Petroleum Development Oman LLC – Contract Number C311606 EPC Contract for Yibal Khuff Cogeneration Power Plant C6-01 – PROJECT INFORMATION & REQUIREMENTS

Petroleum Development Oman LLC

Contract Number C311606

EPC Contract for Yibal Khuff Cogeneration Power Plant



Table of Contents

1.0       Site Conditions. 3

2.0       Soil Investigation. 3

3.0       Environmental and Meteorological Data. 3

3.1       General 3

3.2       Geographic Data. 3

3.3       Ambient Temperatures. 3

3.4       Soil Thermal Resistivity, Seismic and Solar Radiation. 4

3.5       Sandstorms. 4

3.6       Wind. 4

4.0       Design Conditions. 4

5.0       Air Conditioned Rooms (Redundant Systems) 5

6.0       Heat Exchangers. 5

7.0       Electrical Systems. 5

7.1       AC System Voltages, Frequency and Neutral Earthing. 5

7.2       AC Supply Variations. 6

7.3       DC Supply Variations. 6

7.4       Fault Levels. 6

7.5       DC Systems. 6

7.6       Equipment Ratings. 6

8.0       Environmental Impact. 7


10.0      Availability. 7

11.0      Surface Protection and Coating Systems. 7

12.0      Water quality. 7

12.1      Utility Water -Potable/ Polished condensate composition will be confirmed during detailed design. Information provided below is preliminary. 7

12.2      Boiler Feed Water 8

13.0      Instrument Air Parameters. 8

14.0      Fuel Gas Specification. 8 

1.0             Site Conditions

The Yibal Khuff Cogeneration Power Station will be located in Yibal field area, approximately 50 km south west of the Fahud field and 350 km south west of Muscat, in the PDO concession area.

2.0             Soil Investigation

Soil investigation report shall be provided by Company for information during tender submission.

3.0             Environmental and Meteorological Data

3.1              General

Local conditions are severe, the climate being characterised mainly by extreme heat and humidity.

3.2              Geographic Data

Location                                                                    Yibal Khuff

Elevation above MSL:                                                80 – 100 m

3.3              Ambient Temperatures

The climate is mainly hot and humid.  Summer runs from April to October with June and July being the hottest months. The following are the standard ambient conditions that shall be considered for Yibal Khuff.


Ambient Air and other Temperatures
Maximum shade temperature:

Minimum shade temperature:

Maximum black bulb temperature:

Maximum daily variation in temperature:







Maximum ground temperature at various below-grade-levels:




Minimum ground temperature:

30°C @ 1000 mm

35°C @ 800 mm

38°C @ 650 mm

40°C @ 500 mm


22°C @ 1000 mm

Maximum Relative Humidity:

Minimum Relative Humidity:



Barometric Pressure
Barometric Pressure range: 98.8 to 100.5 kPa
The minimum and maximum values have been extrapolated using Yibal elevation of 90 m above MSL from OceanMetrix report.
Maximum infrequent heavy rainfall:


38.1mm / hour (Considering 50 year return period from Ocean Metrix Data)

3.4              Soil Thermal Resistivity, Seismic and Solar Radiation

Soil thermal resistivity value to be used for arriving at de-rating factors for cable capacity calculations: 240oC cm/W
Seismic activity

The seismic coefficient to be applied is Zone 2A of Uniform Building Code, UBC 97




Maximum Iso-keraunic level 10 days per annum
Solar radiation: 1200 W/m2.

3.5              Sandstorms

Sandstorms are both frequent and severe and can continue for days with the atmosphere heavily laden with dust particles.  Fine dust in these sandstorms can be as small as 2 microns.

3.6              Wind

The wind rose shall be based on the OceanMetrix report as shown below:



Design Wind Speeds:

Design wind speed (twice/month)        46.6 m/s (3 sec gust for 50 years return period as per Ocean Metric data)

For Process design, wind speed of 23.8m/s shall be used.

4.0             Design Conditions

Design temperature for transformers shall be 55°C as per SP – 1117 and ratings for other electrical equipment shall be as per site conditions spelt out in SP – 1103.

The output of the gas turbine generator shall not be limited by the generator, or interconnecting cable or generator transformer over a temperature range 5ºC to 55ºC.

All instrumentation shall be designed to function correctly with an ambient temperature of 60ºC if shaded or 82ºC if not shaded.

In general, the design temperature conditions for all the instrument equipment shall be as described below:

  • All instruments, systems and related components in hazardous areas shall comply as a minimum with the environmental conditions associated with hazardous area rating Zone-1, Gas Group IIA/B, Temperature Class T4.
  • Plant-mounted instruments shall be suitable for operation in industrial, humid, saliferrous and corrosive atmospheres and shall be adequately protected according to the electrical area classification.
  • For outdoor locations the climatic conditions of location class Dx(4k6/4Z2/4Z4/4Z6/4C2/4S4/4M1) of IEC 60654-1 (IEC 60721-3-4 incl. Amendment 1) applies.
  • The minimum degree of protection of plant instruments shall be IP 65 as defined in IEC 60529.
  • For mechanical influences, classification in accordance with IEC 60654-3 shall apply. For corrosive influences, classification in accordance with IEC 60654-4 shall apply. The corrosive influence class shall comply with the requirements of Tropicalisation (conformal coating) of printed circuit boards is required for all equipment in outdoor areas.
  • Installation and inspection of Ex equipment/instruments shall be carried in accordance to PR 1483 and IEC 60079 (Part 14 and 17) under the supervision of Ex inspector approved by Company.
  • The glands, seals etc. required for the completion of installation of all Ex equipment/ instruments shall be Ex rated.

For the design of air coolers the summer design temperature shall be 50ºC with a 10ºC approach. The winter design temperature shall be 20ºC with a 10ºC approach; however the equipment must be able to function at a shade temperature of 5ºC.

The maximum shade temperature occurs for short periods only.  Equipment shall be designed to achieve its rated capacity with a shade temperature of 50°C except for compressor auxiliaries, which shall be rated for 60°C.

The outdoor electrical equipment, instruments (switchgear, transformer, motor, transmitters etc.) shall be designed for 55°C ambient temperature. The indoor equipment shall be designed for 40°C ambient temperature.

5.0             Air Conditioned Rooms (Redundant Systems)

Inside design temperature is:

  • Maximum 21 ± 2°C with all units operating,
  • 35 ± 2°C °C with one unit out of service.

Equipment installed in such rooms shall be specified for a continuous operating temperature of 40°C, and for two hours in a day, at 55°C.

6.0             Heat Exchangers

For the design of air coolers the summer design temperature shall be 50ºC with a 10ºC approach. The winter design temperature shall be 20ºC with a 10ºC approach; however the equipment must be able to function at a shade temperature of 5ºC.

7.0             Electrical Systems

Details of the electrical systems are as follows: –

7.1              AC System Voltages, Frequency and Neutral Earthing

Frequency:                                                            50Hz


High voltage                                                          132kV, 3 phase, solidly earthed

33 kV, 3 phase, – Neutral earthing through resistance

11 kV, 3 phase, resistance earthed

(See SP- 1103)


Medium Voltage                                                    6.6kV, 3 phase, resistance earthed

(See SP-1103)


Low voltage                                                          415/240V, 3 phase & neutral solidly earthed


7.2              AC Supply Variations

Steady state Voltage 132kV:                                  + 10% at consumer terminals

Steady state Voltage below 132kV                         + 5% at consumer terminals

Steady state Frequency:                                       + 2% at consumer terminals

Dynamic Voltage:                                                  + 15% at common buses


7.3              DC Supply Variations

The output voltage shall be limited to within ± 10% of the nominal value. This limitation applies during, float-charge operations and during battery discharge operations corresponding to the maximum load current and for the specified discharge period.  The output voltage dynamic response of the DC UPS unit, with battery connected, shall not vary more than +20% or -10% of nominal output voltage in the event of instantaneous load changes of up to 50% rated output.

7.4              Fault Levels

132kV System Short Time Current – 31.5kA for 3 seconds
Short Circuit Withstand Current – Company will advise the rms value, including the direct-current (dc) component, at the major peak of the maximum cycle as determined from the envelope of the current wave form over a given time period. (The Short Circuit Withstand Current shall be used in electromechanical force calculations)
Rated Short time current rating of OPGW -25kA, 1sec as per SP-1114B Appendix-01
Medium Voltage System Switchgear shall have minimum short time fault rating based on the actual calculated Fault Level plus 10% with the minimum being 25kA for 1 sec.
Cable screen shall have min. fault level 3kA for 1sec
Low Voltage System


10% margin above actual calculated Fault Level

Earthing system shall be designed for Switchgear fault rating e.g. for 132kV earth grid, 31.5kA 6.6kV earth grid 25kA if applicable.

7.5             DC Systems

Nominal service voltages                                     110V   2 pole unearthed

125V   2 pole unearthed

24V   2 pole unearthed

48V    2 pole – positive earthed

7.6             Equipment Ratings

Equipment will be suitable for operation at the following voltages:


Motors 185kW‑2200kW                        6.6kV

Motors up to 160kW                             415V

Lighting supply                                     415/240V; 3 phase & neutral

Lighting systems                                  240V; phase & neutral

Instruments (non-vital)                          240V; phase & neutral

Instruments (vital)                                240V; phase & neutral

Instruments (vital)                                24V DC floating

Instruments (non-vital)                          110V DC floating

Instruments (vital)                                110V DC floating

Welding outlets                                     415V; 3 phase & neutral

Convenience outlets                             240V; phase & neutral

Switchgear closing                                110V DC floating

Switchgear tripping                  110V DC floating

Electrical SCADA system                         48V DC positive earth


The requirements of system for HV (132/6.6/11kV) and LV (415 V) systems shall be as stated in SP–1113 and SP–1103 except for the following equipment operating voltages


  • Welding & Oil filtration sockets : 415 V 3Ph, N
  • Switch Gear Spring charging        : 110 V DC
  • SCADA Interposing relay : 48 V DC
  • Transducers        : 110 V DC
  • 6kV System : Resistance earthed as per

SP 1103

8.0             Environmental Impact

Transformers contain oil, which will be contained in a catchment bund in case of leakage. The 132kV circuit breakers use SF6 gas as a current breaking medium. GIS switchgear also contains SF6 gas as an insulating and current breaking medium. SF6 gas is non-toxic in normal situations, however after a fault clearance the byproducts of SF6 gas decomposition are very toxic and special precautions must be taken when servicing the interruption chambers of these circuit breakers. Safety procedures set out in Company SPs will be followed when handling SF6 gas and in the event of gas leakage.

9.0             NOISE EMMISSIONS

The noise level of all equipment shall not exceed the limits as specified in DEP The maximum permissible noise level (sound pressure level) at a distance of 1 m and 1.5 m above reference level from the complete pump package shall be 85 dB (A). EPC contractor shall submit the guaranteed sound power levels and sound pressure levels of the equipment. The equipment shall meet the maximum noise limits by design and not by corrective measures.

10.0          Availability

Supplies to each switchboard will be designed to provide N-1 redundancy.


11.0          Surface Protection and Coating Systems

Specification SP-1246 covers the minimum requirements for protective painting and coating systems, materials and application methods for the internal and external surface of steel structures and equipment.

12.0          Water quality

12.1          Utility Water -Potable/ Polished condensate composition will be confirmed during detailed design. Information provided below is preliminary.

Description Unit  
pH 7
TDS mg/l 997
Ca mg/l 90
Mg mg/l 42
Na mg/l 163.4
K mg/l 5.5
Ba mg/l 0.05
Sr mg/l 8.3
Fe mg/l 0.01
Cu mg/l 0.04
CO3 mg/l 0.1
HCO3 mg/l 184.3
SO4 mg/l 213.6
Cl mg/l 279
F mg/l 0.9
NO3 mg/l 0
B mg/l 0.05
SiO2 mg/l 10
CO2 mg/l 29.17
O2 mg/l 1.5-5
Cl2 mg/l
Turbidity mg/l


12.2          Boiler Feed Water

Boiler feedwater will be supplied by the Central Processing Facility. The supply condition at battery limit is at 30 barg and 140 deg C. HRSG and auxiliary boilers. Feedwater parameters shall meet BS EN 12952-12:2003 guideline.


13.0          Instrument Air Parameters

The typical Instrument Air parameters will be as following:

Pressure:               550 kPa (g) Minimum, 1,000 kPa (g)  Maximum

Temperature:         50 °C Maximum

14.0          Fuel Gas Specification

The fuel gas composition is given below. Facility design shall be based on the following cases.

  1. YK-0°C cricondentherm gas
  2. YK-17°C cricondentherm gas: Design case for GTP and GT
  3. GGS-7°C cricondentherm gas


  Case 1 Case 2 Case 3
Component YK – 0°C Cricondentherm YK – 17°C Cricondentherm GGS – 7°C Cricondentherm
Nitrogen 0.0783499 0.0780200 0.0463
CO2 0.0000008 0.0000008 0.0050
H2S 0.0000007 0.0000007 0.0000
Methane 0.8326226 0.8291984 0.8668
Ethane 0.0470996 0.0469266 0.0468
Propane 0.0234892 0.0234657 0.0204
i-Butane 0.0047099 0.0048525 0.0042
n-Butane 0.0080707 0.0085556 0.0054
i-Pentane 0.0021622 0.0026765 0.0018
n-Pentane 0.0023011 0.0031113 0.0015
n-Hexane 0.0009485 0.0022262 0.0014
Mcyclopentane 0.0000486 0.0001180 0.0000
Cyclohexane 0.0000462 0.0001271 0.0000
n-Heptane 0.0000679 0.0003303 0.0005


Mcyclohexane 0.0000168 0.0000744 0.0000
n-Octane 0.0000063 0.0000570 0.0001


n-Nonane 0.0000004 0.0000045 0.0000
FC7* 0.0000469 0.0001840 0.0000
FC8* 0.0000090 0.0000614 0.0000
FC9* 0.0000006 0.0000065 0.0000
M-Mercaptan 0.0000004 0.0000004 0.0000
E-Mercaptan 0.0000004 0.0000005 0.0000
2Propanthiol 0.0000001 0.0000002 0.0000


H2O 0.0000010 0.0000013 0.0002



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