Avoiding disasters

Middle East industrial gas detection sales are expected to exceed US$20 million each year, so Petrochemicals Middle East investigates how vendors aim to win your plant manager's approval.

Gas is ever-present in the petrochemicals industry, but a gas leak can prove disastrous to staff and plants alike. Lurking around faulty valves or cracked pipes is the combustible feedstock the industry cannot operate without, so early and reliable detection is a top priority for every plant HSE manager.

Petrochemical plants usually have ethane as the key feedstock, although in some cases it is a mixed feedstock of butane, propane or methane, or liquid naptha.

"Many industrial gases and chemical compounds are invisible to the naked eye.

Yet companies transport, measure and transform these ingredients every day. They use a range of instruments to monitor these assets from the loading dock, throughout the refinery and chemical processing plant and back to the storage tanks, pipes and railcars," says Johan Tegstam, product manager at Sweden's FLIR Systems.

Having gas running through the plant means that the whole facility is designated a hazardous area, and any leakage of gas could in theory cause an explosion. Gas detection has therefore been a vital and growing part of a plant manager's arsenal against disaster.

"There are many hazardous gases to be found in petrochemical plants, including hydrogen sulphide, carbon monoxide, chlorine, sulphur dioxide, ammonia, nitric oxide, nitrogen dioxide, hydrogen cyanide and hydrogen chloride," says John Warburton, a strategic marketing manager at City Technology.

"There are many flammable gases and vapours, but another major life-threatening hazard is reduced oxygen concentrations, particularly in confined spaces which includes tanks and vessels," he adds.

Gas detectors therefore aim to detect flammable gases, toxic gases as well as a lack of oxygen.

Fixed or mobile?

Gas detector instruments are either portable, designed to be worn or carried by individuals to give personal life safety protection, typically against a range of  industrial gases, or are fixed installation, which give protection against known specific hazards to personnel and cover a specific area of the plant or industrial facility.

"As they are life safety critical detectors, both types of instrument have to be independently certified to meet international safety and performance standards, must be  easy to use, robust, reliable and, for portable instruments in particular they must be ergonomically designed and lightweight so that they are easy and unobtrusive to wear," explains Warburton.

Many companies are introducing infrared cameras. "Using infrared imaging to spot leaks, damaged pipes, breached seals or valves and other emissions makes both business sense and common sense. The results are powerful, immediate and yield bottom-line results," says Tegstam.

"Infrared imaging now allows workers to ‘see' volatile organic compounds that are invisible to the human eye," Warburton adds.

The detection technology is designed specifically to deal with the severe threat presented by the presence of these gases. "For the last 30 years or so, in portable equipment, electrochemical sensors have been used for the detection of oxygen and toxic gases, with pellistor (catalytic bead sensors) used for the detection of flammable gases. Infra-red sensors are increasingly popular as an alternative to pellistors for detecting hydrocarbons, but they do suffer some limitations. In particular, they measure the concentration of a hydrocarbon rather than measure the flammability," says Warburton.

Finding the thresholds

Thresholds, also called occupational exposure limit (OEL) values, are set by the relevant Health and Safety Executive that either has jurisdiction in the particular country or area or is often defined in international standards. "Generally the thresholds are set by approved legislation bodies for different gases in different locations such as OSHA," explains Alaa Ayoub, regional manager at RAE Systems. "These thresholds are determined according to the nature of the hazards."

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