By: Cas | Posted on:

A compressed air leak detector is a device specifically designed to find compressed air leaks. Because it works by listening for ultrasonic sounds, it's often called an 'ultrasonic leak detector'. Compressed air leak detectors are frequently used for compressed air audits. If you're not familiar with what a compressed air audit is, let me explain.

Compressed air audits

The goal of a compressed air audit is to reduce energy cost of your compressor installation. It does so by both looking at the supply and demand side of the compressed air system. The supply side includes your compressors, they pressure setpoints, the control system (especially when there are multiple compressors) and more. The demand side of the audit looks at things like compressed air usage, changing to equipment that use less compressed air, lowering pressure drop in the piping system, and... finding (and fixing) compressed air leaks! ## Compressed air leaks

All compressed air system have leaks. Leaks can be anywhere: pipe joints that are leaking, valves that are leaking, equipment that is leaking and (quick connect) couplings that are leaking. It is said that in a typical industrial compressed air system, 20 - 30% of compressed air is wasted because of leaks. When you consider that 70% of compressed air costs is electricity, you will understand that a 20% leakage is a HUGE waste of electricity and money! A typical 100 kW air compressor uses about $40.000 per year in electricity! 20% compressed air leakage equals $8.000 per year! Wasted! ## Finding compressed air leaks with a compressed air leak detector

You can find big leaks simply by listening for them. Do this when the factory is shut down, in the weekend or evening. You will be able to spot many big leaks this way. But, it's harder to find the small leaks this way. And you will not notice any leaks in the overhead piping system. Most sound coming from a compressed air leak is ultrasonic. It is of such high frequency that we can not hear it. A compressed air leak detector, converts the ultrasonic sound to a lower frequency that humans can hear. ## Leak detector models

There are basically two types of ultrasonic leak detectors: close range and long range. The long-range type looks like a microphone and is used to detect air leaks at a distance, for example at the overhead piping system. [caption id="attachment_463" align="alignnone" width="300"] Ultrasonic leak detector (photo: Atlas Copco)[/caption] The close-range type is better suitable for finding air leaks inside and around equipment. It looks like a 'sniffer' on a tube. Since (generally) only 5% of the leaks is in the piping system and most leakage occurs at the working floor (inside and near the pneumatic equipment), a close-range type is probably the best to buy. Some compressed air leak detectors have a headphone, others have an indicator or peeping sound to indicate a leak is found. It is easiest to find a compressed air leak with a leak detector that has a headphone and that amplifies and lowers the frequency of the sound. With those devices you can really hear the leak, instead of some beeping sound or indicator. ## From ultrasound level readings to leak air flow

When you receive the results of a compressed air audit, you will notice that leak detector readings are converted into airflow and annual energy costs. While this is nice and gives a rough estimate, don't take it too seriously. The leak detector usually gives a reading in dB (decibel) to indicate the loudness of the compressed air leak. This dB level is converted into a leak size. The conversion factor difference between brands and models. But, it will always be an estimate and nothing more. For example, a 60 dB reading might convert into a 2 cfm (56 l/min) leak at 100 psi (7 bar). ## Buying a leak detector

An ultrasonic compressed air leak detector will cost you anywhere between $350 and $3500. The more expensive are mostly units that can be used for many applications (bearing monitoring, electrical equipment monitoring, hydraulics monitoring, and of course compressed air leak detection). The cheaper units are mostly dedicated leak detectors. Here are some places I found online where you can buy a compressed air leak detector: STD They have 3 different high-end professional models. SKF SKF has two different leak detectors. Professionalequipment.com Lots of different makes and models. From very expensive to relatively cheap.