify if critical: flow-under-seat (standard, easier to open against pressure) or flow-over-seat (better shutoff, used for high-pressure bypass). Mark arrow direction on datasheet. | Flow-under-seat |
| Actuation | Handwheel, gear operator, pneumatic actuator, electric actuator | Handwheel |
Optional / Special Attributes
Include these when the service, project specification, or client requirements demand it.
| Parameter | What to Specify | When Required |
|---|---|---|
| Bellows seal | Bellows-sealed bonnet per EN 12516, specifying bellows material (AM 350, Inconel 625) and cycle life (minimum 10,000 cycles typical) | Toxic service, volatile fluids, hydrogen, vacuum, zero-leakage requirement on stem |
| Y-pattern body | Y-pattern (oblique) body design instead of standard T-pattern | High-pressure service where lower pressure drop is critical; also used for high-pressure bypass and drain globe valves |
| Throttling trim | Characterized plug with linear, equal-percentage, or quick-opening flow characteristic; specify Cv if known | Manual throttling or modulating service |
| Cryogenic extension | Extended bonnet per BS 6364 or MSS SP-134, specify cold box distance | Cryogenic service (LNG, ethylene, liquid nitrogen) |
| NACE MR0175 / ISO 15156 | Sour service compliance with hardness and chemistry restrictions | H2S-containing environments |
| Fire-safe certification | API 607 fire-test certification | Hydrocarbon service, offshore, fire-risk areas |
| Fugitive emission testing | API 624 or ISO 15848-1 with leakage class | Environmental compliance, volatile organic compounds |
| Certificates | EN 10204 Type 3.1 (MTR) or Type 3.2. Pressure test certificate per API 598. | Always specify; 3.2 for critical and sour service |
Example Line Item
Correct:
10 pcs - Globe valve, BS 1873, NPS 4, Class 600, FL-RF, PS bonnet, OS&Y, plug disc, ASTM A217 WC6 body, Stellite 6 trim (seat + disc), handwheel
This line item defines: quantity and UOM, design standard, size, pressure class, end connection and face type, bonnet type, stem configuration, disc type, body material, trim materials, and actuation.
Incorrect:
10 - Globe valve 4 inch
This is missing the design standard, pressure class, end connection, face type, bonnet type, disc type, body material specification, trim, and actuation. The supplier cannot determine the pressure rating, material, or whether the valve is cast or forged.
Common Pitfalls
- Not specifying the disc type. Plug disc, conventional disc, and needle disc have different flow characteristics and shutoff capabilities. A conventional disc provides basic on/off isolation but poor throttling. A plug disc (also called a balanced plug) is the standard choice for throttling service. If you do not specify, the manufacturer selects the default for that product line, which may not suit your application.
- Ignoring flow direction. Globe valves are directional. Flow-under-seat is standard and allows easier opening against line pressure. Flow-over-seat provides tighter shutoff but requires more opening torque. If the valve is installed in the wrong orientation relative to the specified flow direction, shutoff performance and controllability are affected. Always specify and verify arrow direction against the piping arrangement.
- Forgetting to specify bellows seal for toxic service. Standard packing (graphite rings) will always have some fugitive emission through the stem. For toxic, carcinogenic, or volatile fluids (benzene, ethylene oxide, hydrogen fluoride), a bellows-sealed globe valve eliminates stem leakage entirely. This must be specified at the time of ordering; it cannot be retrofitted.
- Ordering a T-pattern globe valve for high-pressure drop service. The standard T-pattern body creates a significant pressure drop (high Cv loss) due to the tortuous flow path. A Y-pattern body reduces the pressure drop considerably by angling the seat relative to the flow axis. For high-pressure bypass valves or applications where pressure drop is a design constraint, specify Y-pattern explicitly.
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