ACG+

Five Parameters at Once, Continuously

Compressed breathing air can go wrong in several ways at the same time, and each has a different cause.

The ACG+ continuously monitors oxygen, carbon dioxide, carbon monoxide, volatile organic compounds and water vapour (dew point), and displays them together. A sample port allows oil mist to be checked as well.

All five matter because they point to different problems. Low oxygen or high carbon dioxide points to the intake or the process. Carbon monoxide can point to a combustion source near the intake, such as vehicle exhausts, or overheating in the compressor. VOCs and rising water levels can point to a compressor problem. Measuring one and assuming the others are fine is how contaminated air gets breathed.

Continuous monitoring is the other half. Even new, well sited and well maintained compressors can fail, and contaminants can enter through the intake at any time. A spot check, such as testing with colorimetric tubes at intervals, only tells you the air was acceptable at the moment it was tested.

It Can Shut the Compressor Down

This is what separates the ACG+ from a testing instrument, and it’s the specification worth building the installation around.

Audible and visual alarms are backed by relay outputs. A relay can drive a beacon, or shut the compressor down when an alarm is triggered.

The difference matters. An alarm tells someone there’s a problem and depends on them acting. A shutdown stops the contaminated air source without waiting for a person. On a system supplying breathing apparatus, that’s the difference between an indication and an engineering control.

Early Warning of Compressor Problems

The continuous sensors also say something about the compressor itself.

Analox explains that water vapour is usually what exhausts the desiccant filters first, so rising water levels are a good sign that filters are overdue for replacement or service. Elevated water can also point to high operating temperatures, or seals beginning to fail. Rising VOCs and CO can likewise point to a compressor running hot.

So the monitoring helps diagnose the compressor, as well as protecting the people breathing from it. When these readings rise without an obvious cause, Analox recommends an oil mist check using the sample port. Catching a problem early helps prevent contaminated air being used, and lets the repair be scheduled rather than forced.

The ACG+ doesn’t replace regular preventative maintenance on the compressor, but it gives the maintenance team better information.

Checking for Oil Mist

Oil mist is checked through the sample port, using industry standard colorimetric tubes or a device such as an impactor. That’s a one shot check, not continuous monitoring.

The continuous VOC, CO and water sensors fill that gap. Many of the faults that generate oil mist also produce these contaminants, so a rise in any of them is the prompt to carry out an oil mist test. With mineral oils, the VOC sensor (a 10.6 eV PID) is a reliable way of detecting oil mist. With synthetic oils, it’s an indicator that a fault may have occurred.

Field Replaceable Sensors

The ACG+ uses Analox intelligent sensors: MEC electrochemical sensors for oxygen and CO, an MEC PID sensor for VOCs, and a 5S3 NDIR sensor for CO2. Analox has made the sensors easy to change out.

A proprietary humidifier option prolongs the life of the electrochemical CO and O2 sensors in continuous use.

Portable or Fixed

The same instrument covers both, and the choice changes what it does.

In a robust carry case, the ACG+ is a portable analyser that’s taken to a compressor, connected, and used to check the air. A proprietary dew point sensor lock out system gives fast start up, which suits multi point checking for a business with several compressors, or a service provider checking client systems. Battery options give up to 12 hours of portable use.

In a purpose built housing, it’s a fixed installation monitoring one compressor continuously, with the relay wired to shut the compressor down. That’s the arrangement for a critical system where air is being breathed continuously.

It connects after the compressor and before the end user or cylinder, so contaminants are detected before they reach their destination. Inlet pressure is regulated down to 5 to 10 bar. 90 days of data logging is kept either way, retrieved over USB.

Standards

The ACG+ is certified to BS EN 12021, the European standard for compressed air for breathing apparatus, as well as DEF STAN 68-284 for military vessels, NAVSEA SS521-AK-1-010, the US Navy Dive Manual and BS 8478. That’s worth having where a client specifies an international standard, which is common in marine, defence and diving work.

For Australian work, check the requirements against the standard your client specifies. Our Technical Consultants can help.

One honest limitation: the ACG+ measures the five parameters it measures. Where a risk assessment identifies a hazardous substance producing another harmful gas, additional detection is needed.

Where It’s Used

Breathing air compressor installations. Commercial and offshore diving. Fire and emergency services breathing air. Marine and naval vessels. Confined space entry using airline breathing apparatus. Spray painting and coating. Abrasive blasting. Chemical plant and refineries. Mining. Any operation where breathing apparatus is fed from a compressor rather than a cylinder.