Oil flooded rotary screw air compressor - low ambient temperature 1

[lghqh]

My company just purchased two air-cooled oil flooded screw air compressors. The actual site temperature range is -15 to 40 C,but the manual says the air compressors can only operate at the minimum ambient temperature above 0 C.

Is the 0 C degree limit applied for all oil-flooded air compressors?

Is there any solution for that problem? Since the air compressors are indoor installed with duct on outlet. I plan to have an electrical damper on the outlet duct, when the compressor room temperature is below zero C degree, the damper will close, and a bypass opening will conduct the exhaust hot air to the compressor room to warm it. Please see if it is practical.

 

[crjones]

It is applied to all screw compressors, but your supplier should have optional features that will permit lower temperature operation. The concerns are freezing of condensate in the aftercooler, moisture/separator trap, and controls. And as it is oil flooded the low temperature viscosity performance of the oil needs to be examined. This not only on start-up but also the flow of oil through the air cooled heat exchanger. If there is no oil when the thermal bypass valve opens to the cooler you have a high temperature shutdown or worse.

 

[lghqh]

Thanks crjones.

I contacted with the Vendor, it seems that 0 C is their standard. They don't want the room temperature under zero degree. Using exhaust hot air to warm the room in the winter is their proposed solution. Since oil flooded screw compressors are widely used in the world, I am wondering if they are operating in this way in the winter, anyhow, only a small portion of the world are tropical.

 

[zdas04]

The answer to your question has a lot of answers but they all start with your assumptions. The concern is about the process gas being below 0C at the compressor suction. So a flooded screw that is compressing wellhead gas at -50C in northern Alberta in July is seeing gas that came from deep in the earth and is generally above freezing when it gets to the compressor. An air compressor in a plant on the North Slope of Alaska or southern Patagonia can't be designed to handle raw inlet air and will have the ability to blend heated air or go through an air-to-air heat exchanger to use engine exhaust or air from a heated space to blend enough heat to stay above freezing.

There are a lot of possible techniques, but they all require knowledge of the local conditions and of the heat sources that a clever engineer can adapt to his needs.

David

 

[crjones]

Well there are things that you can do to help yourself. First install a heater in your moisture/separator trap, this is usually an add on kit from the manufacturer of the trap. Second if your unit is enclosed you can put a heating lamp or space heater that shuts off when the motor starts. Local regulations will direct you as to what is allowed. Use an ISO 32 synthetic lubricant. In operation, allow the unit to idle for ten to fifteen minutes before bringing it into your system. Two other adjustments that require a bit more effort are to put a weep hole in the thermal valve so it constantly bypassing a small flow of oil maintaining flow in the cooler. The second is to put a temperature switch on the fan so it does not start until it is needed. However do not cycle the fan, once it comes leave it on. Otherwise you will thermal stress the cooler.

I hope this helps.