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  #101  
Old 9th March 2020, 11:15
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Originally Posted by Tim Gibbs View Post
Our 750 mm Doxfords were indeed horrors. They all had new crankshafts before the ships were 5 years old and one of them broke the replacement shaft 8 years later when I was 2/E and then that second shaft was badly damaged by microbial attack after another 4 years when I was Superintendent.
Interestingly, the Doxfords with 670 mm bore or less were relatively trouble free by comparison.
Too many millimetres spoiled the broth?
We did have a twin screw 3 cylinder 60LB that ran on diesel . That was really good (if you could hold the fuel pressure!). However, you were never quite sure which way the engines were going to start but as far as I know it was never the cause of a City of Brooklyn / Cato type disaster
I think you are right about the increased bore increasing the rate of bearing failure, at least initially. The reason to my mind was the distance between the main bearings, already large because of the side rod bearings increasing the bore caused more flexing over the increased distance increasing the risk of main bearing failure.

This brings me to another thought, the reason for the demise of the Doxford. Ship Owners wanted higher powers, there are only 3 ways of increasing the power per cylinder:

1) Increase the MEP, this will increase the crankshaft load, causing more flexing....

2) Increase the bore - this increases the bearing distance....

3) Increase the stroke - we now run into the difficulties of either casting a very long liner or go back to the difficulties of sealing a tripartite liner

Could these difficulties be solved with modern technology - maybe. Is there any appetite for investment to do so - almost certainly not
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  #102  
Old 9th March 2020, 13:50
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I think you are right about the increased bore increasing the rate of bearing failure, at least initially. The reason to my mind was the distance between the main bearings, already large because of the side rod bearings increasing the bore caused more flexing over the increased distance increasing the risk of main bearing failure.......
Yes, on the 75LB6 the " perfect" centre crank deflection at No.6 was 0.045 inch(1.1mm) ! In fact if the deflection gauge didn't fall out it was sometimes considered okl! Goodness knows what the deflection was in the running condition. On the ship I was on that fractured the crank at No.4 side crankweb ,we fitted a huge strap around the crankweb and had to cut a bit out of the bedplate to allow it to rotate. However, when we started the engine for a trial there was a clonk, clonk at about 40 rpm and inspection showed we had to cut out a bit more! In my experience with these engines the cause of many of the bearing failures was locked sphericals, either from incorrect adjustment or ridges being allowed to develop.
I agree about the 3-part liners of the "J" type. We had sister ships, two with 76J7 Doxford engines and one with a 6RND90 Sulzer. If it wasn't for the liner sealing problems the Doxford would have been a much superior engine. Your analysis of the Doxford demise is probably correct in the long run but I'm convinced they would have been keep in production for longer had it not been for the seriously c**p British Shipbuilders management
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  #103  
Old 9th March 2020, 20:20
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Yes, on the 75LB6 the " perfect" centre crank deflection at No.6 was 0.045 inch(1.1mm) ! In fact if the deflection gauge didn't fall out it was sometimes considered okl! Goodness knows what the deflection was in the running condition. On the ship I was on that fractured the crank at No.4 side crankweb ,we fitted a huge strap around the crankweb and had to cut a bit out of the bedplate to allow it to rotate. However, when we started the engine for a trial there was a clonk, clonk at about 40 rpm and inspection showed we had to cut out a bit more! In my experience with these engines the cause of many of the bearing failures was locked sphericals, either from incorrect adjustment or ridges being allowed to develop.
I agree about the 3-part liners of the "J" type. We had sister ships, two with 76J7 Doxford engines and one with a 6RND90 Sulzer. If it wasn't for the liner sealing problems the Doxford would have been a much superior engine. Your analysis of the Doxford demise is probably correct in the long run but I'm convinced they would have been keep in production for longer had it not been for the seriously c**p British Shipbuilders management
Tim
Doxfords Liverpool and Hull Sulzer London. Coasted Hull and London
Alan
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  #104  
Old 10th March 2020, 12:37
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..... In my experience with these engines the cause of many of the bearing failures was locked sphericals, either from incorrect adjustment or ridges being allowed to develop.
.....
All this has given me a severe attack of RAS*
Not unreasonably we had become paranoid about the 75LB6 crankshaft alignment but then the company decided to check the immediately post war built 67LB6s although they had run without any significant alignment problems. I have a memory that one of then was found to 40mm low at the forward end so the engine was realigned. What a trip we had after that. We had several BE bearing failures and all showed signs of locked sphericals - the sphericals that had previously been able to move to suit the crankshaft position couldn't now move to the required position due to the ridges that had formed by running so long in that original position.
*Repetitive Anecdote Syndrome
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  #105  
Old 11th March 2020, 13:38
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This is an aside but I was told (Can't remember where, possibly an IMarEST event) that sometime after Doxford's final closure a vessel required a new crankshaft. A world wide search revealed no one capable of building one!!
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  #106  
Old 11th March 2020, 17:45
Steve Hodges Steve Hodges is offline  
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I only sailed on one of this class, and we had field days fro drydock to signing off some 6 months and boiler water and its purity, and generation in the scam vaps was a problem, as the ships grew disgracefully older? They broke many a budding engineer. The stories of any of the six IT ships was a Story book to behold-Grimmes Fairy Tales.
Shakespeare clearly had a premonition about BP's Eyeties..... to quote from "Macbeth" - " O horror, horror, horror! tongue nor heart cannot conceive nor name thee! "
One of these beauties was my first trip as engineer cadet, so I didn't know any better at the time. I think the steelwork was all from recycled Fiats, you could almost watch it corrode before your eyes, and I quickly became adept at applying Thistlebond bandages to the bilge mains. That and sootblowing by hand - all the wiring to the electric motors had rotted away. If any ex-BP engineers want a walk down this particularly nasty memory lane, my cadet's logbook has
full details of most of the engineroom systems drawn on the back of old charts. Six separate steam systems! ( Superheated; desuperheated; auxiliary exhaust; high, intermediate and low pressure bled steam) What were they thinking! Perhaps it was their revenge for losing WW2?
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  #107  
Old 12th March 2020, 00:24
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I thought their revenge was the Grande Motori di Trieste.

A quick Google suggest then Bard knew them: Affliction is enamoured of thy parts, And thou art wedded to calamity.
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  #108  
Old 12th March 2020, 08:07
Engine Serang Engine Serang is offline  
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I thought their revenge was the Grande Motori di Trieste.
Or the Fiat 131. Or ham and pineapple pizza.
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  #109  
Old 12th March 2020, 10:41
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........Six separate steam systems! ( Superheated; desuperheated; auxiliary exhaust; high, intermediate and low pressure bled steam) What were they thinking! Perhaps it was their revenge for losing WW2?
There was certainly a correlation between complexity and the number of field days on the 1970s era steam ships. It was all supposed to improve efficiency and probably looked great in the design office but the through-life costs would have told a different story.Sadly those responsible for the design and approval of these systems were rarely around to take responsibility when the truth emerged.
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  #110  
Old 17th May 2020, 10:55
Chillytoes Chillytoes is offline  
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Duncan - post #101
You missed the 4th way to increase power - increase the revs. This is the solution of choice for a number of engine manufacturers.
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  #111  
Old 17th May 2020, 12:23
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When I was sailing in CP Ships in the 80's I sailed with a number of engineers who had been on the large diesel engined VLCC's they had built in Japan in the early 70's when they decided they did not want any steam ships, to get the power they needed it was Mitsui B&W FF 980 bore 9 cylinder.
One story I remember a 4/E told me he got out of the lift and could not see accross the E/R for exhaust and steam leaks, believe one of them the Port Hawksbury I think went through three ecconomisers, molten steel falling from above, they had fire hoses rigged around them and soot blowing had to be done wearing BA sets.
The two ships with those engines had the problems, the third I.D. Sinclair had a 10 cylinder GF and I never heard of them having much problems.
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  #112  
Old 17th May 2020, 19:42
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Sort of the opposite on Barber Perseus, built by MHI.

A mate was on watch, doing a round, and heard a creaking, groaning sound. Just then, the economizer (waste heat boiler) came crashing down from way aloft onto the ME cylinder heads.

The investigation revealed that the heat exchange rate was too high at low revs and the exhaust gas was condensing acid rain! It just rotted the entire economizer.

The secret, as I soon learned on Barber Priam, was to leave the auxy BLR on until normal operating temps had been reached and stabilized.

Rgds.
Dave
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  #113  
Old 18th May 2020, 16:30
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Duncan - post #101
You missed the 4th way to increase power - increase the revs. This is the solution of choice for a number of engine manufacturers.
Yes, but propellors are more efficient at lower speeds, unless of course we use a reduction gearbox which will entail further losses. A very vicious circle.
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  #114  
Old 28th May 2020, 08:40
Peter Hewson Peter Hewson is offline
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Sort of the opposite on Barber Perseus, built by MHI.

A mate was on watch, doing a round, and heard a creaking, groaning sound. Just then, the economizer (waste heat boiler) came crashing down from way aloft onto the ME cylinder heads.

The investigation revealed that the heat exchange rate was too high at low revs and the exhaust gas was condensing acid rain! It just rotted the entire economizer.

The secret, as I soon learned on Barber Priam, was to leave the auxy BLR on until normal operating temps had been reached and stabilized.

Rgds.
Dave
Reminds of a Non Maritime event. Newly built on a Farm 2 package Steam Boilers designed to run on Sewage Gas. At the First Annual, one was opened up and I found the tubes pretty much at the end of service life and already 20% wasting, on the tube plates, the rear was much worse. The cause was the high sulphur content in the gas, being of "Animal" origins. When the boiler was "turned down" the resulting condensation produced Sulphuric Acid. They had a big re-think, and went to Natural gas, pending possible introduction of a "scrubbing" system.

Taking deflections on Doxfords was always an interesting exercise, You never really knew what you where going to get, But we never did have any major failure on the Strick Ships, most of which had a Doxford of one type or another. I`ve Hung pistons and run on 5 on other`s Though?.
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  #115  
Old 31st May 2020, 21:39
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[QUOTE=Peter Hewson;3055271]Reminds of a Non Maritime event. Newly built on a Farm 2 package Steam Boilers designed to run on Sewage Gas. At the First Annual, one was opened up and I found the tubes pretty much at the end of service life and already 20% wasting, on the tube plates, the rear was much worse. The cause was the high sulphur content in the gas, being of "Animal" origins. When the boiler was "turned down" the resulting condensation produced Sulphuric Acid. They had a big re-think, and went to Natural gas, pending possible introduction of a "scrubbing" system

This was a frequent problem in the 1960's to 1980's when NZ was importing Iraq crude oil with 3.5% sulphur in exchange for our mutton.
All modern firetube boilers were almost too efficient if ran on low fire for any length of time when the exhaust gas used to reach near dew point and deposit the acid on the rear tube plate or up the chimney .
Widely reticulate natural gas fixed that .
Had a case where the Taranaki Dairy factory manager insisted on putting a Chinaman's hat on the chimney top of his new 20,000 lb/s per hour Steambloc packaged oil fired boiler to prevent rain entry.
It stopped the rain OK but the down wash of sulphuric fumes caused his pride and joy camellia and rhododendron gardens to develope leaf burn etc.

Off came the hat and the more widely dispersed sulphur laden exhaust actually made the acid soil loving plants thrive even more

Bob
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  #116  
Old 1st June 2020, 00:38
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Surely the choice is simple. Sacrifice efficiency and keep the uptake above (around) 145 C and consume more fuel or rip all you can from the fuel and consume economisers.
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  #117  
Old 1st June 2020, 01:51
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Yes David , there is always a happy medium but slack operators / process demand swings / far less sophisticated control instrumentation in those days added to the pile

Bob
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  #118  
Old 1st June 2020, 05:52
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[quote=spongebob;3055895]
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Originally Posted by Peter Hewson View Post
Reminds of a Non Maritime event. Newly built on a Farm 2 package Steam Boilers designed to run on Sewage Gas. At the First Annual, one was opened up and I found the tubes pretty much at the end of service life and already 20% wasting, on the tube plates, the rear was much worse. The cause was the high sulphur content in the gas, being of "Animal" origins. When the boiler was "turned down" the resulting condensation produced Sulphuric Acid. They had a big re-think, and went to Natural gas, pending possible introduction of a "scrubbing" system

This was a frequent problem in the 1960's to 1980's when NZ was importing Iraq crude oil with 3.5% sulphur in exchange for our mutton.
All modern firetube boilers were almost too efficient if ran on low fire for any length of time when the exhaust gas used to reach near dew point and deposit the acid on the rear tube plate or up the chimney .
Widely reticulate natural gas fixed that .
Had a case where the Taranaki Dairy factory manager insisted on putting a Chinaman's hat on the chimney top of his new 20,000 lb/s per hour Steambloc packaged oil fired boiler to prevent rain entry.
It stopped the rain OK but the down wash of sulphuric fumes caused his pride and joy camellia and rhododendron gardens to develope leaf burn etc.

Off came the hat and the more widely dispersed sulphur laden exhaust actually made the acid soil loving plants thrive even more

Bob
Some years ago, I visited a lead smelting works that had gas engines installed to burn gas from a nearby refuse tip, as the gas became exhausted the concentration of Sulphur etc in the gas increased. Suffice to say the cylinder heads didn't cope well!!
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  #119  
Old 1st June 2020, 14:12
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Looks like I have opened a good can of worms on the question of XS sulphur/acid rain!
Rgds.
Dave
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  #120  
Old 1st June 2020, 21:49
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Thank goodness those days of bartering with Saddam with Halau killed mutton for high sulphur Iraqi crude are long gone.
Come to think of it our Dairy Board did a sililar deal with Russia with surplus milk powder for Russian cars .
We had acres of them parked in the Waikato that were so unreliable they wouldn't sell, long after the mutton was hotpotted and scoffed !

Bob
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