Yokogawa 415 Steam and Gas - Manual (Page 9)

1. INTRODUCTION
The Model 415 Gas Flow Computer incorporates compensation for gas and
vapours to the following equations:
1. Ideal Gas Law using temperature & pressure correction, but where
compressibility is ignored.
2. General Gases where compressibility is calculated using the
Redlich-Kwong 1 equation.
3. Natural Gas using NX-19 2 equation for supercompressibility.
4. Steam Equations for both saturated and superheated steam. Mass and
energy flowrates are calculated using standard equations to determine
the specific weight and enthalpy of steam.
Inputs from a wide range of flowmeters are handled including vortex, turbine,
orifice plate, averaging pitot tubes, wedges, V-Cones and target flowmeters. In
addition, where two differential pressure transmitters are used across an orifice
(or similar device) to increase the measured flowrange, both D.P. transmitter
inputs can be accepted into the Flow Computer and scaled separately with
automatic crossover.
Options include a 4-20mA re-transmission, high and low flow alarms and an
RS232/422/485 output. A unique feature available with the RS232/422/485
output is the ability to print flowrates and totals at programmable time intervals.
This enables the instrument to function as a data logger when used in conjunction
with a printer, or other storage device.
Two versions of the instrument are available, the Model 415R with direct RTD
input, and the 415A with a 4-20mA temperature input. Both accept a 4-20mA
pressure input.
The Model 415 is designed to supersede the Models 405GS and 405ST.
1 Redlich & Kwong. "An equation of State". Chem Rev, vol 44, p233, 1949.
2 Par Research Project NX-19. "Extension of Range of Supercompressibility
Tables", American Gas Association, 1962.
Introduction 7