Cheap, leaky air can raise costs is not checked

Today, compressed air is used in every conceivable sector of industry and sometimes gains the idea that it is 'cheap', but leakage can be costly, says David Share.

Today, compressed air is used in every conceivable sector of industry.

The fact that it is so commonly used has, for decades, led British industry to conclude that it is 'cheap' to produce, says David Share of Asco Joucomatic UK.

The truth, however, is that it never has been.

Compressed air is produced using electricity; its generation being equivalent to about 10% of industry's total electricity usage, rising to 30% in some sectors.

These are weighty figures and highlight why companies have compelling reasons to investigate the potential for energy saving in this area.

Avoiding Leakage - one of the most fundamental ways in which the efficiency of any compressed air installation can be improved is by reducing leakage.

This is undoubtedly the most logical place to start as research has revealed that leakage rates exceeding 50% of site consumption are common across many industries.

There are however, some general guideline ways of reducing opportunities for leaks: * Don't generate at a higher pressure than necessary - the higher the pressure, the more air that will escape through a given-size hole.

* Don't keep your whole system pressurised during non-productive hours just because a few items of machinery require a constant supply of compressed air.

* Do isolate parts of the system that require air at different times.

Isolation valves can be operated manually or automatically using simple control devices like time switches or interlocks, or they can be controlled using your building energy management system, if you have one.

* Do take advantage of the fact that under the Pressure Systems and Transportable Gas Containers Regulations, you must inspect your compressed air system regularly.

These inspections are an ideal opportunity to find and repair leaks.

Where to look for leaks: * Pipe work, flanges and fittings - the main artery for delivering compressed air is ring main pipe work systems.

In many factories the pipe work is old and a prime source of leaks.

A check of the system for pipe work sections that are leaking or corroded, followed by their replacement, will not only improve the system but will also improve safety.

In addition to the pipework itself, large leaks are often found at connection points where screw fittings or flanges are employed.

These leaks are frequently caused by pipe strain due to inadequate supports, inadequate joints or twisting.

Manifold connection points - another potential problem area is where connections to a usage point are made using snap connectors with flexible hoses.

Sometimes several are used together, forming a manifold arrangement.

Such manifolds can leak due to worn connectors and poorly jointed pipework.

In addition, where flexible hoses are used to make connections between the piping network and usage points, leaks can be caused by any number of factors.

These include: damage to the hose, due to abrasion by surrounding objects; strain on the joint because the hose is too long or short; by deterioration of the hose material, or just by choosing the wrong material, especially where the working environment is aggressive, oily or hot.

* Automatic drain traps - if a compressed air system uses automatic drain traps, these should be 'zero loss' types, and should be checked to determine whether they are functioning correctly.

Some drain traps are not reliable and, in practice, they are often bypassed so that the condensate can be released from the system.

This is undesirable as large amounts of compressed air can be lost.

A way to overcome this is to use electronically operated zero loss condensate traps.

These are very reliable, and by fitting them the requirement for bypassing can be removed.

* Filters - filters are an indispensable part of any pneumatic system.

They can, however, be the source of quite large leaks.

Potential problem areas are drainage points on the filter bowls, including poorly sealing automatic drains, badly fitted bowls and bowls that have been contaminated by synthetic compressor lubricant.

Downstream from the filter is not normally the area where the factory engineer would expect to make major savings by reducing leakage.

This is true in the main, but useful contributions to the overall plant savings target can still be obtained by checking such things as connections to regulators, lubricators, valve blocks and sensors, and the internal air seals on pneumatic cylinders, which can cause large leaks * Air tools - air tools consume large quantities of compressed air in operation.

In many instances their consumption is exacerbated due to leaks that occur at the hose connection and/or the speed control valve.

Worse still, occasionally air tools are left running, even when not in use.

* How to look for leaks - the most simple and cost-effective method of checking for leaks is using the time-honoured soapy water method.

However, this is messy and has to be performed directly on the equipment or pipework being tested - a problem when the leaks are high up in factory ceilings.

A better method is an ultrasonic detector.

These can detect leaks from over 50 feet away, even in areas of a plant where noise is a problem.

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