My gas turbine has got a tripping on high lube oil header temp. at 80 degrees celsius.

Could you people share your experiences in this regard on your machines?

Also what effect could it cause to the machine?

Thanks. Hoping great participation.

The lube oil needs cooling, isn't it?

Was there proper cooling or spurious trip?

As a mechanical person, this is almost certainly an instrument problem but, just in case it isn't, then the following might help:

The lube oil performs 2 functions:

a) lubrication
b) removing heat (from bearings).

The lube oil tanks of many GTs are fitted with thermostatically controlled heaters to ensure that the oil reaches a certain minimun temperature before the control system will 'allow' a start to take place: this is to ensure that the oil meets viscosity (and flow)requirements for that particualr engine. Too high or low a temeperature means that the oil viscosity might not meet the flow requirments during a start from cold. Too high an oil temperature will give a low dT which will not allow adequate heat removal as well as a reduced viscosity.

So... as a starting point, check the operation of any thermostatically controlled heater in the lube oil system (make sure it is switching off when temeprature is made).

Secondly, following start-up, whilst the oil in the tank/system is warming through as it passes through the engine, the oil cooler is not yet required and the oil flow can be made to by-pass the coolers via a 3 way thermostatically controlled valve - you need to check to see if this is working properly and not stuck in by-pass position - you can do this by touching the discharge piping of the valves and seeing which branch warms up when the valve opens (or use a non-contacting temperature measuring device if access is difficult).

Similarly, using a non-contact temerature measuring device, follow temperature changes around the entire oil system after a start from cold to see if these provde any indiction of the problem location (e.g. Location 1 would be a measure of temperatures before and after any lube oil component e.g. leaving and re-entering lube oil tank, location 2 would be temperature before and after cooler, location 3 would be temperature before and after any valve etc - measure and plot these tempratures each 30 seconds or so in order to highlight possible problem locations.

You should check that the oil cooler fans are working as specified.

You might have a hot gas leak inside the GT which is heating an oil flow passage or a carbon build up in an internal passage which is restricting flow and adding execssive heat to the lower volume of oil that does flow.

Dear Josh Cooling is thru skid fans.

But there has been an larm persisting for two days of high temp ( at 75 degrees Celsius) before trip. We didn't see to it as actual rise of temp.

As Buzz Light Year says we thought it to be an instrument malfunction.

Now I would check the temp. control valve and temp. on lines before and after oil coolers.

Dear Buzz Light could u explain how can I check thermostatic valve in running.

Too high an oil temperature will give a low dT which will not allow adequate heat removal as well as a reduced viscosity.

By low dT you mean higher viscosity index limit?
Think I am bit weak in getting your detailed answer. Hope you will help me.
Thanks

Did the GT trip during start up or during normal running?

Dear Josh it tripped on normal running

yahoo, Is it the same turbine for which you complained about high mist generation earlier ?

No its another machine. Though it too has similar problem of very small scale.

I checked the cooling water valves on lube circuit and found them to be fully open manually.

This message has been edited. Last edited by: yahoo,