Centrifugal Compressor- Flow Sensor

[Tony Pan]

Dear All,

Does anyone know how to calibrate a flow sensor on centrifugal compressor?

Regards

Tony

[ptsac]

lets have some details, make, model some more description please.

[Tesla]

Hi Tony
Welcome to the forum. Yes please lets have some details here. - Chilled water?, Padle switch?, Differential pressure switch?, Flow sensor like siemens?.

[Tony Pan]

I was asked this question by someone and i did not know what he was talking about hence my query to you all out there.

A flow swith/paddle switch is readily adjusted using the small grub screw.

A flow sensor was mentioned, because of my limited experience on centrifs, i was not clear if there is flow dsensor fitted that monitors refrigerant flow and thereby controlloing the speed of inlet vane positions?

PS apolagies for posting the same thread 3 times, it is my first thead and i am just getting used to the system.

Regards Tony

[ptsac]

Tony,
I have never came across a refrigerant flow sensor on any centrifs. That doesn't mean they don't exist, maybe something used on vfd models!! There should be an oil diff pressure switch or sensor and the usual pressure switches. the vanes should control from leaving chilled water and desired load and motor current. Some screw compressors have an oil flow switch.

[Tony Pan]

Dear ptsac,

Thanks for clearing this up for me. Varaible frequency drive would just not draw as much refrigerant from the evap at a low speed thereby reducing the flow of refrigerant at part load conditions. The vanes position as you say are controlled by the leaving chilled water temp but how is motor current related to the vane positions? Is it to maintain a certain motor temp i.e. if motor current rises above a preset limit then the vanes open up to draw more refrigerant and therefore cooling the drive motor.?

Thanks

Tony.

[ptsac]

Dear ptsac,

Thanks for clearing this up for me. Varaible frequency drive would just not draw as much refrigerant from the evap at a low speed thereby reducing the flow of refrigerant at part load conditions. The vanes position as you say are controlled by the leaving chilled water temp but how is motor current related to the vane positions? Is it to maintain a certain motor temp i.e. if motor current rises above a preset limit then the vanes open up to draw more refrigerant and therefore cooling the drive motor.?

Thanks

Tony.

I,m not sure that vfd models would have a refrigerant flow sensor, I am only sure that I have never come across one. I dont wish to mislead you. Some manufacturers may have control elements that I have not come across.
The difference between evaporator and condenser pressure ( the lift pressure) are an indicator of system conditions and perhaps some may use that as a flow for your original question.
Motor current is related to vane control as the vanes will dictate how much refrigerant volume through the compressor. Motor amps are a deciding factor in the range of vane opening. The motor will not be allowed to exceed 105% of rated load Amps. The vanes must be closed on start to prevent an overload condition.
Motor cooling is normally via liquid injection to the windings.