Fluid Components International FLT93 Nuclear - Manual (Page 50)

APPENDIX C - TEMP COMP FLT ® Series FlexSwitch TM
50 Fluid Components International LLC
7. Adjust pot R8 (below the yellow LED) until the ohm value for R8 is as shown on the Temp Comp Cal sheet.
8. Remove the DMM and reinstall jumpers J10 and J11. (Leave the heater jumper removed.)
Note: Steps 10 through 13 are the fl ow element balance procedure required to complete the Temp Comp restoration.
9. Connect the DMM to P1 (the adapter cable on older control circuits) with the positive lead connected to position 2 (red wire on older
control circuits) and the negative lead connected to position 2 (blue wire on older control circuits). Re-install the control circuit on the
socket. Set the DMM to volts DC.
10. Turn on the instrument power and wait fi fteen minutes for the instrument to stabilize. During this time make sure that the process media
is fl owing or the sensing elements are submerged. Do not make the following adjustment in still gas.
11. Adjust potentiometer R13 (next to R8) until the DMM reads 0 volts ±5mV.
12. Turn off the instrument power and remove the DMM. Re-install the heater jumper in its original position.
The Temp Comp adjustments are now restored. Turn on the power and make sure the instrument is functioning properly. Make adjustments
to the alarm set points if needed.
Field Temp Comp Calibration
If the application of the instrument changes the Temp Comp may need to be re-calibrated. An example of when the Temp Comp needs to be
re-calibrated is as follows: The process media is gas, the factory set Temp Comp is 40 to 140 °F. The instrument is then placed in an applica-
tion that varies in temperature from 300 to 400 °F. In this case the instrument’s accuracy would be greater with a new Temp Comp calibration
performed.
Another example of where the accuracy will be affected and a Temp Comp calibration would need to be done is when the process media is
changed, i.e. from water to heavy oil.
Temp Comp calibration is possible to do in the fi eld if the test conditions are met and the data is measured correctly. However, in many ap-
plications it is diffi cult to achieve these parameters and it is easier to have the switch factory calibrated. To do the procedure the following
parameters are required:
• The maximum temperature range does not exceed 100 °F.
• The maximum temperature does not exceed the instruments rated maximum temperature.
• The velocity at which the switch will alarm needs to be known.
Equipment Required
1 each DC Power Supply, 0 to 20 Vdc minimum, at 0.5 Amps.
2 each 5-1/2 Digit DMM with 4 wire clip leads.
1 each #1 Philips screw driver.
1 each #1 Flat blade screw driver.
1 each Flat screw driver, capable of adjusting control circuit potentiometers.
Insulating varnish or equivalent to reseal the potentiometers.
Procedure
1. Turn off the instrument power.
2. Install the instrument into the pipe or a test stand where it can be calibrated. Start the process media fl owing at a normal rate. Cool the
process media to the lowest temperature in the expected operating range.
3. Remove the control circuit. Disconnect the wires on terminals 6 through 10. Removal of the socket from the enclosure may be necessary
for access to the wires.
4. Connect the DMM’s and the power supply to the sensing element as shown in Figure D-1.
5. Set the power supply voltage to the proper voltage as shown in Table D-1. Turn on the power supply and check the voltage setting.
6. Stop the process media fl ow and make sure that the media is at no fl ow and then let the instrument stabilize for fi fteen minutes.
7. Record the resistance values of the sensing elements and calculate the resistance differential (DR). If DR does not exceed the maximum
DR of 280 ohms then proceed with the calibration. If the DR is above 280 ohms use the next lower heater wattage setting and let the
instrument stabilize. Recheck the DR