Gas Turbine

Lube Oil System

1. The Lube Oil System performs the following functions:

• Supplies lube oil for lubrication and cooling to the bearings of the gas
turboset.
• Supplies oil to the power oil system .
• Supplies oil to the jacking oil system .

2. The system supplies lube and cooling oil to all bearings of the train shaft:
• Gas turbine bearings
• Generator bearings
Pre-pressurized forwarding oil to the:
• Power oil system
• Jacking oil system

Component Description

3. Lube Oil Tank: Lube oil is stored in the tank , which is the supply source
for the entire auxiliary block.

4. Oil Vapor Exhaust Fan: The tank volume above the oil level is ventilated by
oil vapor exhaust fan . The drain orifice and the ventilation flap valve
maintain a slight vacuum not only in the tank but also prevents oil from
leaking through the oil retaining rings of the bearing pedestal and in lube
oil return pipes from all bearings. If there are bearing leaks, this vacuum
prevents lube oil or oil vapor from leaking outwards

5. Main Lube Oil Pumps: supplies all lube oil required

6. Emergency lube oil pump: The pump itself is of similar type as the main
oil pumps, but it is powered from batteries or UPS (Uninterrupted Power
Supply) and runs only for test purposes during start up of the gas turbine or
in case that the pressure of the main lube oil pump in operation should
drop below the preset level or if a manual switch over from operating to
stand by pump is performed during operation of the GT. The discharge of
the emergency oil pump is located after the coolers and filters for two
reasons:
 • Oil can be delivered to the system when these components are block
• Elimination of the pressure loss from these components allows the DC
pump to be designed for a lower discharge pressure and less power
consumption.
For safety reasons, the DC motor is not protected against overload. For
additional safety, the DC cables are protected by steel pipes and heat
resistant insulation. For sufficient lubrication and cooling, the emergency
lube oil pump will run at fast speed during shutdown. During the following
cooling time the pump will run at low speed. This feature prolongs the
availability of the batteries

7. Lube Oil Temperature Control: Downstream from the cooler, the

thermostatic valve maintains the oil temperature
at a constant value by passing part of the oil around the cooler.
• Hot oil from the pump and the cold oil from the cooler are mixed in the
internally-sensed thermostatic valve;
• A cartridge with the expanding (controlling) thermostatic element moves
the
control cylinder to open either the cold or hot oil supply.
• During longer operation all oil flows over the cooler

8. Lube Oil Filter: To ensure trouble-free operation of the bearings, the lube
oil must meetrequirements as specified in the document “Lubricating and
Control Oils forTurbines” which is part of the Operation and Maintenance
Manuals. For this reason, a filter is provided capable of removing particles
down to 6 μm

Jacking Oil System

1. System Function

The jacking oil system

- Supplies high-pressure oil to the journal bearings of the gasturboset
where it forms hydrostatically a lube oil film between journal and lower
bearing shell at standstill or at low rotational speed of the rotor. This
means lifting the shaft, ensuring the complete separation of the two
 surfaces, and thus enabling the rotor to “float”.
As soon as the rotor turns at higher speed, the oil film will be formed
hydrodynamically enabled by the design of the bearing, the bearing’s
clearance and the quantity and viscosity of the supplied lube oil. The
jacking oil system is then switched off.
- Reduces the starting torque during start-up of the gasturbo set.

2. The jacking oil is not in service:

- During a complete standstill of the gasturboset.
- When the rotational speed is above 90 % of nominal speed

Hydraulic Rotor Barring System

1. System Function

- Uniform Temperature Distribution. The hydraulic rotor barring system is

used to turn the rotor before start-up and after run-down of the gas
turboset to ensure uniform cooling of the rotor in order to prevent
bending.
After shut down when the rotor has come to standstill the upper and lower
stationary and rotating components experience a temperature difference
whichresults in deformation.
For the rotor this thermal deformation means bending in upward direction.
A bent rotor might lead to a contact between the blade tips and/or the
casing and between the vane tips and the rotor shaft during the cool-down
period. Under this circumstances the gas turboset would severely be
damaged when a start-up is initiated.
To avoid this possibility, the hot gas turbine is slowly and continuously
turned by the rotor barring system ensuring uniform temperature
distribution in the rotor.
The operation of the hydraulic rotor barring must continue until the
turbine has cooled down to the “cold GT release temperature” shown in
the Operation Concept.
- Stress Relieve In order to maintain a steady readiness for an immediate
start of the gas turbo set we recommend to operate the hydraulic rotor
barring also after the gas turbine is cooled down.

Power Oil System

1. System Function

- The power oil system supplies pressurized and filtered oil via power oil
distribution system to the protection system and to the hydraulically
operated equipment of the gas turbine under all operating conditions:
• Gas turbine hydraulic trip unit.
• Control valves, trip shutoff valves and relief valves in fuel (natural) gas,
fuel oil and NOX water supplies.
• Compressor variable inlet guide vanes (VIGV).

- The operating power oil pump is provided with pre-pressurized oil from
the lube oil distribution system.

Electro Hydraulic Safety

1. System Function

In the case of an emergency situation for the gas turbine detected either
- by the protection system of EGATROL or
- by the operator.
Immediately the fuel supply to the gas turbine must be shut-off, the blow-
off valves must open and the generator must be disconnected from the
electrical grid – with other words the gas turbine must be tripped.
An immediate and safe trip of the gas turbine is performed by the hydraulic
trip unit which is the link between the protection system of EGATROL and
the gas turbine.
The gas turbine is tripped via the electro hydraulic safety system (EHSS).
- By the EGATROL’s protection system.
- By following the programmed protection rules
(1out of 1, 1 out of 2, 2 out of 3).
 - By manually pushing one of the emergency push buttons.
- By a loss of the electric power supply (power cut, blackout).

The hydraulic trip unit is connected to the power oil system. When
controlled by EGATROL in a way that:
- The three trip valves are energized.
- The staging valve controls the oil flow from port P to port B.
Pressurized oil is leaving port B. This oil is called safety oil and enables –
when
reaching the correspondent steps during a start-up sequence – the opening
of the fuel shut-off valves and the closing off the blow-off valves.

Fuel gas system

1. System Purpose

Fuel gas supply MBP01 supplies pressurized fuel gas, at a flow rate
corresponding to the power output demanded by the gas turboset, via the
fuel gas control block to the EV burners of the combustor and to the
ignition gas unit

2. Abnormal Operation

# Protective Load Shedding (PLS) PLS is a protective action, which is

implemented wherever possible instead of trip to reduce thermal stress on
the gas turbine. PLS is a controlled unloading of the gas turbine at a
predetermined gradient until separation from the grid and idle load
reached.

-If the process parameter, which has caused the protective action, can be
brought back within safe limits before the shut-off valves close, the
unloading procedure is automatically interrupted. Once the cause of the
malfunction has been eliminated, the gas turbine may be reloaded after
the PLS command has been acknowledged.

# Protective Load Shedding Trip (PLST)

- PLST means a controlled unloading of the gas turbine similar to protective

loadshedding PLS, except that no cooling time is implemented. As soon as
 the gas turbine is separated from the grid and idle load is reached, the
shut-off and control valves are closed. This protective action is
implemented in cases where not only unloading but also speed reduction is
required.

Load / Grid Rejection

- Load rejection:
Generator breaker opens at any load. A load rejection is initiated in the
case of generator or electrical equipment failures. The gas turbine load will
be reduced immediately. The gas turboset is thereafter controlled in idle
operation. Load rejection is always accomplished via the speed controller.
If the failure can be solved the generator can be synchronized and loaded
again.
Grid rejection:
High Voltage (HV) breaker opens at any load. A grid rejection is initiated in
case of grid failures or equipment failure of the HV breaker. The gas
turboset load will be reduced immediately down to house load (Island
Mode) and remains in this status. Grid rejection is always accomplished via
the speed control. If the failure can be solved the generator can be
synchronized via the HV breaker and loaded again

Gas Turbine Trip

A gas turbine trip is initiated in case of an emergency. The immediate

shutdown of the fuel supply causes an instantaneous decrease in load,
temperature and mass flow. At the same time the generator circuit breaker
is opened and the automated shutdown program is started. The shutdown
program secures a proper and save shutdown sequence of all systems.
Generally, the signals, which lead to initiation of a trip are measured and
evaluated in a two out of three redundancy within the gas turbine
controller.
 WATER STEAM CYCLE
Main condensate system
Condensate:

• Is the water that comes up after steam from steam turbine condense in
the condenser

• Is inappropriate for use as feedwater for HRSG as it needs chemical

dosing first

• Can be replenished into condenser hotwell by demin water make up

system

 The main condensate system fulfils the following tasks:

 Condensing the steam from the steam turbine exhaust and bypass
stations

 Delivering the main condensate from the hotwell to the deaerator /

feedwater tank

 Delivering condensate to the bypass stations for desuperheating

 Delivering condensate to the flashbox and the steam turbine exhaust

hood desuperheater system for desuperheating

 Delivering condensate to be used as a sealing water

 Collecting non-condensable gases for removal to the atmosphere

 Collecting condensate from the steam turbine drains, the ejector system
and the gland steam system

 Compensating water losses with demineralized water (make-up water)

 Ensuring the required minimum flow rate through the service ejector
inter and after condenser and gland steam condenser
 Ensuring the required minimum flow rate through the condensate
extraction pump

Feedwater Storage and Deaeration System

 The feedwater storage & deaeration system fulfils the following tasks:

 Storage of feedwater for the HRSG

 Controlling the feedwater tank level by compensating water losses with

demineralized water (make-up water) via the condenser

 Controlling the pressure/temperature in the feedwater tank by

recirculation of feedwater through the HRSG economizer and with pegging
steam from the LP steam line

 Separating non-condensable gases from the feedwater to the deaerator

Feedwater Pump System

 The feedwater pump system fulfils the following tasks:

 Feeding the HP and LP drums of the HRSG with feedwater from the
feedwater tank

 Providing the LP economizer recirculation line with feedwater for heating

of the feedwater tank

 Providing the fuel gas efficiency heater with feedwater from LP

economizer as a heating medium

 Providing the HP main steam attemperator/desuperheater of the HRSG

with feedwater for water injection
 main steam system
The main steam system fulfils the following tasks:

 Transfer the HP steam from the HRSG to the steam turbine

 Transfer the LP steam from the HRSG to the steam turbine

 Providing the air removal system with motive steam

 Providing steam to gland steam system of the steam turbine

 Providing the deaerator with pegging steam

 Providing warm up steam for the HP bypass control valve

turbine bypass system

The turbine bypass system fulfils the following tasks:

 Taking over the produced HP and LP steam of the HRSG during plant start
up and shut down while the ST is still not in operation or the ST is not able
to take over the whole HP and LP steam

 Taking over of the produced HP and LP steam of the HRSG in case of ST

trip or ST load rejection

 Keeping the HP and LP steam pressure and pressure gradient within

defined limits

clean drain system

 The clean drain system fulfils the following tasks:

 Draining of condensate out of the steam lines and the steam turbine

 Initial warm up of steam lines

 Steam and condensate separation

 Collecting the condensate and forwarding it to the atmospheric drain
system

Main and auxiliary cooling water system

The main and auxiliary cooling water system fulfils the following tasks:

 Transfer waste heat from the condenser and CCW intercoolers to the
external environment (e.g. sea)

The closed cooling water system

The closed cooling water system fulfils the following tasks:

 Transfer waste heat from various Closed Cooling Water System (CCW)
heat sources to the Main Cooling Water System (MCW) via the CCW
intercooler water/water

The air removal system

The air removal system fulfils the following tasks:

- Air evacuation of the steam turbine, condenser neck, condenser, flash box
and feedwater tank during start-up of the plant

- Venting of the non-condensable gases from the deaerator and the

condenser during normal operation
 The chemical dosing system
The chemical dosing system fulfils the following tasks:

 To establish conditions that

 avoid corrosion

 avoid deposition

in the Water Steam Cycle

 Chemistry control by injecting 3 chemicals in the Water Steam Cycle

circuit :

 Ammonia (e.g. Ammonium Hydroxide)

 injected at the pipeline in main condensate system

 the purpose is to control the pH at around 9.2 – 9.6 in order to minimize

corrosion

 Oxygen scavenger (e.g. Hydrazine) (1/2)

 injected at the pipeline in main condensate system

 the purpose is to remove the remaining oxygen in order to minimize

corrosion which is still trapped inside Water Steam Cycle circuit after being
removed in the feedwater tank (through deaerator) and condenser
(through service ejector)

 Hydrazine reacts well with dissolved oxygen in water > 150 0C

N2H4 + O2  N2 + H2O.

 Oxygen is not good for Water Steam Cycle circuit as it creates insoluble
ferric hydroxide (rust)

 Phosphate (e.g. Trisodium Phosphate)

 injected at the HRSG HP and LP drums

 the purpose is to control the pH at around 9.2 – 9.6 in order to minimize
corrosion

 Ammonia can’t be used in HRSG drums as it tends to evaporate in the

steam

 Phosphate is non volatile and will remain in the drum and can only be
removed by HRSG blowdown

Water and steam sampling system

 The water and steam sampling system fulfils the following tasks:

 Measure, monitor and control the process parameters of the Water

Steam Cycle such as

 water conductivity

 pH

 dissolved oxygen

 silica

 hydrazine

in order to comply with the requirements for correct operation and good
preservation of the plant

The fuel gas supply system

 The fuel gas supply system fulfils the following tasks:

 To transfer the contractual fuel gas received at the plant boundary into
the condition required by the gas turbines in regards of mass flow,
pressure, temperature and content of dust and liquids
STEAM TURBINE

Lube oil system

The turbine lubrication (lube oil) system performs the following function:
• Lubricate the bearings of the generator and steam turbine.
• Supply of lube oil to the jacking oil (shaft lifting) and electro hydraulic
safety system.
• Removal of heat generated in the journal bearings by shaft rotation.

This is reached by the following:

• Maintaining a constant lube oil flow and pressure.
• Maintaining sufficient lube oil flow during emergency situations.
• Providing a specific lube oil flow to each bearing.
• Maintaining a constant lube oil temperature to consumers.
• Cleaning lube oil.
• Guiding lube oil to consumers.
• Returning lube oil from consumers.
• Deaerating lube oil returning from the consumers.
• Storage of lube oil at sufficient temperature.

Jacking Oil System

The jacking oil system performs the following purposes:
• Prevents metal-to-metal contact in the journal bearings by producing a
hydrostatic oil film when the rotational shaft speed is too low to create a
continuous hydrodynamic oil film.
• Reduces the break away torque during run-up of the steam turbine rotor.

This is reached by the following functions:

• Generates jacking oil pressure and flow.
• Guides and distributes jacking oil to the steam turbine journal bearings.
• Drains the jacking oil into the bearing pedestal.

The hydraulic oil supply system

The hydraulic oil supply system performs the following function:
• Supplies hydraulic oil to various consumers, mainly for control purposes.
This is achieved by the following:
• Maintaining a constant hydraulic oil pressure throughout all operating
situations.
• Maintaining a constant hydraulic oil temperature.
• Filtering hydraulic oil.
• Guiding hydraulic oil to consumers.
• Returning hydraulic oil from consumers.
• Deaerating hydraulic oil.
• Storage of hydraulic oil at sufficient temperature.

The following components are needed:

• Hydraulic oil tank.
• Hydraulic oil pumps (main and standby).
• Constant pressure valve.
• Duplex filter.
• Hydraulic oil accumulator with safety valve.
• Supply and return lines.
• Instrumentation and controls.

Control & Safety System

The electro hydraulic control system is functionally divided into two
systems:
• Control system with closed loop controls.
• Safety system with open loop controls.

The control system performs the following functions:

• Controls the stroke of control- and extraction control valves.
• Feeds process variables back to the controller.

The safety system performs the following function:

• Protects the steam turbine from possible damage as a result out of
inadmissible operating conditions.
This is achieved by the following:
• Initiation of steam turbine trips.
• Closing of stop- and control valves.
Gland steam system
The steam turbine gland steam system fulfils the following functions:
• Seals the steam turbine prior to start-up to enable condenser evacuation.
• Seals the steam turbine during operation to prevent steam losses on
casings operating under overpressure.
• Seals the steam turbine during operation to prevent air leaks into turbine
sections running operating under vacuum.

This is achieved by the following:

• Providing external steam into the system prior to and during start-up of
the turbine to all seals.
• Removing excess steam out of the system during higher load operation.
• Maintaining a constant gland steam pressure throughout the entire
operating range.
• Limiting gland steam temperatures to match steam turbine materials
properties.
• Avoiding air leaks into the turbine sections running under vacuum
conditions.
• Removing leak steam out of each seal and discharging it safely to the
atmosphere.
• Removing leak steam out of each seal and condensing it in the gland
steam condenser (optional).

LP turbine hood spray system

The LP turbine hood spray system performs the following function:
• Prevents inadmissible temperature of the LP last stage blading during no-
load and low-load operation. The injected water absorbs the heat.
This is achieved by the following:
• Injection of condensate into the LP turbine exhaust section.

Vacuum breaking system

The vacuum breaking system performs the following functions:
• Partial vacuum breaking in case of a turbine shut-down in order to slow-
down through the critical speed ranges more quickly.
• Full vacuum breaking in case of an emergency.
This is reached by the following:
• Admitting ambient air to enter the condenser through a valve.
Drain system
The drain system fulfils the following functions:
• Removes condensate from steam lines to prevent water hammer during
start-up.
• Removes condensate from the steam turbine to prevent thermal stress
during start-up.
• Removes condensate to protect the turbine and heat exchangers from
water damage.
• Removes condensate from steam systems that forms during normal
operation.
• Guides condensate to the appropriate collection vessels.
• Handles flashing of condensate in the collection vessels.
• Separates steam and condensate in the collection vessels.
• Desuperheats flash-steam to desired temperature levels.

This functions are implemented by performing the following tasks:

• Providing start-up drains equipped with pneumatically actuated shut-off
valves.
• Providing continuous drains equipped with steam traps and/or drain
orifices.
• Providing a vacuum drain collection vessel for drains out of systems,
which may run under vacuum conditions.
• Providing an atmospheric drain vessel for drains out of the systems,
which never run under vacuum conditions.