Procurement guide
Wafer, Lug and Flanged Butterfly Valve Comparison
Direct answer: Wafer valves fit between pipe flanges; lug valves add body attachment points; double-flanged valves connect through a flange at each end. Compare the exact bolting, dimensions and disc clearance, and require model-specific confirmation for end-of-line service. Body style alone does not establish pressure rating or control suitability.
Wafer vs Lug vs Double-Flanged: What Changes?
These terms describe the body connection. They do not, by themselves, establish the seat design, control performance or pressure-temperature limits. Compare the exact assembly drawing and operating conditions before treating two valves as alternatives.
| Body style | Typical connection arrangement | What to confirm before ordering |
|---|---|---|
| Wafer | The valve is positioned between the mating pipe flanges; the bolting arrangement holds the assembly together. | Mating flange standard and facing, centering, bolt arrangement, face-to-face length and disc clearance. Do not infer permission to remove downstream piping from the word “wafer”. |
| Lug | Lugs around the body provide attachment points; threaded-lug designs allow bolts to attach from each side. | Thread specification, bolt length and engagement, and the manufacturer's explicit end-of-line rating. Lug construction alone is not an approval for a particular isolation procedure. |
| Double-flanged | The valve has a flange connection at each end. | Flange drilling and facing, face-to-face dimension, assembly weight and pipe support. A matching nominal size is insufficient to establish interchangeability. |
Connection terminology: Emerson Control Valve Handbook, Chapter 10. Installation checks: NIBCO installation guide.
Can a lug valve be used at the end of a line?
Only when the selected model's documentation permits the proposed arrangement at the required pressure and temperature. For example, Emerson expressly rates the Keystone F222 lugged version for bi-directional end-of-line duty. That is a model-specific statement, not a rating for every lug valve or any BAODUN catalogue record. Confirm the downstream-flange condition, flow direction and installation instructions in writing. Source: Keystone F221/F222.
Two installation checks that nominal size can miss
- Disc clearance: the open disc can interfere with adjoining lined pipe, fittings, reducers or another valve. Check the manufacturer's clearance drawing against the actual pipe bore.
- Seat-to-flange sealing: some resilient-seat designs provide their own flange seal. Do not universally add or omit gaskets; follow the selected model's installation instructions.
NIBCO's guide documents both issues for its product families. Its numerical limits and installation details must not be transferred to a different product.
Isolation and control are separate selection questions
Some butterfly designs support throttling, but the connection style does not establish control suitability. Emerson's high-performance valve guidance emphasizes sizing and operating-load considerations. For control duty, supply minimum, normal and maximum flow, inlet/outlet pressure, medium and temperature, then request model-specific flow and actuator data. Source: Emerson high-performance butterfly valve guidance.
This guide supports procurement, not engineering approval. Confirm final materials, pressure-temperature limits, allowable differential pressure, leakage criteria and documents against your project. PN, ASME Class and JIS designations are not interchangeable assurances of suitability. Conflicting catalogue size or rating fields require a confirmed datasheet.
Technical References
- Emerson Control Valve Handbook, Chapter 10, butterfly-valve body styles.
- NIBCO Butterfly Valve Installation and Maintenance Guide, pages 2–3 and 5, flange compatibility and disc clearance.
- Emerson Keystone Figure 221/222, model-specific end-of-line service and seat sealing.
- Emerson High Performance Butterfly Valves, control-selection considerations.
References checked September 30, 2026. These manufacturers' documents are technical references, not evidence of BAODUN ratings, certifications or affiliation.
Information to Compare
| Comparison field | What to state | Why it matters to the RFQ |
|---|---|---|
| Wafer | State the adjoining flange, drilling and installation requirements supplied by the project. | The piping interface and installation constraints must be compared together. |
| Lug | State the required lug arrangement and adjoining piping requirements. | The requested lug construction must be confirmed against the project interface. |
| Flanged | State the required flange standard, drilling, facing and dimensional requirements. | The valve flange and adjoining flange requirements must be reviewed on the same basis. |
| Seat and disc | List specified seat, disc, stem and body materials. | Material fields should be checked against the medium, temperature and project specification. |
| Size and pressure | Provide DN or NPS and PN or pressure class. | Every quoted line should match the requested size and pressure fields. |
| Actuation | State lever, gearbox, pneumatic, electric, or another requested method. | Actuation changes the requested assembly and control information. |
| Service conditions | Provide medium, temperature, orientation, and installation constraints. | Service data helps identify fields that require confirmation before quotation. |
Buyer Questions
Is nominal size enough to compare butterfly valves?
No. Include pressure rating, connection, materials, actuation, medium, temperature, and project requirements with the size.
Why should the adjoining pipe connection be included?
It helps confirm that the requested valve connection and the piping interface are being compared on the same basis.
How should missing material details be handled?
State the known medium and operating conditions, mark the material field for confirmation, and avoid substituting an unverified material.
Prepare the Inquiry
Use the checklist to organize known requirements and mark missing fields for confirmation.
Send Your RFQ or BOM