Marine Engineering - Practical Tips & Tricks

A place to exchanges questions and ideas of a technical / procedural nature. Go ahead, try to stomp us !
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Big Pete
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Marine Engineering - Practical Tips & Tricks

Postby Big Pete » Tue Dec 01, 2009 3:54 am

There hasn't been much activity on the site recently, so maybe we can start a new thread.
Some things that I wish someone had told me, right at the beginning....

Finding the liquid level in a tank.

Where a liquid tank is against the ships side it is possible to measure the liquid level by feeling the side of the tank with your hand.
The liquid is a good conductor of heat between the outside and the inside of the ship while the air is a good insulator.
Usually, the outside of the ship is colder than the inside, so the side of the tank immersed in liquid will feel colder than the part of the tank with air inside.
If the ship is not rolling the level can be felt to an accuracy of about 4m.m.

Go on try it!



How to tighten/loosen an Allen bolt without a hexagon wrench.The standard sizes of hexagon bolt are the same as the female hexagon heads on Allen bolts.
Simply fit the head of the right sized hex. bolt in the socket of the Allen bolt and lock 2 nuts together on the hex. bolt and then turn the Allen bolt with an ordinary spanner on one of the lock nuts.


How to check the liquid level in a condenser (steam or refrigerant)Feel the side of the condenser shell with your hand, the condensate will be the same temperature as the cooling water, the vapour above it will be considerably hotter.

No rocket science involved and I am sure many other people have useful tips and tricks they can post.
It is always better to ask a stupid question than to do a stupid thing.

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JK
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Re: Tips & Tricks

Postby JK » Wed Dec 02, 2009 10:05 am

Always loosen the bolts in a flange on the side opposite to where you are standing, first.
Add baking soda to the cement you are using in a cement box. Makes it cure faster....of course it may not either. This could be an old engineers tale, but I always did, just in case.
Always make sure the valve is in the open postion when the flange is tightened. It makes for great fun, when you discovered that the newly flashed boiler has a blow down valve that was put together with the valve closed and the flange tightened.
(The most amazing part is the boiler passed a hydrostatic test. Shipyards :roll: )
That water that you drain out of the intercooler, really is condensation, not a leaking coil. Especially in the summer.
If you turn all of the exhaust fans on high in a spce that includes a boiler, it really will misfire and smoke.
If you have a central cooling system in your engineroom and you loose SW cooling, isolate your refrigeration condensor and shut the fridge compressors off immediately or you will blow the freon out the safety.

and If you continue to play at DD forum, you don't get the work you are paid to do done, so back to refit planning.

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Big Pete
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Re: Tips & Tricks

Postby Big Pete » Tue Dec 08, 2009 2:07 am

Welding

1)Ordering Oxygen & Acetylene
During my time at Sea I have found that normally 3 cylinders of Oygen are consumed for every 2 of Acetylene, so I always aim to have this proportion in stock.

[u]2)Correct welding procedure.

I have often seen people welding something, then throwing it in a bucket of water to cool it rapidly.
This rapid cooling locks in stresses and makes failure more likely. Correct welding procedure is to slowly preheat the components before welding then slowly cool them after welding. For large items welded ashore they can be heated up in large furnaces for several days before welding, then cooled slowly, at a controlled rate for several days afterwards.
For most items welded on a ship, covering the component with a fibreglass fire blanket immediatly after welding and leaving it to cool naturally is good enough. If the component is particularly large or has a complex shape, it is better to preheat it, if it is practical.

3)Choice of welding rods/electrodes
On some ships I have seen the crew using stainless steel electrodes to weld mild steel, they claimed this made the weld stronger!! Totally ridiculous. The correct electrode for the material welded has a composition that when mixed with the parent metal of the component being welded, will be stronger than the the parent metal, it is also chosen to be compatible for corrossion prevention.
Deliberatly using the wrong type of electrode is likely to make the weld weaker and /or cause corrossion problems.


4)Weld Failure.
Welds almost never fail at the place where the material has been melted.
99% of welds fail in the "Heat Affected Zone" (HAZ) which is the metal next to the metal that melted. That is beacause it has been heated to high temperatures and cooled rapidly, locking in stresses. (see 2 above)

5) I would strongly reccommend acquiring a copy of the "Handbook for Maritime Welders" by Unitor, the welding & chemical supplier.

This book covers everything you need to know, starting with identifying what material you are trying to weld.

Happy welding.

BP
Last edited by Big Pete on Wed Mar 10, 2010 1:43 am, edited 1 time in total.
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offshoresnipe
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Re: Tips & Tricks

Postby offshoresnipe » Tue Dec 08, 2009 8:25 am

Also a very good book on welding,
The Procedure Handbook Of Arc Welding.
By the Lincoln Electric Company.

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JK
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Re: Tips & Tricks

Postby JK » Tue Mar 09, 2010 2:15 pm

I was just thinking of one f the engineers I sailed with, who has since passed over the bar.
He always carried flat washers in his pocket to use as a spacer if his wrench was a size too big. He would slide the washer in to fill the space.
He was a machinist by trade and had all kinds of little tricks. Too bad the booze got him. :(

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Big Pete
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Re: Tips & Tricks

Postby Big Pete » Wed Mar 24, 2010 3:12 am

Another old tip, that I wasn't taught at College.
"Washing" with Oxy acetylene. If you have a metal stub where a bracket or something has been cut off, it can be removed with any oxy acetylene cutting torch. Set the flame to be oxygen rich and point the flame parrallel to the main surface of the metal so that the flame washes over the lump that you wish to remove. Any metal proud of the surface will become red hot and slowly burn away in the oxygen rich flame, leaving a smooth flat surface behind.
BP
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Re: Tips & Tricks

Postby jwinsor » Sat Mar 27, 2010 7:21 am

Some really great stuff

I have lapped in many fuel pumps, compressor valves, injectors etc...even using 800 grit I couldn't get better than a satin finish. Then one day someone introduced me to Jewlers Rouge. Its like a red piece of hard puddy and it gives you a mirror finish.

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Re: Tips & Tricks

Postby JK » Tue Mar 30, 2010 7:48 am

For underwater surveys carried out by divers with cameras:
Black hull coating is very difficult to discern damages on video. Red coatings are much better, divots show up.
It is amazing the amount of info on hull damage you can get with a good video.

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Re: Tips & Tricks

Postby rlivsey » Sun Apr 11, 2010 5:37 am

My favorite "trick" is using valve grinding compound on screw and allen bolt heads to get extra traction. This is particularly effective on worn heads, but is a good initial move when the fit-up is poor before you strip the head.

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Big Pete
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Re: Tips & Tricks

Postby Big Pete » Sat Apr 17, 2010 12:32 am

If you run out of grinding paste you can make your own.
Many years ago I sailed on a tanker, the Dilmun Tern, with a medium speed Mak engine.
It is fair to describe her as a clapped out old banger. She had been re-engined and the new MaK engine was capable of running on IFO180.
The ship had previuosly run on MDO. The owners got a charter based in Jamaica claiming that the ship could run on IFO but hoped to talk the charterers into supplying MDO instead -they wouldn't! (and why should they?)
To cut a long story short, the engine was designed with 4 different types of exhaust valve, Stellite the same as the inlet valves for MGO operation, another one for MDO, a third for IFO and a fourth for IFO with a High Sulphur/Vanadium content.
We were bunkering fuel from the Jamaican refinery, crude sourced from Venezuela, which was high in Vanadium, but we only had Stellite valves in the engine. 6 months stores had been ordered a year before but not delivered.
At sea we were stopping every few days to change cylinder heads because of burnt out valves, and we ran ran out of grinding paste so we mixed ordinary grease with the dust at the the bottom of the pedestal grinder guards and used that. When that ran out we found a damaged grinding wheel and broke that up.
By the time I paid off we only had a couple of sparte cylinder head valves left and no complete head. The Super visited the ship and I tried to explain to him about the different types of exhaust valve but he just kept insisting he would sove the problem by ordering Stellite ones "Because they are the best"...
I was supposed to fly from there to another ship with the same company in the Persian Gulf, but I had had enough and I quit insttead.

BP
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JK
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Re: Tips & Tricks

Postby JK » Mon May 03, 2010 2:13 am

I've seen glass used as well, in a pinch. In that case pieces of a fluorescent tube that was smashed and ground to dust.

My favorite product was "Timesaver", probably can't get it now. After scrapping the bushings you injected this stuff in with a grease gun and it would take off the last little bit you were having trouble with. It was great on winches with slightly bent cranks that you just couldn't get the bearings right, despite days of work.

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Big Pete
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Re: Tips & Tricks

Postby Big Pete » Tue May 04, 2010 7:56 am

Good one JK.
I guess "elf an safety" wouldn't allow it now.
The Fluorescent coating on the fluorescent tubes is Thorium Oxide, a Toxic and carcinogenic heavy metal and the tubes also contain a drop of Mercury, which is why they are all classed as Toxic waste now.

Another tip:-
If for example, you want to drill an 20 mm diameter hole and the largest drill bit you have is 18mm you can re- grind the drill so that the point is one m.m. off centre, the bit will then drill an oversize hole.
You have to have the nearly lost skill of sharpening drills by hand of course.......

BP.
It is always better to ask a stupid question than to do a stupid thing.

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JK
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Re: Tips & Tricks

Postby JK » Tue May 04, 2010 11:57 am

:oops: Yes, since that was over 23 years ago, there weren't many of those 'elf guys around. We were not much past the days of sweeping asbestos dust up into a pan and throwing it in the skiff.

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Big Pete
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Re: Tips & Tricks

Postby Big Pete » Tue May 04, 2010 7:18 pm

Yes JK,
I remember my first ship as Assistant Engineer Officer, (5th Engineer), she was a steam turbine ship, back in 1975, she was as old as I was (1953) and the asbestos insulation on one of the turbines was damaged. One of the jobs of the Junior Engineer on watch was to keep the damaged patch damped down with a bucket of water and a big brass syringe. There must have been an awareness of the dangers of asbestos dust even then, although I wasn't told why I was doing it.
BP
It is always better to ask a stupid question than to do a stupid thing.

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Big Pete
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Re: Tips & Tricks

Postby Big Pete » Wed May 05, 2010 10:48 pm

I have been thinking about the home made grinding paste. I can see the practical advantages of the Fluoresent tubes. they are thin and all the material is the same thickness making it easy to produce an even sized abrasive particle.
Maybe a solution is to build your own ball mill to break up the bits of glass or old grinding wheel or oil stone?

Put your raw materials in an old coffee tin, (or similar) with a slack handful of ball bearings, or steel rods, put the lid on, and put the tin in the lathe chuck and run the lathe at slow speed, until everything has been ground down to a powder of the required grade. It should work, but I haven't tried it!
Happy Grinding.
BP
It is always better to ask a stupid question than to do a stupid thing.


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