Chemical Manufacturing

In most industries the gas list is predictable. In chemical manufacturing it is whatever your process handles, which means the detection question is never generic and the wrong sensor is a real possibility rather than a theoretical one.

Three applications below are worth reading even if they are not yours, because each demonstrates a principle that applies more widely. Most of what follows comes from work our Technical Consultants have done on Australian sites.

Sulphur Storage, And Why You Cannot Use A Flame Detector

This is the clearest example of a hazard where the obvious detection method is the wrong one.

Sulphur storage divides into two categories by temperature. Solid sulphur sits below 119 degrees Celsius and is generally held in covered warehouse facilities at transport hubs and shipping ports. Molten sulphur sits above 154 degrees and is held in heated tanks and vats within processing plants.

The inherent risk with solid sulphur is fire, and here is the problem. When sulphur combusts it produces very low to no infrared radiation. The flame is blue and barely visible to the human eye. That means most standard infrared flame detectors will not see it, and neither will the person standing in the warehouse.

So the answer is not optical detection at all. Sulphur combustion produces relatively large volumes of sulphur dioxide, which makes SO2 gas detection the preferred method for safety monitoring in solid sulphur storage. You detect the fire by detecting the gas it produces rather than by looking for the flame.

Two further requirements follow from the material itself.

Solid sulphur creates extremely dusty environments, and a hazardous area classification of Zone 21 or 22 will very often apply. That requires detectors carrying dust ingress protection certification, Ex tb, which is a different certification from the gas certification most people check. Extreme dust levels may also mean dust covers or air shields on the detectors.

Molten sulphur behaves differently. It also produces sulphur dioxide, but it emits high levels of hydrogen sulphide as well, so a molten facility needs both. Dust is generally not an issue in a molten plant, though the plant’s own hazardous area classification still applies.

One placement note that gets missed. Sulphur dioxide is heavier than air, so detectors have to be mounted low. Typical ranges are 0 to 20 ppm for sulphur dioxide across both facility types and 0 to 100 ppm for hydrogen sulphide in molten storage. AS/NZS 60079.29.2 covers detector selection and installation, and NFPA 655 is the reference standard for sulphur handling.

Methanol, And The Twenty Times Problem

Methanol has a sweet alcohol odour, which sounds reassuring and is not.

That single fact is the argument for instrumented detection rather than relying on people noticing. Exposure occurs through inhalation, skin absorption, eye contact and ingestion, so anywhere methanol is used, stored, loaded or unloaded warrants monitoring, and a well designed system alarms well before either the toxic threshold or the lower flammable limit is reached.

Methanol needs both measurements, and they are not the same instrument. A photoionisation detector measures at the parts per million level that health exposure requires. A catalytic LEL sensor covers the flammability risk on a percent LEL scale. An LEL sensor reading zero tells you nothing useful about a 500 ppm exposure.

Placement is more subtle than the datasheet suggests. Methanol vapour has a relative density of around 1.1, so slightly heavier than air, which argues for low mounting. But if it is warm it will rise, and if it is cold it will accumulate in low areas. Detector position needs to account for the actual temperature conditions on the site rather than the density figure alone.

Ozone, And Detecting At Very Low Levels

Ozone is a powerful oxidising agent and it is gaining ground as a cleaning and disinfection method, being effective against bacteria, fungi and moulds and able to inactivate viruses. It is also used to disinfect personal protective equipment for re-use.

The concern is that ozone generators are increasingly sold as air cleaners, which is a different proposition from an industrial oxidising agent and can be dangerous in the wrong hands.

The concentration an ozone generator actually produces depends on more variables than users expect. A more powerful device produces more, as does running several. A small space concentrates it more than a large one. Closed interior doors raise it. And a room with fewer materials and furnishings to absorb or react with the ozone will hold a higher concentration than a furnished one.

That variability is why measurement matters rather than calculation. The detection challenge is the level: ozone requires monitoring at very low concentrations, with typical portable ranges around 1 ppm and fixed detection around 2 ppm full scale. Sensors at that sensitivity need appropriate handling and calibration, and the D-Guard² covers the fixed installation.

Whatever Your Process Actually Handles

The three applications above are examples rather than a list. Chemical manufacturing covers a range of gases wider than any single detector platform, and the specification question is which sensor for which gas rather than which brand.

The S-Guard electrochemical variant covers more than 50 target gases, including specialty and semiconductor materials such as arsine, diborane, disilane, germane, boron trifluoride, boron trichloride, chlorine trifluoride and fluorine, alongside the common toxics. Where volatile organic compounds are the concern rather than a specific named gas, the Falco 2 provides fixed photoionisation detection across hundreds of compounds.

For large process areas, open path detection covers volumes that would need impractical numbers of point detectors, with the caveat that it suits lighter than air gases because the beam mounts above obstructions. Heavier than air gases need the beam low, and low is where the obstructions are.

Flame detection covers process areas, tank storage and loading, and the technology choice depends on the fuel and on what else is in the field of view. Where the plant contains running engines or exhaust, a conventional infrared detector will see the same hot carbon dioxide it is tuned to find.

Controllers matter more here than in simpler installations, because a chemical plant typically needs detection driving automatic action rather than only reporting. The 4100R runs one processor per channel, so a processor failure costs a single channel rather than the panel.

Confined Space Entry

Reactors, vessels, tanks, sumps and pipework are confined spaces, and chemical plant adds a complication: residue from a previous product can produce an atmosphere that has nothing to do with what the vessel currently holds.

Pre-entry testing and continuous monitoring during occupancy both apply. There is also a specific problem with catalytic bead LEL sensors that anybody doing this work should understand, covered on our confined space page.

Who Regulates It

Chemical manufacturing falls under general work health and safety law, so the regulator is WorkSafe WA, SafeWork NSW or Workplace Health and Safety Queensland depending on location. Safe Work Australia publishes the model laws and the code of practice for managing risks of hazardous chemicals, but does not regulate or inspect.

Two additional frameworks catch chemical sites specifically.

Major hazard facilities are regulated separately from ordinary workplaces. A facility holding more than threshold quantities of scheduled chemicals requires licensing and a safety case, which brings its own expectations about detection and about demonstrating that controls work. In Western Australia major hazard facilities and dangerous goods storage sit under the Dangerous Goods Safety Act 2004 rather than the Work Health and Safety Act, which is a distinction worth knowing before assuming which regulator applies.

Dangerous goods storage and handling is also regulated in its own right in each state, with transport covered by the Australian Dangerous Goods Code.

Standards relevant to detection include AS/NZS 60079.29.2 for gas detector selection, installation, use and maintenance, AS 2865:2009 for confined spaces, AS 1670.1 for fire detection systems, and NFPA 655 where sulphur is handled.

What Gastech Supplies

Fixed gas detection across a wide gas range including specialty and semiconductor materials, with electrochemical, catalytic, infrared and photoionisation sensing, and dust rated certification where the area requires it.

Open path detection for large process areas and fence lines.

Flame detection for process, storage and loading areas, with exhaust immune variants where engines run nearby.

Portable multi-gas, single gas and PID instruments for maintenance, confined space entry and exposure monitoring.

Controllers with the relay capacity to drive shutdown, isolation, ventilation and alarm.

Behind them sit project engineering, NATA calibration and service, field service, fleet management and hire for turnarounds, from WA, NSW and QLD.

If your process handles something unusual, or you are not certain the sensor you have will see it, talk to our Technical Consultants.