Doc. No. 06EN003291 Rev. A
5 - 3
Model ST98 Flow Meter
CHAPTER 5 - TROUBLESHOOTING
FLUID COMPONENTS INTL
Application Verification
After verifying that the flow meter is functioning, review the application parameters as shown 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 of each other.
Check the Instrument Installation
Review the information in Chapter 2 - Installation, to verify correct mechanical and electrical installation.
Verify that 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 on the flow transmitter 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. 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 may occur with first time application instruments, although the 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.
Verify Standard Versus Actual Process Conditions
The flowmeter 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:
Q
Q
S
A
=
×
×
P
T
T
P
A
A
S
S
(Metric: Where bar(a) and °K are used
Where:
for pressure and temperature.)
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.
