DRAWING/DOCUMENT STATUS A FOR REFERENCE 2006-04-10 First issue Steenmeyer DATE DESCRIPTION Bearb Coord Rev Liedtke Sudhoff Geprüft Checked APPD PROJECT : CAMAU 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 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 of 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 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 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 ... 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... 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... 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