Fluid Components International MT91 Manual Troubleshooting - Manual (Page 2)

FLUID COMPONENTS INTL CHAPTER 5 - TROUBLESHOOTING
Model MT91 Multipoint Flowmeter 5 - 2 Doc. No. 003185 Rev. B
Check Application Design Requirements
Application design problems usually occur with first time application units, although the design should also be
checked on units 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 flowmeters, such as an orifice plate or a pitot tube, measure the volumetric flow rate. The volumetric
flow rate is the volume of gass per time. If the readings displayed by the MT91 does 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 temperture at the point of measurement must be known. Use the following
equation to calculate the mass flow rate (Standard Volumetric Flowrate) for the other instrument.
Equation:
Q Q
S A
= Ч Ч
P
T
T
P
A
A
S
S
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
and Pressure and Temperature are in absolute units.
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)
Troubleshooting Process
Verify Units
Observe the normal display screen to verify that the unit of measure for channel 1 and 2 are the expected units.
If units are correct, proceed to the next section. If units are not correct, refer to Chapter 3 for instructions on
selecting measurement units.
Verify Channel Assignment
If there is no reading or faulty reading, make sure that the sensing points are assigned to the correct channel.
Refer to Chapter 3 for instructions on assigning sensing points if they need to be assigned.
1. Go to menu level 2.2.1 and select the desired channel (Setup Þ Outputs Þ Assign Heads) .
2. Select 5=View Assigned. An ‘x’ will appear under the sensing point number if it is assigned.
If the correct sensing points are assigned, continue with the next section.
( ) 530° R .
14.7 PSIA
= 1485 SCFM
( ) 19.7 PSIA
580° R
( ) 1212.7 ACFM
1