diesel engines - a cautionary tale

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Your solution adds complication and failure points. The extra valve can either leak due to corrosion, scale, contamination or fail to open due to electrical or mechanical failure. Personally I would be much happier with the anti syphon loop and syphon breaker properly installed, plus adequate exhaust volume to accomodate a sensible amount of cranking.


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Fully support Vic's, and above advice. However, a friend's new-to-him boat engine was filled with seawater over a few days. Turned out the installation was such, that a Y-deverter with restriction was installed on the injector point. Seawater went in a narrow tube towards the stuffing box, as to lubricate the seal.
When the engine was shut off and the seacock was closed, the seawater would syphon slowly from the seal back to the injector point. He later found out there was a small valve installed on the tube to prevent this-not a practical solution.
Damage was very limited, as he spent two days changing the oil about twenty times with (at the time..) cheap oil.
 
Yes, if you have a feed to the shaft seal it should be connected to the intake side of the antisyphon loop not the exhaust elbow side. It should probably be arranged so that it is not prone to air locking, ie not looping up too high.
I'm glad I had a shallow bodied boat with the engine above the waterline now!
 
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If you leave the sea cock on, and remove the hose to the exhaust elbow, and let it drain into a bucket, it fills up at a rate of 1.1 ltres per day ( 24hrs). This is nothing to do with siphoning, it is due to pressure of water through the raw water pump.

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There's something wrong here in the way I am understanding your description. The anti syphon valve should be in a high loop of pipe between the sea cock and the raw water pump and should prevent any flow of water - other than what is in the pipe when the engine is stopped. If you have a continuous flow then by definition the anti siphon isnt working / installed right.

Mind you, a new rubber impellor type raw water pump shouldnt allow flow through either.

And as for turning off the sea cock when there is prolonged cranking - well with a new engine there should not be prolonged cranking anyway. But if there ever is, for example to clear air after changing filters, then as everyone has said its standard procedure to turn off the sea cock. I'm sorry you werent aware of that but the professional installer should have been.

I'm not the claiming / moaning sort by nature but in your position I would definitely be making a claim against the installer. The problems you describe arent normal, and as I read your description are down to a less than good installer. If you have doubts, talk to another engine installing company. Or get a surveyor to have a look.
 
Take the hose between the engine and the exhaust injection point up 16" above the water level and fit an antisiphon valve at that point. If for some reason that hose cannot be so diverted then the hose between pump discharge and engine will do, even the hose between inlet and pump!

You imply that the original Perkins antisiphon valve is still fitted and works but where the hell in the system is it fitted. If it allowed your engine to fill with water it is not frigging well working!
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You said it a lot more politely than I was going to

/forums/images/graemlins/laugh.gif /forums/images/graemlins/laugh.gif :

I wonder if the antisyphon device was engine mounted on the big tall Perkins and this professional installer moved it to a lower position on the minute Beta???????????

Where ever it is it is too low!!!!! Reminds me of a few years ago when a very well known tv celebrity bought a yanmar powered Cornish Pilot...... /forums/images/graemlins/laugh.gif /forums/images/graemlins/laugh.gif /forums/images/graemlins/laugh.gif
 
AsI read his reply, the water pump is slack enough to allow water to flow through it by way of being below waterline. He gets water to his bucket because basically all is low. In that case what good is an anti-siphon ? Yes if pipes can be brought higher than waterline by good margin and anti-siphon placed at high point, but usually piping from water-pump through to exhaust and all it's various are already set on the engine and how many do replace or alter ? I would hazard a guess that engine has standard piping, standard set-up. This added to the new engine being significantly lower than the Perkins set-up results in this situation.
We know that if we ever change the engine on our boat from the Perkins, we would have to modify seriously installation as we have straight exhaust without muffler or any anti-siphon to transom. The engine end of exhaust is higher than waterline, with exhaust pipe in a slight downward gradient to exit. The Perkins exhaust manifold is curved down at rear end before the pipe. No need for extra items.
Change the engine to later lower and there is now no way that set-up could remain. He may have suffered similar.
But as hubby says, his water pump surely shouldn't allow water to feed through on it's own ? Sounds like impellor may be worn out or pump itself faulty ?
Closing sea-cock if any significant long cranking is expected is standard practice. This also is similar to if you force feed water when shore running an engine via hose pipe. Use of a bucket system is many peoples answer, but a hose inserted into top of seacock but not tight so excess water can flow out to sides is OK. If not then the water pressure is enough to fill system and cause similar trouble.
 
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AsI read his reply, the water pump is slack enough to allow water to flow through it by way of being below waterline. He gets water to his bucket because basically all is low. In that case what good is an anti-siphon ?

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He says that he took the flow from the exhaust elbow - ie after the anti-siphon. In which case he is experiencing flow through the block, up the pipe to the anti-siphon (which should be sited above the waterline) and down the other side.

This should not happen if there is an anti-siphon which is mounted correctly and is working corretly. Something is wrong somewhere - and in all proabablility is something to do with anti-siphon.
 
To sum up. Anywhere water can get in which is below the water line is a potential flooding point and all should have anti-syphon loops fitted.
The installation is wrong and you have a claim against the "engineer". Vic knows what he is saying, so listen to his time served advice. Shut of valves are not necessary if the installation is done properly. They would simply be a non too good remedy rather than a proper solution.
 
But as hubby says, his water pump surely shouldn't allow water to feed through on it's own ? Sounds like impellor may be worn out or pump itself faulty ?
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All impeller pumps ;eak to a certain degree and should never be assumed to be water tight..

Yes the Beta comes with custom pipework from the pump to the elbow however it is an easy enough matter to remove the hose to the mixing elbow and replace with a loop through a correctly positioned anti syphon loop. This is plain simple good practice as Vic has politely said.


Hose to convert to anti syphon
 
The loop must be after the pump and before the mixing elbow.

On most volvos it can either be inserted between the pump and the engine inlet replacing an existing hose or if not then immediately before the mixing elbow.
 
Water leaking into the exhaust while the engine is not running doesn't have a path to the sump until the exhaust has filled up. There should be no need to start the engine with the seacock closed as the impeller pump will take a long time to fill the exhaust to this level. Only exception is when it is slow to start for some reason, eg if you are bleeding the injection
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It is quite simple.....the water fills the exhaust via the mixing elbow. It is a slow process and needs a long period however it DOES happen I can assure you. The exhaust fills then the water backflows into the engine via an open exhaust valve.

If you catch the engine before starting then it can be saved especially old Volvo's but an attempt to start can lead to immediate damage from hydraulic locking such as bent con rod ,stretched head studs and blown gaskets.

I have seen an MD11 flooded about 5 times in a week before the source was located but no damage. Once the punctured liner was replaced together with rings and pison it worked as good as ever.
 
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antisiphon is NOT the problem.

If you leave the sea cock on, and remove the hose to the exhaust elbow, and let it drain into a bucket, it fills up at a rate of 1.1 ltres per day ( 24hrs). This is nothing to do with siphoning, it is due to pressure of water through the raw water pump. [ QUOTE ]

Exactly the opposite is true, it is nothing to do with the pump, and everything to do with the anti-syphon system. You say the anti-syphon loop has ben tested OK, but it MUST go above the water-line and MUST have a suitable air-bleed at the high point. If it has, then you won't get the flow that you observe. As previously said, it's basic physics.
 
These faults have not got anything to do with anti siphon loops. The Perkins original loop was in use for 28 years and worked and still works and has be tested as such!
 
Earlybird. The the antisiphon loop is installed ina locker and is 4.2 feet above the water line and has worked for 30 years. These3 faults are nothing to do with siphonage
 
These faults have not got anything to do with anti siphon loops. The Perkins original loop was in use for 28 years and worked and still works and has be tested as such!

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I am afraid you are WRONG.....as many folk here have tried to tell you. If the anti syphon loop is correctly placed high enough then water which leaks past the pump will NOT reach the mixing elbow.

Your problem is exactly what happens when one takes out an old fashioned high engine and replaces it with a more compact lower engine and incorrectly positions the new antisyphon loop.

The antisyphon loop must be attached to the boat and placed high enough to work. If high enough then the water leakage can not pass it. If the water leakage is passing the antisyphon loop then the loop is not high enough in the boat so is ineffective!

I can understand your installation engineer not agreeing with us. He has a financial interest not to!!!!

Did you not consider the Beta high rise elbow as an option as this might have prevented your problem .
 
Hello,

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If you leave the sea cock on, and remove the hose to the exhaust elbow, and let it drain into a bucket, it fills up at a rate of 1.1 ltres per day ( 24hrs).

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Just to check if I understand the situation:

Does the hose to the exhaust elbow go via the anti-syphon loop?

If so, are you disconnecting the hose where it leaves the engine, or where it enters the exhaust elbow to get the above result ?

If not, where are the ends of the anti-syphon loop connected?

Trying to help, but want to make sure I've understood the set-up first.

Andy
 
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The the antisiphon loop is installed in a locker and is 4.2 feet above the water line and has worked for 30 years.

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Can we be clear about this loop, Unless I have overlooked it, you nowhere actually say that this loop has an air bleed at its high point. This is essential. A loop is NOT an anti-syphon device, it just presents a static head to prevent water flowing into the boat if the inboard end is open, as it is in an exhaust system. This loop can work as a syphon given the right conditions. The air bleed in the loop is the "anti-syphon" device. If there is an effective air bleed, then you do indeed have a strange problem.
 
Perhaps some basic diagrams will help to illustrate the principles which we all seem to be having great difficulty explaining adequately

My first shows a situation with the exhaust injection point below water level but with no anti-siphon device. In this situation water WILL seep past the vanes of the water pump unless it is exceptionally tight and it will slowly fill the exhaust system and eventually cause the problem you experienced.

Antisiphon.jpg


My second diagram shows the same engine in the same boat with the same exhaust injection point etc BUT in this case the plumbing leading to the exhaust injection point has been taken via an anti-siphon valve situated well above the water level. Installed like this the anti-siphon device WILL prevent the continuous inflow of water and will therefore prevent the problem you experienced

Antisiphon2.jpg



There are some similar but more professional diagrams on page 153 of the Vetus catalogue

I cannot comment any further on the old anti-siphon device except to say that if it has allowed the engine to fill with water it is clearly NOT working in as much that it has failed to do its duty, be that due to failure of the device or incorrect connection to the new engine.
 
To VicS and other thanks for all your help. Today we have replaced the 30 year old Perkins loop, with a new antisiphon system using a Vetus valve.
On disassembly of the old system it was found that there is a short "Tee" made of 28mm copper tube with 10mm copper side arm. Attached to the flow and return is 28mm Id rubber tube, in excellent condition and also original.
During the conversion process the longer lengths of rubber tube were shortened and then linked into new plastic pipe for the new engine.
Having taken out the "tee" we found crumb rubber coating the inside and also blocking the oriface on the sidearm, helped by a coating of brown algae.
This crumb rubber is the swarf from when the rubber tubes were cut with a hacksaw, and it is extremely unlikely that the swarf existed for the 28 years the Perkins was doing its job.
Rubber floats so it is natural that the swarf floated to the highest point in the system which was about 4 feet above sea level. The algae obviously glued the swarf together, and blocked the anti siphon sidearm so preventing the system from working.
As the system was professionally installed, I shall be looking for full compensation from the Beta installer.

It is still worth noting the Yanmar routine, of "open seacock.. start engine .... close seacock.. stop engine"

Even if the loop in not working, there will be no danger to the engine.

Finally never crank the engine for more than 30 seconds with the seacock open. If the bugger wont start, switch off the cooling water until it does start. Water in the oil is very expensive a new diesel pump is £610+vat!
 
As far as the prolonged cranking is concerned, do you often have to do this? I have a 30 year old engine and I only had to bleed it once with more than 2 30 second cranks. Every other time it started within 10 seconds. Shouldn't modern engines start swiftly?

If this is rare, surely shutting off the seacock after the first 30 second crank will do?
 
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