Calculating compressed air system leakage

In summary, the compressor has a load, unload and off mode, but the equation used to calculate leakage does not take into account that load and unload are doing opposite things. This leads to an incorrect calculation of 17.68% leakage.
  • #1
sagaris
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I am looking to quanitfy our compressed air system leakage and have followed the usual steps of ensuring all air consuming products are off and then measuring load/unload times.

I intended to use the following formula as found in relevant articles and webpages:

% Leakage = (Tx100) / (T+t)​

where T = total load time
t = unload time

the problem is that our compressor (an Atlas Copco GA 75) has a load, unload and OFF mode (its NOT variable speed) and the only reference i can find that includes load, unload and off into the calculation quite crudley uses the above equation but bundles load and unload together as 'T' then the off mode as 't'.

doing this puts our losses at 17.68% but i am 99% positive this is incorrect, as we have 375 m of 3inch ring main that has never had any air leakage assesment and you can hear it leaking everywhere now that we are in shutdown and then much more so with our ultrasound equipment! apparently 10-15% leakage for a compressor system of our size is acceptable but this just doesn't seem right?! expected plant losses for somewhere that hasn't had leakage assesment before are typically around the 25-40% range.

the load, unload and off equation completely ignores the fact that load and unload are doing opposite things! the off is merely to save energy where as unload is to regulate the desired air pressure. if anything it should be OFF time and unload time together as at that point the rest of the system is not being fed and only the leaks are affecting the system pressure. But by putting unload and OFF times together means the calculation puts leakage at 7.58%...and that is 100% incorrect! (10% is considered a good level of leakage)

any ideas?

thanks in advance
 
Last edited:
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  • #2
I should add that the GA 75 (75KW) compressor is one of two and there is an additional 90KW Variable speed drive compressor, so three in all. its just that this is the only time in the year where just one is running so the load, unload and off times can be measured.

with regards to calculating the system leakage it doesn't matter if one or all 3 compressors are running as the reciever is still being filled to the same pressure as during production, with the exception that there is no production load, so just the one can cope.
 

1. How do I calculate the leakage rate of my compressed air system?

To calculate the leakage rate of a compressed air system, you first need to measure the total volume of air in the system. This can be done by using a flow meter or by timing how long it takes for the compressor to fill an empty tank. Next, measure the pressure drop in the system over a set period of time. The leakage rate can then be calculated using the following formula: Leakage Rate (L/min) = (Volume of air in system (L) x Pressure drop (bar)) / Time (min).

2. What is considered an acceptable leakage rate for a compressed air system?

An acceptable leakage rate for a compressed air system is typically around 10-20% of the total compressed air usage. However, this can vary depending on the specific needs and requirements of the system. It is important to regularly monitor and reduce leakage in order to optimize efficiency and reduce energy costs.

3. How can I locate and fix leaks in my compressed air system?

One way to locate leaks in a compressed air system is by using an ultrasonic leak detector. This device can detect high-frequency sounds that are emitted by compressed air leaks. Once a leak is located, it can be fixed by repairing or replacing the faulty component. Regular maintenance and inspections can also help identify and fix leaks before they become larger issues.

4. What are the consequences of having a high leakage rate in a compressed air system?

A high leakage rate in a compressed air system can result in significant energy and cost losses. Not only does it require the compressor to work harder and consume more energy to compensate for the lost air, but it can also lead to decreased system performance and increased downtime due to the constant need for refilling the system. This can ultimately affect productivity and profitability.

5. How can I prevent or reduce leakage in my compressed air system?

One of the best ways to prevent or reduce leakage in a compressed air system is through regular maintenance and monitoring. This includes identifying and fixing leaks, properly sizing and maintaining equipment, and using efficient control systems. Additionally, implementing a leak detection and repair program and investing in high-quality components can also help minimize leakage in the long term.

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