Hi,
Contaminant could be responsible for foaming, lack of control of Ph is also an indicator.
I would ask support from the supplier of chemicals for your cooling system .
My view.
Pierre

Is this a new system or a new installation or a new charge of antifreeze? Did it ever not foam?

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There is probably a leak in one of the heat exchangers, most likely the refrigerant - glycol chiller HX. The refrigerant ( ammonia or HCFC ?) would have to be at a higher pressure than glycol solution at the leaking HX.

Thank you for your help.
Our refrigeration system is a newly applied system. We know of no leaks in the system.
When We shook the EG 30vol% solution in a PET bottle, we saw that many small bubbles were formed, and the bubbles disappeared in a short time.
During pumping, It seems to be originally generated, So I'm concerned that the efficiency in the heat exchanger and the generated bubbles would affect the pump.

Seems like either it's boiling or air is being entrained.

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Is there is a vortex breaker at the liquid outlet nozzle of the glycol solution expansion drum that feeds this pump ? Low level at / inadequate size of this drum can also result in gas carry under ( from the vapor space of this expansion drum) into the liquid exit feeding this pump.

Hi,
Weird, from Foaming tendency now we are talking about bubbles, air ingress, vortex!
Real problem or just a fear? Did you check the performance of the unit and what is the result?

Pierre