INSTRUMENTATION DESIGN CRITERIA

BASIC INSTRUMENTATION PROJECT STANDARDS 

INSTRUMENTATION SYSTEM PHILOSOPHY

Instrument Philosophy

1. All the offered instruments / equipment or equipment of similar design
manufactured by the same supplier shall have been:
- Type tested by the authority approved by the Company.
- In continuous satisfactory service on offshore for a minimum period of two
years.

2. Field Instruments
All field instruments connected with well monitoring and control, and all
facilities that are not to be operated from a central control room, shall be
pneumatic except those that are connected to RTU, which shall be electronic,
SMART type. The type of output for smart transmitter shall be in HART
Protocol.
All instruments connected to control room and remote unit control panels of
related systems shall be electronic, SMART type.
For remote control application, remote telemetry, telecontrol and data
gathering, electronic instruments shall be used.
All final actuation / control device, controlled from remote / Central Control
Room (CCR) shall in general be pneumatically actuated.
Instrument ranges shall be selected such that the normal operating point is
between 35% and 75% of the instrument total range.
Hand-held Intrinsically Safe calibration / configuration units shall be supplied
to enable online diagnostics, configuration or calibration of electronic
instruments from any point in the loop. The number of such calibration /
configuration units shall be as per the Basic Bid Work.
a. Pneumatic Field Instruments
Each pneumatic instrument supply shall be provided with independent
filter regulator. For pneumatic instruments, dry instrument gas / air supply
shall be as follows:
- 5.5 Kg/cm2 (min.)
- 7.5 Kg/cm2 (nor.)
- 10.5 Kg/cm2 (max.)
All related equipment shall be suitable for operating in the above-specified
range. For pneumatic analog control applications, the actuating signal
range shall be 0.2 to 1 Kg/cm2g.
For pneumatic on-off applications, the actuating signal shall be 0 or 5.5
Kg/cm2g

b. Electronic Field Instruments
All electronic transmitters shall be 24 V DC loop-powered type with 4 –20
mA Smart analog output signal. Electronic Transmitters shall have integral
LCD display. Where this is not possible, a suitable separate local loop
indicator shall be provided.
Local electrical control and field alarm switches shall be hermetically
sealed SPDT Micro Switch activated. The switches shall be rated for 110
V AC 5 Amps. or 24 V DC – 2 Amps.

3. Control Room Instrumentation
All signals to and from the Central Control Room shall be electric / electronic.
The standard signal shall be analogue 4-20 mA using 2-wire system,
standard thermocouple, RTD output, and / or suitable pulse signal.
Instruments located on control panels and central control room (CCR) shall
be microprocessor based.
On platforms with processing facilities, a Distributed Control System (DCS)
shall be provided for monitoring and controlling the process, and for
generating alarms in case of process upsets.

4. Safety Instrumentation System
The new platforms shall be provided with the following safety systems:
a. Emergency Shut Down (ESD) System: The ESD system shall initiate
process shutdown in case of abnormal condition of the specified process
parameter.
b. The F&G system: The F&G system shall initiate emergency shutdown
(ESD) upon detection of appropriate level of hydrocarbon and/or H2S and
fire shutdown (FSD) upon accumulation or fire
c. Manual ESD & FSD Stations: The ESD & FSD stations shall be provided
at all strategic locations on the platform for manual initiation of ESD and
FSD.
All shutdown and alarm switches shall be “Fail Safe” and the targeted
abnormal conditions shall cause a loss of actuating signal to the final control
element.
Parameters used for shutdown shall be sensed by independent / individual
sensors at independent tapping points. Such sensors and tapping points shall
not be shared by any other loop.





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