Kaeser air compressor SX 21 model over heating

by kilari naveen kumar
(Al jubail, kingdom of saudi arabia)

this compressor we are using in our sea port site, we are facing over heating issue all the time can u suggest us from mechanical side and electrical side, we try by cleaning all the things but still the same. there is regulate witch connected to the oil separator tank through the small hoses, when we close the regulator the pressure building up up to 5.5 bar but at the same time temperature also building up and trips when it reach 110 deg, when we open the regulator completely temperature going down and pressure building only 1.5 bar so can u suggest us what need to do to rectify the issue

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Mar 02, 2016
In addition
by: Carl

In addition to my previous comment, whilst your compressor is onload (pressurizing the air) make sure that it isn't venting at the same time (listen closely to the air filter for rushing air).

If it is, then it is possible that the vent diaphragm is split or damaged.

The diaphragm is located in the square brass valve held together with 4 allen screws, one of the hoses goes to the air filter.

You could also try servicing the MPV (minimum pressure valve) it could be stuck open or the seals worn. It is located after the separator and before the cooler, also made of brass, BE VERY CAREFUL WHEN TAKING THIS VALVE APART, YOU CAN CAUSE SERIOUS DAMAGE TO YOURSELF IF HANDLED INCORRECTLY. YOU MUST DRAIN THE AIR FROM YOUR WHOLE SYSTEM BEFORE ATTEMPTING TO DISMANTLE. It is also spring loaded, so keep hold of it, my advice is to get a compressor engineer to do it for you.

Mar 02, 2016
by: Carl


When you say you "turn the regulator at the separator" what does the regulator look like? If you mean it is a valve that turns 90 degrees then that isnt a regulator, it stops the separator tank from venting, allowing the oil to be ejected when you switch the machine off.

Please could you take a photo of your machine and the "regulator" you speak of, so i can get a better idea of what your problem might be? (Start a new thread to upload photos and cross reference to this post)

But in the meantime, check your oil level and top it up if needed, blow out the cooler, check to make sure the air filter isn't blocked.

Please reply to this message when you have checked all of the above.

Kind Regards,


Mar 01, 2016
by: Doug in s.d.ca

Is that the right model? I'm only finding sx20...

Is this a new problem on an existing installation?

Anyway, You've verified the fans are all working?

Serviced the separator?

Sort of sounds like poor oil circulation.

And the weather has been nice there... if this is in a building, what's the ambient temperature?

You've checked the power to be correct for the machine's configuration?

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