FCI FLT93B Installation, Operation & Maintenance Manual Download Page 98

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APPENDIX D - TEMP COMP FLT

Series FlexSwitch

Fluid Components International LLC

Balance Procedure

The following steps are the flow element balance procedure required to complete the Temp Comp restoration and must be used when install-

ing remote units with more than 10 feet of cable.

1. Connect the DMM to P1 with the positive lead connected to position 1 (Red) and the negative lead connected to position 2 (Blue). Re-

install the control circuit on the terminal board. Set the DMM to volts DC. Place the heater jumper on J33.

2. Turn on the instrument power and wait fifteen minutes for the instrument to stabilize. During this time make sure that the process media

is flowing or the sensing elements are submerged. Do not make the following adjustment in still gas.

3. Adjust potentiometer R13 (to the right of S1) until the DMM reads 0 volts ±5 mV.
4. 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 setpoints 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 field if the test conditions are met and the data is measured correctly. However, in many ap-

plications it is difficult 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 change 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, and the same at both test temperatures.

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 flat blade screw driver.

1 each

Flat screw driver, capable of adjusting control circuit potentiometers.

As req.

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 flowing at a normal rate. Cool the

process media to the lowest temperature in the expected operating range.

3. Remove the control circuit. Disconnect the element wires on terminal board, TB2A AND TB2B.

Note: These are spring terminals.

4.  Connect the DMMs 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 flow and make sure that the media is at no flow and then let the instrument stabilize for fifteen 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.

8. Start the process media flowing at the desired switch point velocity and at the low temperature, let the instrument stabilize for fifteen minutes.
9. Record the resistance values of the active and reference RTDs at the low temperature.