Gas Turbine Safety and Protective Equipment

Description Flame Monitor Arrangement

Function The space between the two plates (5) is open to the
atmosphere via a small radial slot so that the space
The optoreceivers measure the radiant energy given off between the two quartz glass lenses (7) is not pressurized.
by the flames inside the combustion chambers. If the seal of the inner quartz glass lens is not absolutely
Since the optoreceivers are only designed for operation tight, warm air enters the space between the two quartz
at atmospheric pressure, however, and a positive pressure glass lenses and escapes to the atmosphere from there
exists inside the combustion chambers, openings are radially at (X). Even in this case, the optoreceiver is not
needed in the combustion chamber which allow the radiant exposed to hot air.
energy to pass through but seal tightly against the pressure In order to test the proper function of the optoreceiver,
prevailing inside the combustion chamber. the radiant energy to the optoreceiver can be interrupted by
holding a piece of sheet metal or cardboard between
Construction and Functional Principle endplate (4) and thermal insulation plate (2).
The optoreceivers can be removed and reinstalled
2 optoreceivers (1) are mounted on each combustion
during operation. First disconnect the cable from the
chamber, each in a flanged pipe (8) welded into the
optoreceiver, then loosen the threaded connection between
combustion chamber shell. Two quartz lenses (7), arranged
the optoreceiver and the thermal insulation plate.
in tandem, are set in plates (5) and gaskets (6) and bolted
to the flanges (9) by means of an end plate (4). The In order to prevent turbine trip, both
optoreceiver (1) is bolted with thermal insulators (10) to optoreceivers on one combustion chamber
thermal insulation plate (2) which, in turn, is bolted to should not be checked or removed at the
same time.
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endplate (4) with spacer (3).

This arrangement ensures that the optoreceiver, which
contains electronic components, among other things, does
not become too hot.
a utility model or design, are reserved

Fig. 1: Flame Monitor

1 Optoreceiver
2 Thermal insulation plate
3 Spacer
4 Endplate
5 Plate
6 Gasket
Class: RESTRICTED

7 Quartz glass lens

8 Flanged pipe
9 Flange
10 Thermal insulator

Siemens AG 3.1-4380-6431
Power Generation 0300E
 Gas Turbine Safety and Protective Equipment
Description Flame Monitoring

Function housed in control equipment cabinets well away from the

vicinity of the combustion chamber.
Liquid (fuel oil) or gaseous (fuel gas) fuel is injected into
The electric signals are transmitted from the flame
and burned in the combustion chambers. The function of
sensors to the flame monitors by special cables. The
the flame monitoring system is to detect whether the fuel
evaluation of the flame signals in the flame monitors is
actually burns. If the fuel is being injected but not burned,
such that there is a flame signal above an upper setpoint
damage can be caused to the gas turbine.
and there is no flame signal below a lower setpoint. This
If it is detected that the injected fuel is not burning, fuel signal controls a relay, the contracts of which are closed
injection is interrupted. This automatically shuts down the when there a flame and open when there is no flame.
gas turbine (turbine trip).
The two above-mentioned setpoints can be set
A distinction is made between the situation in which the independently of one another. When the gas turbine is at
flames go out during normal operation of the gas turbine, standstill, no flames burn and consequently the contacts of
i.e. during power operation, and the situation in which the the output relay are open.
flames do not even ignite during gas turbine startup.
Flames form during gas turbine startup. If the intensity
In the former case, the turbine is tripped; in the latter of the flame radiant energy is so high that the signal
case the startup procedure is interrupted. setpoint is exceeded, the contacts close. If the flames
In order to ensure on the one hand that the fuel supply extinguish during normal operation, the intensity of the
is automatically shut off when the flames go out and on the radiant energy drops. When the intensity has dropped
other hand that the turbine does not trip as a result of a below the lower signal setpoint, the contacts open. The
malfunction in the flame monitoring system when the opening of the contacts when the intensity of the radiant
including rights created by patent grant or registration of
The reproduction, transmission or use of this document

authority. Offenders will be liable for damages. All rights,

or its content is not permitted without express written

flames are still burning, the flame monitoring system must energy drops below the lower setpoint occurs only when
be appropriately sophisticated, both in terms of safety and the radiant energy has been below the lower setpoint for a
availability. certain time, generally for more than one second.
The devices used for flame monitoring are intrinsically
a utility model or design, are reserved

Construction and Functional Principle safe and conform to the applicable German regulations.
Their conformity with these regulation is tested and certified
Depending on the gas turbine type, each combustion by German inspectors who are independent of the
chamber has between three and eight burners. During the manufacturers of the instruments. Flame sensors and
combustion of fuel oil or gas, radiant energy is released flame monitors continuously perform self-tests. Appropriate
which is detected by flame sensors. circuitry inside the flame sensors generates an output
The amount of fuel injected and burned differs widely, signal which lies below the lower setpoint at intervals of one
as the power of the gas turbine is controlled by the fuel second for the duration of approx. eight seconds. The
flow. For example, the fuel flow during startup is only flame sensors then check internally that the "flame" output
approx. 5% of the volume at the gas turbine rated power signal disappears but the contacts of the output relay do
and only approx. 20% when idling. The intensity of the not open. If the "flame" signal does not disappear during
radiant energy thus also differs accordingly. this internal test, this is regarded as a criterion for a fault in
In view of the arrangement of the burners within the the flame monitoring instrumentation. In this case, the
combustion chamber, it is not possible to determine using contacts of the output relay are opened. A fault in the
flame sensors whether or not flames are alight at individual instrumentation of the flame monitoring system generates
burners. The monitoring system is a flame zone monitoring the same output signal as the extinguishing of the flame.
system and not a burner monitoring system. It is therefore not possible for the flames to extinguish
Each of the two combustion chambers of the gas without this being detected by the flame monitoring
turbine has a separate flame monitoring system. The instrumentation. This would mean, however, that the
system consists of two flame sensors mounted on the availability of the gas turbine is limited as the turbine would
outer shell of the combustion chamber and directed trip even if only the flame monitoring instrumentation
towards the zone in the flame cylinder of the combustion malfunctions. In order to compensate for this limitation on
chamber in which the flames burn. These flame sensors the availability, each combustion chamber has two flame
generate signals which are proportional to the intensity of monitors. Both are identical, but completely independent of
the radiant energy. These signals are evaluated in the one another. Only when the contacts of the output relays of
Class: RESTRICTED

flame monitors. both monitoring devices open is the turbine tripped. If the
contacts of only one output relay of a flame monitor open
These flame monitors are, as with the other
while the contacts of the other flame monitor remain
components of the gas turbine control instrumentation,

Siemens AG 3.1-4381-0001/1
Power Generation 0892E
 Gas Turbine Safety and Protective Equipment
Description Flame Monitoring

closed, only a fault signal is issued. The output relays of ignition flame is burning, but that the upper signal setpoint
the flame monitors are connected in parallel in the general is exceeded when there is a main flame. Since a certain
gas turbine controller, not in the instrumentation of the length of time is required for the formation of the main
flame monitoring system. flame, injection of the fuel during startup of the gas turbine
During gas turbine startup, an ignition flame is first lit is interrupted only if, after a certain time (generally 12
using ignition gas. The ignition gas is independent of the seconds) from the start of injection (start of opening of the
main fuel (fuel oil or fuel gas). When the ignition flame is emergency stop valve), both flame monitors signal no
burning, a certain amount of the main fuel is injected and flame. If, during operation of the gas turbine, both flame
ignites at the ignition flame so that the main flame forms. A monitors signal no flame, fuel injection is stopped
certain length of time is required for the formation of the immediately by closing the fuel stop valve. The flame
main flame. sensors of the flame monitoring system can be removed
during operation of the gas turbine, e.g. to clean the lenses
The flame monitors are set so that the upper signal
or replace a defective flame sensor.
setpoint mentioned above is not exceeded when only the
including rights created by patent grant or registration of
The reproduction, transmission or use of this document

authority. Offenders will be liable for damages. All rights,

or its content is not permitted without express written

a utility model or design, are reserved Class: RESTRICTED

Siemens AG 3.1-4381-0001/2
Power Generation 0892E
 Gas Turbine Safety and Protective Equipment
Description P+I Diagram Blowoff System

Refer also to:

List of Measuring Instruments 3.1-2620

List of Electrical Loads 3.1-2630
Equipment List 3.1-2640
Blowoff System 3.1-4411
The reproduction, transmission or use of this document
or its content is not permitted without express written

including rights created by patent grant or registration of

authority. Offenders will be liable for damages. All rights,

Cover Sheet for Drawing Number

13-9022-00307-
a utility model or design, are reserved Class: RESTRICTED

Siemens AG 3.1-4410-9022
Power Generation 0401E
 / I I ...... I
10 11 12

Kundenansch luss oder Ansch I uss zu e i nem Systemp I an i m Betri ebshandbuch.

PURCHASER 5 CONNECTION OR CONNECTION TO AN P+I DIAGRAM INCLUDED

IN THE OPERATION MANUAL.

Einige Endflansche (siehe 91!1731!1*l sind nicht bei jeder Anlage vorhanden.
SOME PURCHASER S CONNECTIONS (REFER TO 90730*) DO NOT EXIST AT EACH UNIT.
Nr. der Endflansche siehe Baugruppe 91!1731!1*
I MBA40 I I MBA40 NO. OF PIPING CONNECTIONS SEE DESIGN GROUP 90730*.

I AA201 I I AT001
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Contract No.: I 4042117/00

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UNID: 451876704

- 10 II 12
PROCHEM CAD
 Gas Turbine Safety and Protection Equipment
Description Blowoff System

Refer also to: Extraction Compr. Blowoff valve KKS

Stage (butterfly type)
List of Control Settings (SREL) 3.1-2020
List of Measuring Instruments 3.1-2620 Ea1 5 1.1 MBA41AA051
List of Electrical Loads 3.1-2630 Ea1 5 1.2 MBA41AA052
Equipment List 3.1-2640
P+I Diagram, Blowoff Equipment 3.1-4410 Ea2 10 2 MBA42AA051

Associated Systems:
Because the blowoff lines routed below the machine
P+I Diagram, Gas Turbine 3.1-2600 centerline act as siphons, drain lines are attached at the
Gas Turbine Instrumentation 3.1-2601 lowest points of these lines. Water that may have
Drainage system 3.1-4966 accumulated via these lines during compressor cleaning
P+I Diagram, Drainage System 3.1-4969 can be drained off through these lines (see “Compressor
Cleaning”).
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 Compressed Air Supply
(SREL). Air is the working medium used by the pneumatic
actuators of the blowoff valves.
Schadensersatz. Alle Rechte für den Fall der Patenterteilung
ausdrücklich zugestanden. Zuwiderhandlungen verpflichten zu
Weitergabe sowie Vervielfältigung dieser Unterlage, Verwer-
tung und Mitteilung ihres Inhalts nicht gestattet, soweit nicht

Function Air is extracted from the compressor outlet and routed

through filter MBA40AT002 to the receiver.
The axial compressor of the gas turbine is designed to
Receiver MBA40BB001 ensures that sufficient control
run at the rated speed of the turbine-generator. In a certain
air is available for each switching operation.
speed range below rated speed, the front stages of the
compressor are so highly loaded aerodynamically that flow Swing check valve MBA40AA201 prevents compressed
separation occurs at the compressor airfoil surfaces due to air from flowing from the receiver back into the gas turbine
when compressor outlet pressure drops.
oder GM- Eintragung vorbehalten.

excessive deceleration. As a result, the overloaded

compressor stages are no longer capable of generating the Shutoff valve MBA40AA401 is open during operation of
necessary increase in pressure, the phenomenon known the gas turbine. It shall only be closed for performing
as compressor surging occurs and the compressor maintenance.
throughput becomes unstable. The breakdown of flow Orifice MBA41BP001 limits the air throughput that can
results in periodic flow reversals, manifested outwardly by occur in the event that the condensate drain line develops
pronounced, periodic fluctuations in the compressor outlet a leak.
pressure together with severe vibration of the turbine-
And condensation that accumulates is routed out of the
generator and pulsating noise synchronous with these
condensate drain line MBA40AA203. A venting line is
pressure fluctuations. This subjects the compressor airfoils
connected to the pressurized end of the condensate drain
to both high alternating bending stresses and high
line.
temperatures.
If the blowoff valves are to be actuated for performance
Compressor surging is prevented by bleeding air from
of maintenance work and the tank is vented, the receiver
certain locations of the compressor when the speed range
can be charged with compressed air from another source
that is critical in terms of surging is reached.
or inert gas via shutoff valve MBA40AA251.

System Configuration
Valve Actuation
Blowoff lines are connected to the compressor casing
Actuation of the blowoff valve actuators using the
as follows for bleeding air: two at extraction point Ea1 and
associated solenoid valves is explained below with valve
one at extraction point Ea2. The blowoff lines open into the
MBA41AA052 as an example.
exhaust duct downstream of the gas turbine. As a result,
the exhaust silencer also functions as a silencer for the The valve is actuated to the OPEN and CLOSED
blowoff air. Each blowoff line is equipped with a butterfly- positions by a piston which is pressurized from both
type valve which is opened when air is to be bled from the plenums. To open the blowoff valve, solenoid valves
Klasse: RESTRIKTIV

compressor. These blowoff valves are actuated MBA41AA052A and MBA41AA052B are first deenergized.
pneumatically to the positions “OPEN” and “CLOSED”. This permits compressed air from the tank to flow through
solenoid valve MBA41AA052A (3-2 open; 1 closed) to one

Siemens AG 3.1-4411-9022/1
Power Generation 0305
 Gas Turbine Safety and Protection Equipment
Description Blowoff System

piston plenum. Simultaneously the other piston plenum is − Shutdown

vented via solenoid valve MBA41AA052B. When the valve During normal shutdown of the gas turbine, all blowoff
is to be closed, the solenoid valves are switched, reversing valves are opened simultaneously when the fuel
the pressures in the two piston plenums. system emergency stop valves are closed.
Because two butterfly valves (MBA41AA051 and − GT Trip
MBA41AA052) must be vented via solenoid valve
In the event that gas turbine trip is triggered, all blowoff
MBA41AA052B, solenoid valve MBA41AA052C is opened
valves are opened immediately as it is now inevitable
as well. This shortens the opening time of the two blowoff
that the axial compressor will pass through the
valves.
unfavorable speed range.
The limit positions of all blowoff valves are equipped
− Compressor Cleaning
with position limit switches for monitoring.
After compressor cleaning the blowoff valves can be
opened manually if necessary. This is only possible at
Open-loop Control low output and when speed is not in the range critical to
Opening and closing of the blowoff valves is controlled surging. Blowoff valves are automatically opened in the
automatically as a function of plant operating conditions. correct sequence when this is necessary. They must
then be closed manually. The correct closing sequence
− Startup with Natural Gas or Fuel Oil:
is automatically ensured.
All blowoff valves are open at the onset of startup. They
− Protection Functions
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ausdrücklich zugestanden. Zuwiderhandlungen verpflichten zu
Weitergabe sowie Vervielfältigung dieser Unterlage, Verwer-
tung und Mitteilung ihres Inhalts nicht gestattet, soweit nicht

are closed sequentially as of about 76% rated speed as

a function of shaft speed. This minimizes the − Startup of the gas turbine is aborted if any blowoff
associated abrupt changes in temperature and output. valve is not open.

− Power Operation − A pretrip alarm is annunciated if a blowoff valve

opens during power operation or could not be
The blowoff valves always remain closed during power
closed during the startup sequence. No automatic
operation.
measures are triggered by this.
oder GM- Eintragung vorbehalten.

− Speed Decline
An alarm is annunciated if any blowoff valve is
Blowoff valves 1.1 and 1.2 are opened if speed spuriously not OPEN in the speed range critical to surging.
declines below the minimum permissible limit during If this operating condition causes compressor surging,
power operation. surge protection monitoring (cf. description “Gas Turbine”)
As speed increases again, the blowoff valves are triggers gas turbine trip.
closed in the sequence used in the GT startup process.
Klasse: RESTRIKTIV

Siemens AG 3.1-4411-9022/2
Power Generation 0305