ABB C1300 User Manual Supplement page 6

...2 MATH CONFIGURATION
...2.1.3 Mass Flow 1 and 2
Example A – calculating the mass flow of water from the volume flow.
At a temperature of 60°F (520°R) and an absolute pressure of 14.696 psia, 1 gallon (US) of water has a mass of 8.334 lbs.
To calculate the mass flow of water from the volume flow the following settings are used:
PV1 – volume flow of water (gal/min)
PV2 – temperature of water (°F)
PV3 – pressure of water (psia.)
PV4 – result of math block 1 (lb/min)
therefore the equation is:
The example below shows the construction of Math block 1 with the following selected:
• math block function–
• input A source –
Process Variable 1
• input t source
Process Variable 2
• temperature units –
• temperature reference (process conditions using maximum flow rate) –
input P source –
• Process Variable 3
• pressure reference (process conditions using maximum flow rate) –
• scaling constant –
8.334
Notes.
• Ensure that the temperature input/temperature reference have the same units and the pressure input/pressure reference
have the same absolute units.
• The basic mass flow equation must use absolute temperatures (K or °R). The C1300 converts automatically from °C or °F
to absolute.
• If temperature or pressure correction is not required, set the temperature or pressure inputs to
4
Mass 1
Deg F
60.0
14.69
None
– see Section 2.2.3.