Check Valves for Marine & Offshore

Marine and offshore check valves must resist seawater corrosion, biofouling, and the vibration and shock loads of ship and offshore platform environments. Vajra Industrial Solutions supplies swing, dual-plate, and lift-type check valves in naval brass (C83600), gunmetal (LCC), duplex stainless (A890 2205), and super duplex (A890 2507) for ballast water, fire main, bilge, seawater cooling, and cargo transfer service - with classification society approval from DNV, Lloyd's Register, Bureau Veritas, and ABS.

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What check valves does the Marine & Offshore industry use?

Marine and offshore check valves must resist seawater corrosion, biofouling, and the vibration and shock loads of ship and offshore platform environments.

Key Applications - Check Valves in Marine & Offshore

Seawater Cooling Systems

Check valves for seawater cooling water loops - sea chest to heat exchangers and overboard discharge. Naval brass (C83600) or gunmetal (LCC) for low-pressure seawater (PN 6–10). Duplex SS 316 for higher pressure and longer service life. Swing check or dual-plate configuration. DNV or Lloyd's Register type approval required for class vessels.

DN50–DN300, PN 6–25, Naval Brass C83600 / Gunmetal / A890 Duplex, DNV/LR

Fire Main and Deluge Systems

Non-return (check) valves on fire pump discharge to prevent back-flow when multiple pumps are online. Must be fail-safe - no check valve should stick open or closed. Dual-plate spring-assisted check valves are preferred for fast response. All-bronze or SS 316 to resist seawater corrosion in saltwater fire main.

DN50–DN200, PN 16–25, Bronze / SS 316, SOLAS compliant, IMO

Ballast Water Treatment

Check valves on ballast pumps, treatment system by-pass, and overboard discharge lines. Must resist seawater and ballast water chemical treatment (hypochlorite, electrolysis). Duplex 2205 or super duplex 2507 for long-term seawater and chlorine resistance. IMO-compliant ballast water management systems require type-approved valves.

DN100–DN600, PN 10–16, A890 Duplex 2205 / 2507, IMO BWMC, DNV

Bilge and Ballast Pump Discharge

Swing or dual-plate check valves on bilge pump discharge to prevent backflow into bilge. Bilge check valves must be accessible for maintenance at sea and suitable for oily water service. Cast iron with SS disc for non-seawater bilge; bronze for seawater-exposed bilge system. SOLAS and MARPOL compliance for oily water system.

DN50–DN150, PN 6–10, Cast Iron / Bronze, SOLAS / MARPOL compliant

Offshore Platform - Firewater and Topside

Dual-plate check valves for offshore platform firewater ring mains and deluge system pump packages. Compact, lightweight design critical for offshore weight budgets. API 6D certified for production process check valves on topsides. NORSOK M-630 material compliance for Norwegian Continental Shelf (NCS) service.

DN50–DN300, Class 150–600, A890 Duplex / CF8M, API 6D, NORSOK M-630, DNV

Required Certifications

DNV (Det Norske Veritas) Type Approval - Norwegian and international shippingLloyd's Register (LR) Type Approval - UK and international shippingBureau Veritas (BV) Type Approval - French and international shippingABS (American Bureau of Shipping) - US flag and internationalNORSOK M-630 - Material requirements for Norwegian North Sea offshoreSOLAS (Safety of Life at Sea) - Fire main and life safety systemsIMO BWMC (Ballast Water Management Convention) - Ballast systemsAPI 6D - Topside process check valves on offshore platforms

Recommended Materials

Naval Brass C83600 - seawater service to 50°C, low pressure (PN 6–16)

Gunmetal (ASTM A494 Grade CZ100) - seawater and brine, slightly higher strength

A351 CF8M (SS 316 cast) - seawater with moderate chloride, higher pressure

A890 Grade 4A (Duplex 2205) - long-term seawater service, crevice corrosion resistance

A890 Grade 6A (Super Duplex 2507) - highly aggressive seawater (subsea, deep sea)

Inconel 625 (N06625) - extreme seawater and high-temperature offshore service

Selection Factors

Material: Select based on chloride content, temperature, and flow velocity - seawater at high velocity causes erosion-corrosion in less noble alloys

Classification Society: Confirm which class society the vessel or installation is registered with - type approval must match

Check type: Dual-plate (compact, lightweight - preferred offshore) vs swing (low Δp - preferred for large bore ship cooling water)

Pressure rating: PN 6–10 for most ship systems; PN 16–25 for firewater; Class 150–600 for offshore topsides

SOLAS: Fire main check valves must be non-return and accessible for maintenance without shutting the ring main

Weight: Offshore - duplex SS reduces weight vs SS 316L at same corrosion resistance; naval brass lightest at low pressure

Technical FAQs

Which check valve material is best for seawater service?

For low-pressure, lower-temperature seawater (ship cooling water, fire main): Naval brass (C83600) or gunmetal provides the best cost-to-corrosion-resistance ratio. For moderate-pressure seawater with higher velocity or temperature: SS 316L or Duplex 2205. For long-term offshore subsea or high-chloride seawater: Super Duplex 2507 or Inconel 625. The critical failure mode in seawater is crevice corrosion - all seats, seat rings, and body interior surfaces must be in corrosion-resistant material, not just the body exterior.

What is DNV type approval for a check valve?

DNV (now DNV GL) type approval certifies that a valve design has been tested and evaluated against DNV's rules for classification of ships. Type-approved valves have a DNV certificate number that a ship owner or shipyard can reference. For vessel class compliance, check valves on DNV-classed vessels must use DNV-type-approved valves for critical systems (fire main, seawater cooling, bilge). Vajra supplies DNV, LR, BV, and ABS type-approved check valves for marine applications.