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Concentric Butterfly Valve Zero Offset Resilient Seated
Butterfly Valves

Concentric Butterfly Valve (Zero Offset) – Resilient Seated

The concentric butterfly valve features a centrally positioned stem and disc, providing economical quarter-turn operation for isolation and throttling. Resilient rubber seat ensures bubble-tight shutoff. Available in wafer, lug, and flanged configurations.

What is Zero Offset?

In a zero offset (concentric) design, the stem passes through the exact center of the disc. The disc rotates symmetrically around the pipe centerline. This is the simplest and most cost-effective butterfly valve design.

Key Standards

API 609 BS EN 593 MSS SP-67 API 598

Size Range: DN50 to DN1200 (2" to 48")

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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 concentric butterfly valve?

A concentric butterfly valve (also called zero offset or centric butterfly valve) has the stem passing through the center of the disc and the disc center aligned with the pipe center. The disc rotates around its own center axis. This is the most common and economical type of butterfly valve, ideal for low-pressure applications.

What is the difference between concentric and eccentric butterfly valve?

In a concentric butterfly valve, the stem is centered in the disc and pipe. In an eccentric (offset) butterfly valve, the stem is offset from the disc center, reducing seat wear. Concentric valves are more economical but have higher seat friction, while eccentric valves offer longer service life and better sealing.

What seat materials are used in concentric butterfly valves?

Common seat materials include EPDM (for water, air, weak acids), NBR/Buna-N (for oil, petroleum, hydrocarbons), Viton/FKM (for high temperature, chemicals), PTFE (for corrosive chemicals), and Silicone (for food grade applications). The seat material is selected based on the media and temperature.

What is the maximum temperature for a rubber seated butterfly valve?

Maximum temperature depends on the seat material: EPDM up to 120°C (248°F), NBR up to 82°C (180°F), Viton/FKM up to 200°C (392°F), PTFE up to 200°C (392°F). For higher temperatures, metal seated butterfly valves are recommended.

What is the pressure rating of concentric butterfly valves?

Concentric butterfly valves are typically rated for PN10 (10 bar/145 PSI), PN16 (16 bar/232 PSI), or ANSI Class 150 (20 bar/290 PSI). They are designed for low to medium pressure applications. For higher pressures, double or triple offset butterfly valves are recommended.