Atomizing Air Temperature Control not steady


Thread Starter


Please i have facing badly fluctuation in Atomizing Air System in all Gas Turbine. In fact every ten minute Alarm appear (Atomizing Air Temperature Low & Atomizing Air Temperature High). The Fluctuation between temperature around 60 °C. The atomizing air cooler has two VFD Fan. Turbine control mark VI and Fram V. The fuel use diesel liquid .

Please can you give me what the problem or fluctuation causes ?
Please, you have a Frame <b>5</b> and a Mark VI.

When did this problem start? After a maintenance outage? Or has it persisted since commissioning or some other event?

I have never seen an atomizing air cooler that doesn't use water, but, I haven't seen everything.

If the cooler uses VFDs, what are they doing? Are they increasing and decreasing speed rapidly?

Have you looked at the Atomizing Air temperature gauge? I presume that if the coolers use VFDs then there is a mA input from an atomizing air temperature transmitter, and the VFDs are driven by mA outputs.

So, it would seem that something is amiss with the temperature feedback, or with the wiring to the VFDs.

Please write back with the results of your troubleshooting.
it persisted since commissioning. CSA cooler control only by VFDs and that strange fan only working when alarm coming high then temperature decrease quickly to level of 85 DGR C then fan stop after 15 minutes again the same situation.

Maybe there are some mistake in the control of fans ..
Okay, the problem has persisted for some time and the supplier was allowed to leave without correcting the problem. Which follows, since all the questions were not answered. They were:

>If the cooler uses VFDs, what are they
>doing? Are they increasing and
>decreasing speed rapidly?
>Have you looked at the Atomizing Air
>temperature gauge? I presume that if the
>coolers use VFDs then there is a mA
>input from an atomizing air temperature
>transmitter, and the VFDs are driven by
>mA outputs.

I apologize for not putting the last question in the form of a question punctuated with a question mark.

To me, VFD means <b>Variable</b> Frequency Drive, a device that will vary the speed of the motor that it's powering, usually in proportion to a variable signal supplied to it (usually a 4-20 mA signal). So, the first question was asking if the fan speeds are varying or just running at a constant speed or how they are operating.

The second question asked if you have verified that the <b>actual</b> AA temperature was unstable by looking at a temperature gauge that is probably installed somewhere close to the suction of the AA compressor.

It implied that a temperature sensor/transmitter is being used to provide an indication of the AA temperature to the Mark VI, and was attempting to ask if that signal and its source has been verified (is the sensor/transmitter working properly?) Is it a T/C or multiple T/Cs, or a temperature transmitter or multiple transmitters, or an RTD or multliple RTDs, or a couple of temperature switches? Are they working correctly?

Lastly, I was trying to find out if you've monitored or checked the output(s) driving the VFDs, which are probably 4-20 mA outputs, to see if they are operating properly.

Best of luck with your problem.
Okay,yes it is increasing and decreasing speed rapidly when alarm coming to 115 deg.

it never seen VFD working constant speed and during normal temperature the fan stop condition. and when the temperature increase up to 115 deg the only one fan from their working rapidly to decrease the temperature but temperature reach to 125 deg then second fan start. i see the control of fan reached to 1800 rpm sorry i do not know about 4~20 mA.

And, for AA temperature gauge it is install after cyclone separator. There are three transmitter
I'm presuming the fans are being controlled by the Mark VI,, which isn't a big stretch, but never having seen a configuration like you're describing it could be an entirely self-contained "skid" with its own controller.

If you can determine the fans are controlled by the Mark VI you need to find someone to look through Toolbox and decipher how the fans are being controlled (inputs and outputs) and then run the Toolbox Trender to record the inputs and outputs and see what's happening to determine if the problem is with the Mark VI or something else.

It would seem that if VFDs were used for cooling, they would be controlled by varying their speeds in proportion to the temperature, and even possibly operating them by staring one fan and running it up to near rated speed before starting the second, possibly with some lead/lag motor selection as well. But these are all presumptions.

But, without more information (Toolbox .m6b file; P&IDs; etc.) it's really hard to say what the problem might be with any degree of certainty.

I would have to believe the commissioning crew wouldn't leave something as critical as this system not working properly, but it has been known to happen. If the unit is still under warranty you should request the supplier/packager to return to rectify the problem.

Please write back to let us know how the problem is resolved.