Function before name
The requisition should state whether the valve must isolate flow, prevent reverse flow, or do both under the governing standard.
Valve type decides what the pipeline asks the valve to do: isolate, resist reverse flow, combine both functions, or limit pressure loss. This procurement guide separates those functions from standard scope, installation limits, and certificate requirements.
The requisition should state whether the valve must isolate flow, prevent reverse flow, or do both under the governing standard.
Flow direction, pipe orientation, access for operation, and face-to-face dimensions can reject an otherwise similar valve.
A similar DN or pressure class does not transfer product scope, seat design, test basis, or class-certificate coverage.
Marine requisitions often use local names, old ship drawings, IMPA references, and product standards together. The table below is a procurement communication aid; the governing product standard and installation drawing remain decisive.
| Valve type | Primary function | Confirm separately |
|---|---|---|
| Globe / stop valve | Manual isolation; can provide throttling resistance where the service and seat design allow it | Flow direction, pressure drop, seat and stem scope, body type, standard, size, pressure, temperature, material, and flange |
| Gate valve | Full-open or full-close isolation with a straight-through flow path | Gate or wedge construction, seat sealing, media, flushing risk, face-to-face length, and whether throttling is excluded |
| Stop-check valve | Combines manual shut-off with a check function to resist reverse flow | Flow direction, installation orientation, manual-closure scope, standard body type, and whether the system requires both functions |
| Check valve | Opens for forward flow and closes automatically against reverse flow | Lift, swing, wafer, or piston construction; direction arrow; vertical or horizontal limit; pressure loss; and pulsation risk |
A valve should not be replaced only because two products look similar or share a connection size. The safer approach is to record the function required by the piping system, then compare it with the standard product scope.
| Situation | Risk if only the valve name is copied | Stronger confirmation |
|---|---|---|
| Replacing a stop valve with a stop-check valve | Operation, pressure drop, or reverse-flow behavior may not match the system design | State the required function, direction, standard body type, and installation drawing reference |
| Replacing a gate valve with a globe valve | Flow capacity, pressure loss, face-to-face length, and operating purpose can change | Compare flow function, pressure drop allowance, material, and installation dimensions |
| Replacing a lift check with a swing or wafer check | Orientation, pulsation, slamming, and space limits may differ | Give flow direction, installation plane, velocity or flow requirement, and available length |
| Using a generic "marine valve" description | Standard scope, body type, trim, and certificate coverage remain unknown | Send standard or model, size, pressure, temperature, material, connection, medium, and documents required |
These product pages show how the same material family can contain different valve functions. They are entry points for confirmation, not substitution approvals.
| Catalog entry | Function family | Still confirm |
|---|---|---|
| GB/T 584 cast-steel stop valve | Globe / stop | Body type, DN-pressure combination, material list, media, and documents |
| GB/T 585 cast-steel stop-check valve | Stop-check | Flow direction, orientation, body type, and pressure-temperature basis |
| GB/T 586 cast-steel check valve | Check | Lift or swing construction, installation limit, and service media |
| JIS F 7364 cast-iron gate valve | Gate | 10K pressure-temperature basis, size, material, and flange details |
Subject: Marine valve RFQ - valve function confirmation Required function: isolation / reverse-flow prevention / both Original valve type and nameplate information: Standard / model / drawing / IMPA code: Body type or construction: Size: DN / NPS / A-B Pressure rating and temperature basis: Medium and system: Flow direction and installation orientation: Body / bonnet / disc / seat / stem materials: Connection and flange details: Face-to-face or end-to-end dimension: Certificate or inspection requirement: Quantity and destination port:
| Question | Answer |
|---|---|
| Is a stop-check valve a direct substitute for a globe valve? | No. A stop-check valve adds a backflow-prevention function, while a globe or stop valve is primarily an isolation and throttling valve. The governing standard and installation function must be confirmed. |
| Can a gate valve be used for flow regulation? | A gate valve is normally used fully open or fully closed, not for continuous throttling. Partial opening can create seat, gate, or sealing risks, so the product standard and service conditions govern the decision. |
| Does every check valve install in any orientation? | No. Lift, swing, wafer, and piston check valves have different flow-direction and orientation limits. The installation plane, flow direction, and standard scope must be checked before quotation. |
| What is the minimum information for a valve-type replacement? | Send the original standard or model, function, size, pressure and temperature, body and trim materials, connection and flange details, service medium, flow direction, installation orientation, quantity, and certificate requirement. |
This guide supports procurement communication. It does not replace the governing product standard, ship specification, piping drawing, class requirement, or supplier review for the specific order.
Send the original valve reference and the function required by the piping system. We will check catalog scope, installation limits, connection compatibility, and document requirements.