15.5 MONITORING INSTRUMENTATION
15.5.1 All the instruments required for safe, efficient and reliable operation of plant shall be supplied along with all necessary usual accessories as a system. The Bidder along with the Bid shall submit list of instruments (Quantity, type, make, model, rating etc.) and it shall be subject to approval by the purchaser during electrical engineering. Monitoring instrumentation shall include but not be limited to the following :
i) Pressure gauges, temperature gauges, level gauges, flow gauges etc. shall have dust and weatherproof enclosures
ii) Switch devices for protection/interlock/alarm purposes viz. pressure switches, temperature switches, level switches etc. shall have dust and weather proof enclosures and shall be of suitable rating.
iii) Thermocouples and RTDs for temperature measurements and temperature transmitters
iv) Flow elements viz. orifice plates, nozzles, venturies, etc.
v) Pressure/Differential pressure/level/flow transmitters.
vi) Receiver indicators & Recorders
vii) All special instruments, measuring instrument for water analysis system and waste water disposal system,
viii) Complete erection hardware as required including impulse pipes, fittings, valves, cables, cable glands, junction boxes, supporting and protective arrangements etc. for erection of above instruments.
ix) Adequate redundancy (1 out of 2 or 2 out of 3) for switches/transmitters shall be provided for critical controls and protections. The same shall be subject to approval during detailed engineering.
15.5.2 Local Gauges :
i) Pressure gauges shall conform to IS:3624 or equivalent and employ stainless steel movement. Stainless steel bourdon tube type pressure gauges shall be supplied. Diaphragm/bellow shall be used for vacuum and low pressure applications. All pressure gauges shall be glycerin filled. Accuracy of pressure gauges shall be ±1% FSD or better. Dial size shall be minimum 150 mm. Standard accessories like snubbers, chemical seal diaphragms, siphon, 3 way valves, drain valves etc. shall be included in the scope of the bidder. Connection size of pressure gauges shall be M20×1.5.
ii) Temperature gauges shall be filled thermal system with mercury in steel type with sufficient length of the capillary tube. Accuracy of temperature gauges shall be ±1% FSD or better. These shall employ stainless steel movement and dial size shall be 150 mm minimum. Mercury in glass thermometer is not acceptable.
iii) Level gauges shall generally be transparent or reflex type with illumination arrangement as required and protection cage.
iv) Local gauges shall not be mounted directly on pipeline or equipment where vibrations or other disturbance is expected.
v) Explosion proof construction shall be provided for all hazardous area applicable in accordance with area classification requirements.
vi) All temperature elements shall be of duplex type. For all RTD/thermocouple or any other sensor, secondary instruments along with associated cables shall be provided and mounted on the control Panel.
vii) Thermocouples shall be stain less steel sheathed, compact magnesium oxide insulated type.
15.5.3 Local Switches:
i) Non-indicating type switches shall be supplied and mounted on local enclosures/racks as required. The switches shall be used for alarm, interlock and protection purposes. The switches shall have plug in type connection. Contacts of these switches shall be changeover type and suitably rated for the application. Accuracy and repeatability of these switches shall be ± 1% and ± 0.5% respectively.
ii) Pressure switches and differential pressure switches shall be diaphragm/bellow/bourdon tube/piston actuated.
iii) Temperature switches shall be filled thermal system type and shall be provided with thermo well of SS:316 or suitable material for handling corrosive materials.
iv) Level switches shall be of the following type;-
a) Static head devices for vessels exposed to atmospheric pressure ,.
b) Differential type for high-pressure and high-temperature
c) Displacement float type for enclosed vessels
d) Moving float type for open tank and sumps.
e) Capacitance or radio frequency based for bulk material applications like solids, slurries etc.
f) level switches for different chemical solution tanks of DM plant/effluent treatment plant shall be capacitance/conductivity type.
v) Flow switches shall be variable area or differential pressure type actuating element for low flow and low pressure applications.
vi) Positive displacement type transmitter for oil flow application and the size and flow range shall be suitable for application.
vii) Connection sizes for local switches and gauges shall be as follows:
a) Pressure switches and gauges M20 x 1.5
b) Temperature switches and gauges M33×2
c) Level switches and gauges 25 mm NB
viii) All thermo wells shall be provided with sealing plugs that shall be screwed on whenever the temperature element is not inserted. The plug shall be of stainless steel and be fastened to the boss with a chain.
15.5.4 Transmitters for pressure, differential pressure, level flow etc.
i) Smart type electronic transmitters (for pressure/differential pressure) employing diaphragm, bellow or bourdon tube as sensing elements shall be supplied. The transmitters shall be capacitance type or inductance type. Output signal of the transmitters shall be 4-20 mA dc and circuit shall employ two-wire transmission. Measurement accuracy of all types of transmitters shall be ± 0.25% with least long term drift and maintenance.
ii) Transmitters shall be provided with enclosure having a degree of protection IP-65 as per IS: 2147.
iii) Range elevation/suppression facility shall be provided in all the transmitters.
iv) Level transmitter shall be of the following type :
a) Differential pressure or displacement float type for enclosed vessels
b) Moving float type for fuel oil storage tanks.
c) Radio frequency type for ash hopper ,coal feeder sand ash slurry applications.
d) Strain gauge type load cells for coal hoppers.
15.5.5 Receiver Indicators and Recorders
i) Following general requirement of indicators and recorders shall be complied with :
a) Indicators/recorders shall be suitable for flush mounting on the panel and shall be provided with a bezel of colour that matches the panel colour and shall have semi gloss finish. Instruments shall be capable to withdrawal from the front.
b) Connection to the instruments shall be by means of individual plug and sockets arrangement.
c) Instruments shall be provided with transparent non-reflex type front covers.
d) Visual indication shall be provided on instruments front to indicate failure of supply to the instrument, wherever applicable.
e) Instrument scales shall be in metric units and shall be linear with respect to measurement variable.
f) Facility for zero and span adjustment shall be provided.
g) Signal monitor cards shall be used to initiate alarms where 4-20 mA signal is available. Solid state relays may be suitably incorporated in the amplifier circuit when the signal is directly connected to the receiving indicator/recorder to generate alarm contacts. Alarm contacts generated by pointer movement shall not be acceptable.
ii) Indicators
Vertical Bargraph indicator with four digital display on top or bottom of the indicator shall be provided.
Indicators shall be with multi-channels and shall accept universal input signal (TC/RTD) 4-20ma,Voltage range shall be configurable and programmable with measurement accuracy ± 0.2% of span or ± count. Requisite mounting accessories and mounting bins shall also be provided.
iii) Recorders
The recorders shall be microprocessor based, chart less recorders with multi-channels shall be provided. The recorders shall have accuracy of ± 0.2%
iv) Integrators/Totalisers :
The integrator unit shall accept an input signal of 4-20 mA/1-5 V DC. It shall indicate the quantity of flow with minimum 6 digit displays and 4 mm height and provided with manual reset facility. The indicator shall be suitable for 240 volts A.C. supply and accuracy of indication shall be +/- 0.5%. It shall be provided with plug-in type current to pulse rate converter and shall have adjustable pulse rate compatible with the process measured values.
