Power Plant INSTRUMENTATION AND CONTROL WORKS

 

Power Plant

       INSTRUMENTATION AND CONTROL WORKS

 

            Instrumentation and control works standards, and the requirements as described hereunder:

a]         All Instrumentation equipment shall be suitable for the local environmental conditions as specified herein.

b]         All outdoor devices, equipment, and enclosures shall be suitable for use in the classified hazardous area in accordance with the latest issue of the Codes and Standards specified.

c]         Control signal, analog signal, and status signal wiring shall be terminated in junction boxes, which shall be an integral part of the skid.

d]         All design, calculations, drawings, and equipment selection shall be subject to the approval of the COMPANY Engineer.

e]         Control, analog, and status signals wiring shall be terminated in different junction boxes.

f]          Transducers, Transmitters, gauges, meters, etc. shall be protected from direct sun rays.

g]         Signal transmission system shall be designed to protect the integrity of instrument signals from electric noise brought by electromagnetic induction, electrostatic or capacitive coupling, and electrical conduction.

 The following points shall be observed in the design of the signal transmission system:

i.          Shielded signal cable shall be used for all analog signals. The equipment manufacturer's advice shall be followed in selecting the proper cable to be used, but as a minimum, this shall be a twisted pair of stranded copper (16 AWG) wire braided over with an aluminum mylar shield covered by a plastic insulating overall cover.

ii.          To prevent ground loop effects, the grounding of the cable shield shall be done at the readout ends only. The grounding of parallel readout devices and other panel-mounted instruments shall follow the manufacturer's recommendations.

iii.         Conduit for transmission cable shall be made of rigid galvanized steel to provide maximum shielding against spurious electromagnetic radiation.

h]         Adequate access to the instruments for their operation and maintenance shall be provided.

i]          Control and monitoring of the complete system shall be through a computer-based operator’s workstation with all necessary components such as 21” TFT monitors, processors, keyboard, trackball, alarm printer, a screen copier, etc.

Emergency Shutdown (ESD) System

a]         Emergency shut down system  consisting of an emergency shut down valve (ESDV) with a local shutdown cabinet, associated instrumentation, and control system shall be provided.

b]         In addition to the local shutdown cabinet, closing of emergency shutdown valve shall also be possible through a discrete hard-wired push button installed in the control room.

c]         Open and close status indication and analog indication for pressure upstream and downstream of the emergency shut down valve shall be available on the operator’s workstation. Remote control.

 

Fuel Gas Separators/Filters

Fuel gas filtration shall be effected via four (4) fuel gas separators/filters with three (3) duty/one standby configuration. The control system shall be designed to provide:

a]         Provide alarm for high differential pressure across filters.

b]         Monitoring of differential pressure across separators/filtering units, as measured by the differential pressure transmitters,.

c]         Local indication for high differential pressure across the filters

d]         Automatic changeover of filters from “duty” to “standby” in case the duty separator/filter is saturated.

e]         The liquid drain system of separator/filtering units shall have all the necessary instrumentation including level gauge, level switches, level controller, and level control valves.

Metering

a]         The custody meter, The flow meter shall be designed for a maximum flow of required fuel gas. The flow metering system shall consist of skid-mounted four (4) meter runs including but not limited to the following:

     Orifice Plate

    Orifice Fittings

  Orifice Meter Tube

    Straightening Vane

    Instrument Connection Taps

  Control Valves

   Secondary Instrumentation and Control

  Signal Cabling / Junction Boxes

    Flow Computers

      Flow & Energy Counters

   Local Printer

b]         Flow rate, pressure, and temperature data shall be made available in the system for direct calculation of corrected flow volumes and total energy units through the use of a dedicated real-time flow computer station. Flow control capability shall also be made available.

c]  referred for Meter Run Installation.

d]         The metering system control panel shall be furnished with complete flow computer station hardware/software, flow controllers, flow and energy counters, printers, communication interfaces, and other accessories. 

The panel shall be designed and fabricated.

e]         The flow computer station shall be provided with a field-proven and reliable computer system conforming to the requirements.

f]          Metering system control panel shall be installed in the control room. Control panel enclosed equipment and wiring shall be designed for continuous operation at 550C, and relative humidity 95% maximum (non-condensing) and 5% minimum.

g]         Control and monitoring of the metering system shall be made available at the operator’s workstation, PP- DCS.

Flow Control Facility 

a]         The flow control shall be effected via four (4) pressure control valves (PCVs) with one valve per metering stream.

b]         Control valves (PCVs) shall be furnished.

c]         The control system shall be designed to provide necessary monitoring and to receive setpoints from the operator’s workstation located in the control room as well as from the control center.

d]         Each control valve shall be provided as one operable unit complete with the actuator, positioner instrumentation, all accessories, and interconnecting tubing.

Pressure Reducing Station (PRS)

a]         Pressure control valves actuators and smart type electro-pneumatic positioners-. 

The three (3) runs/streams of the pressure control station shall operate in two duty/one standby configuration. The control system shall be designed to:

i.          Provide fuel gas at constant supply pressure toPP- regardless of varying inlet pressures from the supply pipeline.

ii.          Provide automatic change-over/cut-in of the standby PCV into operation in case of failure of any one of the duty PCV. The changeover shall be bumpless ensuring a smooth and continuous supply of fuel gas to PP-.

iii.         Provide control and monitoring of the PRS at the operator’s workstation located in the control room.

b]         A pressure relief valve shall be installed downstream of the pressure reducing station.