O-Rings for Marine Applications
Seawater-resistant O-ring sealing for marine equipment, offshore systems and subsea applications.
Overview
Marine environments present a combination of challenges: continuous seawater exposure, UV radiation, ozone from sea air, biofouling and — in subsea applications — high hydrostatic pressure at depth. O-rings for marine service must resist corrosion, maintain elasticity after years of saltwater immersion and withstand ozone degradation in deck-level applications.
The selection of O-ring material for marine service depends primarily on the fluid being sealed (seawater, fuel, hydraulic oil or pneumatic) and the exposure conditions (deck-level/UV exposure vs below waterline vs subsea).
Recommended Materials
NBR 70 Shore A
Fuel system seals, mineral oil hydraulic seals on marine vessels, general mechanical sealing
Temp: -40°C to +120°C
Note: Good seawater resistance but poor UV/ozone resistance — not for deck-exposed positions
EPDM 70 Shore A
Seawater-exposed positions, deck fittings, water systems, HVAC, positions with UV and ozone exposure
Temp: -50°C to +150°C
Note: Excellent seawater, UV and ozone resistance. Not for oil or fuel.
FKM 75 Shore A
Subsea hydraulic systems, offshore wellhead equipment, sour service offshore, high-performance marine engine seals
Temp: -20°C to +200°C
Note: For demanding offshore and subsea applications requiring chemical and temperature resistance
VMQ (Silicone)
Electrical cable entry seals, navigation equipment seals, marine electronics waterproofing
Temp: -60°C to +230°C
Note: UV stable and flexible — suitable for outdoor equipment sealing
Typical Applications
- Seawater pump seals
- Hydraulic steering seals
- Propeller shaft seals
- Engine room seals
- Ballast system seals
- Bilge pump seals
- Fuel transfer seals
- Submersible seals
Relevant Standards
Frequently Asked Questions - Marine
What O-ring material best resists seawater?
NBR, EPDM, FKM and Silicone all have good seawater resistance. For deck-level applications with UV and ozone exposure, EPDM or Silicone are preferred as NBR degrades under ozone. For subsea hydraulic systems, FKM is standard for its broad performance envelope.
What O-rings are used in subsea ROV and hydraulic systems?
Subsea hydraulic systems typically use FKM O-rings rated for the specific hydraulic fluid. For deep-water applications (high hydrostatic pressure), explosive decompression resistance is important — specify ED-resistant FKM compounds for gas-containing or high-pressure applications.
Can standard O-rings be used in saltwater?
Yes. Seawater does not attack common elastomers. The primary concerns for marine O-rings are UV and ozone degradation (above waterline) and the fluid being sealed (oil vs water vs fuel). Select material based on the fluid and UV exposure, not the salt content.
What O-ring for marine electrical cable glands?
EPDM or Silicone are preferred for cable gland O-rings exposed to UV and weather. Both are UV stable and maintain flexibility in outdoor conditions. NBR is not recommended due to ozone cracking. IP-rated cable glands typically specify EPDM or Silicone.