D-Guard²R

Automatic Response Without a Siren

Not all gas detection should make a noise.

In an unmanned plant room, a siren alarms nobody. In a carpark, the right response is to start the fans, not startle the public. On a dosing skid, the right response is to close a valve. In a building with an existing fire and alarm system, a second independent siren creates confusion rather than safety.

Those installations need a detector that acts. The D-Guard²R has three relays built in, so it can start extraction, trip a solenoid, drive a remote beacon or signal a building management system on its own. There’s no controller, and no extra relay board wired in alongside it.

Where a local audible warning is what you want, the D-Guard²S adds a sounder strobe to the same relay board.

What the Relays Do

The low and high alarm relays are changeover contacts, which gives you two stages to work with. Start extraction on low and shut the supply off on high, or signal a BMS on low and trip a plant interlock on high. Both alarm relays can be set as energised or de-energised, to suit your control logic.

The fault relay is normally energised, and that detail matters. Because it’s energised in normal operation, a power loss, cut wire or dead board drops the relay and reports a fault. A normally open fault relay would stay silent in exactly the situation you most need to hear about.

Full Ingress Protection

This is the specification that separates the D-Guard²R from the D-Guard²S, and it decides which one suits the location.

The D-Guard²R is rated IP66, IP67 and IP68, with an IP68 rated M20 nylon cable gland supplied as standard. The D-Guard²S, with its sounder opening, drops to IP65.

In practice, the D-Guard²R can go outdoors, into washdown areas, into pits and wet wells that occasionally flood, and into coastal and tropical installations.

The housing is a highly impact resistant, non conductive acetal plastic that’s anti static, UV stable and chemically resistant.

Methane and Flammable Gas

The D-Guard²R supports NDIR methane detection, in 0 to 5% volume and 0 to 100% LEL ranges, plus propane at 0 to 100% LEL.

NDIR sensing gives long sensor life, with no risk of poisoning from silicones or sulphur compounds, which is the usual failure mode for catalytic sensors on landfill and wastewater sites.

Combined with the relays, that makes it a straightforward choice for landfill gas extraction control, digester plant and pump stations, where methane and hydrogen sulphide both need watching.

HART, With an Optional Side Port

Optional HART 7.0 runs alongside the 4-20 mA output. It carries real time readings, diagnostics, remote sensor testing and current loop rescaling.

The D-Guard²R can also be fitted with an optional HART port on the side of the unit. That gives a technician HART access without opening the enclosure, which is quicker and keeps the ingress rating intact while working.

18 Gases, One Board

A single electronics board covers toxic gases, oxygen, flammable gases and carbon dioxide, with 4 series plug in sensors and configuration through the interface. Hydrogen tolerant CO sensors are also available.

For a maintenance team, that means one detector type to learn and one spares line to hold, whether the point is hydrogen sulphide at a wet well, methane at a landfill, chlorine at a dosing plant or carbon dioxide in a plant room.

Calibrate It Without Opening It

Calibration and configuration use a service tool with a built in magnetic stylus, used against the closed housing. Nothing is unscrewed or exposed.

On screen prompts guide the process, which reduces mistakes by someone who calibrates a detector twice a year rather than twice a day. A detector isolate feature takes a point out of service for maintenance. Drift is less than 3% signal loss per year, which keeps calibration intervals long and predictable.

It Tells You When It Has Failed

A detector that has quietly failed is worse than no detector, because the site believes it’s protected.

A sensor self test runs on a timer, or on demand over HART, and operating conditions are monitored continuously. Response time testing is built in, giving a real measurement of dynamic performance rather than an assumption. As standards begin to require this kind of testing, the detector is already equipped for it.

Important: Not a Hazardous Area Detector

The D-Guard²R is a general purpose detector and carries no Ex certification. Gastech’s documentation states that it must not be used in applications that need certified equipment.

Classified hazardous areas need the D-Guard², which carries IECEx, ATEX and ANZEx certification across Group I and Group II. The certified D-Guard² doesn’t have relays, so a certified installation that needs relay outputs uses a controller.

If you’re not sure how your area is classified, our engineering team can work through it with you. Getting this wrong is a safety issue, not a paperwork one.

Choosing Across the Range

Where It’s Used

Landfill gas extraction and monitoring, wastewater pump stations and wet wells, digester and biogas plant, carpark ventilation control, outdoor and rooftop plant, washdown areas in food processing, chemical dosing skids with automatic shut off, unmanned plant and boiler rooms, coastal and tropical installations, buildings with an existing central alarm system, and mineral processing and surface plant in non classified areas.