Butterfly Valve Series

What is the difference between wafer and lug butterfly valves?

The key difference is how they connect to the pipeline and whether they can handle dead-end service. A wafer butterfly valve is designed to be clamped between two pipe flanges with the flange bolts passing around (not through) the valve body — it is lighter and more economical but cannot be used at the end of a pipeline because removing downstream piping would break the seal. A lug butterfly valve has threaded metal inserts (lugs) cast or mounted into the valve body that accept individual flange bolts — each pipe flange is independently bolted to the valve. This means the downstream piping can be removed while the upstream side remains under pressure, making lug valves essential for services requiring periodic maintenance or when the valve acts as a line end isolation point. Lug valves are also preferred when the pipeline experiences significant thermal expansion.

What is a triple offset butterfly valve?

A triple offset butterfly valve incorporates three distinct geometric offsets relative to the pipe centerline: Offset 1 — the shaft centerline is offset from the disc sealing face plane (behind the seat). Offset 2 — the shaft centerline is offset from the pipe/seat centerline (lateral displacement). Offset 3 — the seat cone axis is inclined/offset at an angle from the disc face (conical seating geometry). Together, these three offsets create a right-angled conical seating surface where the disc contacts the seat only at the final moment of closure — there is zero rubbing friction between the metal seal ring and metal seat during opening or closing. This enables torque-seated, position-independent, zero-leakage metal-to-metal performance without seal wear. Triple offset butterfly valves are used for critical services: high-temperature (up to 650°C), cryogenic (-196°C), fire-safe (API 607 certified), high-cycle operation, and any application requiring absolute zero leakage with metal seats. TANGGONG triple offset valves are helium leak tested and available from DN80 to DN2000.

What materials are butterfly valve seats available in?

TANGGONG offers butterfly valve seats in a comprehensive range of materials: PTFE (virgin polytetrafluoroethylene, -20°C to +180°C) for excellent chemical resistance against acids, alkalis, and solvents; RTFE (15% glass-filled PTFE, up to +200°C) for improved strength and wear resistance in cycling applications; EPDM (ethylene propylene diene monomer, -30°C to +120°C) for water, seawater, hot water, and mild chemical service — the most common waterworks seat material; NBR/Buna-N (nitrile, -20°C to +80°C) for hydrocarbon oils, fuels, and greases; Viton/FKM (fluoroelastomer, -20°C to +180°C) for aggressive chemicals, high-temperature oils, and chlorinated solvents; Metal-to-Metal (Inconel 718 heat-treated / Stellite 6 or 21 hard-faced, up to +650°C) for triple offset high-temperature and fire-safe service. The metal seat is also used in high-performance double offset designs for refinery and steam service. Our engineering team recommends the optimal seat based on your media type, concentration, operating temperature, and required cycle life.

Can butterfly valves be used for throttling?

Yes, butterfly valves can be used for throttling (flow regulation), but their throttling performance varies significantly by design type. Standard concentric (resilient-seated) wafer and lug butterfly valves provide moderate throttling capability — the disc position provides progressive flow control from approximately 20° to 70° of disc rotation, but continuous high-velocity throttling below 20° open can cause cavitation in liquid service and vibration in gas service. High-performance double offset butterfly valves provide superior throttling — the cam-action disc motion reduces seat contact during partial opening, and the PTFE or metal seat tolerates higher flow velocities. They are commonly used for modulating flow control in process industries. Triple offset butterfly valves are primarily designed for on/off isolation and emergency shut-off (ESD) due to their metal-to-metal seating — they are not recommended for continuous throttling as the metal seat is optimized for zero leakage at full closure rather than flow modulation. For demanding throttling applications, TANGGONG recommends high-performance double offset butterfly valves with positioner-controlled electric or pneumatic actuation.

What size range do TANGGONG butterfly valves cover?

TANGGONG manufactures butterfly valves from DN40 (1½") to DN3000 (120") in nominal diameter — one of the widest size ranges in the industry. Standard wafer and lug butterfly valves cover DN50–DN1200 (2"–48"), available from stock in most popular sizes. Flanged butterfly valves extend the range to DN3000 (120") with double flanged body construction for large-diameter water and process applications. High-performance (double offset) butterfly valves are available from DN50–DN1200 (2"–48"), and triple offset butterfly valves from DN80–DN2000 (3"–80"). Pressure ratings span Class 150 to Class 600, with standard Class 150 and Class 300 being most common. For applications requiring sizes or pressure ratings outside these standard ranges, our engineering team can develop custom designs. Contact [email protected] with your pipe diameter and service conditions for availability and lead time.