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Diesel Generator, Radiator Coolant Thermocouple

05/19/2011 3:43 AM

We have a 400KVA Diesel Engine driven generator that works as a standby power source to one of our housing facilities.

An issue recently came up as the thermocouple installed on the Radiator Coolant line started to give out sporious readings varying the temperature display to faulty readings and even tripping the Diesel engine on high temperature. When i took it up with the OEM, he suggested me to cover/insulate the exhaust piping of the engine from the end of the Turbocharger till above the radiator height since the thermocouple is installed in vicinity of the exhaust piping and it is effected by heat radiated from the piping.

I'm unsure if it is going to effect the performance or life of the engine or turbocharger in some way?

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#1

Re: Diesel Generator, Radiator Coolant Thermocouple

05/19/2011 5:11 AM

Hey!

I am not quite sure, but I don think that covering the exhaust pipe is a good idea, though I am not the OEM!! I think a better idea would be just to make a shield of sorts using a metal sheet perhaps between the exhaust pipe and the thermocouple, if that is possible. Also I would suggest that if possible maybe have the thermo couple checked. Remember the time when there was a problem with the voltage regulation of one of the DGs?

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#2
In reply to #1

Re: Diesel Generator, Radiator Coolant Thermocouple

05/19/2011 8:15 AM

@ rediah

I dont exactly remember the voltage regulation issue, please mention if you can with some detail.

About the thermocouple, i did get it tested by the OEMs representative team responsible for the instrumentation, and they after not finding a fault with it suggested the stated solution.

I hope you rememeber this DG, this is the one that was installed in with the acoustic canopy. The OEMs representative suggest that you can cover up the whole part of the exhaust piping that is inside the canopy(Starting at the Turbocharger exhaust till when the piping exits the canopy).

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#3
In reply to #2

Re: Diesel Generator, Radiator Coolant Thermocouple

05/19/2011 9:09 AM

About the voltage issue, it was that when the DG was places under load it worked for a while, but then the voltage started to hunt. Also the frequency started to fall later. We cleaned the fuel valves ect and had it checked by our own electrical team, but they said the problem is in the engine and not on their side. So we checked again, only to find nothing really wrong! A detailed view however resulted in the fault identification in the generator coils etc.

Now to the current problem, I guess this is the start of the peak demand season, and the amb temp too will be high! Covering the exhaust could make the problem better, but could also result in the over heating of the turbo charger, and the leakage of its seals and so forth!

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#4
In reply to #3

Re: Diesel Generator, Radiator Coolant Thermocouple

05/19/2011 9:15 AM

is the coolant level above the thermal coupling at full throttle full load at operating temp because it sounds like it is being exposed to steam or air

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#5

Re: Diesel Generator, Radiator Coolant Thermocouple

05/19/2011 11:35 AM

Has someone used some 'extension cable' to the thermocouple wiring with the slightest difference in wire materials than the thermocouple itself? If yes ALL the extra joint temperatures MUST be in a controlled temp exactly same with the meters input cirquit (else you're just adding around thermocouples in series and expect to have correct output). If you can't control that, use a single piece premanufacrtured thermocouple-wiring. They're available at more than 10m long to address this exact problem and are not too expensive.

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#6

Re: Diesel Generator, Radiator Coolant Thermocouple

05/19/2011 12:51 PM

While this won't solve your problem directly, our motto was always "get it in writing". So if the OEM suggests a modification to the original design, the liability sits back square in their lap from the results of the modification.

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#7

Re: Diesel Generator, Radiator Coolant Thermocouple

05/19/2011 8:20 PM

I don't believe insulating the exhaust piping would compromise the engine or turbo at all and getting it in writing should allay your concerns

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#8

Re: Diesel Generator, Radiator Coolant Thermocouple

05/19/2011 11:12 PM

I recommend you check that the thermocouple is working properly and is not intermittent. After you have a known good thermocouple, I suggest you find a location for it that is not sensitive to the temperature of adjacent components. For measuring coolant temperature, I have put thermocouples under the radiator hose and held them in place with the hose clamp. Immersing them in the coolant is better but not always practical.

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#9

Re: Diesel Generator, Radiator Coolant Thermocouple

05/20/2011 2:38 AM

Has any 1 even thought to test the temperature gauge to make sure it is not faulty & is reading correctly as I have found similar faults in gauges going wild with the readings & the thermocouple has no fault & worked properly on another gauge

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#10

Re: Diesel Generator, Radiator Coolant Thermocouple

05/20/2011 8:07 AM

OEM help can be very misleading. If your thermocouple reading is being influenced by radiation from the turbo outlet, you can try to shield it from that radiation or find a better location for the thermocouple. When the thermocouple is properly located, it won't be sensitive to radiation from the turbo. Think about why you are asked to close your mouth when thermometer is under your tongue. The sensor should be immersed in the environment being measured and not subjected to external sources of hot or cold. Choosing an optimum location for coolant temperature measurement is not a trivial task because of the delta T across the coolant ports and because of post heating effects after the engine is shut off.

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#11

Re: Diesel Generator, Radiator Coolant Thermocouple

05/20/2011 9:41 AM

As pointed out, insulating the turbine end of the turbo charger and the exhaust line should not affect engine operation.

If the siting of the thermocouple is a problem, it will not only be a problem with your gen set, most or maybe all gen sets of this type would have the same problem. It would be a design problem. If this is not the case, I would suggest, that it may well be a faulty thermocouple or fittings thereof. (It could be a loose or dirty connection, this could cause the problem that you are experiencing)

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ali_shujah (1); brettj1au (1); bwire (1); ChaoticIntellect (1); fire (1); MOBI (1); Rediah (2); SimpleMind (1); welderman (2)

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