Model NGA 2000 HFID

Instruction Manual

760004-A February 2002

SECTION 1

DESCRIPTION AND SPECIFICATIONS

1-1 OVERVIEW

This manual describes the Heated Flame Ioni- zation Detector (HFID) Analyzer Module of Rosemount Analytical's NGA 2000 Series of gas analysis components. See Figure 1-1 and Figure 1-2.

The HFID Analyzer Module is designed to continuously determine the concentration of hydrocarbons in a flowing gaseous mixture at a user-selectable temperature setpoint between 93°C and 204°C (200°F and 400°F). The concentration is expressed in ppm or percent of volume.

The entire HFID Analyzer Module is designed as a stand-alone module, with gas connections made from the rear. All electronics relative to sample detection and conditioning are included in this module.

1-2 TYPICAL APPLICATIONS

The monitoring of atmospheric air for low-level hydrocarbon contaminants and determining the hydrocarbon content of exhaust emissions from internal combustion engines are examples of typical applications for the HFID Analyzer Mod- ule.

1-3 SAFETY GAS FEATURES

The HFID Analyzer Module is designed with a factory-installed continuous dilution purge system in accordance with standard ANSI/NFPA

496- 1993, Chapter 6. Front-panel LEDs indi- cate that the burner flame is lit and that the purge system is enabled. In addition, fuel gas is automatically shut off when a flame-out condi- tion occurs or the safety system is disabled.

The purge system is enabled only if there is proper purge gas flow in, purge gas pressure, and internal case pressure, and after five times the case volume has been exchanged.

All tubing ahead of the burner is rigid metallic tubing assembled with ferrule/nut type compression fittings. However, should an internal fuel leak occur, a worst-case leak would be dissipated below 25% of the LEL of hydrogen through the combination of an inlet fuel flow restrictor and purge gas flow.

This module is designed to use 40%

H2/60% He fuel at a maximum inlet pressure of 3446 hPa-gauge (50 psig).

A standard HFID Analyzer Module is only equipped to analyze a non-flammable sam- ple, below 100% of the LEL.

WARNING

POSSIBLE EXPLOSION HAZARD

Protection against explosion depends upon a special fuel flow restrictor in the fuel inlet fitting. Do not remove fuel inlet restrictor. Do not use 100% hydrogen fuel. Replace only with a factory supplied fitting.

1-4 THEORY OF TECHNOLOGY

This Analyzer Module uses the flame ioni- zation method of detection. The sensor is a burner in which a regulated flow of sample gas passes through a flame sustained by regulated flows of a fuel gas (a hydro- gen/diluent mixture) and air.

Within the flame, the hydrocarbon components of the sample stream undergo a complex ionization that produces electrons and positive ions. Polarized electrodes collect these ions, causing current to flow through an electronic measuring circuit.

The ionization current is proportional to the rate at which carbon atoms enter the burner, and is therefore a measure of the

Rosemount Analytical Inc. A Division of Emerson Process Management

Description and Specifications

1-1