Quick answer
Which valve end connection should you choose?
Start with the piping specification and the existing pipe interface. A flange, weld or thread is a connection choice; it does not establish the pressure-temperature rating or fluid compatibility of the complete valve. Select an offered configuration that meets the service requirements and fits the installation.
Updated: · Added plug-valve installation and jacket-connection references.
KEHUA VALVE procurement guidance based on public standard scopes and the existing product catalogue. It is not an installation procedure or a statement that every connection is available on every KEHUA series. Confirm the offered configuration and contract edition with the approved drawing and datasheet.
| Connection | How the interface joins | Purchase-order checks |
|---|---|---|
| Flanged | Mating flanges, gasket and bolting form the joint. | Flange standard, size, rating, facing, gasket, drilling and assembly clearance. |
| Butt weld (BW) | Prepared valve and pipe ends form a welded joint. | Pipe bore and wall thickness, bevel details, material, weld procedure and examination requirements. |
| Socket weld (SW) | The pipe fits into the socket; the joint is welded at the socket opening. | Socket and pipe dimensions, material, fit-up and welding requirements from the approved specification. |
| Threaded | Matching male and female threads form the connection. | Exact thread standard and type, size, mating direction, sealing method and service restrictions. |
Check maintenance and installation constraints
Ask whether removal for inspection is important, whether site welding is permitted, and which drawings and inspection records the project requires. A lower purchase price is not a complete comparison if installation, access or replacement work changes. For a change in piping geometry, compare the angle globe valve and Y-pattern globe valve series as separate candidates. Confirm the actual flow path, interface drawing and permitted duty before treating either as a replacement.
With a lubricated plug valve, identify installation access needed for the proposed lubrication and operating arrangement. For a jacketed plug valve, show process connections and jacket connections separately and request their positions and service limits on the offered drawing. Use the six-series plug valve comparison to shortlist the construction before approving a replacement or mating interface.
Flanged valves: check more than the pressure class
A flanged connection can be separated by dismantling the joint after the system is safely isolated under its approved procedure. Specify the mating flange standard, nominal size, pressure designation and facing together. A matching Class or PN label alone does not prove that drilling, dimensions and gasket arrangements match.
Identify the required gasket and bolting system, flange alignment and available space for assembly and valve removal. RF and RTJ are different facing arrangements; do not treat them as interchangeable order descriptions. ASME B16.5 addresses flanges and flanged fittings, while the valve itself needs its applicable product and rating requirements.
Butt-weld valves: agree the actual end preparation
A butt-weld end must be matched to the piping rather than specified only as BW. Review nominal size, actual pipe bore, wall thickness or schedule, bevel geometry and the proposed material combination on the valve drawing. ASME B16.25 covers preparation of buttwelding ends; it is not, by itself, a certificate for a completed field weld.
Agree site welding responsibilities, the governing piping code, qualified procedures, inspection scope and any required treatment with the responsible project team. Evaluate access for welding and future removal. A fully welded valve body and a butt-weld end connection describe different features; confirm each separately.
Socket-weld and threaded valves: define the interface precisely
For socket-weld proposals, identify socket geometry, mating pipe dimensions, materials and the fit-up and welding requirements in the approved specification. Do not use a generic online gap or welding instruction instead of the project procedure. ASME B16.11 covers forged fittings; a fitting class should not be copied onto a valve as its pressure rating.
For threaded proposals, state the exact thread standard, nominal size, taper or parallel form and mating male/female arrangement. A label such as threaded or BSP is incomplete when the actual thread type is unknown. Confirm the sealing method and the suitability of a threaded joint for the service under the project specification.
Compact forged gate or globe valve: define the duty before the ends
For a compact forged gate valve proposal, start with on/off isolation and verify the actual passage, stem travel and bonnet joint. For a forged globe valve proposal, distinguish shutoff from throttling and provide the flow cases and inlet and outlet pressures needed to review the trim and flow capacity.
The same nominal connection size does not make the two valves interchangeable. Reconcile the required function, actual bore, installation dimensions and maintenance access, then approve the offered connection drawing. Identify each connection as a requested or confirmed configuration rather than assuming that every series is supplied with every end option.
Why the connection name does not determine the valve rating
Review the complete assembly: body and trim materials, seat and stem seals, pressure-temperature limits, connection requirements and the governing valve standard. ASME B16.34 includes rating and other requirements for covered valve constructions; the appropriate project standard and offered design still need confirmation.
Agree inspection and test records separately from the interface drawing. A pressure-test report for the valve does not, by itself, establish acceptance of a later field-welded or bolted piping joint. Keep supplier records and site assembly or examination responsibilities identifiable.
A mating-flange check and a pressure-temperature review are separate tasks. The PN vs ASME Class valve pressure-rating guide explains why nearby nominal labels do not prove that two complete valves are interchangeable.
Copy this connection checklist into your valve RFQ
Complete the known fields and mark unresolved items for technical review. Request the final interface details on the offered model drawing before order approval.
- Valve type / series / quantity: ___.
- Fluid, operating and design pressure / temperature, with units: ___.
- Nominal size; mating pipe bore and wall thickness or schedule: ___.
- End connection: flange / BW / SW / thread; exact standard and edition: ___.
- Flange facing, gasket and bolting; or weld preparation; or exact thread form: ___.
- Face-to-face length, orientation, assembly space and removal access: ___.
- Materials, valve rating, applicable tests and required documents: ___.
- Site installation, welding and examination responsibilities: ___.
Compare valve families
Use this guide together with the relevant valve family and project operating data.
Primary technical references
Confirm the edition required by the contract. The project specification and purchased standard remain controlling.
More technical notes