ACCURRA-Zr Flue Gas Oxygen Analyser

Quick answer

ACCURRA-Zr measures percent oxygen in flue gas in situ with a zirconia sensor, calibrated on plain air, with built-in automatic blowback. Options cover high dust loads and process temperatures up to 1400 C, for boilers, furnaces and stacks.

Updated 2 November 2026 · Figures from Sarvesh datasheets

Why ACCURRA-Zr

A longer sensor life

Expected sensor life above 10 years on clean gas, above 5 years on low-sulphur natural gas and above 3 years on biomass or coal.

Calibration with air only

Single-point calibration uses air as the span gas, after an automatic blowback, so no special calibration gas is needed.

A clean probe and a steady reading

Programmable auto blowback with power-on and pre-calibration cycles; the output can hold its last value during blowback.

Specifications

Item	Specification	Notes
Measurement	0.1 to 21 % oxygen	Zirconia; no reference gas
Repeatability	Better than 1 % of FS
Response time	T90 below 15 s
Expected sensor life	Clean gas above 10 years; low-sulphur natural gas above 5 years; biomass or coal above 3 years
Calibration	Single point with air	Blowback runs before every calibration
Probe	300, 500 or 1000 mm; wetted parts SS316; 2 inch ANSI flange	Blowback connection 1/4 inch OD SS316
Process	Gas 200 to 500 C; dust up to 10 g/Nm3; velocity 5 to 20 m/s	Probes for up to 1400 C and high dust load are optional
Fuels	Oil, gas and natural gas without blowback; coal and bagasse with blowback
Electronics	Head mounted with display and keypad; backlit LCD 2 x 16	Cast aluminium head, 285 x 165 x 230 mm, IP 66
Outputs	Isolated 4-20 mA, dual range, max load 500 ohm; blowback relay; Modbus RTU over RS 485	Read value, status and set-up; write blowback
Power and ambient	100 to 240 V AC, 50/60 Hz, 45 W; ambient 10 to 50 C	Safe area

From the current Sarvesh product datasheets and company profile. Specifications may change without notice as products improve. The final responsibility to check that a product meets the process and analyser requirement remains with the customer.

Key features

Sensor located outside the stack or furnace, so it is protected from flow, dust and temperature variation; flue gas reaches it through a guide tube
Single-point calibration with air, so no special calibration gas
Built-in auto blowback with relay and solenoid valve, programmable from the keypad or Modbus; power-on, manual and pre-calibration blowback
Dual-range 4-20 mA: a fixed 0 to 25 % range for start-up and a second user-set range
Output freeze or follow during blowback and calibration
Sensor and hardware diagnostics with sensor protection
Rugged all-SS design; options for high dust load and up to 1400 C

How it works

A zirconia cell is a ceramic element that generates a voltage proportional to the difference in oxygen between the flue gas and a reference, usually air. In a conventional flue gas analyser the zirconia sensor, heater and thermocouple sit at the tip of the probe, exposed to furnace turbulence, temperature swings and abrasive dust, which causes reading errors and frequent sensor or heater failures.

ACCURRA-Zr places the sensor just outside the stack or furnace wall and draws the flue gas to it through a guide tube. The sensor stays at a constant temperature and away from the dust load, which gives a stable reading and a long sensor life. There is still no sample line to condense or block.

Oxygen in flue gas is the main measure of excess air. Controlling it down to the lowest safe level saves fuel. ACCURRA-Zr's air calibration and automatic blowback keep routine maintenance short in dusty ducts.

Requirements and limits

For extractive measurement of other flue components, use SGI-320.
Mount the probe horizontally. ACCURRA-Zr is not suitable where the flue gas flows from top to bottom.

On site: utilities and calibration gases

What to have ready at your plant before installation and commissioning.

Item	Requirement	Notes
Power at the tapping point	100 to 240 V AC, 50/60 Hz, 45 W
Blowback air	Instrument air, up to 4 kg/cm²	Blowback solenoid valve supplied
Calibration	Air, single point	No calibration gas cylinder needed
Mounting	Horizontal, on a 2 inch ANSI flange with gasket, nuts and bolts	Not suitable where the flue gas flows from top to bottom
Process	Gas up to 500 °C; dust up to 10 g/Nm³; velocity 5 to 20 m/s

Selection guidance

Choose ACCURRA-Zr for boilers, heaters, furnaces, HRSG and thermal oxidisers. For trace oxygen in process gas or protective atmospheres, choose ACCURRA-S, which uses an extractive sample.

Applications

Application pages where this is part of the recommended solution:

Compatible products

SGI-300 / SGI-320

Peltier sample cooler with integrated pump, filter and condensate detector; SGI-320 for emission monitoring.

View SGI-300 / SGI-320

i-Cons

Smart Peltier sample conditioner with diagnostics, auto blowback and Modbus, in a compact 19 inch cabinet.

View i-Cons

SP and SRP sample probes

Heated and non-heated probes with blowback, and retractable probes, in SS316, Inconel or ceramic.

View SP and SRP sample probes

ACCURRA-S

Online analyser for trace, percent and purity O2, CO, CO2, CH4 and dew point; can measure two gases from one sample.

View ACCURRA-S

Frequently asked questions

How is ACCURRA-Zr calibrated?

With plain air at a single point, after an automatic blowback.

What gas temperature can it take?

The standard probe suits 200 to 500 C; probes for up to 1400 C are optional.

How long does the sensor last?

Above 10 years on clean gas, above 5 years on low-sulphur natural gas and above 3 years on biomass or coal.

Does it handle dust?

It has built-in automatic blowback and an option for high dust load samples.

Can it measure CO?

No. Use an extractive system for CO.

ACCURRA-Zr zirconia oxygen analyser for flue gas