Marine propeller shaft seal

01

Choose the seal type, position and split design

Wärtsilä's Sternguard OLS is an oil-lubricated lip seal in outboard (OLS3-P, OLS4-P) and inboard (OLS2-P) versions for merchant, cruise and ferry, offshore, inland waterway vessels and thrusters. Its seal rings are Viton rubber running on a wear-resistant liner that protects the propeller shaft; it is supplied partially split, or fully split so it can be retrofitted without removing shaft-line components. [1]

For tugs, trawlers and coasters, Wärtsilä's Sternguard E Series uses flexible elastomer bodies with integral face inserts that accommodate vibration and axial and radial movement, in a non-split outboard (EK), non-split inboard (EJ) and partially split inboard (EL) version, with oil or grease, and meets classification society requirements for wear and corrosion protection in silty or abrasive water. [2]

Its Sternguard IWSS is a face seal in which pressure springs hold the lapped surfaces together while allowing axial movement; fully split versions can be overhauled in the water without dry-docking, shaft withdrawal or draining stern tube oil. [3]

Give the supplier the vessel type and class society, shaft and liner diameter, shaft speed, draught at the seal (seawater head), stern tube lubricant (mineral oil or EAL), seal type and position (outboard, inboard), split requirement, operating waters (clean, silty, sandy), air or fresh-water supply available, and the planned docking and service interval.

02

Set pollution protection, abrasion protection and service interval

Wärtsilä's Airguard is a lip seal that feeds compressed air into the void between seal rings, automatically kept above seawater pressure so a small amount of air escapes outboard; any seawater or oil entering the void drains to an inboard collection system, preventing oil leaking out or seawater entering the stern tube. Wärtsilä says this removes the oil-to-sea interface, so the seal can run on mineral oil in accordance with the 2013 Vessel General Permit. [5]

For abrasive or polluted waters, Wärtsilä's Sandguard adds a face seal and protection ring with fresh water purged into the aft seal chamber to keep muddy or sandy water out, combined with air, automatic drain collection and automatic pressure control. [4] Its IWSS accepts environmentally acceptable lubricants (EALs) and mineral oil and is stated to comply with the 2013 US EPA Vessel General Permit when used with EALs. [3]

Wärtsilä offers a Bio Seal ring for OLS seals with a service interval of at least 5 years when used with EALs, against a recommended change every 2.5 years for conventional seal rings. [1]

Editorial calculation: a 5-year interval is twice the 2.5-year interval, so over 10 years the ring set would be changed about twice instead of four times. [1]

03

Shaft size, speed, class approval and in-water service: questions for a seal maker

Ask any supplier for seal type and model for your shaft and liner diameter, maximum shaft speed and seawater head, seal ring and liner materials, split options, lubricant compatibility (mineral oil, EAL), air or water supply requirements, class approval, service interval and spare kits, and in-water service capability.

04

Seal rings, liner, face springs, air void, drain tank and fresh-water purge

The rows draw on four different Wärtsilä seals: Viton rings and the liner from Sternguard OLS, spring-loaded faces from IWSS and the E Series, the air void and inboard drain from Airguard, and the fresh-water purge from Sandguard. [1] [3] [2] [5] [4]

05

Shaft diameter, speed, seawater head, leakage and seal materials for a stern tube seal

Wärtsilä's product pages give no numeric values for shaft diameter range, speed, temperature, face hardness or weight; take these from the maker's drawing for your shaft line.

06

Send the vessel, shaft and lubricant data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Vessel: [type; class society]
Shaft: [diameter; liner; rpm]
Position: [outboard; inboard]
Type: [lip; face; split]
Lubricant: [mineral oil; EAL]
Waters: [clean; silty; sandy]
Protection: [air; fresh water; drain]
Service: [docking interval; in-water service]

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