S-Guard

Three Variants, One Platform

Sharing a platform means one housing style, one configuration method and one calibration procedure across a site running all three. For a maintenance team, that’s the difference between learning one detector and learning three.

Catalytic or Infrared for Hydrocarbons

This is the decision that matters most when specifying flammable gas detection, and the answer depends on the atmosphere rather than the budget.

Catalytic sensing, in the S-Guard Ex, burns the gas on a heated bead and measures the temperature change. It responds to a wide range of hydrocarbons, it’s proven over decades, and it costs less. It needs oxygen to work, and it can be poisoned by silicones, sulphur compounds and lead. Long exposure to high concentrations can also damage the bead.

Infrared sensing, in the S-Guard Ir, measures how much infrared light the gas absorbs. Nothing is consumed and nothing burns. It works in oxygen free and inert atmospheres, it can’t be poisoned, and high concentrations don’t harm it. In exchange, it’s gas specific rather than broad, and it can’t detect hydrogen at all.

The practical rule: choose infrared for nitrogen blanketed vessels, inert atmospheres, or anywhere silicones and sulphur compounds are present. Choose catalytic where the atmosphere is normal air and the target gas mix is broad. For hydrogen, the Ex variant’s thermal conductivity option, or the Tx variant’s hydrogen sensor (0 to 2,000 ppm), are the routes to look at.

Our engineering team can work through the choice against your actual gas mix.

The Toxic Variant Reaches Gases Most Detectors Can’t

The S-Guard Tx covers the usual industrial toxics: hydrogen sulphide, carbon monoxide, chlorine, ammonia, sulphur dioxide, nitrogen dioxide and oxygen deficiency.

It also covers specialty gases that very few fixed detectors handle, including arsine, diborane, silane, disilane, germane, dichlorosilane, phosphine, boron trifluoride, boron trichloride, chlorine trifluoride, fluorine and bromine.

That list is the semiconductor and electronics industry’s hazard register: dopant gases, etchants and cleaning agents, many of them acutely toxic at fractions of a part per million. For a fab, a solar plant or a specialty gas facility, having those gases on the same detector platform as general plant monitoring is a real simplification. The full list is in the Measuring Range download.

Certified for Hazardous Areas and Marine Use

All three variants use an Ex d flameproof enclosure, certified to ATEX and IECEx at Ex d IIC T6.

The Tx variant also carries ABS type approval and MED approval, for shipboard and offshore installations where classification society approval isn’t optional.

For Australian projects, confirm the certification against your area classification before ordering. Our engineering team can review it with you.

Configure It Without Opening It

Setup, calibration, maintenance and alarm settings are done with a magnet bar against the closed housing, and read on the built in backlit display.

That makes it a one person job, with no need to open the enclosure. Auto calibration handles the routine, and a self diagnosis function with a built in microprocessor reports internal faults rather than failing quietly.

Integration

All three variants output 4-20 mA DC. The Tx adds optional Modbus RTU (RS485) and HART, and the Ir adds optional RS485 Modbus. The Ir also has three relays (two alarm, one trouble) and four status LEDs, for local control without a separate panel.

Power and signal run over a 3 wire cable of 1.5 mm2 or larger, up to 500 metres. That means a remote detection point can be served from a central supply, rather than needing power brought to it.

The series is designed to fit into existing systems, including installations built around other manufacturers’ detectors, so a staged replacement doesn’t mean replacing the control layer at the same time.

Where It’s Used

Refineries and petrochemical plant, gas turbines, LNG and LPG storage and handling, offshore platforms and vessels, semiconductor and solar manufacturing, specialty gas facilities, chemical manufacturing and storage, mining and mineral processing, wastewater treatment and digesters, landfill gas systems, power generation, and sterilisation facilities.