Hello Cas, my name is John. I'm Interested in buying a new compressor for my body shop.
Currently i'm running (2) 5 horsepower Quincy reciprocating compressors with 80 gallon each. They are old and making a lot of noise and I like to update it with a new reciprocating compressors or screw compressors.
My question is are the screw compressors good for the body shop environment?
The compressors will be on during business hours but will not be running 8 hours straight. They will be going on and off throughout the day to refill the tanks.
I was told by one company that the screw compressors should not go on and off throughout the day, they should be continuously running to prevent premature failure in the future.
If I'm able to use the screw compressors my intentions are to purchase a 5 horse screw compressor for one building that has 2 workers that will be using it for sanding cars and a 10 horsepower screw compressor for the other building that has four workers used for sanding and painting.
Any advice would be greatly appreciated.
That's a great question, and something a lot of people struggle with. And to be honest, there isn't always a clear-cut answer.. so, it depends.
It's right that screw compressors work best when loaded constantly. The screw compressors I have seen that have the least problems are the ones that run all day every day.
But, if they start and stop during the day, that's not necessarily a bad thing. As long as they get a decent amount of work to do each they, that's fine.
The most important thing is that they run long enough at a time to get really nice and hot (around 80 degrees C, or 175 F). That way, all water vapor will be removed from the compressor, preventing a lot of problems.
The most common mistake is to buy a too big air compressor. In that case you are simply not using enough air to make the compressor really work for it.
It's equally important to get the right size air receiver. Bigger is better in your case.
Why bigger is better?
With a bigger air receiver, your compressor will:
- run longer at a time, allowing it to really heat up.
- won't start-stop-start-stop repeatedly.
A lot of start-stops per hour is stressful for a compressor. It puts stress on the motor, main electrical contactors (relays), and compressor bearings (every start and stop is when the bearings will wear down the most).
For example, a too big compressor with small air usage (a % of that the compressor can deliver) and with a small air receiver, might run like this:
- run 2 minutes
- reach maximum pressure setpoint
- go unload 2 minutes
- stopped for 1 minute
(you are using air from the air receiver during this time)
- reach minimum pressure setpoint
- start again
- etc, etc.
This will be really stressful for the compressor and also costs you extra money because of the unload running time (the compressor runs, but it not actually pumping air).
With a bigger air receiver, it might look like this:
- run 10 minutes
- reach maximum presssure setpoint
- go unloaded 2minutes
- stopped for 30 minutes
- reach minimum pressure
This is no problem for a screw compressor, it runs long enough at a time to really heat up, and starts/stops per hour are limited.
So main points are:
- Don't buy a too big air compressor
- Get a big enough air receiver
One last remark: if you're using the air for painting, make sure to get the right compressed air filters! There are different kind of filters that can remove dust and oil.
And if you want to keep your compressor in great shape, one last tip: make it breath fresh air! if you install it inside in a dusty or oily environment.. all that dust and oil will end up inside the compressor and your compressed air!
Best is to install ducting, at least for suction, to make it breath fresh outside air.
Ducting on the exhaust (cooling air) is also a good idea if you live in a hot area.
Hope this helps!
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