gek116357

7/16/2019 gek116357

http://slidepdf.com/reader/full/gek116357 1/4

GEK 11635March 200

GE Energ

Gas Turbine Fuel Purge System

9FA DLN2.0+ Gas Only Unit

These instructions do not purport to cover all details or variations in equipment nor to provide for every possible

contingency to be met in connection with installation, operation or maintenance. Should further information be

desired or should particular problems arise which are not covered suf fi ciently for the purchaser’s purposes the

matter should be referred to the GE Company.

© General Electric Company, 2009. GE Proprietary Information. All Rights Reserved.

7/16/2019 gek116357


GEK 116357 Gas Turbine Fuel Purge System

I. INTRODUCTION

When burning gas in the pre-mix mode, the fuel purge system supplies active high flow purge air to the

diffusion gas manifold. During diffusion gas operation, the fuel gas purge system will provide a low flow

continuous purge to PM4 gas manifolds to sweep unused gas out of the gas piping, manifold and combus-

tion end cover as well as to keep the gas piping hot to prevent condensate formation in the pipes. When

burning gas fuel in all gas manifolds, the purge system is not in operation.

II. SYSTEM OVERVIEW

The 9FA DLN2.0+ Gas-Only machine purges gas manifold D5 and PM4, when fuel is not flowing through

the respective fuel gas passages. These fuel gas passages are purged with turbine compressor discharge air.

The fuel gas purge system components are shown on the schematic diagram (ML 0477).

III. SYSTEM OPERATION

A. Diffusion Gas Purge

When the gas turbine is operating burning natural gas in the pre-mix mode, the diffusion gas purgesystem receives air from the discharge of the gas turbine compressor. This purging air flows through

two fuel gas purge valves (VA13-1 & 2) to the diffusion gas primary manifold. All the components

described in this system will be located in the Accessory Module.

For the diffusion gas purge system, fuel gas purge valve VA13-1 is controlled by allowing instrument

air to flow through quick exhaust valve VA36-1. The quick exhaust valve is opened by the associated

solenoid valve 20PG-1. When the solenoid valve is energized, instrument air pilots the gas purge valve

to the open position allowing air to flow to first the fuel gas purge valve VA13-2 and then to the natural

gas manifold.

Fuel gas purge valve VA13-2 is controlled by allowing instrument air to flow through quick exhaust

valve VA36-2. The quick exhaust valve is opened by the associated solenoid valve 20PG-2. Theamount of instrument air flowing to the actuator of gas fuel purge valve VA13-2 is regulated by a

4-20mA eloctro-pneumatic positioner, 65EP-G1P. Pressure regulator VPR54-22 limits the maximum

instrument air pressure allowed to pass through 65EP-G1P.

The rate of opening of purge valve VA13-1 is manually controlled by needle metering valves located

downstream of solenoid valve 20PG-1. The turbine control panel shall control the opening of purge

valve VA13-2. The opening time of these purge valves shall be set in accordance with the requirements

on the schematic diagram (MLI 0477). Limit switches (33PG-1,2) indicate the open/closed position of

fuel gas purge valve VA13-1. Limit switch 33PG-3, 4, 15, 16 indicates different open/closed position

of VA13-2.

A vent valve VA13-8 is located between these two purge valves which provides a block and bleed

system. Should the leakage past the gas purge valves in either direction become too excessive for the

vent valve to bleed off, pressure switches 63PG-1A,1B,1C will sense the cavity pressure and result

in the turbine control system taking appropriate action should the predetermined pressure set point be

reached.

2 © General Electric Company, 2009. GE Proprietary Information. All Rights Reserved.

7/16/2019 gek116357


Gas Turbine Fuel Purge System GEK 11635

B. PM4 Gas Purge

When the gas turbine is burning natural gas in the diffusion mode, the PM4 gas purge system receiv

air from the discharge of the gas turbine compressor. This purging air flows through fuel gas pur

valves VA13-5,6 to PM4 natural gas manifold. All the components described in this system will b

located in the Accessory Module.

For the PM4 gas purge systems, each fuel gas purge valve is controlled by allowing instrument air

flow through the associated actuator quick exhaust valves VA36-9, 10. The quick exhaust valves a

opened by the associated solenoid valves 20PG-5, 6. When the solenoid valves are energized, pilot a

is supplied to the quick exhaust valves which opens them and allows instrument air to flow to the g

purge valves causing them to open and allowing air to flow to the natural gas manifold. Valve actuatin

air is supplied from customer supplied or a separate instrument air source. The rate of opening

these purge valves is manually controlled by needle metering valves located just upstream of the quic

exhaust valves, VA36-9, 10. The opening time of these purge valves shall be set in accordance wi

the requirements on the schematic diagram (MLI 0477). Limit switches 33PG-9, 10, 11, 12 indica

the position of each fuel gas purge valve.

A vent valve VA13-13, is located between each set of these purge valves which provides a block an bleed system. Should the leakage past the gas purge valves in either direction become too excessive f

the vent valve to bleed off, pressure switches 63PG-3A, 3B, 3C will sense the cavity pressure and resu

in the turbine control system taking appropriate action should the predetermined pressure set point b

reached.

C. Routing of Vent Lines by Customer/Installer

Installer shall route PG1, and PG13 lines separately from other vents, to a naturally ventilated are

outside of any buildings or enclosures, and in an area free from sources of ignition.

D. System Risk Overview

Details regarding operational risk related to the Gas Fuel Purge System can be found in the 012

Equipment Residual Summary for this job and the A160 or 0991 Operation and Maintenance Ma

ual, DIS-201, supplied by the skid vendor (Gas Fuel Purge in applicable manual).

© General Electric Company, 2009. GE Proprietary Information. All Rights Reserved.

7/16/2019 gek116357


GEK 116357 Gas Turbine Fuel Purge System

GE Energy

General Electric Company

www.gepower.com

4 © General Electric Company, 2009. GE Proprietary Information. All Rights Reserved.

Documents

gek116357