Compressor Question

[benchmark]

I need your expert advice.

I have recently assembled a silent compressor,i used an old english model called 'Bambi'  . It is one of the old models, solid construction, yellow in color if you know the series. It is an oil compressor and Bambi is world famous for making quality and silent compressors. I dissected my old but reliable cheap chinese compressor that was as loud as a dumper truck and i used the 24 liter tank, valves and gauges to make this one that is so quiet that it can run at shows under my table without anyone hearing it
. I found the manual online for the engine which states that it is designed to have a 50% duty cycle  and i have done some trials to test it .  In my test trials, i noticed that the compressor is on for about 1 min 54 secs then rests for 2mins 45 secs before it kicks in and switches on again for another 1min 54 secs. So in theory this is within the recommended 50% duty cycle.

Today after running for 2 hours , i used my infra-red thermometer to check the temp through the oil sight glass and it was 60 degrees centigrade so i manually shut it off after 2 hours in fear that itwas too high.


My question is if you think the 60 degrees was normal? if yes how hot should i allow the compressor to get before i shut it off?
 Do you think this compressor can be used with the above described cycle over a 7 hour period for the display ?
Thank you for your time.

Here is a pic.

[Bluechip]

Not all that good on compressors. Mine runs very hot on the air-cooled cylinders. Far to hot too keep your hand on.

If this compressor is run under a similar regime to DC servo-motors, there's two bits to the duty-cycle.

One is the part you have ie. 50% or 1:1.

The other is the 'absolute maximum' ie, how long can it be operated in the ON part.

EG

Duty cycle 33% or 1:2

Max 5 minutes.

So, the most it can be used is 5 mins ON : 10 mins OFF.

After all 1:1 could be 1 day on: 1 day off. Duty cycle would be satisfied, but it would probably not survive.

Dave BC

[John Stevenson]

60 degrees isn't hot for oil, oil will happily run at 90 degrees all day.

Duty cycles are usually based on 10 minute cycles but it all depends on the manufacturer. the 10 minute cycle is very common for welding machines.

John S.

[lordedmond]

Benchmark

as to your trials you say 1 :54 on 2:45 off

is that with no draw ? then you have a leak

try it with a test engine /tool or WHY then see what is the the duty cycle is it could be 90 % on 10 % off


is that Bambi big enough to supply your anticipated draw off at its rated duty cycle


Stuart

[benchmark]

Benchmark

as to your trials you say 1 :54 on 2:45 off

is that with no draw ? then you have a leak

No leak, it is with the compressor supplying air to run 3 model engines.

The compressor gets to 6 bar (where i have set it) shuts off for 2:45 mins , by then the air is down to 4 bar so it kicks in again for 1:54 mins till it reaches 6 bar again...and so on.
This is the cycle i will be running for 7 hours at a stretch and i will like to hear if you guys think that is pushing it too far. As stated i test run it for 2 hours when the oil temp got to 60 degrees centigrade and i turned it off.

[lordedmond]

if thats the run time with the draw that you intend to use then it should be OK but do not come round for a refund if it fails 


Stuart

[Bogstandard]

I used to borrow a friends silent compressor, very similar size to that one, for displaying my engines at shows. An ex pub cellar compressor.

Invariably it stood on grass at most of them (steam rallies), and I used to run it 7 hours a day, none stop for up to 3 days. Never a missed beat. Only problem was the small tank used to be half full of water at the end of each days running because of the damp environment it was in. I knew it was time to empty the tank when the models started to run with more water than air in them.

I did that for about 10 years, and as far as I know, the compressor is still running OK today.

I honestly don't think you need to worry, unless you are doing that sort of running continuously.


Bogs

[Noitoen]

Unless stated otherwise, duty cycle is always based on the hour. It's the same with welding equipment, some of the new inverter machines say 180A 30% duty cycle, others state the same current but 10% duty cycle. 2 minutes on and 2 minutes off means 50% duty cycle and 60ºC isn't hot. If you doubt it, try to measure your refrigerator's compressor on a hot day and you will be surprised with the temperature it reaches.

[Scuba1]

Our compressor at work is factory set to cut out at 110C and on a busy day runs at 85 to 90 c so you are on the cool side with the 60 yours is running at.


ATB

Michael

[dickda1]

Agree, I have a monster 70 gallon, 5HP compressor out of a machine shop that runs quite hot at the cylinder head.  It is important to change the oil periodically if required (also drain the tank of water regularly).  The tank is so big that it only runs about every 10 minutes or so unless I am using a die grinder.

[benchmark]

Thank you for all the advice guys.