Turbine and Idle speed

great differance

and no we can't set idle speed less than minimum governer speed

as per the manual Idle speed is 1200rpm, Min Governar speed set point is 2681rpm, max is 3754.!!!!

That is not correct.

Idle speed is generally the lowest speed at which the engine will run reliably with no load (so saving fuel when off-load).

It seems that the minimum governor speed (in your context) is the lowest value that the maximum engine speed can be set to - the governor in this case is limiting the maximum speed, rather than continuously controlling the speed.

Clearly, the idle speed can be set lower than the governor speed.

In and engine you are correct. In a steam or gas turbine the governor is indeed continuously controlling the speed.

First of all, you need to tell us what kind of turbine you are talking about? This has an effect on the definition of terms. Gas turbine, or steam turbine? If it is a gas turbine then what kind? Single shaft or two shaft? Also what is it driving? A generator or a compressor or a pump?

A governor controls over a speed range, so minimum governor is the lowest speed possible during normal operation.

In a steam turbine, idle speed is a speed below the first critical (usually around 1000 rpm), but above slow roll that during startup you run the turbine in order to get steam flowing through in order to heat it up and allow for turbine thermal growth before starting. Based on the speeds you specified this sounds like your case.

Idle speed in a gas turbine is the max speed of the compressor section while on the starter motor. This allows you to bring the machine up to idle speed to clear any gas from the turbine. Once the turbine is cleared, the machine is shut down and restarted in normal start mode. This also might be a speed around 1200 rpm depending on the turbine model.

it is a steam turbine, model number RLHA24, single stage

The next step, then, is a telephone call to these people.