fuel gas

0 23/9/04Revised as per SEC comments SEC\SIEMENS/127/L

Dated 18/9/04 & Issued for Construction

NS AA KH

B 24-08-04 FOR APPROVALNS AA KH

A 29/07/04 FOR INTERNAL REVIEW NS AA H.K

REV. NO. DATE DESCRIPTION REVD.BY CHKD. BY APPD. BY

Project Name: PP7 EXTENSION 3 PROJECT

Owner: SAUDI ELECTRICITY COMPANY – CENTRAL REGION BRANCH

Contractor: SIEMENS POWER GENERATION

Subcontractor: ARABIAN BEMCO CONTRACTING CO. TITLE:

DESIGN CRITERIA – FUEL GAS SYSTEM

NAME DATE

PREPARED BY

SSD 29/07/04

CHECKED BY

AA 29/07/04

APPROVED BY

H.K 29/07/04

SCALE :

DOC. No. SHEET NO. REV. NO.

SAR687 – XV00 – 00EK – B20500 1 OF 8 0

MANUFACTURER’S DRAWING NO. PROJECT CODE CAD FILE UNID #

- - - 10 780 701

PP7 EXTENSION 3 PROJECTDESIGN CRITERIA – FUEL GAS SYSTEM

Table of Contents

1. Introduction....................................................................................................................3

2. Objective........................................................................................................................ 3

3. Description of Fuel Gas System.....................................................................................3

3.1. Tie in point................................................................................................................4

3.2. Gas pressure reducing station skid........................................................................4

3.3. Gas condensate drain tank......................................................................................5

3.4. Unit Coalescer Filter.................................................................................................5

3.5. Gas consumption metering.....................................................................................5

3.6. Final Chance Filter...................................................................................................5

3.7. Gas Flare system......................................................................................................5

3.8. Fuel gas station control panel.................................................................................5

4. Design Criteria...............................................................................................................5

4.1. Plant Design..............................................................................................................6

5. Arrangement / Layout.....................................................................................................6

6. Control Philosophy.........................................................................................................6

7. Codes and Standards....................................................................................................6

8. Specified Design Data....................................................................................................7

9. Annexure (Fuel gas Analysis)........................................................................................8

PP7 Extension 3 Project – Units 23 & 24 Design Criteria – Fuel Gas System

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1. Introduction

A fuel gas system for existing twenty two (22) simple cycle gas turbines of PP7

station has been installed and is presently in operation. The existing fuel gas system

consists of :

one emergency shut down valve

Three (3) nos. filter separators

Four (4) nos. water bath heaters

Six (6) nos. pressure reducing stations

Twenty two (22) coalescer filters (one for each existing gas turbine)

It is decided to add two simple cycle gas turbines (units # 23 & 24) of model

W501D5A supplied by Siemens. Fuel gas filtration and pressure reduction as per the

requirements of gas turbines is carried out in the new fuel gas extension system. This

design criteria has been prepared in line with Owner’s specification and the offer

submitted by Siemens.

2. Objective

The objective of this Design Criteria is

1) To establish the basic engineering parameters considering the fuel gas

requirement for the extension III power plant for sizing of pressure reducing

valves, coalescer filters, gas condensate drain tank, and connection to existing

flare system

2) To establish the sizing criteria for the equipment, the control philosophy, codes

and standards applicable for the system.

3) To provide specified design data for the ERP of the subject system.

4) To provide a brief description about the system.

3. Description of Fuel Gas System

The new fuel gas extension system shall consist of one main isolation valve with

bypass equalizing, one pressure reducing valve skid (2 x 100% Main PCV & 2 x

Start-up PCV), 2 x 100% coalescer filters for both gas turbines, one gas condensate

drain tank (two cubic meters capacity), 1 x 100 % gas consumption metering for

each GT, 1 x 100 % final chance filter for each GT and Shut off & vent valves for

each GT. Fuel gas is tapped at a maximum rate of 62,800 kg/hr from the down

stream of existing water bath heaters and upstream of the existing PCV #6.

The design fuel gas analysis is the attached Annexure A.


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The new fuel gas system equipment are identified as class 1, group D, division 2

category under hazardous area classification according to API 500 & NFPA 497.

The pressure control valve actuators are operated by instrument gas to be tied-in to

the existing instrument gas system or alternatively to the nearest header of the

existing plant instrument air.

3.1. Tie in point

The tie in point with the existing fuel gas system is with the 16’’ dia. pipe feeding the

existing PRS # 6 which is located in the down stream of existing water bath heaters.

Refer preliminary as built drawing ‘PP7 process flow diagram’ (PP7 – ME – 22 – 02 –

10012), Rev 2, two sheets. The process parameters available at the tie in point are

Pressure (barg) : 20.2 – 40

Temperature (deg. C) : 14.7 – 65

The minimum pressure at the inlet to the unit final chance filter is 350psig as per

Siemens requirement. Based on this minimum pressure requirement, the tie-in point

parameters shall be;

Pressure (barg) : 27.8 – 40

Temperature (deg. C) : 27 – 65

3.2. Gas pressure reducing station skid.

2 x 100 % fuel gas pressure control valves (PCV) are provided to make available fuel

gas to gas turbines at set pressure. The fuel gas maximum pressure is 40 barg. The

control valves can maintain constant pressure in its downstream between a pressure

range (to be confirmed later) meeting the pressure conditions downstream of the PCV

up to the inlet of the Econopac. Each control valve is provided with upstream slam

shut off valve (SSV) for quick isolation purpose. SSV shall have provision to close

manually for isolation and maintenance of the stream and should have provision to

close automatically upon actuation of fire detection system downstream of the PCV.

Each main Pressure Controlling Valve shall have a secondary start up Pressure

Controlling Valve to ensure smooth and reliable start up of the Gas Turbine with the

minimum flow rate requirements.

Each stream of the PRS shall be provided with isolation valve upstream of the

SSV and motorized valve downstream of the PCV.


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Vent lines are provided in the down stream of pressure control valves.

3.3. Gas condensate drain tank

The gas condensate drain tank collects all the condensate drains from new fuel gas extension system and disposes manually to existing oily water drain system to the condensate discharge header of gas condensate tank of units 21 & 22.

3.4. Coalescer Filter

2 x 100 % capacity coalescer filters are provided for both gas turbine located

downstream of the pressure reducing skid. The filters can remove from the fuel gas

particulate matter up to 0.3 -0.5 microns to 99 % to 100 % efficiency and all size liquid

droplets to around100 %.

The condensate collected from the coalescer filters shall be routed to the gas

condensate drain tank and vents shall be routed to existing flare system.

3.5. Unit Gas Flow Meter

1 x 100% unit gas flow meter will be provided for each gas turbine. The gas flow meter will measure the actual gas consumption of each gas turbine.

3.6. Unit Final Chance Filter

1 x 100% unit final chance filter is supplied by Siemens for each gas turbine. For further details, Siemens related drawings will be referenced.

3.7. Gas Flare System

All vents and relief valve’s discharges from the new gas system extension are routed to the existing vent header which connects to the existing flare stack. Wherever not feasible, vents are extended to a safe elevation.

3.8. Fuel Gas Station Control Panel

For PRS skid, local control panel/junction box will be provided. The control panel will be hard-wired to the existing DCS of the gas system.

For Coalescer filter, the junction box will be hard-wired to the Econopac Control system.

4. Design Criteria

Description Criteria

Main Pressure Control Valves

Sized for a capacity of 62,800 Kg/hr for each valve. Design pressure is 60 barg. Tight shut-off, fail to close.

Coalescer Filter Sized for a capacity of 62,800 Kg/hr for both units. Design pressure 40 barg (to be confirmed later)

Start-up Pressure Control Valves

Sized to cater for low flow operation of one GT unit in start-up conditions or full speed no load. At higher flow, the main PCV will take over.


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Condensate drain tank Two cubic meters capacity with pressure control and relief valves directing the drain to the existing oily water drain system the condensate to the discharge header of gas condensate tank of units 21 & 22

Gas Flow Meter Sized for a capacity of 31,400 Kg/hr for each unit. Design pressure 40 barg (to be confirmed)

Final Chance Filter Supplied by Siemens

4.1. Plant Design

The new fuel gas extension system will be designed as mentioned above to supply

the required quantity and quality of fuel gas to GTs. All piping will be of carbon steel

except the stainless steel piping between the final chance filter and the terminal

connections of the gas turbine. Maximum fuel gas velocity of 18.3 m/sec is

considered in selection of pipe sizing. The piping is routed in a built up trench or

above ground on sleepers.

5. Arrangement / Layout

The new fuel gas extension system equipment will be located outdoor. The fuel gas

extension system equipment is located in three different locations as given below:

1. 01UEN area consists of equipment described under clause nos. 3.2 and 3.4.

2. 23UEN area consists of equipment described under clause nos. 3.5 and 3.6

for GT#23

3. 24UEN area consists of equipment described under clause nos. 3.5 and 3.6

for GT#24

The condensate generated in the new fuel gas receiving equipment is routed to a

new gas condensate drain tank located near 01UEN area from which it is discharged

periodically to the existing oily water drain system discharge header of gas

condensate tank of units 21 & 22.

6. Control Philosophy

The control philosophy of the new fuel gas system extension will be detailed in

Vendor technical submittal.

7. Codes and Standards

The fuel gas extension system equipment and all associated piping and fittings will be

designed and manufactured as per well established engineering practices and safety


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codes of the latest applicable American standards. If suitable American standards are

not available equivalent British / DIN / ISO standards will be followed.

Design and manufacture of the equipment will conform to the applicable codes and

SEC standards.

8. Specified Design Data

CL.NO. DESCRIPTION UNIT DATA1.0 Coalescer Filters

a) No. of Coalescer Filter No 2 x 100% for both GT’s

b) Type Coalescer

c) Gas Flow Capacity Kg/hr 62,800

d) Material of construction Carbon Steel as per ASME Sec. VIII Div. 1Vessel: SA 516 Gr. 70Vessel Internal: SA 36/304 SS

e) Filtration Degree 99 – 100 % removal of all solid particles larger or equal to 0.3-0.5 microns.

(100%) removal of all liquid droplets.

2.0 Pressure Reducing Station

a) No. of Main PCV No. 2 x 100%

b) No. of Start-up PCV 2

c) Gas Flow Rate (Main PCV) Kg/hr 31,400 62,800

d) Gas Flow Rate (Start-up PCV) Kg/hr 0-10% of Main PCV Flow Rate (To be Confirmed)

c) Type Fail to close, tight shut off valve

d) Operating pressure range barg To be confirmed

4.0 Unit Gas Flow Meter

a) No. of Unit Gas Flow Meter No. 1 x 100% for each GT

b) Type To be decided later

5.0 Unit Final Chance Filter Supplied by Siemens


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9. Annexure (Fuel gas Analysis)

SHEDGUM AND UTHMANIUYAH GAS PLANTS DRY GAS Nitrogen 0.5 mole % 12.0 mole %Methane 80.7 mole % 82.7 mole %Ethane 16.0 mole % 5 mole %Propane 2.8 mole % 0.3 mole %Total 100 mole % 100 mole %

Hydrogen Sulfide Less than 2 ppm Less than 2 ppmOther sulfur compounds Nil NilHHV (at 14.696 psi) 44 MJ/CM

(1170 BTU/SCF)35 MJ/CM(930 BTU/SCF)

The temperature of dry gas is 150° F (65°C)


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