Fuji Electric ZKM Zirconia Oxygen Analyzer Converter

A zirconia oxygen converter for combustion control in boilers and furnaces

The Fuji Electric ZKM is the signal converter of an in-situ zirconia oxygen analyzer. Paired with a ZFK8 probe (or the ZTA ejector probe), it measures oxygen in boiler and furnace flue gas continuously, without a gas sampling system, so the fuel-air ratio can be controlled and combustion efficiency improved. The microprocessor converter manages inputs and outputs, display, diagnostics of the sensor and a heater cut-off safety function, with RS-485 Modbus or HART communication as options.

Technical specifications

Configurations

The data sheet covers ZFK8 probes with flow guide tube for general-use or corrosive gas (insertion lengths 0.3, 0.5, 0.75 or 1 m, and a version for high particulate gas with blowdown nozzle) and the ZTA ejector system for high-temperature gas (insertion 0.5, 0.75, 1 or 1.5 m), each paired with a ZKMA or ZKMB converter. Fuji Electric France lists the converter with options for blowback, auto calibration and a digital link, and lists accessories such as the ZRZ cable and convection tube.

Selection notes

State the stack temperature and pressure, dust and corrosive content, insertion length, flange, voltage and whether Modbus, HART, automatic calibration or blowback is needed. The sensor diagnostic function shows depletion so replacement can be planned. Zirconia sensors need oxygen-bearing, non-combustible gas, so they are not for gas with unburnt combustibles at the sensor. Other analyzers are under gas analyzer systems.

How the Fuji Electric ZKM zirconia oxygen converter works

A zirconia sensor measures oxygen by comparing the gas under test with a reference gas, usually air, across a heated zirconia ceramic element. At high temperature the ceramic conducts oxygen ions, and the voltage between its two electrodes depends on the ratio of oxygen concentrations on both sides. The ZFK8 probe holds the element in a heater at the flue gas, so the measurement is made in situ with no sampling line. The ZKM converter powers the heater, reads the sensor signal, linearizes it and outputs the oxygen concentration as a 4 to 20 mA or 0 to 1 V signal, with relay contacts for alarms.

Because the probe responds in 4 to 7 seconds for 90 percent of a step change, the oxygen reading can be used for continuous control of the fuel-air ratio in a boiler or furnace.

Applications for the ZKM converter

• Oxygen trim control in industrial and utility boilers.
• Furnaces and kilns where combustion air has to be controlled for efficiency and emissions.
• Flue gas monitoring for combustion efficiency display.
• High-temperature gas duties with the ZTA ejector system.

Selection checklist for the ZKM converter

• Probe type: ZFK8 with a flow guide tube for general or corrosive gas, a version with a blowdown nozzle for high particulate gas, or the ZTA ejector system for high-temperature gas.
• Insertion length: 0.3, 0.5, 0.75 or 1 m for ZFK8 and 0.5, 0.75, 1 or 1.5 m for ZTA.
• Gas temperature: -10 to +600 degrees C with the flow guide tube, or up to +1500 degrees C with the ejector.
• Measured gas pressure within -3 to +3 kPa.
• Converter housing: ZKMA with IP66 or ZKMB with IP67, for panel or pipe mounting, with the cable length to the detector below 100 m.
• Power supply: 100 to 120 V AC or 200 to 240 V AC, at 50 or 60 Hz.
• Communication: RS-485 Modbus or HART as an option.
• Options: combustion efficiency display, declogging, automatic calibration, selection valve and flow meter.

Installation, commissioning and maintenance notes

The probe is mounted on a flange in the duct or stack at a position where the gas is representative, away from air leaks and dead zones. After switching on, the sensor takes 10 minutes or more to warm up before the reading is valid. Calibration with zero and span gases is part of commissioning and can be automated with the optional calibration kit. The converter monitors the sensor and cuts the heater power if the thermocouple burns out or an external emergency input is activated. Regular inspection of the sensor, filter and reference air supply keeps the response time and accuracy within specification, and a key lock prevents unauthorised changes to the settings.

Requesting a quotation for the Fuji Electric ZKM

Send the stack temperature and pressure, dust and corrosive content, insertion length, flange, supply voltage and communication or calibration options. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

Wiring and signal handling for the ZKM

The converter provides analog output for the control system and several contact outputs and inputs for alarms and calibration commands. Use shielded cable for the probe signal and keep it away from power cables. Check the supply voltage setting before switching on, and make sure the cable run between converter and detector stays within the stated limit so the heater and thermocouple signals remain reliable.

Documents and quotation

The attached data sheet EDSX3-151c (20 June 2018) covers the ZFK8 detector, the ZKMA/ZKMB converter and the ZTA ejector. Confirm the exact code and options before ordering.