Instrument Technician Using PPE (Personal Protective Equipment)
Safety Document
Maintenance Work Permits. & SCC (Safety Clearance Certificate) If Required
Tools/ Special
I &C Tool Kit & special tools (if Required)
Test Equipment
Tools
Test Equipment:
Note: Select test equipment according to the max. Range & Medium.1– Digital multi-meter / mA meter / SMART HART Calibrator
2- Deadweight Tester, Standard Pressure
Gauge (0.5 Bar to 200 Bars) 3– Hydraulic pressure pump and standard pressure gauge (0 Bar to 250 Bars). 4– Air pressure pump with digital multifunction calibrator used for very low and low pressure (0 to 20000mmH2O or 0to 2 Bar or 0 to 20 Bars). 5– Water manometer or mercury manometer with air pump (0 to 1500 mm H2O or 0 to 1500mmHg). 6- Vacuum pump with digital multifunction tester.(0 to -760 mmHg / 0 to -30 inches of Hg or 0 to -1 Bar)
Stores &Materials
Cleaning spray, brush and cloth
Job Description
Process
Steps
During Maintenance
Isolation& Removal
1
Isolate the transmitter by closing inlet valve of many fold or isolate from the main isolating valves of impulse lines.
2
In case of oil or chemical process use secondary container to avoid spill of oil / chemical when isolating. Depressurize the transmitter and draining tapping lines.
3
Confirm that power supply is OFF. Remove the wires from the transmitter terminal by the core identification and insulate all wires terminals by insulation tape (Ensure it isn’t in contact with each other, short circuiting or producing any earth).
4
Move away the tapping lines to avoid spill of oil or chemical from transmitter connections. Disconnect the SMART pressure transmitter or differential pressure transmitter form the process carefully.
5
Carry out the Pressure transmitter / diff. pressure transmitter external cleaning, using a brush and approved cleaning spray to remove contamination or solid particles.
6
Inspect the Pressure or Diff. Pressure Transmitter for external physical damage, general appearance & fitness. (Check whether cover seals are intact).
Preparation
7
Write all the details of pressure or diff. pressure transmitter: tag no., range, service and unit no. in the calibration sheet.
8
Collect the calibration range from Engineer of each transmitter (Millimeter WC till maximum range in bars) and note in the calibration sheet.
9
Set up the test equipment as shown in the diagram:
10
Ensure that the medium used for calibration is same as that of medium of the process (if possible) where transmitter is installed.
11
Carry out purging (if required) to remove the process medium completely from the transmitter internals (Pressurize, Fill & Drain).
12
Carry out the leak test by applying the pressure, to the transmitter & check for leakages. (Pressurize at max. range and wait for at least one minute). If there is any leakage in connections, tighten. Note:1– Always use high pressure port of Diff. pressure transmitter and keep low pressure port free in air for reference. 2- Never apply pressure more than the rated pressure; otherwise pressure sensor of transmitter will be damaged.
13
Connect multi-function HART communicator as shown in diagram and
VIP
switch ON and wait for stabilize. Before start calibration, check configuration & confirms all parameters (If required) which are supplied by Engineer by SMART calibrator. {Like: tag no, service name, process name, (pressure, level or flow), engineering units, in case of flow
check square root extractor for local indication, input minimum and
maximum ranges, output current range set on 4~20mADC, Damping
values, burn out at LRV & URV, date of calibration, next time schedule for calibration, etc.} Note: Make the damping 0% before calibration. After calibration readjust the damping on original values as before.
14
Exercise the pressure element to stretch for full range and back to zero to make sure that element can operate normal.
Calibration
15
Without apply pressure check the output of transmitter should be 4mADC.
16
Now apply 100% pressure according to range provided by Engineer and note the output of transmitter. It should be 20mADC.
17
If output of the above both values are correct then check middle 3 points (at 25% input pressure, output = 8mADC, at 50% input pressure, output =12mADC and at 75% input pressure, output=16mADC) for rising and fallen values.
18
In case of Vacuum transmitter. Without creating vacuum check the output current should be 4.00mADC. Now create the vacuum in the vacuum transmitter and note the other 4 points input / output values. (At 25% vacuum: output should be 8.00mADC, at 50% vacuum: output current should be 12mADC, at 75% vacuum: output should be 16mADC & at 100% vacuum: output should be 20mADC). Note: If we consider 0% vacuum at 20mADC then at 100% vacuum, current should be 4.0mADC
19
Record these input/output values in the calibration sheet as found column or before calibration column.
20
If all reading are correct and error is in limit & below the design values then record these values in as found column or before calibration column and go to step 29.
21
If there is difference in reading more than error and adjustment is required. Then remove covers (If available) to gain access to zero adjustment and span adjustment screw. Note: (1) In case of Mfg.: Yamatake Co. SMART Transmitters following calibration procedure is used. (2) In case of Mfg.: YEW Co. SMART Transmitters there is mechanical Zero adjustment screw is available but span adjustment screw is not available. So digital span trim adjustment is possible by the SMART communicator. (3) In case of any other Mfg. Co. SMART transmitters, Zero and span adjustment according to their procedure.
22
Depressurize the transmitter completely to check 4.00mADC. At 0% input pressure, adjust transmitter output 4mADC by touch screen with magnetic stick. Touch the magnetic stick at the bottom of screen, Zero adjustment will appear. Change the position of magnetic stick (Left or Right to Increase or decrease mA) it will change mA on the mA meter. So adjust exact 4.0mADC. (Adjust bye zero screw if available)
23
Apply 100% input pressure to the transmitter sensor and view the output of transmitter, should be 20mADC. If it is less or more, then adjust the span 20mADC by magnetic stick. Move the stick on the top of screen. Span adjustment will appear. Change the position of magnetic stick (left or Right) it will change mA on the mA meter. So adjust exact 20.00 mADC on the mA meter. (Adjust by span screw if available)
24
Repeat steps 22 and 23 till at 0% input pressure, output should be 4.00mADC & at 100% input pressure, output should be 20mADC.
25
If zero and span is corrected then check the other 3 points (at 25% input pressure = 8mADC, at 50% input pressure = 12mADC and at 75% input pressure=16mADC by increasing and decreasing the pressure.
26
Check repeatability by increasing and decreasing pressure and confirm all 5 points (0%, 25%, 50%, 75%, & 100%) input / output values match with standard values. Check the error is in limit and under design value.
27
Record these input & output values in calibration sheet in after calibration columns.
28
Readjust the damping after calibration on original values as before.
29
The pressure transmitter or diff. pressure transmitter input / output values should be inspected by Inspector and Quality Inspector for witness and record these values to sign the certificate after completion of job.
30
It is necessary to adjust head correction (If any) to avoid any wrong reading.
Completion
31
Once the test is completed, remove the test equipment and clean the tested device.
32
Install the SMART transmitter back to its position and reconnect the instrument fittings, tubing without bending or damaging and ensure that connector is not cross fitted that can damage threading.
33
If there is damper or capillary tube used before the transmitter. It should be inspected and cleaned or overhauled. (Replace gaskets or O-rings if necessary in damper).
34
Close the drain valve and open the inlet valve slowly to avoid sudden pressure entering in the transmitter sensor.
35
In case of water / oil / chemicals, purge the air completely from the transmitters, tub lines / capillary tube and fill the transmitter carefully to avoid showing any wrong readings.
36
Check for leakage during commissioning.
37
Complete the check and calibration sheet and handover to the concerned Instrument & Control Engineer for inspection and signature.
