Relief valve MBX21AA191 protects the compressor against excessive pressure.. Solenoid-type pressure relief valve MBX21AA501 is installed downstream of the compressors to prevent the reci
Trang 1DRAWING/DOCUMENT STATUS FOR REFERENCE
PROJECT :
CAMAU 1 750MW COMBINED CYCLE POWER PLANT
PETRO VIETNAM CPMB
s
DRAWING TITLE :
System Description Pneumatic System
Ursprung/Original Ursprung-Nr./Original-No Urspr.-PKZ-Nr Orig.-PC
Datum
Date
Name Maßstab
Scale N/A A4 UA/DCC Type XS00
gezeich
Drawn 06-04-10 STEENM Benennung/Title
Inhaltskennzeichen Contents Code bearb
Coord 06-04-10 LIEDTKE
geprüft
Abtlg
Dept P415 sgd
System Description Pneumatic System
Zähl.-Nr
Reg.-No 355025 Dienstst./Dept UNID Index/Rev Version
Blatt-Nr./Page-No
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Refer also to:
List of Control Settings (SREL) 3.1-0210
List of Measuring Instruments 3.1-0220
P+I Diagram, Pneumatic Valves and Piping 3.1-9810
Settings, limits, and measuring ranges of the devices
referred to here are given in the List of Measuring
Instruments, Equipment List, and List of Control Settings
(SREL) The values stated in this description are only given
as examples
Description
Compressed air is the working medium used by the
pneumatic actuators of various components in the gas
turbine auxiliary systems As a rule, these
pneumatically-actuated valves are relevant to safety For safety reasons,
the supply of compressed air to the gas turbine is therefore
independent of the power plant compressed air network
and is generated by a pneumatic station Optionally, valves
in other systems can be supplied in addition to the blowoff
valves In such cases, this information is depicted in the
corresponding P+I diagrams
Configuration and Function of
Compressor Train
The compressed air station is equipped with two
redundant trains Each train essentially comprises a
compressor, a cooler, and a filter The system has full
redundancy, i.e., the capacity of each compressor train is
sufficient to ensure a reliable supply of control air to the
auxiliary systems (2x100%)
The two trains have an identical configuration, for this
reason only one train is described in the following
Electrically-driven compressor MBX21AN001
compresses air Filter MBX21AT001 prefilters the air as it
is drawn into the system
Relief valve MBX21AA191 protects the compressor
against excessive pressure
Solenoid-type pressure relief valve MBX21AA501 is
installed downstream of the compressors to prevent the
reciprocating compressors from having to start up against
pressure (startup assistance) This solenoid valve is open
when the associated compressor is at standstill and is
closed after the compressor is switched on
The escaping compressed air and any condensation
that forms are fed into condensation collecting tank
MBX23BB001 The condensation collecting tank is
equipped with silencer MBX23BS001 to reduce noise when
discharging compressed air to the atmosphere
Condensation that accumulates in the condensation collecting tank is then fed to disposal tank MBX23BB002 that is at atmospheric pressure Because the condensation may contain oil, its disposal must comply with requirements that apply to used oil
Swing check valve MBX21AA201 prevents venting of the train when the compressor is shut down
Compressed air is dried in the next step Compressed air is cooled in chiller-type compressed air drier MBX22AT001 Moisture condenses, thereby bringing the air to the prescribed dew point pressure The separator system in the cooler separates water and oil from the stream of compressed air Condensation is removed via drain MBX22AT011
Any dirt particles or oil droplets still present in the compressed air are removed by filter MBX22AT003 An optical differential pressure indicator equipped with differential pressure switch MBX22CP001 is provided at the filter A group fault alarm is annunciated if the differential pressure setting of this switch is violated (cf
subsection “Monitoring”) Then the filter element must be replaced Condensation is removed via drain MBX22AT013
Shutoff valve MBX22AA251 can be used to isolate the train for maintenance purposes, even during plant operation
The two trains merge downstream of the shutoff valve
Swing check valve MBX23AA201 prevents the escape of large volumes of air from the tank if there is a leak in one of the trains
Compressed air tank MBX24BB001 is used to store the compressed air after it has been dried and cleaned
Pressure control valve MBX24AA151 maintains system pressure even during extended outages and in the case of minor leaks It only opens if pressure in the tank exceeds the startup pressure of the compressors Orifice MBX24BP001 ensures that only a very small flow or air can
be returned even in the event the pressure control valve malfunctions
Tank pressure can be read off gauge MBX24CP501
System pressure is limited by safety valve MBX24-AA191
Shutoff valve MBX24AA401 can be used as necessary
to check whether condensation has formed in the tank
Open-loop Control
The open-loop control system for the pneumatic station constitutes a black box for the gas turbine I&C system
Once the pneumatic station has been started up by manually actuating the main power switch, no further
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switching actions on the part of the gas turbine I&C system
are required for control of the pneumatic station
The open-loop control equipment and power supply for
the electrical components are located in a separate
junction box for each compressor train (MBY40GH001 and
MBY40GH002 not shown)
Each of the compressors is provided with a dedicated
pressure switch (MBX24CP003 and MBX24CP004,
respectively) for startup and shutdown These two switches
have the same pressure setting
Monitoring
The tank pressure is monitored by pressure switches
MBX24CP001, MBX24CP002, and MBX24CP008 If tank
pressure drops below the setting of pressure switch
MBX24CP001, the pretrip alarm "PRESSURE LOW" is
annunciated If pressure in the tank continues to decline,
pressure switches MBX24CP002 and MBX24CP008
operate, gas turbine trip is triggered (2-of-3 logic gating), and the alarm message “Pressure TOO LOW” is annunciated
The messages “Compressor 1 ON” and “Compressor 2 ON” are displayed on the operation and monitoring system
If the compressors are in operation for extended periods, it can be assumed that the system is no longer leak-tight
The pneumatic system, including all piping, must then be checked for leaks
The alarms “Fault in train 1” and “Fault in train 2” are group fault alarms and are displayed on the operation and monitoring system If one of these alarms is annunciated, the affected compressor train must be shut down and serviced Potential causes include, for example: response
of compressor circuit breaker, drier malfunction, condensation separator malfunction, startup assistance solenoid valve NOT CLOSED, response of filter differential pressure switch, loss of power supply