FIELD OF INVENTION
The invention generally relates to jacking oil system for gas turbine application.
More particularly, the invention relates to an improved jacking oil system for
heavy duty gas turbine applications.
BACKGROUND OF INVENTION
Gas Turbine (GTs) also known as internal combustion engines, are the common
prime movers for many applications. GTs have been utilized widely in standby
and peaking applications due to their several technical advantages, in particular
for the low cost installation of the machines. Open or simple cycle gas turbines
are used in virtually all power plant applications. Combined cycle systems, where
heat is recovered from the gas turbine exhaust and used to produce steam which
then drives a steam turbine to produce electricity, have become much more
common in recent years.
The lubrication and jacking oil device is one of the more complex and critical
components of a gas turbine engine. The lube oil system provides lubrication to
various bearings in the gas turbine generator assembly, whereas the jacking oil
provides adequate lift to the turbine and generator rotor during the gas turbine
operation. There is a plurality of known methods used to meet the turbine
hydraulic operation including the jacking requirements.
Figure 01 presents a schematic of a known jacking oil system. In case of gas
turbines of ratings 250MW and above, the jacking oil is required for lifting the
rotors of the gas turbine and generator to reduce the friction. In such gas
turbines, the jacking oil for turbine and generator is received from a common
hydraulic oil system. The hydraulic oil system is normally a 2 x 100% AC motor
driven system, where one pump acts as a main hydraulic oil pump and the other
acts as an auxiliary hydraulic oil pump. Normally, the main oil pump is in
operation. In case of any drop in pressure sensed by a disposed pressure switch
PS-1, the auxiliary hydraulic pump takes over. In case of power failure, both of
these pumps cease to operate leaving the rotors without any jacking oil supply
and subjecting to the rotors to a high level of friction. This in turn reduces the
life of the bearings.
It is known that the jacking oil pressure required for a generator is much lower
than that required for a turbine. In the prior art system, the oil taken from the
hydraulic system is throttled to reduce the pressure and then it is utilized for
jacking of the generator rotor, which does not constitute an efficient utilization of
the existing resources.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an improved jacking oil
system for gas turbine application, which eliminates the disadvantages of prior
art.
Another object of the invention to propose an improved jacking oil system for
gas turbine application, which improves utilization cycle of the gas turbine by
introducing a separate low pressure jacking oil system for the generator.
A further object of the invention to propose an improved jacking oil system for
gas turbine application, which enables increase in life of the costly bearing of the
gas turbine and thus improving maintenance cycle,
SUMMARY OF THE INVENTION
Accordingly, there is provided An improved jacking oil system for heavy duty gas
turbine, comprising a hydraulic oil distribution device comprising of at least two
A.C. motor operated hydraulic pumps, a first of the hydraulic pumps acts as the
main hydraulic pump to supply hydraulic oil to the turbine, and a lift to the rotors
of the turbine during operation, the second hydraulic pump acts as an auxiliary
pump to take over the operation of the main pump on failure and a first pressure
switch provided to sense any pressure drop in oil flow and allowing a transfer of
the operation to the auxiliary pump when the pressure drops below a threshold
value, the improvement is characterized by introduction of a D.C motor operated
hydraulic pump for turbine rotor which ensures availability of jacking oil to
turbine rotor in case of power failure and a dedicated jacking oil system
comprising of an A.C motor operated pump and a D.C motor operated pump
along with a second switch for generator rotor jacking, which enable an
improvement in operational reliability including improved utilization of the jacking
oil without the requirement of throttling to decrease oil pressure.
DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 01: Shows a common jacking oil system of prior art for heavy duty gas
turbines.
Figure 02: Shows a jacl