D-Guard²

Two Wire Loop Power Changes the Install Cost

Most fixed gas detection needs three or four wires, with power going one way and signal the other. The D-Guard² runs power and signal on the same two wire 4-20 mA loop. That includes NDIR methane and carbon dioxide, which usually draw too much current for loop power.

That has three practical effects. More detectors run from one power supply, cable diameter comes down, and barrier arrangements get simpler. On a small install the saving is modest. Across a plant with dozens of detection points, it changes the install budget and the running cost.

Certified for Underground Coal and Surface Plant

This is the specification that sets the D-Guard² apart in the Australian market.

It’s certified IECEx Ex ia I Ma for Group I mining, and Ex ia IIC T4 Ga for Group II surface industry. The LEL, methane and CO2 versions are certified Ex ia IIB T4 Ga. It also holds ATEX Ex I M1 and II 1G certification, and an ANZEx certificate.

A business running an underground operation and a surface plant often holds two different detectors, two sets of spares and two calibration procedures. The D-Guard² can cover both.

18 Gases, One Board

The D-Guard² uses a single electronics board across toxic gases, oxygen, flammable gases and carbon dioxide. Sensors are 4 series plug in units, and configuration is done through the interface.

For a maintenance team, that means one detector type to learn and one spares line to hold. It’s the same whether the point is monitoring hydrogen sulphide at a wastewater plant, methane underground, phosphine in fumigation or ethylene oxide in a sterilisation area.

NDIR is used for methane and carbon dioxide, giving long sensor life with no poisoning risk.

Calibrate It Without Opening It

Setup and calibration are done with a magnetic stylus against the closed housing, so nothing is unscrewed or exposed. On screen prompts guide the technician through calibration and configuration, which reduces the chance of a mistake by someone who calibrates a detector twice a year rather than twice a day.

A detector isolate feature lets a point be taken out of service for maintenance without triggering a system alarm.

It Tells You When It’s Not Working

A gas detector that has silently failed is worse than no detector, because the plant believes it’s protected.

The D-Guard² runs a sensor self test on a timer, or on demand over HART, and monitors its operating conditions continuously. Response time testing is built in too. It gives a real measurement of dynamic performance, rather than assuming a detector that responded last year still responds today. As standards begin to require this kind of testing, the D-Guard² is already equipped for it.

HART Gives You More Than a Number

A 4-20 mA loop carries one value. Optional HART 7.0 over the same two wires carries much more: real time gas readings, diagnostic information and remote sensor testing. Current loop rescaling and test mode can also be triggered remotely.

For a remote installation, that’s the difference between sending someone out to check a detector and checking it from the control room. HART is optional, so a straightforward install can do without it.

A Display You Can Actually Read

The display is a 400 x 240 pixel graphical backlit LCD, chosen for ultra low power draw so it works within the loop power budget. It’s readable from low light spaces right through to direct sunlight. Clear text and graphics make the reading and detector status obvious at a glance.

Built for Rough Conditions

The housing is a highly impact resistant, non conductive acetal plastic. It’s anti static, UV stable and chemically resistant, which suits intrinsically safe applications. It’s rated IP66 and IP68, tested to 1.2 metres for 1.5 hours.

Sensor temperature compensation, available on selected models, corrects both the zero point and the gas response as the temperature changes. The detector stays steady in clean air and accurate when gas is present. Drift is less than 3% signal loss over 12 months.

The certified operating range is -20°C to +70°C for Group IIC, and -20°C to +55°C for the NDIR versions and all other variants.

Certified or General Purpose

Two versions are available. The IECEx certified D-Guard² is for hazardous areas. The D-Guard²G is a general purpose version for safe area installations, at lower cost, with the same function and interface. The D-Guard²G also offers hydrogen tolerant CO sensors.

Our engineering team can confirm which version your installation calls for.

Where It’s Used

Underground coal mining, mineral processing and surface plant, wastewater treatment and pump stations, landfill gas monitoring, chemical manufacturing and storage, oil and gas processing, fumigation and grain handling, sterilisation areas in healthcare, semiconductor and electronics manufacturing, carparks and plant rooms, breweries and beverage production, and power generation.