Energy (Oil & Gas)

Oil and gas is the industry gas detection was invented for, which means most of what gets written about it is generic. This page covers the parts that are specific: the moments when exposure actually happens, where open path detection does not work, and which of four different regulators applies to your site.

Most of what follows comes from work our Technical Consultants have done on Australian facilities.

The Exposure Happens During Maintenance

Production runs sealed. The risk arrives when somebody opens it.

Pumpjacks are a good illustration because the hazard is so clearly tied to specific actions. Australia has relatively few compared with North America, but the Cooper-Eromanga Basin across South Australia and Queensland is the country’s most prolific onshore petroleum province, producing since the 1970s. Santos reporting puts it at around 190 gas fields and 115 oil fields in production, roughly 1,220 producing wells, and more than 3,000 wells drilled.

The exposure moments are opening and closing wellheads, tank hatches, surface valves and lines for repair, work on nearby flowlines, separators and tanks, and accidental release when a well is shut down or restarted.

Two of them are worth spelling out because they are fast rather than gradual.

Cracking open a valve can instantly release hydrogen sulphide rich gas that has accumulated in the line. Not a gradual rise, a release. A detector already alarming is no use if the person is standing at the flange when it happens.

The pressure drop when a valve is opened, even slowly, can flash off volatile organic compounds, and that is worse when the line is warm. Benzene, toluene and xylene all appear this way. Benzene is a known human carcinogen with no safe exposure level, and it is invisible on an LEL sensor at the concentrations that matter for health.

The rest of the gas set follows the process. Methane from associated natural gas, with both explosion and oxygen displacement risk, released from most crude reservoirs when surface lines are opened. Carbon dioxide, present in natural gas and crude streams. Oxygen displacement in low lying areas by heavier gases including hydrogen sulphide, carbon dioxide and heavier hydrocarbons. Carbon monoxide where combustion engines, flaring or heating equipment are nearby, though not from the crude itself. Nitrogen where it has been used to purge lines.

That combination is why maintenance crews carry five plus gas instruments rather than a standard four gas, with a photoionisation channel for the volatile organics. Where benzene specifically is the concern, a dedicated PID instrument resolves it at the parts per million level that health exposure requires.

Two practical notes from the field. Pumpjacks can exceed safe noise levels, so an audible alarm alone is not sufficient and vibrating or visual alarm is needed. And dust is constant, which affects both sensor life and calibration intervals.

Open Path Detection, And Where It Does Not Work

A point combustible detector has an effective coverage radius of around 5 metres. On a large processing facility that means a great many detectors, and still no certainty that a leak occurs within 5 metres of one.

Open path detection, also called line of sight, measures across a beam between a transmitter and receiver at distances up to 200 metres. A xenon flash infrared beam responds to most hydrocarbons from C1 through C8, including methane, ethylene and propane.

The limitation is one that gets missed, and it decides whether open path is the right answer at all.

Open path suits lighter than air combustible gases, because the beam can be mounted above obstructions and in the path of a rising gas cloud. Heavier than air gases such as propane are not well addressed, because catching them requires mounting the beam low, and low mounting is where the obstructions are. Specifying an open path system for an LPG facility on the basis that it worked at a natural gas plant is a design error.

Alignment tolerance is around plus or minus one degree, so mounting has to be rigid and secure. A beam across 100 metres on a structure that moves will drift out of alignment.

Common applications are large onshore gas processing including LNG plants, offshore facilities, gas fired power station turbine halls, gas transport and pipelines, storage tank protection, fence line monitoring, engine and turbine air intakes and modules, petrochemical production and storage, and LNG or LPG storage, pumping and filling stations.

The SafEye Quasar and the Searchline Excel cover this range, with the Searchline Excel reaching 330 metres in its longer configuration.

What LEL Metres Actually Mean

Open path readings are in LEL metres and this trips up people who are otherwise comfortable with gas detection.

An open path detector measures the total quantity of hydrocarbon in the beam, not the concentration at a point. The reading is the length of the gas cloud in the beam multiplied by its concentration in percent LEL.

So one LEL metre is one metre of gas at 100 percent LEL. It is also five metres of gas at 20 percent LEL. Both give the same reading, because both contain the same quantity of gas. Five LEL metres is five metres of gas at 100 percent LEL.

The consequence is that a small dense cloud and a large diffuse one read identically, and that is the point rather than a flaw. On a large facility what matters is whether gas is present in the monitored line. Where it is coming from is what point detectors near known leak sources are for. The two are complements, not alternatives.

Typical full scale is 5 LEL metres for methane and 8 for ethylene.

Fugitive Emissions And The Fence Line

A separate question from safety, and increasingly the one that generates the phone call: what is in the air leaving your site?

The drivers vary. Licence conditions and environmental legislation. An ESG commitment that has to be evidenced rather than asserted. Sensitive neighbours such as schools and residential areas. Or simply not knowing, which is an uncomfortable position when somebody complains.

Continuous boundary monitoring answers it differently from the traditional approach. Small monitoring pods such as AQMesh mount on fences, posts or walls with standalone power and communications, streaming data to a cloud platform. A single pod can measure up to six gases from nitrogen dioxide, sulphur dioxide, hydrogen sulphide, carbon monoxide, carbon dioxide, total VOCs, ozone and nitric oxide, along with particulate across PM1, PM2.5, PM4 and PM10, plus wind speed and direction, temperature, pressure and humidity.

Readings at 15 minute or even one minute intervals give a more complete picture than intermittent bag sampling, and arguably than open path monitoring, particularly once wind data is included. Exceedance alerts can be set to trigger a bag sample for detailed composition analysis, so the two approaches work together.

The capability worth understanding is directional. Combining pollutant measurements with wind speed and direction, and modelling where appropriate, allows a source to be identified by direction and approximate distance. That lets an operator distinguish pollution generated on their own site, which they can manage, from pollution arriving from a neighbouring plant or from regional background, which they cannot. In a dispute about who is responsible for what, that distinction is the whole argument.

Installation is genuinely quick. Solar power and mobile network communications mean no infrastructure, and a pod goes onto a post in minutes.

Flame Detection

Where a release can ignite rather than accumulate, gas detection is only half the system.

Flame detection covers process areas, tank farms, loading racks, turbine enclosures and compressor stations. Two selection points matter more here than elsewhere.

Detection range and field of view together decide detector count, and range alone is misleading because coverage is a volume rather than a line. And exhaust matters: where diesel or gas engines run in the protected area, a conventional infrared detector sees the same hot carbon dioxide it is tuned to find. The CO2L variants of the F-Guard IR3 exist for that, and truck loading racks are a named application.

Where hydrogen is present, whether as a process stream or increasingly as a product, a standard infrared flame detector will not see it at all, because hydrogen burns to water vapour rather than carbon dioxide. The F-Guard IR3-H2 is built for that case.

Confined Space And Offshore

Tanks, vessels, separators, pits and pipework are confined spaces, and entry brings its own requirements including pre-entry testing and continuous monitoring during occupancy. There is a specific problem with catalytic bead LEL sensors that everybody doing this work should understand, covered on our confined space page.

Offshore facilities, FPSOs, risers and platforms sit under a different regulator and different certification expectations, including classification society approvals on top of ATEX and IECEx. That is covered on our marine and maritime page.

Who Regulates What

Four regimes, and which applies depends on where the facility is and what it does.

Offshore in Commonwealth waters. NOPSEMA is the regulator for health and safety, well integrity and environmental management of offshore energy operations, under Schedule 3 to the Offshore Petroleum and Greenhouse Gas Storage Act 2006 and the associated Safety Regulations.

Western Australia. The Work Health and Safety Act 2020 is supported by three separate sets of regulations, and petroleum has its own. The Work Health and Safety (Petroleum and Geothermal Energy Operations) Regulations 2022 apply to onshore and offshore petroleum, pipeline and geothermal energy operations, distinct from both the General Regulations and the Mines Regulations. The regulator is WorkSafe WA, which covers general industry, mining and petroleum.

New South Wales. Petroleum sites are regulated alongside mines rather than under general WHS law, under the Work Health and Safety (Mines and Petroleum Sites) Act 2013. The regulator is the NSW Resources Regulator.

Queensland. Petroleum and gas has its own legislation entirely, the Petroleum and Gas (Production and Safety) Act 2004 with safety in Chapter 9, supported by the Petroleum and Gas (Safety) Regulation 2018. The regulator is Resources Safety & Health Queensland.

The Queensland regulation contains a mechanism worth knowing about. It prescribes standards as either mandatory, which you must comply with, or preferred, which you need not comply with provided you hold written evidence that your alternative delivers risk equal to or lower than the preferred standard, and you notify the Chief Inspector. For gas detection that means an alternative approach is available, but only with the documentation to support it.

Separately, major hazard facilities and dangerous goods storage sit under their own framework. In Western Australia that is the Dangerous Goods Safety Act 2004 rather than the WHS Act, which catches a lot of tank farms and terminals.

What Gastech Supplies

Fixed gas detection for wellheads, separators, processing trains, compressor stations, tank farms and loading facilities, including benzene and VOC specific monitoring where health exposure rather than flammability is the concern.

Open path detection for large volume coverage, fence lines and areas where point detection would need impractical numbers.

Flame detection including hot exhaust immune and hydrogen capable variants.

Portable multi-gas and PID instruments for maintenance work, confined space entry and survey, plus area monitors for work fronts and shutdowns.

Controllers with the relay capacity to drive deluge, shutdown and alarm rather than only reporting a value.

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

If you are laying out detection for a facility, or working out whether open path suits your gas, talk to our Technical Consultants.