Keeping it simple saves cash01 March 2004

Factory services like compressed air and steam systems are classic examples of functions that are only noticed when they go wrong. Nowadays, like - thankfully - modern cars, these systems can be relied upon to work consistently. But - also like cars - this reliability often means that failures are more painful, because you're less well prepared. And, while your car not starting in the morning just means you'll be late for work, your air or steam supply failing will usually have a catastrophic effect on the entire operation.

One approach to minimising breakdowns is to run a major programme of planned maintenance. Rather than waiting for a component to fail, service or replace it at predetermined intervals. Planned maintenance is effective - and should form part of an effective servicing regime - but, because failures are inherently unpredictable, it isn't the whole story. Simple good housekeeping - keeping an eye out for obvious indicators of a likely failure - should also play an important role in maintenance activity.

"Most breakdowns happen because of simple things being overlooked or ignored," says Alec Elliott, service director with CompAir. "Call it good husbandry if you like, but you can massively improve your performance just by keeping on top of straightforward maintenance."

Condensate drains

Elliott says that condensate drains are among the most frequently ignored part of compressed air systems. "People either don't install enough drains, or they forget about them," he says. "They get clogged up with bits of rust and clag, and water gets down to the process end. And if you're using compressed air to power a paint spraying system, say, moisture can be a really big problem." Pneumatic components are especially prone to failure, and, while engineers will identify and fix the breakdown, they don't always work back to find the cause - the bunged-up condensate drains. Elliott cites one automotive plant he recently visited, which used a compressed air powered press to stamp out crankshafts. "The company complained about the press continually breaking down," he says. "But they hadn't realised that the lack of working drains was the source of the problem."

Condensate problems can also cause difficulties in steam systems. Surveys made by steam equipment supplier Spirax Sarco at speciality chemical manufacturer Great Lakes Chemicals' Trafford Park site in Manchester - which makes flame retardants and water treatment compounds - have led to substantial energy savings and improvements in maintenance procedures.

Surveys conducted in 2001 analysed all 749 of the site's steam traps and found that 20% of them had failed, wasting an estimated £77,000 of steam generation costs per year. A further survey of the entire steam system resulted in several recommendations for improvements. The most cost effective of these was to return condensate back to the boilerhouse from clean systems. Previously, concerns about contamination had led the company to dump all condensate to ground, losing an estimated £1,000 a week in energy. Now, about 80% of condensate is recovered.

Subsequent replacement of faulty steam traps, the installation of condensate pumps and other measures to recover condensate have all contributed to a substantial drop in steam consumption - saving more than £50,000 in energy costs. This equates to a payback of well under one year.

Proactive approach

The surveys have also helped the site's maintenance procedures to shift from being reactive to a more efficient proactive approach, says maintenance manager Keith Murphy. "Previously, our maintenance engineers would have to work at short notice as faults arose with no diagnostic tools. A key part of our improvement plan is to have tasks actioned in a planned manner with people and materials available before failing equipment causes a problem. This helps avoid production delays and will enable us to cut our overall maintenance and energy costs."

Murphy has instigated annual surveys to help plan maintenance but is looking to increase their frequency to twice yearly in critical areas. A recently completed steam trap survey has identified remedial work that is likely to achieve further annual energy savings of about £11,000. Great Lakes is also planning to install Spirax Sarco steam meters to accurately measure the savings being achieved by the maintenance programme.

When the operating environment is harsh, maintenance procedures must, naturally, be more thorough. Ideally, of course, compressors and similar equipment should be isolated from the main factory floor, but in many companies, this isn't possible. Dirty air being sucked into the compressor will result in more rapid deterioration of components - clogging filters, or destroying the purity of oil - and therefore demand more frequent maintenance. Alec Elliott refers to one plant that machined graphite, resulting in carbon fragments being sucked into the compressor and coating electrical components - with unfortunate consequences. Hot air will require more energy to compress it, and the compressor will consequently run hotter - resulting in more oil penetrating the separator.

Maintenance shouldn't just be focused on the compressor and pipework. A consistent quality of electrical supply is essential for effective operation - higher voltage, in obedience to Ohm's law, forces the equipment to draw more current. More current means more heat, and more heat means more breakdowns.

Most compressors provide an oil temperature gauge, and keeping a close watch on this gauge offers an important warning of forthcoming problems. Between 70 and 80°C is normal; when weather conditions are extreme, the oil may fluctuate slightly in either direction, but any significant moves in temperature may herald a malfunction. Check the oil level, and, if that is OK, check the cooler - which will usually be a cold air blaster. "Hotter oil will cause quality problems, but it will also increase consumption," says Elliott. "Compressors are like cars - most users don't check the oil level anywhere near often enough. When did you last check your car's oil gauge?"

Pressure problems

The pressure of the system is another key sign of impending problems. Upstream and downstream pressure should obviously be pretty similar - if there is any significant pressure drop between the compressor itself and the process end, it may mean there's a fault with the air/oil separator. Again, not only can such problems hurt quality, but they will also increase energy costs. If the requirement is for pressure of 8 bar at the process end, and normal compressor pressure is 8.5 bar, and system problems mean that the compressor in fact has to maintain 9 bar, then electricity costs will increase by 6% - bad enough in itself, but also resulting in increased strain on the compressor's motor, making major failures more likely.

Out of sight, out of mind is a familiar story where compressor and steam systems are concerned. Independent steam consultant Keith Shuttleworth - who specialises in clean steam systems for pharmaceutical operations - says that systems often receive no maintenance whatsoever, and that very basic attention can improve performance dramatically. "A lot of the good engineering practices developed in plant engineering are completely ignored in steam systems," he says. "There's often great emphasis put on quality of pipework, but this is rarely a major problem. Instead, users ought to focus on good engineering practices to deliver steam of appropriate quality." Alec Elliot of CompAir also emphasises a back to basics approach. "Don't be afraid to open equipment up and have a look inside," he says. "Most failures can be spotted by simple signs such as oil leaks or belt wear. These are not difficult to identify, but you have to take the basic precautions."

SOE

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