The importance of gas detection in the Petrochemical Industry

Closely linked to oil and gas, the petrochemicals industry takes raw materials from refining and gas processing and, through chemical process technologies, converts them into valuable products. In this sector, the organic chemicals produced in the largest volumes are methanol, ethylene, propylene, butadiene, benzene, toluene and xylenes (BTX). These chemicals are the building blocks of many consumer goods including plastics, clothing fabric, construction materials, synthetic detergents and agrichemical products.

Potential Hazards

Exposure to potential hazardous substances is more likely to occur during shutdown or maintenance work as these are a deviation from the refinery’s routine operations. As these deviations are out of normal routine, care should be exercised at all times to avoid the inhalation of solvent vapours, toxic gases, and other respiratory contaminants. The assistance of constant automated monitoring is helpful in determining the presence of solvents or gases, allowing their associated risks to be mitigated. This includes warning systems such as gas and flame detectors, supported by emergency procedures, and permit systems for any kind of potentially dangerous work.

The petroleum industry is split into upstream, midstream and downstream and these are defined by the nature of the work that takes place in each area. Upstream work is typically known as the exploration and production (E&P) sector. Midstream refers to the transportation of products through pipelines, transit and oil tankers as well as the wholesale marketing of petroleum-based products. The downstream sector refers to the refining of petroleum crude oil, the processing of raw natural gas and the marketing and distribution of finished products.

Upstream

Fixed and portable gas detectors are needed to protect plant and personnel from the risks of flammable gas releases (commonly methane) as well as from high levels of H₂S, particularly from sour wells. Gas detectors for O₂ depletion, SO₂ and volatile organic compounds (VOCs) are required items of personal protection equipment (PPE), which is usually highly visible colour and worn near breathing space. Sometimes HF solution is used as a scouring agent. Key requirements for gas detectors are rugged and reliable design and long battery life. Models with design elements that support easy fleet management and compliance obviously have an advantage. You can read about VOC risk and Crowcon’s solution in our case study.

Midstream

Fixed monitoring of flammable gases situated close to pressure relief devices, filling and emptying areas is necessary to deliver early warning of localised leaks. Multi-gas portable monitors must be used to maintain personal safety, especially during work in confined spaces and supporting hot work permit area testing. Infrared technology in flammable gas detection supports purging with the ability to operate in inert atmospheres and delivers reliable detection in areas where pellistor type detectors would fail, due to poisoning or volume level exposure. You can read more on how infrared detection works in our blog and read our case study of infrared monitoring in refinery settings in Southeast Asia.

Portable laser methane detection (LMm) allows users to pin-point leaks at distance and in hard-to-reach areas, reducing the need for personnel to enter potentially dangerous environments or situations while performing routine or investigative leak monitoring. Using LMm is a quick and effective way to check areas for methane with a reflector, from up to 100m away. These areas include closed buildings, confined spaces and other difficult-to-reach areas such as above-ground pipelines that are near water or behind fences.

Downstream

In downstream refining, the gas risks may be almost any hydrocarbon, and may also include hydrogen sulphide, sulphur dioxide and other by-products. Catalytic flammable gas detectors are one of the oldest flammable gas detector types. They work well, but must have a bump testing station, to ensure each detector responds to the target gas and is still functional. The ongoing demand to reduce facility down-time whilst ensuring safety, especially during shutdown and turnaround operations, means that gas detection manufacturers must deliver solutions offering ease of use, straightforward training and reduced maintenance times, along with local service and support.

During plant shutdowns, processes are stopped, items of equipment are opened and checked and the number of people and moving vehicles at the site is many times higher than normal. Many of the processes undertaken will be hazardous and require specific gas monitoring. For example, welding and tank cleaning activities require area monitors as well as personal monitors to protect those on site.

Confined space

Hydrogen sulphide (H₂S) is a potential problem in the transport and storage of crude oil. The cleaning of storage tanks presents a high hazard potential. Many confined-space entry problems can occur here, including oxygen deficiency resulting from previous inerting procedures, rusting, and oxidation of organic coatings. Inerting is the process of reducing the oxygen levels in a cargo tank to remove the oxygen element required for ignition. Carbon monoxide can be present in the inerting gas. In addition to H₂S, depending on the characteristics of the product previously stored in the tanks, other chemicals that may be encountered include metal carbonyls, arsenic, and tetraethyl lead.

Our Solutions

Elimination of these gas hazards is virtually impossible, so permanent workers and contractors must depend on reliable gas detection equipment to protect them. Gas detection can be provided in both fixed and portable forms. Our portable gas detectors protect against a wide range of gas hazards, these include Clip SGD, Gasman, Tetra 3, Gas-Pro, T4, Gas-Pro TK and Detective+. Our fixed gas detectors are used in many applications where reliability, dependability and lack of false alarms are instrumental to efficient and effective gas detection, these include Xgard, Xgard Bright, Fgard IR3 Flame Detector and IRmax. Combined with a variety of our fixed detectors, our gas detection control panels offer a flexible range of solutions that measure flammable, toxic and oxygen gases, report their presence and activate alarms or associated equipment, for the petrochemical industry our panels include Addressable Controllers, Vortex and Gasmonitor.

To find out more on the gas hazards in the petrochemical industry visit our industry page for more information.

Gas-Pro TK: Dual readings of %LEL and %Vol

Gas-Pro TK (re-branded from Tank-Pro) dual range portable monitor measures the concentration of flammable gas in inerted tanks. Available for methane, butane and propane, Gas-Pro TK uses a dual IR flammable gas sensor – the best technology for this specialist environment. Gas-Pro TK dual IR features auto-range switching between %vol. and %LEL measurement, to ensure operation at the correct measurement range. This technology isn’t damaged by high hydrocarbon concentrations and does not need oxygen concentrations to work, as are the limiting factors of catalytic bead/ pellistors in such environments.

What problem is Gas-Pro TK specifically designed to overcome?

When you wish to enter a fuel storage tank for inspection or maintenance, you may start with it full of flammable gas. You can’t just start pumping air in to displace the flammable gas because at some point in the transition from only fuel present to only air present, there would be an explosive mixture of fuel and air. Instead, you must pump in an inert gas, usually nitrogen to displace the fuel without introducing oxygen. The transition from 100% flammable gas and 0% volume nitrogen, to 0% volume flammable gas and 100% nitrogen enables a safe transition from 100% nitrogen to air. Using this two-step process enables a safe transition from fuel to air without risking an explosion.

During this process there is no air or oxygen present, so catalytic bead / pellistor sensors will not work properly and will also be poisoned by the high levels of flammable gas. The dual range IR sensor used by Gas-Pro TK does not require any air or oxygen to function, so it is ideal to monitor the whole of the process, from %volume to %LEL concentrations, while also monitoring oxygen levels in the same environment.

What is LEL?

The Lower Explosive Limit (LEL) is the lowest concentration of a gas or vapour that will burn in air. Readings are a percentage of that, with 100%LEL the minimum amount of gas needed to combust. LEL varies from gas to gas, but for most flammable gases it is less than 5% by volume. This means that it takes a relatively low concentration of gas or vapour to produce a high risk of explosion.
Three things must be present for an explosion to occur: combustible gas (the fuel), air and a source of ignition (as shown in the diagram). In addition, the fuel must be present at the right concentration, between the Lower Explosive Limit (LEL), below which the gas/air mixture is too lean to burn, and the Upper Explosive Limit (UEL), above which the mixture is too rich and there is not enough of a supply of oxygen to sustain a flame.

Safety procedures are generally concerned with detecting flammable gas well before it reaches an explosive concentration, so gas detection systems and portable monitors are designed to initiate alarms before gases or vapours reach the Lower Explosive Limit. Specific thresholds vary according to the application, but the first alarm is typically set at 20% LEL and a further alarm is commonly set to 40% LEL. LEL levels are defined in the following standards: ISO10156 (also referenced in EN50054, which has since been superseded) and IEC60079.

What is %Volume?

The percent by volume scale is used to give the concentration of one gas type in a mixture of gases as a percentage of the volume of gas present. It is just a different scale with, for example the methane lower explosive limit concentration is displayed at 4.4% volume instead of 100% LEL or 44000ppm, which are all equivalent. If there was 5% or more methane present in air, we would have a highly dangerous situation where any spark or hot surface could cause an explosion where air (specifically oxygen) is present. If there is 100%volume reading, it means that there is no other gas present in the gas mix.

Gas-Pro TK

Our Gas-Pro TK has been designed for use in specialist inerted tank environments to monitor levels of flammable gases and oxygen, as standard gas detectors will not work. In ‘Tank Check Mode’ Our Gas-Pro TK device is suitable for specialist application of monitoring inerted tank spaces during purging or gas freeing, as well as doubles as a regular personal gas safety monitor in normal operation. It enables users to monitor the gas mix in tanks carrying flammable gas during transport at sea (as it is marine approved) or on shore, such as oil tankers and oil storage terminals. At 340g, Gas-Pro TK is up to six times lighter than other monitors for this application; a boon if you have to carry it with you all day.

In Tank Check mode, the Crowcon Gas-Pro TK, monitors concentrations of flammable gas and oxygen, checking that an unsafe mixture is not developing. The device auto-ranges, switching between %vol and %LEL as gas concentration demands, without manual intervention, and notifies the user as it happens. Gas-Pro TK has real-time oxygen concentrations from within the tank on its display, so users can track the oxygen levels, either for when the oxygen levels are low enough to safely load and store fuel, or high enough for safe tank entry during maintenance.

The Gas-Pro TK is available calibrated to methane, propane or butane.  With IP65 and IP67 ingress protection, Gas-Pro TK meets the demands of most industrial environments. With optional MED certifications, it is a valuable tool for tank monitoring on-board vessels. The optional High H₂S Sensor addition allows users to analyse possible risk if gases vent during purging. With this option, users can monitor over the 0-100 or 0-1000ppm range.

Please note: if the fuel in the tank is hydrogen or ammonia, a different gas detection technique is required – and you should contact Crowcon.

For more information on our Gas-Pro TK visit our product page or get in contact with our team.

An Introduction to the Marine Industry

The marine sector is a global industry and is wide ranging in terms of its applications and different types of vessels including FPSO vessels, ferries and submarines.

The type of gas hazards that will be present, and subsequently the gas detection requirements, are heavily dependent on the application and the type of marine vessel being used. In this blog we’ll take a look at some of the most common gas hazards within the marine industry and in which applications they are most likely to occur.

Floating Production, Storage, Offloading Units and Tankers

Floating production, storage and offloading (FPSO) units, which are used in the production, processing and storage of oil, are home to many potential gas hazards.

Firstly, there is the risk of fire and explosion hazards, which can lead to catastrophic damage and loss of life. Combustible gas risks that may be present include methane, hydrogen, propane, LPG, solvents and gasoline fumes among others. Due to this risk, flammable gas detection is essential on FPSO vessels.

FPSO units also have confined spaces in the form of inverted tanks or voids, meaning oxygen detectors are a must for these areas to protect from the risks of oxygen depletion which can cause mental confusion, nausea, weakness and in extreme cases loss of consciousness and death.

Ferries

Whilst ferries may not be home to as many gas hazards as other vessels, there are certainly still some to be aware of. On vehicle carrying ferries, for example, there may be a large build-up of emissions from vehicle exhausts which contain harmful gases such as carbon monoxide and nitrogen dioxide. Both gases are capable of causing damage to human health, causing issues such as nausea, confusion and disorientation, inflammation of the airways and increased vulnerability to respiratory infection.

Submarines

Submarines may be used for a variety of purposes including salvage and exploration operations, marine science and facility inspection and maintenance. On these vessels there may be a requirement for hydrogen detection in battery storage rooms. Whilst hydrogen is a non-toxic gas, if it builds up in environments without sufficient airflow it can displace oxygen in the air leading to risk of oxygen depletion.

Our solutions

Gas detection can be provided in both fixed and portable forms. Our portable gas detectors protect people against a wide range of gas hazards, and include T4x, Gas-Pro, T4 and Gas-Pro TK. Our fixed gas detectors are used where reliability, dependability and lack of false alarms are instrumental to efficient and effective protection of assets and areas. Now available through Crowcon, the Sensitron SMART S-MS MED fixed detector has been designed specifically for use in marine environments. The SMART S-MS MED is fully marine certified by Lloyd’s Register in accordance with MED/3.54 Regulation whilst also being SIL-2 certified. Also available is the Multiscan++MED control panel, also MED and SIL-2 certified, able to manage and monitor up to 64 gas detectors.

To find out more on the gas hazards in the marine sector visit our industry page for more information.