ST51A/ST75A/ST75AV Mass Flow Meters TROUBLESHOOTING
Fluid Components International LLC 67
5 TROUBLESHOOTING
Application Verification
After verifying that the flow meter is functioning, review the application parameters below to verify the calibration matches the process media.
Equipment Needed
● Flow Instrument Calibration Data
● Process Parameters and Limits
Check Serial Numbers
Verify that the serial number of the flow element and the flow transmitter electronics are the same. The flow element and the flow
transmitter are a matched set and cannot be operated independently.
Check the Instrument Installation
Verify correct mechanical and electrical installation. Check for secure wire/terminal connections (tighten as required). Verify the flow element is
mounted at least 20 diameters downstream and 10 diameters upstream from any bends or interference in the process pipe or duct.
Check for Moisture
Check for moisture on the flow transmitter. Moisture may cause intermittent operation. Check for moisture on the flow element. If a
component of the process media is near its saturation temperature it may condense on the flow element.
Check Application Design Requirements
1. Review the application design with plant operation personnel and plant engineers.
2. Ensure that plant equipment conforms to the actual conditions.
3. Verify operating temperature, operating pressure, line size and gas medium.
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, the volumetric flow rate and the pressure and temperature, 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:
Equation:
=
Where:
Q
A
= Volumetric Flow Q
S
= Standard Volumetric Flow
P
A
= Actual Pressure T
A
= Actual Temperature
P
S
= Standard Pressure T
S
= Standard Temperature
PSIA and °R are used for pressure and temperature units.
[Metric: Where bar(a) and °K are used for pressure and temperature.]
Example:
Q
A
= 1212.7 ACFM Q
S
= 1485 SCFM
P
A
= 19.7 PSIA T
A
= 120 °F (580 °R)
P
S
= 14.7 PSIA T
S
= 70 °F (530 °R)
[Metric: P
S
= 1.01325 bar(a), T
S
= 21.1 °C (294.1 °K)]
.
.
°
°
.
= 1485 SCFM
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