GAS & STEAM FLOW COMPUTER MODEL 415

GAS & STEAM FLOW COMPUTER

MODEL 415

6 December 1999

CONTENTS

List of Symbols

1. Introduction

7

1.1 Model Number Designation

9

2. Specification

10

3. Operation

14

3.1 Front Panel Operation

14

3.2 Flow Equations for Gases

16

3.2.1 Ideal Gas Law

22

3.2.2 General Gas

24

3.2.3 Natural Gas

25

3.3 Steam Measurement

26

3.4 Filtering

31

3.5 Non-Linearity Correction

33

3.5.1 Digital Input Linearity Correction

33

3.5.2 Analog Input Linearity Correction

35

3.6 The Output Pulse

37

4. Options

39

4.1 The 4-20mA Output Option

39

4.1.1 Load Specification

40

4.1.2 Calculation

40

4.2 The RS232/422/485 Interface Option

43

4.2.1 Hardware

43

4.2.2 Multipoint Communication

44

4.2.3 Communication Protocol

46

4.3 Data Logging

48

4.4 The Relay Output Option

49

5. Calibration

50

5.1 Programming Chart

52

5.2 Definitions

59

6. Input Circuits

62

6.1 Frequency Flow Input

62

6.2 Analog Inputs

67

6.3 Remote Switches (Model 415A Only)

70

7. Installation

71

7.1 General

71

7.2 Wiring Designations for the Mode 415

73

Appendix

75

Properties of Selected Gases

75

Index

77

List of Symbols Used in this Manual

Symbol Description

SI Units

A Normalised signal from the flowmeter which will be 0 at 4mA and 1 at 20mA.

G Specific Gravity for Gas.

hB Specific Enthalpy at Reference Conditions.

kJ/kg

hF Specific Enthalpy at Flow Conditions.

KF K-factor (pulses/unit) for a frequency flowmeter.

kJ/kg pulses/m3

N Timebase Constant with which the flowrate is displayed and is: 1 for units/second 60 for units/minute 3600 for units/hour 86400 for units/day

B Density at base conditions. F Density at flow conditions.

PB Pressure at base conditions. PC Critical pressure of gas.

kg/m3 kg/m3 kPa (abs) kPa (abs)

US Units

kJ/kg kJ/kg pulses/ft3

lbs/ft3 lbs/ft3 psia psia

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