Mechanical Technology February 2015

⎪ Proactive maintenance, lubrication and contamination management ⎪

In the light of Eskom’s predictions that load shedding is likely to be implemented regularly during 2015 and until all six units of Medupi are synchronised, Jack Ward (right), MD of Powermode, a power management, backup and standby power systems specialist, gives simple and sensible advice about keeping backup diesel generators healthy so that they always perform when they are needed. Generator reliability through preventative maintenance

T he longevity, performance and reliability of diesel generators, whether for prime or backup power – rest mainly on the quality and frequency of preventative maintenance. Monitoring and mainte- nance regimes also minimise the need for emergency repairs and ensure that when called upon to do duty, the generators will work to full capacity every time. This is particularly important during power out- ages, when standby power systems are required to function first time, every time. Unfortunately, when it comes to regular servicing and maintenance, many critical procedures are overlooked on a day-to-day basis, particularly by owners of standby generator plants who often ignore them until they are desperately needed in an emergency. Because there is no ‘driver behind the wheel’ when a generator is running, regular inspections are vital. First, study the technical data provided by the manu- facturers. Then begin with the exhaust system, including the manifold, exhaust pipe and silencer. Look for leaks at all connections and joints, including welds. ‘Blow-by’ could cause fires.

Inspect the fuel supply lines, return lines, filters and fittings for cracks or abrasions. Ensure that the lines are not in contact with any object that could cause an eventual wear-through break- age. Repair any leaks or change the line’s routing to eliminate wear. The electrical system could be the root cause of many problems. Check the battery terminals for clean and tight connections. 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. Look and listen for misfires, vibration, excessive exhaust smoke, loss of power or increases in oil or fuel consumption. Checking the oil level (when the en- gine is not running) is a simple procedure. Oil should be changed every 12 months

– no matter how much running has been done. Follow the engine manufacturer’s recommendations for API (American Petroleum Institute) oil classification and oil viscosity. When the oil is changed, also change the oil filter – and remem- ber to dispose of it responsibly to avoid environmental contamination. Check the coolant level daily and top up if necessary. Diesel engines require a balanced coolant mixture of water, antifreeze and coolant additives. At the same time, inspect the ex- terior of the radiator for obstructions and remove dirt or foreign material. If available, use low pressure compressed air or a stream of water in the opposite direction to normal air flow to clean the radiator. Change the coolant filter every 12 months and also drain, flush and refill the cooling system. Check that the radiator fan belt is not frayed, cracked or lacks the correct tension. Diesel fuel is hydroscopic, attracting water which contaminates it. Thus it’s important to use stored fuel before it de- grades. In additional to other fuel system services recommended by the engine manufacturer, the fuel filters should be drained on a weekly basis. Water vapour also accumulates and condenses in the fuel tank and must also be drained annu- ally – along with any sediment present. The charge-air piping and hoses should be inspected daily for leaks, holes, cracks or loose connections. Tighten the hose clamps as necessary. The frequency with which air cleaner filter elements is replaced is generally determined by op- erating conditions. Air cleaners typically contain a paper cartridge filter element which can be cleaned and reused if not damaged. Inspect the system’s lead-acid batter- ies, of which there can often be two sets depending on configuration; the starting

Monitoring and maintenance regimes for backup diesel genrators minimise the need for emergency repairs and ensure that, when called upon to do so, the generators will work to full capacity every time.

14

Mechanical Technology — February 2015