Xgard Type 3: The mV Advantage

Xgard Type 3 is the ideal solution for detecting lighter-than-air flammable gases such as methane and hydrogen. Detectors in such applications usually have to be mounted high-up in roof spaces or above equipment where access for calibration and maintenance is likely to present problems.

Gas detectors require calibration (usually every six months) and sensors may need to be replaced every 3-5 years. These activities usually require direct access to the detector to make adjustments and replace parts. National regulations such as the ‘UK Work at Height Regulations 2005’ stipulate safe working practices when working on equipment at height, and compliance usually requires the use of scaffolding or mobile ‘cherry pickers’ which entails significant cost and disruption on-site.

The advantage of mV pellistor type detectors

The terms ‘mV’ and ‘4-20mA’ describe the type of signal which is transmitted through the cable between the gas detector and the control system (for example a Crowcon Gasmaster). Calibration of 4-20mA detector (e.g. Xgard Type 5) entails removing the lid, and zeroing/calibrating the amplifier using a meter, test-points and potentiometers. Even more sophisticated detectors with a display and non-intrusive calibration still require direct access to operate the menu system using a magnet in order to perform calibration.

Xgard Type 3 is a mV pellistor-based detector which has no internal electronics (i.e. no amplifier); just terminals to connect via three wires to the control system (e.g. Gasmaster). Commissioning simply entails measuring the ‘head voltage’ at the detector terminals, and performing zero and calibration adjustments at the Gasmaster input module. Ongoing 6-monthly calibrations are then performed by remotely applying gas (via a ‘spray deflector’ or ‘collector cone’ accessory), and any necessary adjustments are made at ground level via the control system input module.

Hence once commissioned, mV pellistor type detectors do not need to be accessed until the sensor needs replacing; usually 3-5 years after installation. The routine need for expensive access equipment; scaffolding or cherry-pickers in thus avoided.

Xgard Type 3 can be directly connected to Gasmaster and Gasmonitor systems, and to Vortex via an ‘Accessory Enclosure’ accessory which converts the mV signals to 4-20mA.

Remote calibration of a mV pellistor type detector.

The Importance of Gas Detection in the Power Industry

The energy industry is the very backbone of our industrial and domestic worlds, supplying essential energy to industrial, manufacturing, commercial and residential customers around the globe. With the inclusion of fossil fuel industries (petroleum, coal, LNG); electricity generation, distribution and sales; nuclear energy and renewable energy, the power generation sector is essential in supporting the increasing demand for power from emerging countries and an increasing world population.

Gas Hazards in Power Sector

Gas detection systems have been installed extensively in the power industry to minimise potential consequence through the detection of gas exposure with those working within this industry are exposed to a variation of power plant gas hazards.

Carbon monoxide

The transport and pulverisation of coal poses a high risk of combustion. Fine coal dust becomes suspended in air and highly explosive. The smallest spark, for example from plant equipment, can ignite the dust cloud and cause an explosion that sweeps up more dust, which explodes in turn, and so on in a chain reaction. Coal power plants now require combustible dust certification, in addition to hazardous gas certification.

Coal power plants generate large volumes of carbon monoxide (CO) which is both highly toxic and flammable and must be accurately monitored. A toxic component of incomplete combustion, CO comes from boiler casing leaks and smouldering coal. It is vital to monitor CO in coal tunnels, bunkers, hoppers and tipper rooms, along with infrared-type flammable gas detection to detect pre-fire conditions.

Hydrogen

With hydrogen fuel cells gaining popularity as alternatives to fossil fuel, it is important to be aware of the dangers of hydrogen. Like all fuels, hydrogen is highly flammable and if it leaks there is real risk of fire. Hydrogen burns with a pale blue, almost invisible, flame that can cause serious injuries and severe equipment damage. Therefore, hydrogen must be monitored, to prevent seal-oil system fires, unscheduled shutdowns and to protect personnel from fire.

In addition, power plants must have back-up batteries, to ensure the continued functioning of critical control systems in cases of power outage. Battery rooms generate considerable hydrogen, and monitoring is often carried out in conjunction with ventilation. Traditional lead acid batteries produce hydrogen when they are being charged. These batteries are normally charged together, sometimes in the same room or area, which can generate an explosion risk, especially if the room is not properly ventilated.

Confined Space Entry

Confined space entry (CSE) is often considered to be a dangerous type of work performed in power generation. It is therefore important that the entry is strictly controlled and detailed precautions are taken. Lack of oxygen, toxic and flammable gases are risks that can occur during work in confined spaces, which should never be considered as simple or routine. However, the hazards of working in confined spaces can be predicted, monitored, and mitigated through the use of portable gas detection devices. Confined Spaces Regulations 1997. Approved Code of Practice, Regulations and guidance is for employees that work in Confined Spaces, those who employ or train such people and those who represent them.

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 T4x, Gasman, Tetra 3, Gas-Pro, T4, 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, XgardIQ 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 power industry our panels include Vortex and Gasmonitor.

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

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.