INSTRUMENTS SHORT DEFINITION AND CALIBRATION PROCEDURE

INSTRUMENTS SHORT DEFINITION

CONTROL VALVES:-

• Control valve is a small control element, used for controlling process parameter.

• Controlling process parameter is flow,pressure,temperature,level etc.,

TYPES OF VALVES:-

•   Ball, Butterfly, Gate, Globe, Needle, Plug, Diaphragm and Non Return valve etc.

VALVE ACCESSORY:-

• A device mounted on the actuator to complement the actuators function.

•  Make it a complete operating unit; Examples include positioners , supply pressure, regulators, solenoids and limit switches.

ACTUATOR:-

•   A pneumatic hydraulic or electrically powered device that supplies force and motion to open or close the valve.

Actuator Assembly:-

•  An actuator including all the pertinent accessories that make it a complete operating unit.

VALVES CAPACITY:-

•   The rate of flow through a valve under stated conditions.

CONTROLLER:-

•   A device that operates automatically by use of same established algorithm to regulate a controlled variable.

•  The controller input receives the information about the status of the process variable.

•   And then provide an appropriate output signal to the final control element.

  

LOCAL CONTROLLER PNEUMATIC:-

•  It is used to control the control valves.

•   Input of controller from pneumatic transmitter.

•   Output of pneumatic controller is 2 to 1 bar pressure.

PNEUMATIC ACTUATOR:-

•   A part of valve operated by Air.

SHUT OFF VALVES:-

•   Shut Off valve is a control element it maintain status of full open or full close.

DAMPER ACTUATOR:-

•   Damper actuator is a device used to operate a damper vanes in burner corner.

ELECTRICAL INDICATORS:-

•   It is used to TCR (Thermal Control Room) in order to indicate process parameter.

•   Input of the Electrical Indicators either 4 ~ 20 mA or 0 ~ 0 V.

HAND AUTO STATION ELECTRICAL:-

•   It is used for giving control signal to control valve.

•   The command of the control valve indicated in Hand Auto station.

CONTROL DESK AND PANEL:-

• Control desk and panel in which Indicator and Recorder safe stations are mounted.

ER CUBICLES:-

• Cubicles in which modules are installed.

TRANSMITTER ELECTRONIC:-

• Transmitter is a device, used to transmits signal from local to Electronic Room (ER)

• The output of electronic transmitter is 4 to 20 mA; Depending upon the input signal.

• The input signal there is pressure, flow, temperature etc.

• Supply of electronic transmitter is Dc 24 V.

 

TRANSMITTER PNEUMATIC:-

• The output of pneumatic transmitters is 3-15 psi.

• Mainly used for local controlling supply of pneumatic transmitter is 1.5 bar.

BURNER IGNITOR:-

• It consists of Ignitor gun, spark plug and flame detector rod in order to produce pilot flame and flame detection.

IMPULSE LINE AND HAND ISOLATING VALVE:-

• It is the line between process fluid and Instruments such as gauges , transmitter , and switches.

FLUE GAS ANALYSER:-

• In order to study the gas and percentage of Oxygen in flue gas.

SMOKE DENSITY MONITORS:-

• It measure intensity of smoke presents in flue gas.

PH ANALYSER:-

• It is part of water analyzer ph value should maintain requirements.

• PH determines whether the liquid is acidic or alkaline.

SILICA ANALYZER:-

• Silica percentage is water.

LOCAL GAUGES PRESSURE:-

• It is used to measure the pressure.

• It indicate pressure in local sensing element of pressure gauges an bellows, bourdon tubes or diaphragms.

FLOW SWITCHES:-

• Flow switches are used to switching in flow is high or low flow.

• Flow switch output is used for annociation.

LEVEL SWITCHES:-

• The tank level when switching at level high or low.

TEMPERATURE SWITCHES:-

• The temperature switch is switching at high temp or low temp.

• It is used for annunciation.

SOLENOID VALVE:-

• Solenoid valve are pilot valve operating valve for control valve.

• Different types of solenoid valve 24 v dc, 48 v dc and 110v dc.

AIR FILTER REGULATORS:-

• It is used for regulate air pressure to instrument requirements.

THERMOCOUPLE:-

• It is a device. It is used to convert temperature to mV.

• Thermocouple mainly used in Boiler E type.

PRESSURE SWITCHES:-

• Pressure switches there are two types low and high. The switching when increasing pressure and decreasing pressure.

LOOP:-

• The arrangement of instruments to measure or control a process variable is called a loop. Loop classified into two types,

• Closed Loop

• Open Loop

INSTRUMENTS CALIBRATION PROCEDURE:-

TRANSMITTER:

STEP-1

            Close the Isolation Valve

Step-2

            Open the high pressure and low pressure tubes

Step-3

            Drain the transmitter

Step-4

            Note the Lower range value and Upper range value

Step-5

            Apply pressure on H.P side and check the output in mA before check the zero value.

Step-6

            Zero value is 4 mA is not correct; after that adjust the zero value for 4 mA

Step-7

            Apply pressure on H.P side and check the output mA value.

Step-8

            Whether Output mA value is correct, don’t adjust span value, If it is not correct adjust the span value

Step-9

            Apply the pressure to check the output mA. Corresponding 25 %, 50 %, 75 % and 100 %   input pressure.

SINGLE PRESSURE SWITCH CALIBRATION

Step-1

            Close the isolation valve

Step-2

            Remove the tubes higher side and lower side

Step-3

            Note the set point and range

Step-4

            Set points are correct then apply the pressure for getting proper result.

DIFFERENTIAL PRESSURE SWITCH CALIBRATION 

Step-1

            Close the Isolation valve

Step-2

            Remove the tubes higher side and lower side

Step-3

            Note the set point and range

Step-4

            Apply the pressure at higher side. If it is not ok, adjust set point and getting proper result.

LEVEL SWITCH CALIBRATION

Step-1

            Close the Isolation valves

Step-2

            Drain the remaining water

Step-3

            Isolate the normally open / Normally Close supply contact wire and connect multimeter

Step-4

            Attach setup and start pouring water until we get the set point

Step-5

            If result is not ok, adjust and getting proper result.

INSTRUMENTS TROUBLESHOOTING

How to check defective transmitter in running plant?

Step-1

            We will ask the Operation Engineer to give the permit to do check  defective Transmitter.

Step-2

            To get the permit.

Step-3

            By-pass the transmitter in the system from control room (By Operator).

Step-4

            Follow the same procedure for transmitter calibration.

Step-5

            Go to local and check the display of the T.X dead zero. If it is not showing      or dead zero and check the supply volte.  Whether 24 V available or not.

Step-6

            Isolate the T.X and close the isolating valve and open equalizing valve to        check live zero.

Step-7

            Then check the Impulse line whether any choke (blocking) available or           not. If it its available make flush the impulse line.

Step-8

            Calibrate the Transmitter it required.

Step-9

            Normalize the Transmitter and remove the bypass and cancel the work         permit.

 How to check defective pressure switch?

Step-1

            Isolate the pressure switch.

Step-2

            Remove the cable from control room.

Step-3

            Connect the multimeter to both contacts (N / O and N / C)

Step-4

            Apply the pressure to check set and reset value.

Step-5

            If any shift, adjust the set value.

Major problem of pressure gauge?

1. Fitting leak

2. Pointer Showing Zero Out

3. Hair Spring may be damaged.

4. Rack and Pinion may be damaged.

5. Burdon Tube or Sensing element may be damaged.

6. In glycol fill gauges, glycol may be leak.

7. Impulse line may be damaged or choked.