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Application Guide

Valves for Shipbuilding & Marine Repair

Marine valve requirements differ fundamentally from industrial process applications — seawater corrosion resistance is the primary design driver, DNV GL or Lloyd's Register type approval is mandatory for safety-critical systems, and the valve must be maintainable at sea in confined spaces. Vajra Industrial Solutions supplies DNV GL and Lloyd's Register type-approved bronze (CC480K gunmetal), super duplex stainless steel, and Ni-Al-Bronze valves for sea chest, ballast water treatment, bilge, main engine cooling, fuel oil transfer, and sanitary systems.

DNV GL Rules (Ship Valves)Lloyd's Register RulesABS RulesIACS UR L5 (Sea Valves)SOLAS (Safety)IMO BWM Convention (Ballast)ISO 5208NES 747 (Royal Navy)
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Recommended Valve Types for Shipbuilding & Marine Repair

Bronze / Gunmetal Gate Valve

PN 10 / PN 16 / PN 25

Why: Sea chest, ballast, bilge, and low-pressure sea water systems — CC480K gunmetal (DIN 1705) resists seawater dezincification; PN 10–40

Materials: CC480K gunmetal (85Cu-5Sn-5Zn-5Pb) or Ni-Al-Bronze (CA104); bronze disc; PTFE or graphite packing

Standards: DNV GL, Lloyd's Register Type Approval, ISO 5208, BS 5154

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Duplex SS Ball Valve

Class 150 / 300

Why: Ballast water treatment — chemical dosing, electrolytic systems; Super Duplex 2507 for highest corrosion resistance in seawater

Materials: A890 Grade 5A Super Duplex 2507; PTFE seats; fire-safe optional

Standards: API 6D, DNV GL, IMO BWM Convention

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Bronze Butterfly Valve

PN 10 / PN 16

Why: Large-bore seawater cooling and ballast — lightweight, easy operation in confined spaces; DN100–DN600

Materials: CC480K or Ni-Al-Bronze disc; natural rubber or EPDM seat; bronze body

Standards: EN 593, DNV GL, Lloyd's Register

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Check Valve (Marine)

PN 10 / PN 16

Why: Sea suction back-flow prevention, bilge pump discharge, fuel oil anti-syphon

Materials: CC480K gunmetal body and disc; rubber seat; SS316 hinge pin

Standards: DNV GL, Lloyd's Register, BS 5153

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Critical Requirements

DNV GL or Lloyd's Register type approval — mandatory for sea valves, sea chest valves, and essential service valves per IACS Unified Requirement L5
Dezincification resistance — standard brass (70Cu-30Zn) dezincifies in seawater; use CC480K gunmetal, Ni-Al-Bronze, or Super Duplex 2507
Cathodic protection compatibility — all hull valves below waterline must be compatible with ship's CP system; sacrificial zinc anodes on bronze sea chests
IACS UR L5 — all sea valves must withstand 1.5× working pressure test; valve body must not be thinner than class society minimum wall thickness
IMO BWM Convention — ballast water treatment system valves must comply with ballast water management plan; USCG type approval for US-calling vessels
Space constraints — marine valves must be compact; flanged wafer butterfly valves preferred where headroom is limited

Fluid & Service Challenges

⚠Seawater (Cl⁻ 19,000 ppm, biological fouling, seasonal temperature variation 5–35°C) — most corrosive common environment; dezincification of brass; pitting of standard SS304
⚠Fuel oil (IFO 380, MDO, MGO) — heavy fuel oil requires heat tracing; valve must withstand marine diesel at 60–100°C
⚠Bilge water — oily water mixture; pump in confined hull space; SS316 or bronze for corrosion resistance
⚠Ballast water — untreated seawater, potentially with invasive species; BWM treatment (UV + filtration or electrolytic) requires SS316L or Super Duplex valves
⚠Fresh water cooling — demineralised water in closed cooling circuits; standard CS or SS316 acceptable

Material Selection Guidance

Sea chest and seawater below waterline: Ni-Al-Bronze CA104 (UNS C95800) or CC480K gunmetal — both have excellent dezincification and biofouling resistance with DNV/LR type approval. Topside seawater (splash zone): Super Duplex 2507. Ballast water treatment: Super Duplex 2507 for chemical injection; SS316L for UV chamber valves. Fuel oil: WCB with SS316 trim acceptable; rubber seats must be rated for distillate fuel. Freshwater systems: WCB or SS316L.

Typical Service Points

Sea chest (kingstones) — gunmetal or Ni-Al-Bronze gate valves (IACS L5, DNV/LR type approved)
Main engine cooling seawater — bronze butterfly valves (DN100–DN400, PN 10)
Ballast water — SS316L or Super Duplex 2507 butterfly and gate valves (IMO BWM compliant)
Fuel oil transfer and purifier — WCB gate valves with SS316 trim (fuel oil, 60–80°C)
Bilge system — bronze or SS316 gate and check valves (oily bilge water)
Sanitary (grey/black water) — PVC or SS316L ball valves (domestic drain and sewage)

FAQ — Valve Selection for Shipbuilding & Marine Repair

What is DNV GL type approval and is it mandatory for all ship valves?
DNV GL (now DNV) type approval is a certification process where a classification society tests and approves a product design for use on vessels under their class rules. Not all ship valves require type approval — it is mandatory for safety-critical systems: sea valves, sea chests, and valves in essential services (fire, bilge, ballast, fuel oil) per IACS Unified Requirement L5. Internal service valves (fresh water piping, sanitary) may use standard industrial valves. Lloyd's Register, ABS, Bureau Veritas, and ClassNK have equivalent type approval processes.
Why is gunmetal (CC480K) specified for sea chest valves instead of bronze or brass?
Standard naval brass (60Cu-40Zn) dezincifies in seawater — the zinc leaches out, leaving a porous copper sponge with no structural strength. Gunmetal (CC480K: 85Cu-5Sn-5Zn-5Pb) has only 5% zinc and high tin content, making it highly resistant to dezincification. Ni-Al-Bronze (CA104: 9%Al, 4%Ni, 4%Fe, balance Cu) is even more corrosion-resistant and is the preferred material for sea chest boxes and kingstones. SS316 is not suitable for submerged seawater service due to crevice corrosion risk; Super Duplex 2507 is the stainless option if required.

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Shipbuilding & Marine Repair

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Key Standards

DNV GL Rules (Ship Valves)
Lloyd's Register Rules
ABS Rules
IACS UR L5 (Sea Valves)
SOLAS (Safety)
IMO BWM Convention (Ballast)
ISO 5208
NES 747 (Royal Navy)

Products for This Application

Ball ValvesGate ValvesButterfly ValvesCheck Valves

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