Cylinder Liner Deglazing

Bill Davies
4th June 2009, 20:04
Interesting to hear the views of members.
Would you ever consider overhauling a unit without honing/deglazing the liner.
I have heard the arguements but having experienced a crankcase explosion which was directly linked to to lack of deglazing I would say it is essential.

Bill

Satanic Mechanic
4th June 2009, 20:41
Depends on the condition but to be honest I have always liked to give them a quick 'brush' regardless of condition, the theory being that it at the very least interrupts the progressive glazing of the liner.

Don Matheson
4th June 2009, 20:55
If you have the pistons out what would you gain by not doing it. I would think it an essential part of the overhaul and if you are that far along in an overhaul , why not do it anyway? Doesnt take very long to do it, depending on engine and size of course but essential I would say.
Don

Hey SM have they thrown you out of Brazil already?

Satanic Mechanic
4th June 2009, 21:04
If you have the pistons out what would you gain by not doing it. I would think it an essential part of the overhaul and if you are that far along in an overhaul , why not do it anyway? Doesnt take very long to do it, depending on engine and size of course but essential I would say.
Don

Hey SM have they thrown you out of Brazil already?

Nah - I'm sitting here in Rio between jobs away to another vessel on Saturday

Macphail
4th June 2009, 21:11
Interesting to hear the views of members.
Would you ever consider overhauling a unit without honing/deglazing the liner.
I have heard the arguements but having experienced a crankcase explosion which was directly linked to to lack of deglazing I would say it is essential.

Bill

To enlighten you as you are not understanding, a crankcase explosion occurs due to an oil mist , ignited by a bearing running hot or a heat source, eg scavenge fire. The deglazing problem could apply to alternators , small engines.

John.

Satanic Mechanic
4th June 2009, 21:47
To enlighten you as you are not understanding, a crankcase explosion occurs due to an oil mist , ignited by a bearing running hot or a heat source, eg scavenge fire. The deglazing problem could apply to alternators , small engines.

John.


I was going to ask that - what is the mechanism of deglazing to crankcase explosion?, I freely admit to not having heard of that one before.

Bill Davies
4th June 2009, 22:42
I was going to ask that - what is the mechanism of deglazing to crankcase explosion?, I freely admit to not having heard of that one before.

John/SM,

Exactly why the question was posted. The DNV Surveyor Rotterdam gave the lack of degalazing as the reason. The B/Es and Mains were turned out and showed nothing.
Prior to the incident the Graviner Oil Mist detector was indicating a problem with the unit under consideration. It was overhauled and two days out it started again. Within hours of the first alarm the explosion occurred.

Brgds

Bill

Derek Roger
4th June 2009, 23:25
The problem as described is unlikley to have been the cause of a crankcase exposion .
If units were pulled and the normal routine followed there would be no problem . One would assume that the rings were replaced and the usual cleaning done .
One would also asume that the cyliner calibrations were taken ???
If the calibrations showed some abnormal wear ( ovalrity )
Then then liner should have been changed .
The main reason to " deglaze " is to allow the new piston / liner to work in with new rings .

If the engine was a 2 stroke the question is silly as the crankcase and piston compartment are isolated . Question must have been from a 4 stroke .

makko
5th June 2009, 01:59
Bill,
Would you go to a doctor and not have your pulse/BP checked? I am all for honing/deglazing. I am still pondering the findings of the DNV surveyor - suffice to say, on several occasions I have been less than impressed by some of them. More later.
Rgds.
Dave

Peter Short
5th June 2009, 11:24
I have read an account by John Lamb of two 8 cylinder open fronted diesels in a ship (Trigonia) he joined as Chief Engineer in 1923.

Every now and again sheets of flame would shoot out from the bottom of the cylinders, so I did not think it prudent to remove the fire hose which had been laid along the middle grating by the fitters before they went ashore. The purpose of the hose was apparently to extinguish fires, caused by the greasy matter which rapidly accumulated under the cylinders being set alight by the flame passing the pistons.

I guess no danger of an explosion in this type of engine, but in another account of an enclosed early diesel I have read of a red hot piston skirt being hosed with oil while running, the hope being that the oil mist in the crankcase was too rich to explode....

Satanic Mechanic
6th June 2009, 16:29
Bill,
Would you go to a doctor and not have your pulse/BP checked? I am all for honing/deglazing. I am still pondering the findings of the DNV surveyor - suffice to say, on several occasions I have been less than impressed by some of them. More later.
Rgds.
Dave

I am not a fan of class societies in general especially in the building side of the industry as they are employed by the yard and bearing in mind they are a profit making organisation the term 'Yard B**ch' is only too true.