Being aware of the exact nature of the threat posed by gases in the process plant can go a long way towards keeping staff safe, writes Greg Pitcher.
One line stands out from a complex chart produced by industrial equipment supplier Rockall Safety detailing gas presence in different sectors.
The diagram as a whole resembles a chess board – black squares representing the risk of a certain hazardous substance in a particular sector; white squares a safe absence.
But the column denoting ‘combustible gases’ is different. This is entirely black, filled in to show the live risk in each of the 21 industries included. The message is clear: from food and drink production to water treatment, the threat of explosion is real.
Ryan Jenkins, digital marketing executive at the safety equipment specialist, points out that a wide spectrum of dangerous gases are present across different process plants. This includes, but is by no means limited to, nitric oxide in the chemicals field and hydrogen sulphide in oil and gas production.
The right equipment can give users a generous window to exit the premises as soon as possible, which could mean the difference between life and death
Ryan Jenkins, digital marketing executive, Rockall Safety
“Making sure that workers are immediately alerted to the presence of toxic gases in the environment will minimise health and safety risks,” says Jenkins.
“The right equipment can give users a generous window to exit the premises as soon as possible, which could mean the difference between life and death.”
Rockall supplies a range of portable gas detectors for use by individuals working across different process sectors. Ensuring they are well maintained and effectively calibrated to specific requirements is a key challenge.
“If the correct detection parameters aren’t set, this could impact on the device’s ability to alert the wearer effectively and also the success rate of an operation,” says Jenkins. “Also it’s paramount that the user has been properly trained to both follow best practices and ensure the data is read correctly.”
Technology, as ever, is helping. “Well-known manufacturers continue to release new product ranges to improve the user experience. This includes wider product configurations to tailor gas detectors to more diverse applications and streamlining product design to reduce necessary training time.”
Each site has its own unique issues. How is the gas stored, how is it distributed, where is it used and what are its by-products? You must choose the right sensor for the application
Hal Collier, lead marketer, International Gas Detectors
The Crowcon Gas-Pro PID gas detector works on two wavelengths with infrared technology and measures to prevent the device itself being poisoned.
The company also provides fixed sensors with features such as built-in alerts when calibration or sensor tests are due.
A Crowcon spokeswoman said process plant managers needed to be aware of a range of potential gas hazards including carbon monoxide produced by motors or boilers and mains gases used as fuel.
Even a seemingly benign process sector can be full of risk. “Confined spaces are a recognised hazard in the food and drinks industry,” says the spokeswoman. “Reactions that generate harmful gases and deplete oxygen may be occurring naturally in fruit and vegetables or may be deliberately encouraged, such as in brewing and wine making. Oxygen may be deliberately removed to prevent spoilage, creating a potentially harmful environment.”
Explosion is often the final threat from gases rather than the first. “Ammonia is both toxic and explosive, but at different levels. An environment will be highly toxic long before there is a danger of explosion. Detectors for both toxic and flammable levels are required.”
Other challenges can include location of sensors. Some gases rise, while others sink, and in some cases this can vary by temperature. You really need to understand what you’re looking for in order to find it.
Witt UK, a German company with a UK office in Warrington, supplies ambient air monitors to measure concentrations of carbon dioxide. The firm says this colourless, odourless but ultra-dangerous gas is often found and used in the food and drink industry, as well as chemical processing.
“Even small amounts of carbon dioxide can have an influence on the human organism; a concentration of 0.3% in ambient air can be harmful to health – and 8% or more can lead to unconsciousness or even death,” says head of marketing Alexander Kampschulte.
Class monitors
The firm’s devices see a compact gas detector placed within a hazard area and a signalling unit located outside. An audible and visual alarm is sounded if dangerous levels occur, and other systems can be controlled, allowing extraction units to be started or machinery to be stopped.
Similar monitors for other gases such as hydrogen, methane or carbon monoxide are also available and work in the same way. “Wherever gases are used inside, it’s useful to work with ambient air monitors.”
Safety device manufacturer International Gas Detectors recently upgraded a gas detection system monitoring the continuous coating process at a plastic film producer.
“Here they are detecting for a variety of potentially explosive solvent gases, which are by-products of the process,” says lead marketer Hal Collier.
“The gases found at an adhesive factory are different from the oil and gas industry. It’s all site-dependent; the activities being undertaken decide what gases are potentially present.”
As well as the clear and present safety imperatives, there are legal reasons to monitor gases. Both the Control of Substances Hazardous to Health 2002 Regulations and the Dangerous Substances Explosive Atmospheres Regulations from the same year require employers to protect workers from risks of certain gases.
As well as organising professional site surveys, manufacturers can give key staff relevant skills through facilities such as International Gas Detectors’ online training academy. Courses through this portal are approved by training standards body CPD UK.
Addressing the issue
Selecting the correct detector for the specific job is critical. “Each site has its own unique issues,” says Collier. “How is the gas stored, how is it distributed, where is it used and what are its by-products? You must choose the right sensor for the application.”
Types of detection technology include electrochemical sensors, catalytic sensors or pellistors, photoionisation detectors, semiconductor sensors and infrared sensors. Each type has its pros and cons depending on the conditions it is being used in and the job it is required to do. Speaking to experts is important if you want to select the right detector for your requirements.
In the future, addressable technology could play a big part in gas detection in process plants. IGD has developed the 2-Wire Addressable ATEX Gas Detector, which reduces the need for cabling to be draped around a plant in order to highlight a range of gases and has many other benefits.
“Addressable systems can easily control other devices where the client needs to by utilising nodes,” says Collier. “If the client needed to control a beacon sounder or flame detector, then it just needs to add a node near the location and connect from that or from the nearest 2-Wire addressable detector. This gives clients much needed distributed control rather than having a mass of cabling back to a bulky control panel.”
The firm says other benefits of using addressable technology over 4-20 mA analogue devices include scalability, system security and in-built calibration data.
“It is also possible on an addressable system to produce remote reports automatically from the system using GSM modules. This means the head of HSE or lab manager can get a report each week from the gas detection panel to show what happened during that week, ensuring compliance with health and safety audits.
“In our opinion we could see addressable technology becoming the preferred choice for the process industry.”
