Mechanical Technology February 2015

Mechanical Technology — February 2015

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Proactive maintenance, lubrication and contamination management

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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

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.

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.

Generator reliability through

preventative maintenance

– 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