B-Guard

A Detector You Don’t Have to Calibrate

Most of what a fixed gas detector costs isn’t the purchase price. It’s the technician standing in front of it twice a year with a bottle of gas, for the next ten years.

The B-Guard Millennium changes that. Gastech’s documentation states that routine calibrations aren’t required. The optical bench is self compensating, so the sensing and reference elements correct for optical integrity and other signal inhibitors without intervention.

Across a site with twenty detection points, removing the routine calibration visit saves more than anything the purchase price will.

Calibration is still available when you want to prove the instrument, using a smart calibration routine rather than a manual zero and span. We can manage it under a service agreement if your procedures call for periodic verification.

Atmospheres That Defeat Other Detectors

Three conditions defeat conventional combustible gas detection, and the Millennium handles all three.

Poisoning. Catalytic bead sensors lose sensitivity when exposed to silicones, sulphur compounds or lead. The failure is silent, which is the dangerous part. Infrared sensing has nothing to poison, and the Millennium is immune to poisoning and etching.

No oxygen. A catalytic bead works by burning gas on a heated element, so it needs oxygen. Inside a nitrogen blanketed vessel, an inerted tank or a purged enclosure, it can’t work. The Millennium operates in anaerobic atmospheres.

Constant background gas. Where a low level of hydrocarbon is always present, a catalytic detector drifts and eventually reads nothing useful. The Millennium operates in a constant hydrocarbon background and still picks up a change.

Add a heated optical chamber to keep condensation off the optics, and no moving parts to wear, and you have a detector built for the places that wear out instruments.

Where the Catalytic Variant Still Wins

Infrared isn’t automatically the better choice. There are two clear cases where the Catalytic variant is the right call.

Parts per million detection. Infrared works well at percent LEL, but can’t resolve ppm levels. The Catalytic variant uses set gain control for extra low sensitivity, so it reads combustible gas at ppm as well as LEL. If your requirement is a trace level, infrared won’t do it.

Zone certification. The Catalytic variant is certified to the Zone system, with the enclosure marked Ex db or eb T6 to T3 IIC Gb and the sensor Ex db IIC Gb. That’s the system Australian hazardous area installations are assessed against. See the certification section below.

It’s also a very stable instrument. The amplifier can be set as a 4-20 mA source or sink by moving two jumpers. Head voltage runs from 1.4 to 14 VDC, to suit both low and high voltage sensors. Advanced calibration minimises interference between the zero and span adjustments, making calibration quicker and more accurate. Accuracy is ±2% of full scale, and repeatability is better than 1% of applied gas.

Certification Differs Across the Range

This is the most important thing to understand before specifying a B-Guard.

Australian hazardous area installations are assessed under the Zone system, using IECEx or ANZEx certification. The North American Division system is a different framework, and a CSA or FM Division 1 approval isn’t automatically accepted here.

A certificate of compliance is held for the Millennium variants, and our engineering team can confirm what it covers for your installation. If you’re specifying against an Australian hazardous area classification, raise it at quote stage, not at commissioning.

The Variants

The Millennium hydrocarbon detectors are designed as a direct alternative in the same applications where catalytic bead sensors have traditionally been used.

Networking Multiple Points

The Millennium variants have a sourced 4-20 mA output, and can be coupled with an SEC 2000 transmitter for network applications. An RS-485 communication link is available, along with an optional digital display.

That gives three build levels: a single detector reporting 4-20 mA to an existing panel, a detector with a local digital display for a walk up reading, or a networked installation over RS-485, reporting multiple points back to a control system.

Temperature and Environment

The Millennium variants run from -40°C to +70°C at 0 to 99% humidity, non condensing. The housing is copper free, non corrosive, nickel plated aluminium and stainless steel, with a full stainless steel option, and is rated IP66. Mounting is 3/4 inch NPT and the unit weighs about 0.9 kg, so it goes up without a bracket fabrication exercise.

The Catalytic variant runs from -20°C to +60°C at 10 to 95% humidity, non condensing, and is rated IP66 and IP67. The powder coated case resists RFI and EMI, construction is tamper proof, and the electronics have a quoted MTBF of 10 years.

Where It’s Used

Refineries and petrochemical plant, gas turbines and compressor stations, drilling and production platforms, chemical plant, fuel loading facilities and terminals, oil well logging, wastewater treatment and digesters, LNG and LPG processing and storage, landfill gas systems, transport depots and fuel handling, and nitrogen blanketed and inerted vessels.

For carbon dioxide: gas storage, injection oil recovery, breweries and wineries, bottling plants, food processing and packaging, greenhouses, laboratories, environmental chambers, HVAC demand controlled ventilation and engine test cells.