Engineering guides: API 609 butterfly valve guide · API 598 tested butterfly · Butterfly standards hub
Tight Shut-Off

NAB Disc Butterfly Valve – API 609 for Seawater

Butterfly valves with Nickel Aluminium Bronze (NAB) disc and EPDM rubber lining per API 609 for seawater service. Ductile iron body ASTM A536 60-40-18. Tight bubble-tight shut-off. Sizes 3" to 24". Manual lever or gear operated. Ideal for seawater cooling, desalination, and marine applications.

Quick Summary

NAB Disc Butterfly Valve = Butterfly valve with NAB (C95800) disc for seawater contact + EPDM rubber liner protecting ductile iron body. Cost-effective alternative to full NAB valves. API 609 design. Bubble-tight shut-off. Available 3" to 24". Lever for small sizes, gear for 6"+. Applications: seawater cooling, desalination intake/outfall, marine ballast systems.

NAB Disc Butterfly Valve API 609 EPDM Lined Seawater

Key Specifications

Design Standard: API 609
Pressure Rating: PN16 / Class 150
Body Material: ASTM A536 60-40-18
Disc Material: NAB (C95800)
Liner: EPDM Rubber
Size Range: 3" to 24"
Body Style: Wafer / Lug
Shut-off: Bubble-tight
Request Enquiry WhatsApp Download Datasheet

Materials of Construction (MOC)

Component Material Specification
Body Ductile Iron ASTM A536 60-40-18
Disc Nickel Aluminium Bronze ASTM B148 C95800
Shaft / Stem SS316 / Super Duplex (service dependent)
Seat / Liner EPDM
Hardware SS316

Technical Specifications

Parameter Specification / Standard
Design Standard API 609
Pressure Rating PN16 / Class 150
Body Style Wafer / Lug
Body Material ASTM A536 60-40-18 (ductile iron)
Disc Material ASTM B148 C95800 (NAB)
Testing Standard API 598

Frequently Asked Questions

Why use NAB disc in butterfly valves for seawater?

NAB (Nickel Aluminium Bronze) disc provides excellent seawater corrosion resistance while the EPDM rubber liner protects the ductile iron body. This combination offers: (1) Corrosion-resistant disc in contact with seawater, (2) Cost-effective ductile iron body protected by liner, (3) Tight bubble-tight shut-off from resilient EPDM seat, (4) Anti-biofouling properties of NAB, (5) Long service life in marine environments.

What is API 609 butterfly valve?

API 609 is the American Petroleum Institute standard for butterfly valves. It covers lug-type and wafer-type butterfly valves for general and high-performance applications. API 609 Category A covers general purpose valves with resilient seats, while Category B covers high-performance valves with metal seats. For seawater service, Category A with EPDM liner is commonly used.

What is EPDM liner in butterfly valves?

EPDM (Ethylene Propylene Diene Monomer) is a synthetic rubber used as liner/seat in butterfly valves. EPDM provides: (1) Excellent resistance to water, steam, and ozone, (2) Good chemical resistance to dilute acids and alkalis, (3) Temperature range -40°C to +120°C, (4) Bubble-tight shut-off, (5) Suitable for seawater and potable water. EPDM is preferred over NBR for water applications.

What sizes are NAB butterfly valves available in?

NAB disc butterfly valves are available from 3 inch (DN80) to 24 inch (DN600). Common sizes for seawater service include 3", 6", and 8". Smaller sizes (up to 6") are lever operated, larger sizes are gear operated. Wafer and lug body styles available. Pressure rating PN10/PN16 or Class 150.