captain
Contributor
One question is how does the manufacture calculate output, is it strictly based on displacement and speed or is it actually measured and at what conditions.Temperature and humidity can have a significant effect on efficiency. How did the report determine out put and what were the conditions at the time.
There is a significant difference between a compressor operating in 90 degree 85% humidity and one operating in 50 degree 40% humidity.
A difference of a couple of hundred RPM can also have an significant effect.
Sometimes small leaks can be hard to detect while the compressor is running and a leak while the compressor is running may not be readily found once the compressor is shut down if the leak is in a place that can quickly depressurize after shut down.
My compressor was manufactured in 1968 and is still going with mostly original parts, replacement parts haven't been available in 30 years. With synthetic oil piston ring and cylinder wear is usually very little.
Every time I run it I check speed with a hand held tachometer and monitor cylinder head temperature with an infrared hand held thermometer and the time it takes to pump a 1000 PSI change. By tracking those things I can have a pretty good idea how the compressor is operating and spot problems quicker.
You are right most never pump the rated CFM and I tend to believe it is because it is a calculated not actual number. Mine never has pumped rated CFM of 3.5, it usually runs between 2.8 and 3.1 depending on atmospheric conditions.
There is a significant difference between a compressor operating in 90 degree 85% humidity and one operating in 50 degree 40% humidity.
A difference of a couple of hundred RPM can also have an significant effect.
Sometimes small leaks can be hard to detect while the compressor is running and a leak while the compressor is running may not be readily found once the compressor is shut down if the leak is in a place that can quickly depressurize after shut down.
My compressor was manufactured in 1968 and is still going with mostly original parts, replacement parts haven't been available in 30 years. With synthetic oil piston ring and cylinder wear is usually very little.
Every time I run it I check speed with a hand held tachometer and monitor cylinder head temperature with an infrared hand held thermometer and the time it takes to pump a 1000 PSI change. By tracking those things I can have a pretty good idea how the compressor is operating and spot problems quicker.
You are right most never pump the rated CFM and I tend to believe it is because it is a calculated not actual number. Mine never has pumped rated CFM of 3.5, it usually runs between 2.8 and 3.1 depending on atmospheric conditions.
