12
HIRE AND RENTAL NEWS • AUGUST 2014
TECHTALK
One of the most common
maintenance issues faced by
equipment rental companies is the
phenomenon known as ‘glazing’.
This is engine damage caused to
generators either through misuse or poor
sizing. A diesel engine is designed to
operate at above 60% of its maximum load
and ideally closer to 75%.
An engine relies on sufficient cylinder
pressure to force the piston rings to tightly
seal in the bore against the film of oil on
the bore's surface. When an engine is
consistently run at less than 60% load, it
leads to a drop in cylinder pressure which
in turn causes poor combustion and
subsequently low combustion pressures
and temperatures.
The poor combustion allows unburnt fuel
residue to form a treacle like substance
that clogs the piston rings creating an
even greater loss in cylinder pressure.
Now the cylinder rings are not sealing
properly, the hot combustion gases force
their way past the rings and flash bake
the oil on the cylinder into a hard, ceramic
like substance. This is known as glazing or
glazing the bore.
Once glazing has occurred, the honing
marks in the bore which are there to return
oil to the crank case are smoothed over.
The glazing issue becomes a vicious spiral
with poor combustion allowing yet lower
TECH
TALK
Generator “Glazing”
piston pressures and more
unburnt fuel to contaminate
the lubricating oil and
eventually form acids which
would normally burn off if
the engine was operating at
its optimal temperature.
Glazing can cause a diesel
generator to become
irreparably damaged in a very short period
of time. Different engines handle light
loading more or less effectively with some
brands exhibiting significant evidence of
glazing after just 24 hours of misuse.
Once glazing is complete, the engine will
no longer produce its designed output
and in many cases no longer start. This
can only be repaired with a costly engine
rebuild.
So, how to manage this costly problem as a
rental company:
Ensure the generator is sized correctly for
its application. Either use your internal
generator specialists or ask your generator
supplier to assist in developing rules of
thumb around generator sizing.
Regularly ‘load bank’ your generators. A
load bank is a dummy load that enables
a measured load to be delivered to your
generator. Regular load banking can create
heat in the bore and reverse the early
symptoms of glazing.
Train your staff to identify the tell tail
signs of glazing. Early stage glazing will
be evidenced in excess engine smoking
and often a treacle-like substance to
be running over the engine from the
manifolds.
Engage your generator supplier to help
develop preventative maintenance
practices to ensure early detection and
rectification of glazing.
Staying on top of glazing can add years
of life to your rental generator asset and
conversely, failure to do so can lead to
costly rebuilds. Despite this being probably
the most common maintenance issue
rental companies face in their generator
fleets, it is surprising how few companies
have a formal plan to prevent this
expensive problem.
For more information on overcoming
glazing issues or generator sizing contact
Redstar Equipment
Ph: 07 3339 8517
Melbourne:
(03) 9793 9999
Sydney:
(02) 9671 3666
Brisbane:
(07) 3200 6488
Auckland:
(09) 525 8282
Christchurch:
(03) 365 0279
High Quality Dewatering Pumps.
Applications include:
•
Mine dewatering
•
Drainage of pits and quarries
•
Storm water drainage
•
Transfer of liquids carrying sludge or sand
•
General dewatering duties on building and
construction sites
Sakuragawa Pump Manufacturing Company was established in Osaka, Japan in 1953 and is now
recognised as a renown manufacturer of submersible dewatering pumps with a world wide reputation
for quality construction and robust design.
With duties ranging from 100 l/min to 12,000 l/min and heads ranging from 8m to 120m Sakuragawa
is ideally placed to meet the needs of the most difficult dewatering jobs.
Call us today for a Sakuragawa brochure and to see how we can meet your pumping needs.
DELIVERING PUMPING SOLUTIONS
03/14
