Power Plant Engineering

GAS TURBINE POWER PLANT 285

connects to the tail pipe so that the hot gases flowing out of exhaust will burn off any remaining oil

vapor. This vent must be checked for obstruction regularly; otherwise the air may build high pressure in

the tank and result in its failure. The separator is nothing but a simple baffle which causes the air-oil

mixture to follow a devious path, the oil will tire to turning the corners and will find its way out through

the vent into the tank, and the air will find its way out through the vent into the exhaust system. A drain

plug of magnetic type is incorporated in the oil line before oil pump, which can collect any metal

particles circulating in the oil system. A through study is made of debris collected by the plug to decide

whether it is metal chips or else.

9.6.4 Fuel System and Controls

9.6.4.1 Fuel System
Fig. 9.19 shows a fuel system used in gas turbine. Basically there are two sub-system-low pres-
sure and high pressure. The low-pressure system consists of a fuel tank, boost pump, strainer, dual fine
oil filters, ∆p indicator and ordinary valves. There is a two stages filter process on the low-pressure side
of the system. The purpose of 7.5 micron strainer is to collect the large particles impurities. The boost
pump (centrifugal pump) is used to boost the pressure so that it may overcome the pressure drop in the
two stage of filtration. In the fine filter, all small solid particles are collected as well as the water that
may have passed through water separator located in the users fuel supply system. The dual filter ar-
rangement allows for switching to an alternate element without having shutting down for the change. It
is the ∆p indicator, which warns the operator of the filter condition by indicating the red light for switch
over. The red light glows as soon as the oil pressure drop through the working fine filter crosses over a
pre-determined value.

Indicator∆P

Low pressurestrainer

Here fuelled cooled

oil cooler and fuel

heater may be provided

especially for aviation turbine

Fuel

Booster tank

Duplex pump

low

Pressurefilter Relief valve

Main

fuel pump

Fuel

control

Solenoid

valve

Flow divider

Fuel Fuel

C T

Strainer

(Shut-off

valve)

CC

Fig. 9.19. Fuel System for Gas Turbine.