Wafer vs Lug vs Flanged Butterfly Valves: Selection Guide

The difference is how the valve body connects to the pipeline. A wafer butterfly valve fits between pipe flanges. A lug butterfly valve uses body lugs, commonly threaded, to attach the flanges. A flanged butterfly valve has end flanges that connect to the pipe flanges. These terms describe attachment, while seat material and disc geometry are separate choices.

Begin with the piping layout and maintenance requirement. Then check the actual offered construction. KEHUA's published butterfly valve family includes wafer, lug and flanged series, alongside high-performance butterfly valve and triple-offset metal-seated butterfly valve options. Each proposal still needs its own dimensional drawing and operating limits.

A connection name does not establish a pressure-temperature envelope. Review body and disc materials, seat and seal materials, stem design, flange compatibility and the manufacturer's complete valve rating. A soft-seated flanged valve does not acquire a metal seat's operating characteristics simply because its body has flanges.

Provide normal and design pressure and temperature, together with the maximum differential pressure across the closed valve. Also identify operating frequency and any unusual transient conditions. Ask the supplier to document restrictions and resolve differences between the project specification and the offered configuration before approval.

Nominal size alone is insufficient for replacement or new installation. The flange designation, drilling, facing, installed length and actual pipe bore must fit together. ASME B16.5 addresses pipe flanges and flanged fittings; ASME B16.10 addresses installation dimensions within its scope. Identify the applicable standard and contract edition rather than treating these designations as interchangeable.

Check the disc's swept envelope against the mating flange and pipe bore on the supplier drawing. Confirm the model's gasket requirements: some lined designs use the liner as the flange seal, while other arrangements require a separate gasket. Installation instructions for the exact model should settle this choice.

End-of-line operation requires an explicit review of the proposed valve with the downstream flange absent. Obtain written limits for pressure, temperature, medium, pressure direction, bolting and support. Do not transfer a normal between-flange rating to that arrangement without confirmation.

The AVK Series 820 manual listed below is a useful example: it defines additional conditions for end-of-line use and dimensional checks for its own models. Those conditions illustrate why the question is model-specific; they are not KEHUA product specifications. Ask for the corresponding approval for the valve actually being offered.

Describe the fluid composition, phase, solids and cleaning chemicals, as well as operating and design conditions. Review all wetted parts and sealing materials. A corrosion-resistant body does not establish the compatibility of the seat, shaft seals or disc with the same medium.

For throttling duties, request a service review that includes flow conditions and the proposed operating range. For powered operation, agree the torque basis, available utilities, fail position and controls. Put missing data on a clarification list so the buyer and supplier can close it together.

Send the following information as one package. If a field is unknown, mark it for clarification. A complete list makes supplier offers easier to compare and helps prevent an apparently suitable connection from concealing a dimensional or service mismatch.

Compare each offer against the same approved checklist. Record differences in installed length, flange compatibility, seat materials, pressure-temperature limits, actuation and inspection scope. Request a revised drawing or explicit deviation statement where information is missing; resolve the technical differences before comparing the final commercial terms.

For a KEHUA enquiry, begin with the published wafer, lug or flanged series and send your project data for review. The family page is a starting point for discussion. The approved model drawing, datasheet and agreed inspection documents should identify what will be supplied.