Fluid Components International FR73B Complete Manual - Manual (Page 7)

FR78B Flow Switch/Monitor FLUID COMPONENTS INTERNATIONAL LLC
This page is subject to proprietary rights statement on last page 7 Doc. No. 06EN003281 Rev. A
Non-maintenance Observations
At this point, observe the system setup to verify operation. No disassembly or testing is required at this time.
Check Serial Numbers
Verify that the serial number of the flow element and the control circuit are the same when the instrument is used with the remote
enclosure option. The flow element and the control circuit are a matched set and cannot be operated independently of each other.
Check Input Power
Verify that the correct power source is turned on and connected.
Check the Instrument Installation
Review the information on instrument installation beginning on page 2 to verify correct mechanical and electrical installation.
At the time of order, the flow element placement should have been determined. However, if not, the flow element should be
mounted at least 20 diameters downstream and 10 diameters upstream from any bends or interference in the process pipe or duct
for best accuracy.
Check for Moisture
Check for moisture on the control circuit. Moisture on the control circuit may cause intermittent operation.
If a component of the process media is near it's saturation temperature, it may condense on in the flow element tubing. Place the
flow element where the process media is well above the saturation temperature of any of the process gases.
Check Application Design Requirements
Application design problems can occur when instruments are first installed into the process media. The application design should
also be checked 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.
Control Circuit Dash Number Specification
Verify that wiring is connected per the wiring diagram in Appendix A.
Verification of Flow Element Resistance
The measurements are based on a standard (4K ohm RTD at 70°F, or 21°C) flow element. Variation of ±100 ohms from nominal is to
be expected, depending on temperature. The maximum allowable difference in resistance between matched RTD's is 1% at ambient
temperature (immersed in water). The heater resistance should be 221 ±5 ohms.
1. Turn off the operating power to the instrument.
2. Gently remove (pull straight out) the control circuit from the socket. Using a DMM, measure the resistance of the active and
reference RTD sensing elements.
Note: The resistance of the active RTD will be greater than the resistance of the reference RTD whenever the
heater is on.
3. Measure the resistances as found in Table 2 to determine if the flow element is functional. The resistance is dependent on a
temperature of 70°F (21°C). Note: See Figure 5 for pin location.