Butterfly Valve DN80/0 PN25

Engineering guides: API 609 butterfly valve guide · API 598 tested butterfly · Butterfly standards hub

Export-Ready for Large Water & Power Projects Worldwide

origin Mumbai (JNPT) | CIF worldwide | Gear operator standard | FEA-optimized design

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Butterfly Valve — DN800 (32") PN25 — Double Flange Eccentric

Supreme Valves India manufactures double eccentric (cam-centric) butterfly valves in sizes DN600 to DN2400 with PN25 pressure rating and double-flange connections for large-scale water transmission, irrigation, and power plant cooling water applications. The DN800 (32") double flange butterfly valve uses a double eccentric disc design — the stem is offset from the disc centerline and the seating surface is cam-shaped — causing the disc to lift clear of the seat upon opening. This eliminates seat rubbing and dramatically extends seal life compared to conventional concentric designs. The ductile iron ASTM A395 body provides high strength and impact resistance at operating pressures up to 25 bar. Double flanged ends allow direct installation at the end of trunk mains or in dead-end service. Standard with gear operator and EPDM seat for bubble-tight shut-off in water service.

Concentric vs. Double Eccentric — Why Double Eccentric?

Concentric (Standard)

  • Stem centered on disc — disc contacts seat at all angles
  • Seat rubbing throughout full 90° travel
  • Higher operating torque
  • Seat wear limits life to 5,000–10,000 cycles
  • Suitable for DN600 and below only

Double Eccentric (Cam-Centric) — Our Design

  • Stem offset + cam-shaped seating surface
  • Disc lifts clear of seat immediately after opening
  • Minimal rubbing — only at seating and unseating
  • Seal life: 30,000–50,000+ cycles
  • Standard for DN300+ water transmission mains

Materials of Construction (MOC)

Component Material Specification
Body & Bonnet Ductile Iron (ASTM A536 / EN-GJS-400-15)
Stem / Spindle SS 410 / SS 420
Seat / Trim EPDM / NBR / Bronze

Technical Specifications

Parameter Specification / Standard
Manufacturing / Design Standard EN 1171 / AWWA C509 / BS 5163
Testing Standard API 598 / EN 12266-1
Pressure Rating PN16 / PN25

Frequently Asked Questions

What is a double flange (double-flanged) butterfly valve?

A double flange butterfly valve (also called a 'double-ended' or 'flangeless' valve) has flanges on both the inlet and outlet sides of the valve body, making it suitable for end-of-line installations where there is no opposing flange to hold the valve in place. Unlike wafer valves that must be sandwiched between two pipeline flanges, double flange valves are bolted directly to the end of a pipe or into a dead-end header. This design is standard for DN600 and larger sizes in water transmission and irrigation, where valves are frequently installed at the end of trunk mains, at reservoir offtakes, or in pump stations where the opposite flange may not exist.

What does 'double eccentric' (cam-centric) mean for a butterfly valve?

A 'double eccentric' (also called cam-centric or high-performance) butterfly valve has two offset features: (1) The stem is offset from the disc centerline (first eccentricity), which causes the disc to lift clear of the seat as it opens, eliminating rubbing and wear. (2) The disc seating surface is cam-shaped (second eccentricity) — meaning the disc rotates in an arc that moves it perpendicularly away from the seat as it opens. This double offset design dramatically reduces seat wear, allows the use of softer seat materials (EPDM, NBR) while maintaining tight shut-off, and extends the valve's mechanical life to 10–20× that of a conventional concentric design. Double eccentric valves are the standard specification for water transmission mains DN300 and above.

Why is PN25 used instead of PN16 for large butterfly valves?

PN25 (25 bar) is commonly specified for DN800 butterfly valves in large water transmission projects because: (1) Large-diameter pipes in municipal water systems often operate at higher pressures than smaller pipes due to larger pumps and higher flow demands; (2) The PN25 rating provides a safety margin for pressure surge events (water hammer) which are more significant in large-diameter mains; (3) Many specifications (particularly from Middle Eastern and North African municipal utilities) require PN25 for DN600 and above to ensure the valve can handle unexpected surge pressures without failure; (4) The PN25 body can also be rated to PN16 if used with PN16 flanges — the valve body rating is independent of the flange rating in most cases. PN25 is equivalent to approximately Class 300 in ASME terminology.

What torque is required to operate a DN800 butterfly valve at PN25?

A DN800 (32-inch) PN25 double eccentric butterfly valve requires a breakaway torque of approximately 3,500–4,500 Nm for EPDM seats due to the high seating load required for bubble-tight shut-off at 25 bar. The running torque is approximately 2,000–2,500 Nm. This requires a gear operator with a reduction ratio of approximately 50:1 or higher. Typical gear operator specifications for DN800 PN25: maximum input torque 150–200 Nm at the handwheel (requiring approximately 5–8 turns to travel 90 degrees), with an overload clutch to prevent damage. For automated systems, an electric actuator sized at 400–600 Nm output torque is required. We size all actuators with a 1.3× safety factor per ISO 5210.

What is the face-to-face dimension of a DN800 double flange butterfly valve?

The face-to-face dimension for a DN800 PN25 double flange butterfly valve per ISO 5752 Series 14 (long pattern) is typically 450mm. Some manufacturer designs use 480mm or 500mm depending on the body geometry. The double flange design has flanges on both ends — the inlet flange is fully threaded (lugs), and the outlet flange is also fully threaded, allowing the valve to be bolted directly to a pipe end or against a blank flange. This differs from the wafer design which has clearance holes (not threads) and requires an opposing flange to hold it in place.