any hydraulics engineers on here?

Birdseye

Birdseye

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got a small leak from my hydraulic pilot ram ( robertson / simrad HLD1500 see http://www.cactusnav.com/simrad-hld350-hydraulic-linear-drive-p-1160.html ) from the end of the ram with the rose joint for the steering. I need to replace the shaft seal but whilst I know what I am looking at with the typical crankshaft oil seal I dont with a hydraulic one. So I dont know how to get the old seal out.

It looks to me as if the seal goes in from the outside which is a puzzle because I would have thought hydraulic pressure would pop it out again. But there is no way that it goes in from the inside.

And it looks as if its in two parts or has a central metal ring. Or is it the case that the seal holder is macined with a recess and the seal is flexible enough to be pushed into that recess?
 
awol said:
You don't want an engineer, you need a mechanic.
Click to expand...

or perhaps a fitter or service technician :)

have you asked the manufacturer if they do a service kit and whether they have drawings to explain the detail or how to change the seals. That's what I would do.

It may not be designed to be serviced. Its the throw away economy - generates work for manufacturers - don't start me.
 
Ok... Lets try for an informative answer...
Writing as an engineer who has quite a bit to do with hydraulics; from the link it seems as though the cylinder end is held onto the cylinder by 4 tie bolts/studs. If so, the rod seal will fit from inside the end cap and is likely to be a simple lip seal.
I'll guess that it's double acting piston with a common rod sticking out of each end of the cylinder, so if you do decide to open it up to replace one seal, I would advise replacing both rod seals, the piston seal ring, and the cylinder to end cover gaskets.
There's nothing complicated, just treat cleanliness as coming above godliness when working on hydraulics!

Paul

I didn't see Euan's post before I posted mine, but I really hope that a £1091 ram isn't a throwaway component!
 
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I have a very similar piston. It is fairly simple to replace it. You will have to remove the end and the seal sits in a groove in the end casting. You might want to change the other seals when you do this. I'd remove the piston complete and do the job on the bench.

Do make sure that you have the old seal/s with you when you get replacements .... and don't be fobbed off with 'don't worry it will work!'. If it doesn't look like a similar seal in size, design, and material it may not be suitable!

I believe every boat with a hydraulic steering system on board should have a member of crew capable of servicing it. It doesn't take much provided you know how to use a spanner and can bleed the system ..... oh, and mop up any leaks .... All part of the learning process!
 
Thanks. It does look as if the seal is in a recess machined inside the end cap and the plastic seal like thing on the outside of the end cap likely is a dust seal. If I peer into the end cap there is a definite ring of metal between the two plastics. I was not sure initially that this wasnt part of a pne piece seal though I couldnt see how this would work and not be blasted out of the end of the end cap by hydraulic pressure.

So I guess its a matter of getting some hooked implement into the end cap to hook out the seal. I believe is a U shaped cross section.

Bit surprised that there isnt someone on here whose business is hydraulics.
 
I didn't look at the link so didnt suss out the price. I have a vetus ram in my boat and separate hydraulic autopilot pump but had slippage around the piston when I had higher loads the wheel kept turning but the boat wouldn't luff up.

Vetus couldn't supply spares as it was from 1972 but were very helpful. Not being able to get the right seals I bit the bullet and replaced it. It was between 2&300 quid I think.

Vetus suggested service kits were available for more modern rams hence my suggestion to ask the manufacturer!

It wasn't intended to be flippant!
 
Yes, a hook should work, or even a small flat screwdriver - spear the seal and pull it out without damaging the metal faces.

Go to a hydraulics seal supplier. I'd bet that seals will be available however old you unit is as they would have used standard parts. Expecting Vetus or any other manufacturer to keep sets of seals in stock for the older models is asking a lot. A typical end seal should cost about £10 if memory serves ....
 
A small flat screwdriver is all that's needed to hook it out

As others have said take your old seals to buy new ones - but I just did all the seals on two Vetus rams for about £12 in total from an industrial seal and bearing shop whilst Vetus wanted almost £50 each ram for the official seal kit and a seal is a seal is a seal - so whatever Simrad might charge you I bet its too much...
 
Replacing the seals is relatively easy. I replaced all the seals on a similar robertson unit recently. Take the unit to a CLEAN DRY environment. Dissassemble completely and examine. Once apart the removal of the end seals will be obvious. Measure all dimensions and order new seals from http://www.fpe-ltd.co.uk/ rather than robertson and replace carefully ensuring you press them in place without damaging them. Reassemble. Simples!
 
Good advice above...maybe I'll add that as people like fpe are cheap enough, it's worth getting a spare set while you're at it. I've done loads, and nothing's more irritating than inadvertently catching a new seal and having to waste time getting another. Also, do check your piston for any marks, rust spots etc that might damage a new seal...often they can be polished out.
 
I overhauled my HLD 2000 mk2 8 years ago when I had the exact same problem as you, a leak from the ram.
I think that you need some experience of meticulous work in a clean environment but if you can do that there should be no problems.
I will only be able to relay the outline of the service as it has been a long time.
The workshop manual and parts already provided by Alex is a huge help. Always the illustrated parts breakdown is the invaluable part.
The first and most important thing is to buy the Simrad overhaul kit as it is all very well buying pressure seals from a cheaper seal supplier but he will not have the other seals like the cylinder gasket, and the Teflon alignment seal which you are bound to disturb in disassembly. This kit cost me about £45 (from Simrad in Fareham, I think they have moved now )and was a complete set for the whole unit. You will not need the reservoir and pump seals for the repair you are making but like me you will keep them and they will be in the spares box.
The first thing to do is slacken the lock nut (11) and unscrew the ball joint (12) be very careful to count the number of half turns of the ball joint before it falls away. You will need to refit it in the same position.
When I removed the 4 nuts (17) and pulled outer seal housing, the cylinder (6) came away with it. This is no problem if you have the gasket (4).
The seal which you refer to is in fact a protector which they call a cleaner (10) its function is to protect the pressure seal (9) which is retained by the housing. This (9) is the leaking seal. Inboard of this seal assembly is a Teflon bearing bush (8) whose job is to control any radial loads and maintain a smooth and parallel piston movement in and out. Wear in this bush may be the cause of seal failure. This bush is part of the kit and is easy to fit.
When disassembled I noticed a “blueing” of the ram in the area of the seal contact. I polished this out with the finest abrasive readily available, Brasso. It took some time but after about 30 mins polishing with a soft cloth I managed to remove the blue. If you have to do this I recommend do not use any abrasive paper.
With everything meticulously cleaned and wetted with hydraulic fluid reassemble the unit.
Please don’t use any screwdrivers or blunt instruments to scratch the ram face.
Mine has given 8 years of leak free service since overhaul.
 
njthake said:
I overhauled my HLD 2000 mk2 8 years ago when I had the exact same problem as you, a leak from the ram.
I think that you need some experience of meticulous work in a clean environment but if you can do that there should be no problems.
I will only be able to relay the outline of the service as it has been a long time.
The workshop manual and parts already provided by Alex is a huge help. Always the illustrated parts breakdown is the invaluable part.
The first and most important thing is to buy the Simrad overhaul kit as it is all very well buying pressure seals from a cheaper seal supplier but he will not have the other seals like the cylinder gasket, and the Teflon alignment seal which you are bound to disturb in disassembly. This kit cost me about £45 (from Simrad in Fareham, I think they have moved now )and was a complete set for the whole unit. You will not need the reservoir and pump seals for the repair you are making but like me you will keep them and they will be in the spares box.
The first thing to do is slacken the lock nut (11) and unscrew the ball joint (12) be very careful to count the number of half turns of the ball joint before it falls away. You will need to refit it in the same position.
When I removed the 4 nuts (17) and pulled outer seal housing, the cylinder (6) came away with it. This is no problem if you have the gasket (4).
The seal which you refer to is in fact a protector which they call a cleaner (10) its function is to protect the pressure seal (9) which is retained by the housing. This (9) is the leaking seal. Inboard of this seal assembly is a Teflon bearing bush (8) whose job is to control any radial loads and maintain a smooth and parallel piston movement in and out. Wear in this bush may be the cause of seal failure. This bush is part of the kit and is easy to fit.
When disassembled I noticed a “blueing” of the ram in the area of the seal contact. I polished this out with the finest abrasive readily available, Brasso. It took some time but after about 30 mins polishing with a soft cloth I managed to remove the blue. If you have to do this I recommend do not use any abrasive paper.
With everything meticulously cleaned and wetted with hydraulic fluid reassemble the unit.
Please don’t use any screwdrivers or blunt instruments to scratch the ram face.
Mine has given 8 years of leak free service since overhaul.
Click to expand...

A good useful reply...and a good point about the spares kit. At the very least, it would be a bit bothersome to have the ram apart and then decide the bush is best replaced. Then to have to measure the bush material width and thickness and get hold of some spiral bearing material and cut your own with an accurate 45 deg joint. In a previous life I had stocks of the material...but this reply which draws attention to the bush and possible other parts does show the advantages of the kit.
 
I have a Lecroble Schmitt Hydraulic Ram L2 and was looking for backup spare seals.

The agent here in NZ quoted me $1200 = around 840 Euros for the a few rubber seals and the electronic bypass valve! I took that price to the head office in France - and they thought it was acceptable!!

Did I understand you correctly [Tradewindsailor] that many Hydraulic rams may use 3party commercially available standard seals? Head office said something about a 6? piston pump.

I'll also check that link http://www.fpe-ltd.co.uk/ thanks [boatmike]
 
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Construction equipment is always requiring new hoses etc so there are lots of hydraulics firms about
i used to get rams serviced easily on my diggers
Why not see if there is a hydraulic repair firm nearby & drop it in to them
Most normally do a 24/48 hour repair service
 
boatmike said:
Once apart the removal of the end seals will be obvious.
Click to expand...

But thats the issue - it wasnt, or at least it wasnt that obvious to me. I could see a metal ring between the two seals in the end cap and I didnt know whether it was one seal with a metal insert ( like a crankshaft oil seal) or a seal without metal just pushed into a machined recess. Turns out it was the latter.

Did you also strip down the pump and replace the bushes? I was intending to do just the ram. And what did you do about the gaskets between the cylinder and the end cap?
 
birdseye said:
But thats the issue - it wasnt, or at least it wasnt that obvious to me. I could see a metal ring between the two seals in the end cap and I didnt know whether it was one seal with a metal insert ( like a crankshaft oil seal) or a seal without metal just pushed into a machined recess. Turns out it was the latter.

Did you also strip down the pump and replace the bushes? I was intending to do just the ram. And what did you do about the gaskets between the cylinder and the end cap?
Click to expand...

IMHO all you meed to do is take the cylinder apart taling pics as you go. The take the seals to a bearing/seal factor then reassemble in reverse order.

Some sample hydraulic cylinder seal kits giving you and idea for the correct level of pricing.

http://www.ebay.com/bhp/hydraulic-cylinder-repair-kit

This will give you some idea of how to disassemble and reassemble the cylinder.

http://www.ehow.com/how_7815034_change-hydraulic-cylinder-seal.html
 
OK folks. Got it all apart and bought some new polyurethan seals from an industrial supplier.

How on earth do you get the 22mm seal through the 16 mm hole and into its recess? I managed it in the end using a flat blade screwdriver and a small socket but god know what damage I might have done to the new seal. Is there a technique? Shoulkd I soak the seal in boiling water to soften it and make it more squashable?
 
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