Emerson B-106-300NH instruction manual System Overview, Scope, System Description

Instruction Manual

IB-106-300NH Rev. 4.2 July 2002

World Class 3000

1-2 SYSTEM OVERVIEW

a.Scope

This Instruction Bulletin has been designed to supply details needed to install, startup, operate, and maintain the Rosemount World Class 3000 Oxygen Analyzer with IFT 3000 Intelligent Field Transmitter. The Intel- ligent Field Transmitter (IFT) can be inter- faced with one World Class 3000 probe. The IFT provides all necessary intelligence for controlling the probe and optional MPS 3000 Multiprobe Calibration Gas Se- quencer. Appendices at the back of this manual detail each component and option from the standpoint of troubleshooting, re- pair, and spare parts.

Operator/Technician interface to the IFT can be provided from the displays and key- pads on the front panel, and remotely through HART® communications protocol, utilizing the 4-20 mA out-put signal from the IFT interconnect board. HART Communi- cator IFT applications are detailed in Appendix J.

b.System Description

The Rosemount Oxygen Analyzer (Probe) is designed to measure the net concentration of oxygen in an industrial process; i.e., the oxygen remaining after all fuels have been oxidized. The probe is permanently posi- tioned within an exhaust duct or stack and performs its task without the use of a sam- pling system.

The equipment measures oxygen percent- age by reading the voltage developed across a heated electrochemical cell, which consists of a small yttria-stabilized, zirconia disc. Both sides of the disc are coated with porous metal electrodes. When operated at the proper temperature, the millivolt output voltage of the cell is given by the following Nernst equation:

EMF = KT log10(P1/P2) + C

Where:

1.P2 is the partial pressure of the oxygen in the measured gas on one side of the cell,

2.P1 is the partial pressure of the oxygen in the reference air on the other side,

3.T is the absolute temperature,

4.C is the cell constant,

5.K is an arithmetic constant.

NOTE

For best results, use clean, dry, in- strument air (20.95% oxygen) as a ref- erence air.

When the cell is at operating temperature and there are unequal oxygen concentra- tions across the cell, oxygen ions will travel from the high partial pressure of oxygen side to the low partial pressure side of the cell. The resulting logarithmic output voltage is approximately 50 mV per decade. Be- cause the magnitude of the output is pro- portional to the logarithm of the inverse of the sample of the oxygen partial pressure, the output signal increases as the oxygen concentration of the sample gas decreases. This characteristic enables the oxygen analyzer to provide exceptional sensitivity at low oxygen concentrations.

Oxygen analyzer equipment measures net oxygen concentration in the presence of all the products of combustion, including water vapor. Therefore, it may be considered an analysis on a "wet" basis. In comparison with older methods, such as the Orsat ap- paratus, which provides an analysis on a "dry" gas basis, the "wet" analysis will, in general, indicate a lower percentage of oxygen. The difference will be proportional to the water content of the sampled gas stream.

1-2 Description and Specifications Rosemount Analytical Inc. A Division of Emerson Process Management