Centrifugal Compressor- Governor Issues

[Nick47]

Hello,
In our centrifugal compressor- turbine driven the governor position becoming more and more open and intermittently spiking to fully saturated recently.
The governor has been saturating quite frequently but the control also appears erratic.
In addition as I understood recently we are using too heavy an oil in our governor(much heavier than recommended).
Could the governor be sticky, is it possible?- if yes how can I validate it?
Could be any control issues with the governor?
Thanks

 

[3DDave]

For a start confirm the kind of oil that should be in the governor and make sure that's what is used.

 

[JJPellin]

Too little information provided. Could be the electronic governor. Could be the I/P converter. Could be the hydraulic actuator. Could be the linkage. Could be the valve rack. Could be a worn out turbine. Could be steam conditions.

Johnny Pellin

 

[LittleInch]

You've answered your own question.

Put in the recommended oil.

By "heavy" do you mean higher viscosity?

Temperature of the oil

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Nick47]

Thanks for all the responses.
It is haydraulic actuator and yes I mean higher viscosity.
I am thinking about another possibiility which is having new process gas characterstics with higher molcular weight then we need more power/ steam.

 

[georgeverghese]

Or more feed flow which results in higher speed / more power if control scheme is to maintain suction pressure constant. Higher mol wt of feed gas does not increase power demand if suction and discharge pressure remains the same.

 

[LittleInch]

First, fill the governor with the correct viscosity oil!

Then see what happens.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Nick47]

@Georgeverghese
Can you please explain more?
To calculate centrifugal compressor power, we need these gas properties: compressibility factor (Z), molecular weight (MW), inlet gas temperature, inlet gas pressure, outlet gas pressure, adiabatic component (Cp/Cv), and mass flow rate. so change in mol wt will affect, Cp/Cv, mass flow rate, head, R, then it is not easy to say what will happen with power consumption unless doing calculation with the real parameter- still I believe increasing mol wt is high probable reason for this issue.
your thoughts?

 

[georgeverghese]

In all cases, high mol wt increases mass flow. However, power demand remains relatively unchanged (for the same chemical component slate in feedgas), and this is due to a higher polytropic exponent (stemming from higher Cp/Cv) which accompanies the higher mol wt gas. This is, in turn, because polytropic head drops for higher mol wt gas. You can confirm this by actual calcs, assuming you have good values for polytropic exponent for this higher mol wt gas. Discharge temp is affected by higher mol wt gas, also due to higher Cp/Cv; it tends to drop.
Converse occurs for lower mol wt gas. Lower mass rate, lower poly exponent, offset by higher polytropic head.
Higher power demand is in these cases typically due to higher standard volumetric flowrate (Sm3/hr)
What service is this compressor in; presume driver is a steam turbine ( condensing or non condensing backpressure turbine) ?

 

[georgeverghese]

Obviously, power demand will be higher also if, in a steam turbine, the exit steam pressure changes. On a backpressure turbine for example, if backpressure spikes up temporarily, power demand will rise.