FCI MT86, Installation, Operation & Maintenance Manual

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TROUBLESHOOTING MT86/MT86HT Flow Meter
20 Fluid Components International LLC
Check Application Design Requirements
Application design problems usually occur with first time application instruments, but also check on instruments that have been in operation
for some time. If the application design does not match field conditions, errors occur.
1. Review the application design with plant operation personnel and plant engineers.
2. Ensure that plant equipment such as pressure and temperature instruments conform to the actual conditions.
3. Verify operating temperature, operating pressure, line size, and gas medium.
Check Flow Element Placement
If there are measurement errors check for process flow irregularities. A swirling or pulsating flow can exist near valves, elbows and other
obstructions. For optimum flow meter performance place the flow element in a straight run of pipe at least 20 pipe diameters upstream and
10 diameters downstream.
Check Flow Element Orientation
Verify that the flat on the flow element is parallel to the pipe and the flow arrow points in the direction of the flow stream. If the flat and the
flow arrow are not correct, the flow measurement will not be correct. See INSTALLATION , page 35, for the instructions on proper
installation.
Check Proper Flow Element Insertion Depth
The flow element's sensing points must be located at the center line of the pipe unless the factory specifies otherwise. Improper insertion
depth may cause error in the flow measurement. See Chapter 2 for the instructions on proper installation.
Check Flow Meter Switch Positions
Verify that switches SW1-1, SW1-2 and SW1-3 are in the open position. If the temperature compensation mode is used, place switch
SW1-4 in the open position. If temperature compensation is not used, ensure switch SW1-4 is the closed position. An easy way to verify
temp. comp. is used is to see if the top of the null and gain potentiometers have been sealed. If they are sealed the flow meter is setup to
use temperature compensation. If they are not then no temperature compensation is used. An open switch is the switch pressed on the left
or lower side of the switch bank.
Verify that the head-select switch SW2 is set on the number that corresponds to the last sensing point that is connected to the flow
transmitter.
Verify that the switch SW4 is in the OP position.
Check the General Process
Check all inputs and outputs to the system. Verify pump ratings and check damper or valves that might be open or closed causing the flow
to be different from what is expected.
Verify Standard Versus Actual Process Conditions
The flow meter measures the mass flow rate. The mass flow rate is the mass of the gas flowing through a pipe per time. Other flow meters,
such as an orifice plate or a pitot tube, measure the volumetric flow rate. The volumetric flow rate is the volume of gas per time. If the
readings displayed do not agree with another instrument, some calculations may be necessary before comparing them. To calculate the
mass flow rate and the volumetric flow rate the pressure and temperature at the point of measurement must be known. Use the following
equation to calculate the mass flow rate (Standard Volumetric Flow rate) for the other instrument.
Troubleshooting Process
Verify Delta " R" Sheets
Verify that the Delta "R" sheets in the rear of this manual match the flow meter's serial number. If there is a mismatch the calibration could
be incorrect. Contact FCI if the proper Delta "R" sheets are missing.
Verify Faulty Flow Elements
Caution: Inform all personnel involved with monitoring the flow media that the flow meter output readings may change. The
change of output could affect the plant peripheral equipment and or alarms.
To identify a bad flow element rotate the Head-Select switch, SW2, through its numbered positions. Pause at each position to monitor a
red Light Emitting Diode (LED), CR1. CR1 is located on the MT86 Control Board. If a problem exists with a sensing point, the LED will