BANGLADESH POWER DEVELOPMENT BOARD TENDER ... - BPDB

(1) Pressure MeasurementPressure shall be measured near the pump discharges, pump suctions whereNPSH availability is critical, at either side of equipment where pressure drop idsignificant, pressure regulated process, remote end of service lines, and near flowand level measurements affected by compressibility or density changes.Normal operating point shall be approximately 60% of the range, over-rangeprotection of at least 1.3 times the maximum scale reading shall be furnished onall pressure instruments. Accuracy shall be plus / minus 0.5% of calibrated spanfor bellows or bourdon tube transmitters at the minimum.(2) Temperature MeasurementTemperature at appropriate locations at compressor discharge, turbine wheelspace, exhaust gas, rotor shaft bearings, stator windings, critical turbine metalpoints, lube oil, radiators, etc. shall be measured.In general, temperature element shall be thermocouples, resistance temperaturedetectors may be used as sensors for control loops. Thermocouples shall becooper-constan for temperatures upto 200 0 C iron constantan up to 750 0 C, andchromel alumel up to 950 0 C. Cold junction compensation shall be achieved in thecontrol room. All extension wires from thermocouples and resistance temperaturedetectors shall be shielded. Thermocouples shall be accurate to plus / minus 0.75% maximum measured temperature.Resistance temperature detectors shall have platinum resistance windings andshall be connected by the three-wire method. Resistance temperature detectorsshall have an accuracy of plus / minus 2 0 C. Local temperature gauge shall bebimetal thermometers and shall have 80 mm round dial at minimum with blackand white markings.Welded wells for temperature element shall be the same material as theassociated piping systems. All screwing wells shall be stainless steel.(3) Level measurementLevel shall be measured in all tanks and vessels. Measurement of level in large orpressurised vessels shall be by differential pressure. Local level indication of smallbe by gauge glass for clear liquids, and by a top mounted float or bubbler forviscous liquids. Level controllers shall be of the differential pressure, or externalcage displacement type.(4) Flow measurementFlowmeters shall, with the exception of the area meter, operate on therelationship which exists between differential pressure and fluid velocity.Flowmeters shall have liner outputs. Accuracy for fuel flow meter shall be within2.0% at rate of flow higher than 80%.Flow metering of fuel shall be temperature and / or pressure compensated & withintegration.For flow-metering of oil, positive displacement meters or area meters shall beused.Ghorasal 200 MW to 300 MW Gas Turbine Peaking Power Plant Project (Vol-2 of 3)87