31 5300 9070 e 2004 07

DRAWING/DOCUMENT STATUS

A

FOR REFERENCE

2006-04-10

First issue

Steenmeyer

DATE

DESCRIPTION

Bearb.
Coord.

Rev.

Liedtke

Sudhoff

Geprüft
Checked

APPD.

PROJECT :

CAMAU 1 750MW COMBINED CYCLE POWER PLANT
OWNER :

OWNER’S ENGINEER :

PETRO VIETNAM
CPMB
CONTRACTOR :

CONTRACTOR’S ENGINEER :

LILAMA CORPORATION

FICHTNER

SUBCONTRACTOR’S NAME :

SUBCONTRACTOR’S SUPPLIER :

s

DELMAS

POWER GENERATION
DRAWING TITLE :

System Description Drainage of NG System
PKZ

UAS

Contents Code

Ursprung/Original

Reg. No.

UNID

Urspr.-PKZ-Nr.
Orig.-PC

Ursprung-Nr./Original-No.

Projekt/Project

gezeich.
Drawn
bearb.
Coord.
geprüft
Checked

Abtlg.
Dept.

PKZ/PC

Datum

Date

Name

06-04-10

STEENM

06-04-10

LIEDTKE

06-04-10

SUDHOFF

P415

sgd.

s AG
POWER GENERATION

CA MAU 1 CCPP

VIT154

Maßstab
Scale

UA/DCC
Type
Inhaltskennzeichen
Contents Code

N/A

A4

Benennung/Title

System Description Drainage of
NG System
Dienstst./Dept.

P415

UNID

423216859

XS00

MBP40
Zähl.-Nr.
Reg.-No.
Index/Rev.

355063
Version

A
Blatt-Nr./Page-No.

CM1-L1-M-MBP40.08-355063
Erstellt mit/designed with

Ersatz für
Supersedes

0 of 3


Fuel Supply (Gaseous)
Automatic Draining of the NG System

Gas Turbine
Description of Auxiliary Systems

Refer also to:
List of Control Settings (SREL)
List of Measuring Instruments
List of Electrical Loads
Equipment List
Requirements for GT Working Media
Natural Gas System
P+I Diagram, Natural Gas
P+I Diagram, Automatic Draining of the
NG System

damage to the supply piping when the NG burners are
activated.
3.1-0210
3.1-0220
3.1-0230
3.1-0240
3.1-0260
3.1-5000
3.1-5010

Drainage System Components
Drain Valves
NG connecting lines and the NG control valves are
emptied into drainage tank MBP40BB001 via electricallyactuated drain valves MBP31AA401, MBP32AA401, and
MBP33AA401.
Together
with
tank
drain
valve
MBP40AA401 and venting valve MBP40AA501, these
drain valves constitute a dual element shutoff device. The
drain valves are closed when deenergized and each is
equipped with a limit switch for the “CLOSED” setting.

3.1-5310

Overview

The reproduction, transmission or use of this document or its

content is not permitted without express written authority.
Offenders will be liable for damages. All rights, including
rights created by patent grant or registration of a utility model
or design, are reserved.

During operation on natural gas (NG) and fuel oil (FO),
condensation may form in those natural gas connecting
lines between the natural gas package and the ring lines
through which no medium flows at that time. This
condensation is routed into a drainage tank by electricallyactuated drain valves.

Crossflow between the NG DM, NG PM, and PG piping
via the drainage system is prevented by actuating the drain
valves accordingly.

During the draining process it is possible that not only
condensation, but also ignition gas (propane, butane), and
natural gas as well as fuel oil are carried into the drainage
tank. Gas separates from the liquid in the drainage tank.
Gas is released to the atmosphere via a venting valve. The
liquid collects in the tank.

These valves are protected against excessive
temperatures by the drainage procedure itself, limitation of
the drainage time per drainage cycle, and by monitoring
the settings of the associated valves.

A solenoid valve that is actuated on the basis of tank
level allows the condensation collected to flow out of the
drainage tank and into a downstream system for disposal.

Drainage tank MBP40BB001 is used to collect and
separate liquid and gas. Venting valve MBP40AA501 is
used to vent this tank. This tank is equipped with safety
valve MBP40AA191.

Drainage Tank

These drain valves are automatically actuated during
operation on NG and FO as a function of the operating
mode, prior to each start, and after every gas turbine trip.

The drainage tank is equipped with level sensor
MBP40CL101, which is used for actuating tank drain valve
MBP40AA401. Maintaining a minimum liquid level in the
tank ensures that no gas can escape via the drain. The
drainage tank design is based on the assumption that
about twenty liters of condensation form per day.

Accumulation of Condensation in the NG
System

Class: RESTRICTED

During operation in NG premix mode or on FO, minor
localized pressure differences in the combustion chamber
cause cross flows of air from the compressor outlet through
the natural gas burners, the associated branch lines and
the natural gas ring lines to the burners. In the process, the
small flow of air from the compressor outlet cools down.

Depending on the ambient and site conditions, this may
involve temperatures below the dew point and thus
accumulation of condensation in the branch line and in the
natural gas connecting lines up to the respective NG
control valve. The amount of condensation that forms is so
large that the flames can extinguish when the NG burners
are reactivated after an extended period of operation in NG
PM or on fuel oil.

Pressure transducer MBP40CP101 is used to monitor
the pressure in the drainage tank and the leaktightness of
the associated valves.
Measuring
point
MBP40CT101
monitors
the
temperature in the drainage tank, because vaporization of
gas may cause formation of ice in the tank.
This temperature indicates whether liquefied gas has
flashed and whether the condensation has begun freezing.

Safety Valve
Safety valve MBP40AA191 protects the drainage tank
against excessive pressures. If system pressure exceeds a
maximum permissible operating pressure, the safety valve
opens, relieving pressure in the drainage tank.

Small amounts of ignition gas (propane, butane) that
accumulate after a fuel oil start or accumulation of FO after

operation on FO, also in connection with possible
condensation that collects in the NG DM line, may cause

Siemens AG
Power Generation

3.1-5300-9070/1
MBP

0704E-X


Gas Turbine
Description of Auxiliary Systems

Fuel Supply (Gaseous)
Automatic Draining of the NG System

Venting Valve

Depending on the operating mode of the gas turbine,
the liquid and gas that have accumulated in the respective
line (DM, PM, and PG) are routed into the drainage tank
via the respective drain valve. During the draining
procedure, it is only permissible for one of the piping
system drain valves to be open.

The reproduction, transmission or use of this document or its
content is not permitted without express written authority.
Offenders will be liable for damages. All rights, including

rights created by patent grant or registration of a utility model
or design, are reserved.

Gas entrained into drainage tank MBP40BB001 is
released to the atmosphere via venting valve
MBP40AA501. The venting valve is closed when
deenergized and is equipped with a limit switch for the
“CLOSED” setting.

Any faults to the drainage system during GT operation
result in annunciation of a pretrip alarm.

The venting valve is opened for a defined time at
certain intervals, during and/or after each natural gas
piping draining procedure, and during drainage of the tank
itself.

It is also possible to start the draining procedure
manually when the gas turbine is at a standstill.

Tank Drain Valve

Drainage Tank Level Control

Electrically-actuated tank drain valve MBP40AA401 is
used to control drainage of liquid from drainage tank
MBP40BB001. The tank drain valve is closed when
deenergized and is equipped with a limit switch for the
“CLOSED” setting.

If the level in the drainage tank exceeds its upper limit,
the tank drain valve is opened with the venting valve also
open. A pretrip alarm is annunciated if tank level continues
to rise.
The enable for opening the tank drain valve is issued if
the venting valve is open and the pressure in the drainage
tank is below a certain level.

The tank drain valve is only opened to drain the tank.

The tank drain valve can only be opened if the level in
the drainage tank is higher than a certain point. This
ensures that no gas can escape via the tank drain line
when the drain valve is open.

Operating Modes
The automatic draining procedure for the PG, NG, PM,
and/or NG DM piping is started:
−

Before GT startup,

−

After each time the gas turbine is shut down (including
all GT trips),

−

Every two hours during operation in NG PM (applies

only to DM piping),

−

After each start on fuel oil,

−

Every 2 hours during operation on fuel oil,

Monitoring and Fault Considerations

−

After performing off-line compressor cleaning.

In the event of an outage of the drainage system,
startup on NG as well as operation on either NG or FO are
still permissible. Failed starts or fuel changeover problems
may occur, however.

The tank drain valve is closed when the drainage tank
level drops below a defined lower level.
An alarm is annunciated if the level in the drainage tank
declines further. In such cases there is a risk that gas can
escape via the drain line.

Draining Procedure

Class: RESTRICTED

All valves of the drainage system must have a defined
initial setting before commencing the draining procedure,
i.e., the piping drain valves and the tank drain valve must
be closed. Depending on the operating condition of the GT,
the venting valve may be either open or closed. If the GT is
running, the venting valve remains closed during the
draining procedure. After completion of the draining
operation, the drainage tank venting valve is opened and
the gas in the tank can escape to the atmosphere. The
venting valve is open when the draining procedure is
performed with the gas turbine at a standstill.

If faults to or an outage of the drainage system occur
prior to a fuel oil start, startup on this fuel is prevented.

Drain Valve Limit Position Monitoring
The drain valves are each equipped a limit switch for
the “CLOSED” setting. A pretrip alarm is annunciated if
more than one of these valves is not “CLOSED”.
If one of the drain valves (PM, DM, PG) and the venting
valve or tank drain valve do not simultaneously signal
“CLOSED”, an uncontrolled flow of air from the compressor
outlet can enter the drainage system and thus escape to
the atmosphere. Gas turbine trip is triggered in such cases.

At the beginning of draining during gas turbine
operation the venting valve is opened to depressurize the
drainage tank. Thereafter the venting valve is closed to
check the drain valves for leaktightness. The venting valve

is always open when the gas turbine is at a standstill.

A pretrip alarm is annunciated if cross flow occurs
between the PM, DM, and PG piping system drain valves,
because more than one of these valves has signaled “not

Siemens AG
Power Generation

3.1-5300-9070/2
MBP

0704E-X


Gas Turbine
Description of Auxiliary Systems

Fuel Supply (Gaseous)
Automatic Draining of the NG System

Drainage Tank Level Monitoring

‘CLOSED’”. Automatic shutdown of the GT is performed at
the same time.

Automatic draining of the NG piping is blocked if the
level in the drainage tank is too high or too low.

If one of the piping drain valves is to be opened when

the gas turbine is running, the venting valve on the
drainage tank must be closed.

If the level in the drainage tank is below “MIN” and the
tank drain valve is not closed, an interlock is activated to
prevent opening of the drain valves.

If at least one of the piping drain valves fails to open
because of a fault, correct drainage of the NG piping is no
longer ensured. After such a fault occurs there is a risk that
flames will be extinguished the next time the NG DM
burners are activated.

Level monitoring faults trigger annunciation of a
corresponding alarm.
When tank level declines below the minimum limit
during initial commissioning of the plant (e.g., due to
evaporation of fluid), a filling device is used to fill the tank
at a corresponding pressure with the tank drain valve open.
When doing so, it must be ensured that the venting valve is
open.

Monitoring of the Tank Drain and Venting Valve
Limit Positions

Temperature Monitoring in the Drainage Tank

It is only permissible to open the tank drain valve when
sufficient liquid is still present in the drainage tank. This
ensures that no gas can escape via the tank drain line

when the drain valve is open.

If liquefied ignition gas flows into the drainage tank,
there is a risk that vaporization of this gas may cause
formation of ice which can in turn cause disturbances. The
associated temperature monitoring function blocks the
draining system if temperature declines below a certain
limit; this triggers an alarm and the operator is instructed to
open the venting valve manually.

The venting valve is equipped with a limit switch for the
“CLOSED” setting.
If the venting valve fails to close due to a fault, an
interlock prevents opening of the drain valves while the GT
is running.

If the temperature exceeds the tank design
temperature, an alarm is annunciated, the drainage system
blocked, and a close command issued to the drain valves.

A pretrip alarm is annunciated if the venting valve fails
to open due to a fault.

Class: RESTRICTED

The reproduction, transmission or use of this document or its
content is not permitted without express written authority.
Offenders will be liable for damages. All rights, including
rights created by patent grant or registration of a utility model
or design, are reserved.

The tank drain valve is equipped with a limit switch for
the “CLOSED” setting.

Siemens AG
Power Generation

3.1-5300-9070/3
MBP

0704E-X