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23/9/04
Revised as per SEC comments SEC\SIEMENS/127/L Dated 18/9/04 & Issued for Construction
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24-08-04
FOR APPROVAL
A
29/07/04
FOR INTERNAL REVIEW
REV. NO.
DATE
DESCRIPTION
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REVD.BY
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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
PREPARED BY CHECKED BY APPROVED BY
NAME
DATE
SSD
29/07/04
AA
29/07/04
H.K
29/07/04
SCALE : DOC. No.
SHEET NO.
REV. NO.
SAR687 – XV00 – 00EK – B20500 MANUFACTURER’S DRAW ING NO. -
1 PROJECT CODE -
OF 8
0
CAD FILE
UNID # -
10 780 701
PP7 EXTENSION 3 PROJECT DESIGN 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 4 3.3. Gas condensate drain tank..........................................................................................5 3.4. Coalescer Filter............................................................................................................5 3.5. Unit Gas Flow Meter.....................................................................................................5 3.6. Unit 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
SAR687 – XV00 – 00EK – B20500
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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 0
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. PP7 Extension 3 Project – Units 23 & 24 Design Criteria – Fuel Gas System
SAR687 – XV00 – 00EK – B20500
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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 0
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;
3.2.
Pressure (barg)
: 27.8 – 40
Temperature (deg. C)
: 27 – 65
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 0
SSV and motorized valve downstream of the PCV.
PP7 Extension 3 Project – Units 23 & 24 Design Criteria – Fuel Gas System
SAR687 – XV00 – 00EK – B20500
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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.
0
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 Main Pressure Control Valves Coalescer Filter
Criteria Sized for a capacity of 62,800 Kg/hr for each valve. Design pressure is 60 barg. Tight shut-off, fail to close. 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. Sheet PP7 Extension 3 Project – Units 23 & 24 SAR687 – XV00 – 00EK – REV Design Criteria – Fuel Gas System 5 of 8 B20500
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Condensate drain tank
Gas Flow Meter Final Chance Filter 4.1.
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 Sized for a capacity of 31,400 Kg/hr for each unit. Design pressure 40 barg (to be confirmed) Supplied by Siemens
0
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 f rom 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
PP7 Extension 3 Project – Units 23 & 24 Design Criteria – Fuel Gas System
SAR687 – XV00 – 00EK – B20500
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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 1.0 Coalescer Filters
UNIT
No
DATA
a)
No. of Coalescer Filter
2 x 100% for both GT’s
b)
Type
c)
Gas Flow Capacity
d)
Material of construction
Carbon Steel as per ASME Sec. VIII Div. 1 Vessel: SA 516 Gr. 70 Vessel Internal: SA 36/304 SS
e)
Filtration Degree
99 – 100 % removal of all solid particles larger or equal to 0.3-0.5 microns.
Coalescer Kg/hr
62,800
(100%) removal of all liquid droplets. 2.0
Pressure Reducing Station
a)
No. of Main PCV
b)
No. of Start-up PCV
c)
Gas Flow Rate (Main PCV)
Kg/hr 31,400 62,800
d)
Gas Flow Rate (Start-up PCV)
Kg/hr
c)
Type
d)
Operating pressure range
4.0
Unit Gas Flow Meter
a)
No. of Unit Gas Flow Meter
b)
Type
To be decided later
5.0
Unit Final Chance Filter
Supplied by Siemens
PP7 Extension 3 Project – Units 23 & 24 Design Criteria – Fuel Gas System
No.
2 x 100% 2 0
0-10% of Main PCV Flow Rate (To be Confirmed) Fail to close, tight shut off valve
barg
No.
To be confirmed
1 x 100% for each GT
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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 Other sulfur compounds HHV (at 14.696 psi)
Less than 2 ppm Nil 44 MJ/CM (1170 BTU/SCF)
Less than 2 ppm Nil 35 MJ/CM (930 BTU/SCF)
The temperature of dry gas is 150° F (65°C)
PP7 Extension 3 Project – Units 23 & 24 Design Criteria – Fuel Gas System
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