maintain operations, avoid revenue loss.
To safeguard facilities from
the disastrous consequences of power
disruption, more companies are
choosing to invest in standby power systems.
Investing in such a system can be quite expensive — often at a price
tag running into the hundreds of thousands of Naira most expecially in Nigeria.
Companies and Churches must understand what it takes to properly operate and maintain
their power equipment, as a lack of generator maintenance or
operation knowledge will undoubtedly result in generator
failure at a time when they need it most.
With today's complex standby power systems, you must understand
the basic settings of your systems, the methods and procedures
involved in regular maintenance, and the protocol to deal with
alarm conditions in the case of system failure. This
information will keep you from wasting valuable business
time over generator failure due to inaccurate settings or
neglected maintenance. Let's take a look at seven of the most
common reasons generators fail to start in the first place, and what you
can do to try and prevent these from occurring.
Battery failure
For the generator that uses battery,the single most frequent
service call for generator failure is related
to battery failure. Eighty percent of all battery failure is related to
sulfation buildup — the accumulation of lead sulfates on the
plates of lead-acid batteries. This buildup occurs when the sulfur
molecules in the electrolyte (battery acid) become so deeply
discharged that they begin to coat the battery's lead plates. When
enough plate area has sulfated, the battery will not be able
to provide enough current and will normally need to
be replaced. Battery failure is commonly the result of low
electrolyte levels — battery plates exposed to
air will immediately sulfate.
Battery cells are shorted when sedimentary trays fill up with lead debris.
You can avoid shorted batteries if you replace them regularly. Some
experts recommend replacing them every three years.
Although battery failure can result from open cells, this is not a
common occurrence. Open cells are the result of an overcurrent of
the battery system. If a generator system has had several battery
failures determined to be caused by open cells, the unit may require
larger batteries capable of higher cold cranking amps (CCAs).
Frequently, battery failure is due to the charger breaker
being open or tripped — often the result of human error rather
than actual charger failure. This usually occurs after service
on a generator, or some type of maintenance, where the charger has been
turned off and not turned back on again when the service
is completed. Always double check a generator system after
any service or maintenance to make sure everything is functioning properly.
Because many battery problems are caused by dirty and loose
connections, maintenance is critical. Cable connections
need to be regularly cleaned and tightened. Battery charger
failures are difficult to prevent, and cannot be accurately
predicted. However, monitoring the charge rates from month to month
will establish a trend that can help map the potential
for failure. A properly functioning battery charger will have
a constant charge rate for any given system. An increase of amperage
may show signs of a battery or charger malfunction.
Low coolant levels
The most obvious cause for a low coolant level is either an external or
internal leak. Pay close attention to any visible puddles of coolant
during weekly inspections of the unit(s). The color of the coolant varies
by manufacturer and may look like red-dyed diesel fuel. Inspect oil
for any signs of color change or a milky texture and hoses
for “crusties” — the sign of coolant seeping and additives drying
up at the connection. While many generators are equipped with
low coolant level alarms, few have a dedicated alarm indicator for
low coolant. Commonly, this alarm will be tied in to a high coolant
temp shutdown circuit.
Internally plugged radiator cores will also cause low coolant
level shutdowns. When the generator is under load, the thermostats
open completely, and the radiator cannot allow the proper amount
of flow through the core. The coolant has to go somewhere, so it
purges through the overflow line. As the engine cools off and the
thermostat closes, the level drops and activates the low coolant level shutdown.
This also occurs when float switch-type coolant level sensors are used, and
the lines are plumbed to the top and bottom radiator tanks. When the
thermostats open, the path of least resistance is through the float
switch lines, and the flow causes the float to drop and shutdown
the engine. The thermostat will not open enough to cause this during
regular weekly running of the generator. It will have to be tested under
load to cause the thermostats to fully open. A full load test
with an external load bank is the only accurate way to check a cooling system.
Controls not in auto
“Not in auto” messages are the direct result of human error. The obvious
reason for “not in auto” situations is because the main control switch
was left in the off/reset position. This usually occurs after testing or
servicing of a generator. After any service is performed on a unit, always
double check the generator system yourself.
The control switch may have several positions as
in “off/reset” and “cool down,” which will cause the generator
not to start in the event of a power outage. These positions should give
an alarm. “Not in auto” is a generic term for the unit not being shut off, and
may not actually be the main control switch.
Alarms not reset, breakers open, switchgear not reset, and emergency
stop buttons activated are all examples of “not in auto” failures.
Several generator makes/models are set up to short trip the main circuit
breaker during an emergency fault shutdown. When the generator shuts itself
down for any reason, someone has to physically reset the control panel to clear
the alarm. There may be several things to check and reset after
a fault shutdown; however, this should only be done once the cause
of the alarm has been identified and corrected.
Air in the fuel system
This is a common problem with newer generators that are not run on a regular basis.
Closer tolerances within the fuel systems to meet today's emission requirements
make fuel systems more susceptible to air affecting startup. This is not as
common with older generators — many of which may have a leak in a line or check
valves that are not properly holding the fuel in the engine.
Lighter low-sulfur fuel has lower flash temperature, which causes the block
heater to flash off some of the fuel within the injectors. One small bubble
of air within a unit injector solenoid can cause an injector not to
fire at startup. If enough injectors do not fire, the engine will not start.
This failure is 100% preventable by periodically running the engine
during weekly inspections. The engine does not need to be run until
the coolant temp comes to normal. All that is needed is enough time to
verify that the engine will start, that the air is cleared from
the fuel system, and that the generator comes up to voltage and
frequency. This can be completed in less than 5 minutes. Any additional
test running would simply burn up fuel and air quality maintenance run time.
Ran out of fuel
Mechanical fuel level gauges may not always be accurate. Unlike a vehicle
that is moving and using a higher percentage of its tank's capacity, a generator
tank has no movement, causing the fuel to become stagnant.
Mechanical gauges may also stick in a position until vibrations break them free.
Low level alarms must also be addressed, as they provide the
same failure alarm. Some generators are equipped with
“low level shutdown” or “critical fuel level shutdown.” These shutdowns
are there to prevent the fuel system from drawing in air when
running out of fuel is eminent. Bleeding air out of a fuel tank
can be an extremely difficult procedure.
Running out of fuel due to plugged fuel filters can be prevented by
maintaining the fuel tanks and periodically checking them for water
and contaminants. Water or moisture in fuel can be damaging to diesel
engines because the water properties create advanced ignition and
accelerated detonation. If you use fuel polishing as an alternative
to cleaning your fuel, check with your vendor to see if its fuel is
affected by the chemicals; fuel polishing may not be able to remove water.
Fuel filter plugging should be expected with the new ultra-low sulfur
fuel, which has a very high detergent level and will clean out your
lines and whatever else it comes in contact with.
Engines equipped with electric shutoff solenoids should always
have a manual bypass. There are several reasons to have shutoff
solenoids; large remote above ground tanks can gravity feed to the
engine, overpressuring the seals in the pumps or injectors and
causing the fuel to mix with the oil. Solenoids should be DC power
activating at the time of initial crank signal and remaining open until
after the engine makes a complete stop.
Breaker trip
First, verify that nobody has accidentally pushed a remote emergency power off switch.
If a breaker trips after the automatic transfer switch (ATS), the
generator will not start. The status of the automatic transfer switch
should be checked during a power outage. The ATS should have lights or
a display showing the switch position and source availability.
If you find a breaker tripped, make sure you can determine the cause
of the trip prior to resetting.
Never try to manually operate an ATS if you don't know how to do so properly.
Severe bodily injury or immediate death can occur. The transfer switch is
smarter than you think and has a specific reason for being in its current
position; attempting manual operation may drag you into a live bus if done incorrectly.
Oil, fuel, or coolant leaks
Most often, oil leaks are not in fact leaks but the result of
“wet stacking” (or “engine slobber”) caused by excessive no-load run time.
Diesel engine generators are designed to operate with a
load — most effectively in the 70% to 80% range of rated output.
When generators operate considerably below the rated output level, the
engine can start to over-fuel or “wet stack” and damage the engine.
Wet stacking — an accumulation of carbon particles, unburned
fuel, lube oil, condensed water, and acids in the exhaust system — is caused
by low-combustion chamber temperature. When a diesel engine wet stacks, the engine
will need to be cleaned up by loading the unit for a few hours and burning
off the excess fuel. If a diesel engine generator steadily runs loads
considerably below the rated output level, you should pair the generator
with an automatic load bank, which will place a false load on the
generator system, keeping the engine properly loaded and preventing
a “wet stack” condition.
Another cause of oil leaks is directly related to the
crankcase breathers. Most engine crankcase breathers vent directly
under the engine. The fumes that come out of the breather contain an
oil mist, which can produce a puddle under the engine and coat the
generator and radiator with an oil film that collects dirt and debris.
Recirculating breathers are available that can separate the oil and
return it to the engine; remaining fumes get returned to the engine air intakes.
The most common coolant leak occurs in the block heater hoses.
Extreme temperatures on the outlet make block heaters hard on
their hoses. For this reason, you should never use rubber hoses
for block heaters; silicon hoses are specifically designed for use
with block heaters. Always install isolation ball valves for block
heater hose connections.
Cooling system maintenance will help prevent leaks. Replacement of hoses and coolant
every three years is recommended. Generators using newer extended-life
coolant should still have hoses replaced and the additive package upgraded
every three years. Cooling system antifreeze protection and conditioner
should be maintained to the manufacturer's specifications. Radiator core
damage is directly related to the coolant that is in the system. Poorly
maintained coolant will cause liner pitting and eventually severe engine damage.
Most fuel leak service calls are due to overfilling of the base tank. This
is due to either human error or a failure of a pump system. Check remote
tank pump systems and emergency shutoff systems periodically for proper
functioning, and flexible fuel lines regularly for cracks and signs of aging.
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