we have a ZR-450 model from atlas copco company oil free screw compressor
capacity= 2696 Nm3/hr
max outlet P = 10 bar
power consumption= 450 kw
the current cooling loop is such that the CW is entered to after cooler (15C) then goes through inter cooler and then to oil exchanger and then to second stage screw and then to first stage screw and finally to an air preheater and then exit the package at a temp of 25C.
input air P = 0.84bar
first stage compression: 2.6 bar
second stage compression: 8 bar
we want to use fresh cooling water for the first stage because the air temperature goes up to 210C and the machine trips. washing and descaling of pathes doesn’t solve the problem.
Is this change safe? what other problems may occur if this change is done?
Thank you for your question.
Before changing anything with the cooling water flow, please make sure that this is 100% the cause of the problem. Is it confirmed that scaling is the cause of the high temperature?
Many times, the overheating of the HP or LP element is caused by other things, like wear on the rotors or too high or too low intercooler pressure. The LP and HP element work in a perfect balance. Of the capacity/condition one one changes, it will change the whole balance. This might result in over temperatures on the *other* element.
Do you have some recordings of past pressures and temperatures? If you have, please send them and I will have a look. If possible, supply: intercooler pressure, output pressure, LP element temperature in and out, HP element temperature in and out. Ambient temperature maybe.
You mention: “input air P = 0.84bar”. Is this compressor installed on a high altitude? This could be the cause for the high temperature on the LP element. How has the compressor performed in the past?
About the cooling water: I know the cooling water circuit of different Atlas Copzo ZR types are different. Older Atlas Copco oil free compressors (ZR3 – 4 – 5) have separate cooling water flows.
– 1x oil cooler + LP element + HP element + 1x intercooler
– 1x aftercooler
The biggest one, the ZR6 has 3 separate water flows:
– 1x oil cooler + LP element + HP element
– 1x intercooler
– 1x aftercooler
Atlas Copco specifies the cooling water temperatures as maximum 35 till 40 degrees inlet temperature. Maximum 50 degrees outlet temperature.
Your cooling water temperatures are way lower than this (15 – 25 degrees), so should not give any problems.
Did / can you check the pressure (in / out) and flow of the cooling water?