High Seas Yacht Service » Shaft Seal Systems

PSS Shaft Seals

Chris — Mon, 28 Feb 2011 16:04:40 +0000

PSS Seal Refreshed and Ready to go

PSS Seals are found on many of the pleasure yachts. The PSS Seal system is a “face” seal that relies on the pressure between a carbon face stationary to the stern tube and a stainless steel face on the ring installed on the shaft.

Maintenance on these seals is pretty straightforward. If the shaft is out we will usually reface the stainless steel ring in our machine shop. A smooth, flat face, free of debris, is required for a solid seal. The carbon face is inspected for chips or cracks. If cracked they must be replaced. Finally, we inspect the bellow hose for cracks or other signs of wear. The bellow hose acts as a compression spring to keep the carbon against the stainless steel. If the bellow hose is aging, it will lose the spring effect and not apply enough tension. This is sometimes noticed if the seal leaks when throttling up the engines. Depending on the engine mounts, the engine will shift forward under prop load which eases the pressure between the stainless steel and the carbon. If the bellows is not compensating then leaking will occur. PSS recommends replacing the bellow hose every seven years.

Finally, during installation the stainless steel ring is compressed a distance, per the PSS manual (it varies with shaft diameter). Notice in the picture the sharpie mark on the shaft showing the position of the ring in the neutral state prior to compressing the bellows.

PSS Seal are very effective and easy to maintain. Give us a call if you have any questions or concerns with your shaft seal system.

Fluiten Shaft Seal System – Check the Wear

Chris — Mon, 02 Aug 2010 18:48:17 +0000

A Fluiten shaft seal in two halves on the bench

We have just finished a complete shaft system on an 87′ Ferretti that had a unique shaft seal system from Italian manufacturer Fluiten. The Fluiten shaft seals are part of the “face seal” family. There are two main parts to any face seal system; the stationary body (right side of pictures) that is bolted to the stern tube and the “rotary” piece (left side) that is attached to the shaft and rotates. The Fluiten relies on a pre-loaded spring in the stationary unit to keep constant pressure between the halves preventing the sea water from coming in.

During shaft maintenance all components need to be inspected. With Fluiten shaft seals there is a small phenolic ring that is allowed to wear with time similar to a brake pad. This version of the seal has the wearable ring on the rotating half. However, other models from Fluiten have the wear ring on the stationary half.

The ring specification is 2 mm minimum before replacement.

Measure the wearable phenolic ring for proper thickness

Make sure your service provider is checking all of the manufacturer’s specifications. Not all companies will go to this length. Reassembling the boat with a wear item that is past its life is a disservice to you and potentially dangerous to your boating experience.

Replacing Kobelco-Eagle Inflatable Shaft Seal

Chris — Mon, 02 Aug 2010 17:00:00 +0000

Replacement Inflatable Shaft Seal on a Kobelso Eagle System

We see all types of shaft seal systems working on various mega-yachts including this Kobelco Eagle product out of a 130′ Alloy. The vessel is in the yard for updating in many areas and we were given the opportunity to pull the shafts to check for engine and strut alignments.

The Kobelco Eagle shaft seal system includes an inflatable seal in the body. This seal operates similar to the emergency shaft seal bladder system found in Wartsila seals. The prior post also included a video showing how the system works.

If there is a need to change the shaft lip seal, or another emergency occurs, air is injected into the port and the rubber element acts like a bicycle tire inflating around the shaft and sealing off most of the water. The system is designed for emergencies only and the shaft cannot rotate while the seal is inflated.

In this picture you can see the old inflatable seal with a brass air tube removed from the seal housing. The replacement seal is already in place and the new tube is coming through the housing in the top of the picture.

Stay tuned for an updated post on the Kobelco-Eagle replacement lip seals.

Emergency Shaft Seal Bladder Systems

Chris — Mon, 15 Feb 2010 16:46:21 +0000

Wartsila Seal Bladder System Tested on Shaft

Many of the large “Class” vessels have seal systems such as Wartsila or Duramax that have an emergency inflatable bladder. The system is basically an inflatable bladder (like a bicycle tire tube but far more durable) that is housed just aft of the ships seal system. If there is damage to the seal, air pressure is applied from a ship’s compressor or simple bicycle pump to inflate the bladder. The air press causes the bladder to tighten around the shaft and slow the leak to a small drip. If the system is operating properly it should maintain air pressure for hours. However, the systems are not designed to withstand the friction of the shaft turning. Usually the vessel has a shaft brake system to allow movement with one engine without the “down” shaft from turning.

We have just completed a 5 year ABS inspection on the running gear on a 121′ Heesen. We removed the Wartsila seals and tested the inflatable bladder at the shop. The picture below shows the set-up on the shaft (145 mm shafts). The video above shows the inflation of the bladder using a simple bicycle pump. It is a good thing we tested the bladder. We found the fittings on one side to be loose and would not hold air pressure for more than a few seconds.

Confidence at sea comes from careful preparation and testing of all the ship’s systems.

Another Wartsila Shaft Seal Adjustment Tool for ManeBar Seals

Chris — Sat, 06 Feb 2010 15:59:11 +0000

: Wartsila EL Shaft Seal with Compression Tool

Wartsila Shaft Seals are often found on larger Class Yachts. The principal of the system is based on a face seal created by a phenolic ring riding on a graphite base. The phenolic ring does wear with time and use similar to a brake pad.

This seal is out of a 121′ Heesen that is going through a normal 5 year ABS inspection. The running gear is completely removed, cutlass bearings replaced, engine and strut alignment checked, shafts, props and couplers are checked in the machine shop. Finally, the shaft seal system is removed for inspection. This particular seal is the EL ManeBar model. All the components were checked against the manufacturer’s specifications and found to still be acceptable to reinstall in the vessel.

Once the shafts are installed the system must be adjusted or compressed to tolerance in order to create a dry shaft seal system. I wrote about a tool for a different Wartsila Seal model a few months ago. Wartsila has designed their seals with a special installation tool in order to get an even and controlled compression. For the EL Shaft Seal the tool is comprised of threaded rod, a “hook block”, nuts and washers. Each vessel with Wartsila Shaft Seals should have the tool on board. Unfortunately, since the tool is only used once every few (or five) years it is often hard to find. In this case, our machine shop fabricate this tool with Wartsila’s support and permission. A special thanks to Steve and Brian at Wartsila for their excellent customer support.

Shaft Cladding to Repair Crevice Corrosion

Chris — Wed, 27 Jan 2010 11:23:23 +0000

: Cladding or Weld-over on Aquamet shafts

From time-to-time we come across shafts that have suffered from a bad case of crevice corrosion. Crevice corrosion, unlike galvanic corrosion, comes from stagnant water that changes chemical composition with time. We find crevice corrosion on shafts in the seal area, bearing area and inside the stern tube. Usually the crevice corrosion is not found on the part of the shaft exposed under the boat since tidal flow keeps the water moving and “fresh”. Wiki has more explanation here.

Crevice corrosion on the shaft in non-bearing or seal areas are OK and usually left alone. However, if the corrosion is in a cutlass bearing location or seal/packing area it must be repaired. The pitting will cut up a new cutlass bearing in a short time and will not let a shaft seal properly seat and keep dry.

To repair the area, as we are doing on this 87′ Oceanfast, requires machining down the shaft (as seen to the left of the machinist shoulder) and then filling in the area with a welding bead. This is called a weld-over or cladding (more pics here). In this picture there were two different areas requiring repair. The area pictured is right under a half cutlass bearing. The welded area is a smaller section where the Tides seal will run.

Once the weld is complete the shaft will require straightening (600 degree welding will bend the shaft regardless of precautions), then a final machine and polishing. I challenge someone to come to the shop and find the weld when finished – it blends in that well.

Wartsila Shaft Seals – Need the Right Tool for the Job

Chris — Wed, 04 Nov 2009 00:43:48 +0000

Wartsila Seals are commonly found on larger “class” (ABS, Lloyds,…) vessels. Wartsila seals rely on the proper compression to hold the two faces together. Wartsila designed a specific “tool” that bolts onto the seal flange in four places and compresses the stationary half to the right dimension while remaining perfectly square to the shaft. If the seal is not compressed properly it will leak. With the tools holding the seal in the right location it is simple to move the rotating half into position.

The tool comes with each of the Wartsila seals and needs to be kept on the boat in a safe location. The seals only require adjusting after the shafts have been moved during a haul out and running gear job. As such, the tool is only needed once every few years. As you can imagine, that makes it difficult to find when it is needed.

If you have a vessel with a Wartsila Seal look now for the tool. If you do not have one contact Wartsila or send me an email and I will coordinate getting one shipped out to you.

Shaft Crevice Corrosion – Not Good for Tide Lip Seals

Chris — Sat, 17 Oct 2009 01:15:37 +0000

: Crevice Corrosion on Shafts will Destroy a Lip Seal System

While working on a complete running gear service for a new owner on a 103′ Cheoy Lee we came across a few items that needed repair. One item was extensive crevice corrosion on the stainless steel propeller shafts. Crevice corrosion occurs when a vessel sits too long in still water. It is most often found in the cutlass bearing, seal or exit tube area where water is not flowing. Crevice corrosion is most problematic in the Tide Seal (Lipseal) area since the seal requires a tight fit on a smooth turning shaft surface. The pitting in the corroded area immediately leaks and damages the seal.

Fortunately, a crevice corrosion repair is possible using shaft weld-over techniques. Weld-overs require specific training and skills. The final product when done correctly is a clean, perfect shaft surface. Compared to replacing a shaft this is a very economical repair.

A weld-over generates a lot of heat and tends to bend the shaft. This means a shaft straightening is almost always required. Of course, with the shafts out of the boat a check with the optical scope on the strut alignments and an overall engine alignment check is always part of the plan.

Tides Lip Seals – Don’t Torque!

Chris — Sat, 17 Oct 2009 00:52:25 +0000

: Too Much Torque on this Tide Seal Housing – Major Failure

Recently we had an 80′ Lazarra come out for basic bottom and propeller work. A courtesy inspection of all running gear exposed a major problem for this new owner and crew. The Tides Seals – Sure Seal (dripless) system was cracked completely through. The outer ring and collar are solid pieces that should not show signs of cracks or splits. Unfortunately, the repair requires removal of the coupler which is the first step to removing all of the running gear.

Once out of the boat the problem was evident – half of the screws that hold the collar were torqued down and could not be removed without spinning the backing nuts in the plastic housing. We speculate that a prior crew tried to slow a leak by torquing the screws. This, of course, did not slow the leak and just lead to cracking the plastic.

Fortunately, Tides has collar and ring replacements for a reasonable cost and the main housing was saved and reused.

Prior to putting the shafts back in we checked the alignment with the optical scope and made some small adjustments with a minor engine alignment. At High Seas we put the optical scope on EVERY project that involves removing the shafts. This is the perfect time to check alignments. Don’t waste your money by removing running gear without a full alignment check every time.