A replacement butterfly valve needs more than the same nominal size and pressure designation. Confirm that its installed length fits the pipework, its flange connection matches, and its disc can travel without contacting the adjoining bore or equipment. A valve can fit between the flanges yet still fail the clearance check.
Start this review before ordering. The result should be an approved dimensional comparison and an installation plan for the exact configuration. This article concerns flanged piping connections, including wafer and lug arrangements. It does not provide a welding procedure for butt-weld valves or universal installation settings for every butterfly valve.
Build a replacement record from the existing installation
Collect the old valve identification, piping drawing and photographs showing both sides. Record body style, actuator position, nearby reducers and any equipment connected directly to the valve. Include enough context to distinguish an actual pipe bore from a nominal size on a drawing.
Where measurements require opening the line, obtain them only during an approved shutdown after isolation, depressurization and control-energy lockout. Until then, mark inaccessible dimensions as unverified. A quotation based on incomplete information should identify those assumptions rather than present them as confirmed site conditions.
Give every measurement a location and unit. Keep the measured flange separation distinct from the old valve body length: the installed joint may include gaskets or other components. Photographs support the record, but should not replace a measurement where dimensional acceptance matters.
Review fit-up through four separate acceptance checks
The following comparison sheet is a suggested project workflow. Assign an owner to unresolved items and retain the drawing revision used for the decision.
| Acceptance check | Evidence required | Common unresolved question |
|---|---|---|
| Installed length | Valve face-to-face drawing and complete joint arrangement | Does the proposed assembly fit the available space? |
| Connection | Flange details, facing and bolting arrangement | Do the mating parts form the specified joint? |
| Moving envelope | Disc travel drawing and adjoining internal profiles | Can the disc complete its required travel without interference? |
| External envelope | Valve-actuator drawing and access survey | Can the assembly be installed, operated and maintained? |
Do not close one check using evidence from another. Matching a bolt pattern does not establish disc clearance, and a clear disc path does not establish gasket compatibility. Any mismatch should return to engineering review before the installation team receives the equipment.
Specify the face-to-face series, not just a standard number
Face-to-face dimensions describe the valve’s connection length. ISO 5752:2021 defines basic dimensional series for two-way metal valves in flanged systems, including butterfly valves. Its scope is dimensional; citing it alone does not identify every detail of a proposed replacement. [1]
Ask the supplier to state the applicable standard, series where relevant, and actual dimension on the general arrangement drawing. Compare that drawing with the existing installation. If the old equipment has no reliable dimensional identification, treat the site measurement and the proposed drawing as separate records requiring reconciliation.
A different body style may change the replacement package. For example, the KOZO WCB high-performance double-offset butterfly valve is offered in configuration-dependent body styles. Request the drawing for the specific size, class and wafer, lug or flanged arrangement under consideration.
Do not use extra gaskets as an improvised way to fill an unexplained length difference. Ask whether an engineered spool change, a different valve configuration or another approved modification is required. Record the effect on support and access arrangements as part of that decision.
Check the bore around the entire disc travel envelope
A butterfly valve disc can extend beyond the body faces when opening. Bray’s McCannalok installation manual explicitly calls for sufficient adjoining pipe internal diameter and supplies minimum-bore information for its own valve configurations. Those values are not interchangeable with a KOZO drawing. [2]
Request the proposed valve’s disc envelope or minimum adjoining-bore requirement. Provide the actual internal profile on both sides, including liners, nearby restrictions and the distance to adjacent equipment. If a check valve or another moving component is close by, ask for a combined envelope review rather than checking the two bodies independently.
The practical deliverable is a marked drawing showing where the clearance was assessed. State any assumptions about centering, gasket position and adjoining components. A simple nominal pipe-size comparison leaves those assumptions hidden.
A workshop stroke test confirms behavior in that workshop arrangement. It does not establish clearance inside different site flanges or lined pipework. Keep the workshop record and the installed fit-up review together, with their respective limitations clearly stated.
Resolve the flange sealing arrangement for the exact design
Butterfly valves do not share one universal gasket rule. Bray’s resilient-seated manual describes designs whose molded seat-face seals perform the flange-sealing function without additional gaskets. Its high-performance McCannalok manual specifies a different joint arrangement, including suitable flange gaskets. [3] [2]
Use these as examples of why the exact valve instructions matter. Do not transfer a gasket-free instruction from an elastomer-lined design to a double-offset or metal-seated valve. Obtain the supplier’s approved gasket arrangement, flange requirements and bolting instructions for the selected assembly.
For a KOZO CF8M triple-offset butterfly valve, confirm the connection and sealing configuration in the project documentation. A family-level description does not establish the dimensions, bolt lengths or installation procedure of every size and class.
Have the responsible joint designer resolve any disagreement between the flange, gasket and valve instructions. The installation pack should contain one coordinated requirement, not several conflicting torque tables for the fitter to choose between.
Keep installation position and operating limits model-specific
Disc position during insertion is another instruction that should come from the exact manual. Bray’s resilient-seated procedure uses a partially open insertion position to protect its seat and disc arrangement. That is not a general instruction to install every butterfly valve at the same angle. [3]
Review the supplied manual for preferred pressure direction, shaft orientation, lifting provisions and powered-actuator precautions. Identify how unintended movement will be prevented during handling. Where a spring-return actuator is fitted, the work plan must account for stored energy and its natural return position.
Allow room for the equipment that will actually be supplied. Include handwheel movement, actuator removal, electrical or pneumatic connections, and access to serviceable components. A top-view drawing alone may conceal an access conflict that becomes obvious in an elevation drawing.
Make the pre-start inspection a documented hold point
Before returning the line to service, use the approved installation instructions to verify assembly and travel. Do not use extra actuator force to push past unexplained resistance. Stop and investigate a mismatch between the drawing, installation condition and observed movement.
A useful inspection record identifies the valve, drawing revision, joint arrangement, installer and witness. Record the required travel checks and their results, then list any outstanding restrictions. Keep functional movement and pressure or leakage acceptance as distinct records; successful travel alone does not establish leak tightness.
If resistance appears only after final assembly, preserve that observation and the assembly record. It is more informative than a general report that the valve is “too tight.” Engineering can then determine whether the next investigation concerns alignment, adjoining clearances, joint assembly or the valve itself.
What to send with a replacement enquiry
- Old valve nameplate, body style and available manufacturer drawing.
- Size, pressure designation, fluid, temperature and required isolation duty.
- Measured installed arrangement, with inaccessible dimensions marked.
- Mating flange details, facing, pipe bore and any lining information.
- Nearby fittings or equipment, including their distances from the valve.
- Required actuator, failure position, utilities and access restrictions.
- Project dimensional, joint-assembly and acceptance requirements.
Ask the supplier to return a configuration-specific drawing and a list of remaining assumptions. This gives purchasing and maintenance the same basis for judging whether the proposed valve is a direct replacement.
Two questions worth resolving early
Can a spacer solve a disc-clearance conflict?
It may be part of an engineered solution, but it changes the assembly. Have its length, bore, joints, bolting and support implications reviewed. Do not specify one from a photograph alone.
Can an old actuator be retained?
Only after reviewing the replacement valve’s torque requirements, mounting interface and operating limits. A dimensional fit between actuator and valve does not establish suitability for the new duty.
Need a replacement review? Send KOZO your installation drawings and valve duty. Include the dimensions you have verified and identify what still needs checking before a configuration is selected.
Technical references
- ISO: ISO 5752:2021 — Metal valves for use in flanged pipe systems: Face-to-face and centre-to-face dimensions (scope).
- Bray: McCannalok High Performance Butterfly Valve Installation, Operation and Maintenance Manual.
- Bray: Resilient Seated Butterfly Valves Installation, Operation and Maintenance Manual.
