Focus sharpens on maintenance for standby power systems

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By Jack Ward, MD of Powermode

The reliability of diesel generators – whether they are used for prime or backup power – and other standby power systems has largely been associated with the frequency with which they are serviced. Now, as increased incidence of load-shedding and unplanned power outages plague South African power users, the quality of their maintenance programmes is coming into focus.

When called upon to do duty, generators and other standby systems must be able to work to full capacity every time. The costs of a call-out to attend to urgent repairs that might be necessary when a system fails on start-up or during operation at critical times are compounded by the additional downtime suffered by the user.

Unfortunately, when it comes to regular servicing and maintenance, many important procedures are often overlooked on a day-to-day basis by owners who ignore their standby power units until they are desperately needed in an emergency.

In the case of a diesel generator, for example, regular inspections are vital. They should include the fuel lines together with filters and fittings which should be checked for cracks or abrasions. The exhaust system should be checked as ‘blow-by’ could cause fires. The electrical system could be the root cause of many problems. Trouble here will make starting problematic.

In addition, load transfer testing of automatic transfer switches at regular intervals will keep track of the generator’s electrical and mechanical integrity. Other components to be checked regularly include starting and timing relays, start signal continuity and utility power phase sensing.

Regular inspections must include the monitoring of all fluid levels, oil pressure and coolant temperatures. Most engine problems give an early warning. Clues include misfires, vibration, excessive exhaust smoke, loss of power or increases in oil or fuel consumption.

At the same time, inspect the exterior of the radiator for obstructions and remove dirt or foreign material. Change the coolant filter every 12 months and also drain, flush and refill the cooling system.

Diesel fuel is hydroscopic, attracting water which contaminates it. Thus it’s important to use stored fuel before it degrades. In addition, the fuel filters should be drained on a regular basis. Water vapour also accumulates and condenses in the fuel tank and must also be drained annually – along with any sediment present. The frequency with which air cleaner filter elements is replaced is generally determined by operating conditions.

Like their human counterparts, diesel generators need regular exercise. Units that are on continuous standby must be able to go from a cold start to fully operational status in seconds. This imposes a severe burden on engine parts. However, regular exercise keeps engine parts well lubricated, fluid lines unclogged and prevents harmful oxidation of electrical contacts.

Today it is becoming common for generators to be complemented by uninterruptible power supply (UPS) systems within the framework of a seamless, corporate-wide standby power solution.

When a power failure occurs, the role of the UPS is critical. It must be able to operate flawlessly, otherwise data corruption or malfunctioning computer equipment could result in costly repairs.

Because a UPS lies dormant for long periods of time, aside from smoothing out electrical currents when necessary, it’s critical for the device to be checked on a regular basis. Biannual servicing is an important step in ensuring that power outages are dealt with efficiently.

While the life span of any UPS depends on the size, type and environmental conditions of the unit, its servicing schedule – particularly of the UPS battery – could make a significant difference to its longevity.

It’s important to note that merely checking the output voltage of batteries is not indicative of their ability to deliver adequate power. As batteries age, their internal resistance to current flow goes up. Therefore, the only accurate measure of terminal voltage is achieved under load.

Service checks and maintenance should be undertaken from both operational and safety perspectives by qualified technical personnel. Ideally, the task should be outsourced to a specialist firm.

UPS systems are often linked to corporate computer systems which monitor and manage them via a Simple Network Management Protocol (SNMP) interface. This provides monitoring and will indicate any faults enabling fast response and repair.

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