Thermal oil boiler

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Pengze
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Thermal oil boiler

Postby Pengze » Tue Oct 23, 2012 6:34 pm

Dear Gentlemen,
Where could I get more information about the thermal oil boiler?
Anyone with experience working with thermal oil boiler, would appreciate yr kind & valuable input, thank you.

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Big Pete
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Re: Thermal oil boiler

Postby Big Pete » Thu Oct 25, 2012 12:58 pm

Hi again Pengze,

I sailed with a few of these, many years ago as Second Engineer. What exactly do you want to know??

The combustion side is exactly the same as for an oil fired steam boiler, and Economisers can also be fitted in the engine exhaust.

The thermal oil circulates at low pressure and there is no water hammer, and temperature changes tend to be more gradual, so there should be no leakage anywhere in the system. No heat is rejected to a condenser so the system is much more efficient than a steam plant.

Annual oil samples should be sent off to the Thermal oil supplier or "Boiler" maker and the oil changed if necessary. No onboard testing or treatment of the Thermal Oil is required. If you have doubts about the oil it should be clear and the same colour as new oil, if it is dark it has been overheated. Check the viscosity with a "Flo Stick" if the viscosity is high it has oxidised.

It is important to make sure that the maximum Temperature for the Thermal Oil is not exceded, otherwise it will carbonise.

It is very important to circulate the oil before firing the boiler and to continue circulating the oil while the boiler cools down after use, 15 or 20 minutes should be enough unless it is a very large system, or the oil will be thermally degraded by localised overheating.

The hot oil can oxidise and become excessively viscous if it is exposed to air, therefore the expansion tank should not be lagged and the air vents from the various high points in the system, back to the expansion tank, should always be kept shut while the oil is hot. Air should be vented out by circulating the oil COLD. However, it should only be neccessary to vent air after initially filling the system or after a major leak.
I heard of one ship where a new Chief Engineer joined and he thought that the system should be run with all the air vents open, after a while the circulating pumps started tripping out on overload, investigation showed that the Thermal oil had turned into treacle.

I also heard a story where a Thermal Oil boiler was opened up for survey. It was a fairly large top fired boiler and the burner unit was removed and a ladder put down inside so that the combustion chamber could be inspected by the Surveyor. After the Survey was completed, the Junior Engineer was left to refit the Burner unit, when the burner was flashed up, the boiler tubes burnt out. When the burner was removed to make an internal inspection the Aluminium ladder to get inside could not be found. Never leave ladders inside the combustion chamber!

Hope all this helps.

BP
Last edited by Big Pete on Sat Oct 27, 2012 1:45 am, edited 1 time in total.
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: Thermal oil boiler

Postby JK » Fri Oct 26, 2012 3:36 am

and don't overfill the system.....
I'll leave that to your imagination..

Pengze
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Re: Thermal oil boiler

Postby Pengze » Fri Oct 26, 2012 4:59 am

Good day Sir,
Glad to receive some valuable tips from you. Thks.
1. To quote, "expansion tank should not be lagged", my understanding is that hot tank should be lagged for safety purposes , why is that so ? Unquote.
2. It looks like there won't be any safety valves on the boiler compared to a steam plant , correct ?
3. Is there any relief valve on the circulating pump ?
4. What would happen if the thermal oil inside the circulating tubes leaks ?
5. Finally, where could I get more reading materials about the thermal oil boiler ?

Have a nice day ahead.

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Big Pete
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Re: Thermal oil boiler

Postby Big Pete » Fri Oct 26, 2012 7:58 am

Hi again Pengze,

You appear to have a lot of problems on your ship, exploding generators, worn out fuel pumps and now Thermal oil plant without an instruction manual!

1)The expansion tank should not be lagged because it is open to the air, if the oil inside became hot it would oxidise, it is purely an expansion tank. There should be no ciculation through it, so it should not get hot.
For safety you could fit wire mesh around it, to prevent personal injury if the tank became hot because the system was being incorrectly operated.

2) There is no need to fit safety valves because it is not a steam system, and the system is free to expand to the expansion tank. However, it would always be safer to fit a relief valve on the boiler in cause someone tried to fire it up with the valves closed!.

3) If the circulating pumps are positive displacement pumps they would be fitted with internal relief valves, just as Lubricating oil or Fuel transfer pumps would be, because if they were run against a closed discharge valve it would damage the motor and pump.

4) Not sure if you mean the thermal oil leaks inside, say a heated fuel Tank or inside the boiler. However, the great thing about Thermal oil is that the system is full of oil, the pipes do not corrode and you dont have all the problems with pipe failures, gaskets blowing out, leaking valve glands etc, that you have with steam systems. The first ship I sailed on with Thermal oil was 5 years old when I joined and I sailed on her for 3 years, in all that time we never had an oil leak or had to add any oil.
The circulating pumps had never been touched in 8 years, and were still running perfectly. The only work we ever did on the system was to service the burner. If you had a thermal oil leak inside a tank or other heating coil you would notice a drop in the level of the oil expansion tank. Then by isolating all the heating coils in turn you would determine where the leak was. You would then have to open up the tank/heater and flush the leaking line through to make sure it was not contaminated, gas free it and repair it. Then carry out a pressure test, if that is OK circulate cold oil through the system with the air vent valves open, to make sure no air was trapped in the system. Then close the air vent valves, and fire up the plant.
The pipework in the ER will be insulated to protect the crew and I have seen drip trays fitted under every pipe flange on some ships. For safety the oils are always used well below their flash point, several different types of oil are available with different Flash Points.
If there is any leakage inside the boiler, the oil will burn off and you will start making smoke, when you open up the burner to service it you will find the leak.

I have said that you must always make sure that the air vents, from the high points in the system to the top of the expansion tank, should always be kept closed when the Burner is firing, however, it is equally important that the run down valve from the expansion tank to the circulating pump suction, is always kept open, otherwise the expansion of the oil with temperature could lead to serious over pressure in the system.
Good Luck.

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

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The Dieselduck
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Re: Thermal oil boiler

Postby The Dieselduck » Mon Nov 05, 2012 7:27 am

You appear to have a lot of problems on your ship, exploding generators, worn out fuel pumps and now Thermal oil plant without an instruction manual!


ehehehe, yes, my thought are the same...
Martin Leduc
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http://www.dieselduck.net


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