T&D – Crowcon Distributors. Hazardous Area Gas Detectors (ATEX) For Zone 1 & Zone 2.
ATEX Directive – the Ex logo indicates that the gas detection equipment is suitable for use in a Flammable Atmosphere, Typically Zone 1 or Zone 2 hazardous area.
T&D, the specialist distributor of Gas Detection, Detectors & Monitoring Equipment for use in hazardous area industries provide the following overview of Crowcon Gas Detectors suitable for the oil and gas industry.
We begin by generally reviewing the 3 stages of the oil and gas process and focussing on the specific gas risks.
4 types of Crowcon gas detectors often deployed in Zone 1 and Zone 2 hazardous areas (ATEX) forming their hazardous area gas detector range for the detection and monitoring of flammable or toxic gases are highlighted for each of the 3 sectors.
Zone 1 & Zone 2 Crowcon Gas Detectors – Personal, Portable & Fixed Detectors For Toxic & Flammable Gases.
The upstream sector includes exploration and drilling for potential oil and gas fields, followed by the recovery and production of crude oil and natural gas if it is viable. Gas hazards in the upstream sector are compounded by the very harshest of environments providing challenges for the reliable detection of harmful gases.
Enhanced oil recovery (EOR) technologies and unconventional methods are allowing access to new geographic areas, as well as improving the level of recoverable resources within known reservoirs.
Fixed and portable gas detectors are required to protect plant and personnel from the risks of flammable gas releases (commonly methane gas detection) as well as high levels of hydrogen sulphide particularly from sour wells. Oxygen depletion, sulphur dioxide and volatile organic compounds (VOC’s) are also among the most common gas risks.
originaldate 1/1/0001 6:00:00 AMwidth 370height 305Crowcon XgardIQ Gas Detector – intelligent fixed-point Crowcon gas detector, increases safety by minimising the time operators must spend in Zone 1 and Zone 2 hazardous areas.
originaldate 1/1/0001 6:00:00 AMwidth 5421height 4469Crowcon Triple+ Plus Gas Detector – latest generation of the respected Crowcon "Triple" family of toxic, oxygen and flammable gas detectors. Over 90,000 units sold to oil and gas, chemical, utility and manufacturing companies worldwideoriginaldate 1/1/0001 6:00:00 AMwidth 370height 305
The main components of the midstream process are transportation and storage. Raw products are held in storage areas until ready for the next process or to be transported to a refinery.
Maintaining the integrity of storage and transportation vessels as well as protecting personnel during cleaning, purging and filling activities are a constant challenge within the midstream sector.
Fixed monitoring of flammable gases situated close to pressure relief devices, filling and emptying areas deliver early warning of localised leaks. Multigas portable monitors maintain personal safety especially during confined space work as well as supporting hot work permit area testing.
Infrared technology 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.
Portable laser methane detection allows leak location at distance for hard to reach areas, reducing the need for personnel to enter potentially dangerous environments or situations while performing routine or investigative leak monitoring.
The downstream sector refers to the refining and processing of raw natural gas and crude oil, and subsequently distribution and sale of the products derived from this. Such products can include jet fuel, diesel fuel, asphalt and petroleum coke.
The desire to reduce energy consumption, increasing operational efficiency, has driven device manufacturers to innovate both detection principals and the way in which power is used. Gas detectors employ state-of-the-art technologies to deliver industry leading power consumption per device.
The volume of personnel on plant and high number of toxic and flammable gases used and manufactured increase the potential hazards. Some risks can be mitigated by ensuring rugged and reliable portable gas detectors and monitors are used, that are well suited to individual on-site requirements. Fleet management tools such as bump test stations deliver exceptional reporting to track site compliance and calibration status.
The ongoing demand to reduce facility down-time whilst ensuring safety, especially during shutdown and turnaround operations, ensures that gas detection manufacturers must deliver solutions offering ease of use, simple training, reduced maintenance times with local service and support.
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Detecting Hydrogen Sulphide Gas
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Hazardous area industries including offshore oil/gas platforms and FPSOs, onshore oil refineries, processing plants, pipelines, storage farms and LPG/LNG plants all utilise or produce a wide range of hazardous flammable liquids and gases that can be detected using correctly specified flame and gas detectors.
Detecting toxic and flammable gases requires the detectors to be classified and certified according to the specific IECEx or ATEX standard – we distribute flame and fire detectors manufactured by Spectrex to operate in the harshest environmental conditions including self-contained stand-alone devices designed for direct connection to control and alarm systems or automatic fire extinguishing systems.
Our range of Hazardous Area Fire & Gas Detection System products also includes Explosion Proof Warning Systems & Hazardous Area Lighting – comprehensive range of intrinsically safe, flameproof and explosion proof alarm sounders, sirens, bells and horns, loudspeakers and beacons.
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Liquid gases such as butane and propane are created in crude oil distillation processes.
The gases are stored either under pressure in horizontal or spherical tanks or at incredibly low temperatures. There are operational issues as the level measurement sensors need to be highly reliable as the tanks cannot be open for several years at a time.
The ATEX hazardous area directive consists of two EU directives describing the type of equipment and work environment allowed in an environment with an explosive atmosphere. ATEX derives its name from the French title of the 94/9/EC directive: Appareils destinés à être utilisés en ATmosphères EXplosibles.
Selecting electrical, process or instrumentation equipment for hazardous areas can be complex and several factors must be considered in the decision making process.
Hazardous area classification must be carried out according to established codes (such as ATEX) or quantitative methods requiring a detailed knowledge of the plant. Sources of flammable gas or vapour release must also be identified, located and attributed to the specific potentially explosive Gas Group (G) or Dust Group (D).
Furthermore, explosive gases and dusts have an ignition temperature – the ATEX certified level sensors according to the equipment marking should be matched against the equipment temperature class (T).
Ambient temperatures, protection concepts and hazardous area zone also dictate the selection process and level sensor specification – should you require any assistance with the selection or specification of process instrumentation equipment including level sensors please do not hesitate to contact us.
Due to its high pressure resistance and impermeability, VEGASWING 63 is especially suitable for all level measurement and detection applications in LPG. The vibrating level switch is absolutely impervious and can be provided with an additional gas-tight lead through. The level sensors can also reliably detect the empty condition.
Especially for measuring ranges up to 6 metre, the VEGAFLEX 67 guided microwave instrument offers the best solution for continuous level measurement, with simultaneous detection of the water level in LPG applications. Part of the transmitted signal penetrates the surface of the liquefied gas and is reflected by the water surface that exists close to the bottom of the vessel. Both levels are indicated via the analysis of the two signals.
Retrofitting with standpipes for level measurement is work and cost-intensive, especially in large vessels. The high-sensitivity radar instrument VEGAPULS 68 can acquire level data of liquid gas without the usual standpipes. A ball valve separates the level sensor from the process and enables retrofitting without emptying the vessel.
VEGAPULS 63 is the ideal sensor for all applications in extremely low temperatures. Due to the antenna cover of PTFE, the level sensing instrument can be used even when product temperatures drop to -200 °C. An additional temperature-isolating elastomer seal is not required – for products with poor reflective properties, such as liquid nitrogen, application with a standpipe is recommended.
For more information about the VEGA range of level measurement instruments please contact T&D.
T&D UK & International: Project Suppliers To The Onshore & Offshore Oil, Gas, Petrochem & Hazardous Area Industries.
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VEGAPULS 62 Non Contact Radar Level Sensor Used In The Oil And Gas Industry
Thorne & Derrick International, based in the UK, distribute Explosion Proof & Hazardous Area Process Instrumentation Equipment (ATEX & IECEx Certified): this includes industrial measurement probes, humidity sensors, data loggers, handheld instruments and transmitters for temperature measurement and monitoring of relative humidity. Additionally, hazardous area instrumentation is also available for monitoring carbon dioxide, differential and process pressure, flow, dew point, water activity and analog signals.
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ABOUT US
Thorne & Derrick International are your single-source supplier of Electrical, Mechanical, Process & Instrumentation Equipment. T&D provide an outstanding service to UK and international customers – we are highly customer responsive and absolutely committed to providing a world-class service.
T&D supply utilities, power, renewable energy, construction, rail, manufacturing, food/beverage, mining, oil, gas and petrochemical industries – distributing 100,000+ products from 100+ manufacturers from multi-million pound stocks. Since 1985 we have established a solid reputation based on service, integrity and trust.
Hydrogen Gas Detection – Crowcon portable and fixed gas detection solutions
Hydrogen sulphide (H2S) is a naturally occurring gas and can be found in many of the worlds crude oils. The gas is colourless and has a distinctive rotten egg odour at low levels however at high concentrations the gas will numb the human sense of smell which can be fatal.
Heavy oils such as crude oil, residual fuel and gas oil tend to have large concentrations of hydrogen sulphide and this can become a concern if the oils are to be stored over extended time periods.
This Blog looks at the dangers of hydrogen sulphide gas in the oil refining industry and the working areas that may have H2S present and the gas detection solutions available.
Image: Valero
Working in and around an oil refinery is naturally fraught with dangers and potentially hazardous areas. One of the most common and most underestimated problems faced by personnel is the presence of toxic gases and particularly hydrogen sulphide (H2S) gas.
H2S is a colourless gas and therefore invisible. The gas does have a distinctive rotten egg smell that can only be smelt at low concentrations as at higher and more dangerous levels, peoples sense of smell is significantly numbed and therefore without adequate fixed or portable gas detectors, they can succumb to the harmful effects of the gas.
Inhalation of hydrogen sulphide gas can lead to acute poisoning and death by suffocation occurs extremely fast. This Blog looks at where hydrogen sulphide gas can occur within refineries and which situations are particularly dangerous including hazardous areas.
The above case studies highlight just how dangerous this gas can be and how essential it is to install effective, working gas detection systems.
Valero St. Charles Refinery’s major process units were built or substantially reconstructed in the late 1990s, making the refinery one of the newest in the USA.
Hydrogen Sulphide – H2S Fact Card
Hydrogen sulphide gas is colourless and at certain low concentrations it has a distinctive rotten egg odour which is instantly recognisable and as a result of this smell, H2S is commonly know as sewer gas, digester gas or marsh gas.
However, at higher concentrations the gas numbs olfactory nerves and starting at a concentration of 100ppm. People are therefore no longer able to smell the gas – concentrations higher than 1000ppm can be instantly fatal.
in addition to the numbing of senses, H2S gas is heavier than air and therefore will often collect in low-lying areas and working sites near ground level. The gas will ignite itself at a temperature of 270°C and due to its highly inflammable properties an explosive atmosphere may occur when combined with air.
Strong reactions are possible that can trigger spontaneous combustion, explosions and detonations. In addition, H2S gas combined with air and humidity or moisture can corrode metals through the formation of sulphuric acid.
90% of hydrogen occurs naturally in the environment for example in hot sulphur springs and rock masses, however there are many areas within the oil and gas industry in which the presence and bi-production of H2S gas is a common occurrence.
The refining process commonly produces H2S as a bi-product however the gas also occurs at wellheads, oil and water tanks, pumps, piping systems and flare heads.
The most common locations for the presence of hydrogen sulphide within refineries are:
Storage – The crude oil is transported via either a pipeline or barge and is stored waiting to be processed. Hydrogen sulphide can be found in the head space of the tank and can corrode the tank reducing it’s product lifespan and as the tank fills the headspace concentration increases.
Distillation Columns – The crude oil is separated into various components in the distillation columns based on boiling points. The lightest components are used for gas with the heaviest elements used for asphalt. Hazards occur even though this is a closed system and the gas can be present in the heat exchanger, furnace, tower flash column, vacuum furnace and bottom exhcanger.
Hydrotreater & Hydrocracker – The hydrotreater is used to remove the sulphur and the hydro cracker breaks long hydrocarbon chains into shorter chains in order to create more efficient petroleum products. These actions are performed over a catalyst at high pressure and temperature with excess hydrogen. Hydrogen and sulphur combine and create H2S which is then sent to a recovery unit to create water and sulphur. H2S content in the feedstock must be monitored along with any leaks.
Blending – This is the physical mixing of various hydrocarbons in order to produce an end product with desired characteristics. H2S hazards can occur during sampling, inspection, maintenance and turnaround.
Solution: Safety considerations to undertake include fixed and portable gas detectors to be installed in and around maintenance equipment and on turnaround equipment.
Chemical Treatment Process – This process removes contaminants such as sulphur, nitrogen, oxygen, dissolved metals and salts. This in turn improves the odour, colour and oxidation stability. Hydrogen sulphide is commonly used during the recovery of sulphur and the hydrogen sulphur scrubbing process.
Gas hazards will occur during sampling, inspection, maintenance and turnaround.
Solution: Portable and fixed gas detector solutions should be used in and around maintenance and inspection equipment to ensure gas detection safety.
Power Generation – Oil refineries have many other operations including electric generation, steam generation, cooling towers, wastewater treatment and flaring systems. The potential for H2S hazards to occur are around cooling towers and contaminated wastewater. Caution should always be taken during sampling, inspection and maintenance.
Solution: Portable gas detectors should be used along with respirators and air purifiers.
Hydrogen sulphide gas is a so called ‘nitrogen’ gas and causes damage to the lungs, central nervous system and can also cause skin and mucous membrane irritation. Typical symptoms of poisoning include headaches, dizziness, fatigue, dry mouth, anxiety, confusion and lack of coordination.
Even in low concentrations and a low dose, H2S can be harmful if exposure is continuous over several hours or days. High concentrations can lead to unconsciousness almost instantly and a coma followed by death in just a few short breaths – these effects show exactly how dangerous this gas is and highlights the need for effective gas detection.
There are a number of gas detection solutions available from Thorne & Derrick including fixed, portable and transportable suitable for use in safe and hazardous areas. Each working area and gas hazard requires a different gas detection solution in order to provide the proper, effective protection for personnel and buildings.
Typically, smaller confined spaces require personal and portable gas detection solutions to be carried by workers.
Fixed point gas detectors provide constant, 24 hour gas monitoring 365 days a years which is important for the detection of random gas release. T&D are distributors for the Crowcon ranges of gas detection equipment. Our gas detection specialists can help you determine exactly the correct product for your requirements.
The ever-present safety protection provided by Crowcon fixed gas detectors means personnel working in areas such as distillation columns and chemical treatment plants are able to work freely – improving safety figures and increasing productivity.
Fixed gas detection systems are favoured in many oil and gas areas for their constant gas safety protection, monitoring of any gas leaks and providing both audible and visual warnings when there are no personnel on site.
Portable gas detectors provide an excellent solution for the detection and monitoring of hydrogen sulphide among other hazardous gases. There are many benefits of using portable gas detection and differences compared to the use of fixed point detection systems.
The use of portable gas detection allows personnel the freedom to move between working areas safe in the knowledge that they are carrying their safety devices with them to detect and alert the presence of hazardous gases.
The difference between portable gas detectors and fixed is the length and continuity of detection – portable detection equipment must be tested, re-charged and have its own power supply whereas a fixed point detection system is hard wired and will provide constant, 24/7 detection however the flexibility and portability is compromised
Hazardous areas can occur when the presence of hazardous vapours, dusts or mists exist in a high enough volume. There are three categories of risk that must be identified reliably in order to protect human life and assets:
Without the use of auxiliary tools, people are often unable to recognise these dangers early enough to take action and prevent a serious incident or accident occurring.
Any equipment to be used in hazardous areas for gas monitoring purposes must fulfill the Essential Health And Safety Requirements (EHSR). In addition, as gas detection systems are products of safety technology, it is important not to misinterpret their role within oil refinery safety.
They are not simply a handful of detectors spread across and manufacturing plant, they are and should be considered a bespoke solution developed to fulfill the requirements of individual protection objectives.
Hazardous Area Gas Detectors Certified To International Classifications
All equipment to be used in zone 1 and zone 2 hazardous areas must be explosion proof and certified for use under the relevant local hazardous areas classifications such as ATEX and IECEx.
Hydrogen sulphide gas is extremely corrosive and causes metals to become brittle when exposed. All oil well drilling sites and areas within oil refineries must be classified according to areas of potential or actual exposure to H2S gas.
The four hazard levels are:
In any working area where there is the potential for exposure to hydrogen sulphide, a gas monitoring strategy is recommended to ensure exposure levels are kept below acceptable levels and that the appropriate action is taken if there is ever exposure above these levels.
In order to protect workers from exposure to harmful levels of hydrogen sulphide, the American Conference Of Governmental Industrial Hygienists (ACGIH) modified the Threshold Limit Value (TLV) for H2S in 2010.
From 1976 to 2009, the 8 hour time weighted average TLV (TLV-TWA) was 10 parts per million (PPM) and the 15 minute short-term exposure limit TLV (TLV-STEL) was 15 PPM. In 2010 a TLV-TWA of 1 PPM was adopted along with a TLV-STEL of 5 PPM for H2S.
The ACGIH is a globally recognised authority on the establishing of exposure limits for chemical agents including toxic gases, and the changes to the H2S limits followed a five year review period during which industry experts had the chance to express any concerns they had.
The best protection would be an electronic instrument that could measure and store both the 1 PPM TWA and 5 PPM STEL H2S levels and also provide and alarm when concentrations reached 5 PPM.
A portable gas detector is ideal for users who want to accurately and reliably measure H2S levels. It provides a noticeable visual, audible and vibration alarm notification to alert the user to dangers levels of hydrogen sulphide gas that is present.
The detector features an easy-to-use intuitive interface and also features data logging which records the entire history of the monitor for complete analytical and safety uses.
Thorne & Derrick are Specialist Distributors of Hazardous Area & Explosion Proof Equipment with IECEx & ATEX Certifications to the onshore and offshore oil, gas, petrochemicals and process industries.
Key Product Categories: Control Panels | Plugs & Sockets | Isolators | Enclosures & Junction Boxes | Lighting | Control Stations | Motor Starters | Heat Trace Cables & Systems | Gas Detection & Detectors | Fire Detection & Detectors | Heat Detectors | Electrical Heating & Heaters
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Gas detection systems have been used for centuries in various forms (from feathered to infrared) and today are an essential element of plant safety throughout industry – gas detectors save lives, protect workers and safeguard property.
However if they are not installed, commissioned or maintained properly they will not provide the protection against dangerous toxic and flammable gases.
The risks of not having adequate gas detection systems and procedures in place can be catastrophic resulting in serious harm or death to personnel and significant financial damage done to equipment.
How do you ensure that your gas detection system will respond as expected when you need it most? Do you know if it is working right now?
In many industries, the installation and correct placement of gas detection equipment is a key part of the safety plan for reducing risks to personnel – industries such as oil and gas are at the most risk from explosive gases due to the nature of the products they are transporting, storing and refining.
T&D look at the 5 main best practices that you should consider in the installation, commissioning and maintenance of your gas detection systems.
Once upon a time underground miners used canaries to test air quality in mines – today gas detection is provided by instruments manufactured by market-leaders
There is no legislation or specific standards governing gas detector location as there are for fire detection systems there are however general guidance documents including:
Ensuring the gas detector in use, whether it is portable or fixed, provides adequate gas detection coverage for the assets being protected. With fixed gas detectors this is often decided during the initial design and survey of the site to be monitored.
For portable gas detectors, this typically means ensuring the gas detector is located within the breathing space of the user. For retrospective installations, it is vital to ensure the gas detectors are given adequate space and will come into contact with any gas that may be present.
For the detection of heavier gases, such as hydrogen sulphide (H2S), it is essential to ensure the gas detector is placed close to ground as H2S gas is heavier than air – if the detector is located at high level then it will fail to detect gas.
Portable gas detectors are often subject to extremely diverse working conditions and environments – the many different applications require solutions tailored to the individual requirements and respective application conditions.
Portable gas detection can be distinguished between personal and area monitoring, confined space entry and leak detection:
If the gas detector is being installed in a dock mount, it is vital to ensure there is adequate airflow so that it is not in a dead zone. Proper airflow to the gas detector ensures that new air that may contain harmful gas can be detected.
It also means any stagnant air that may set off the gas detector erroneously will not linger around the detector causing a false alarm. In addition, any air inlet filters should be clean to allow unrestricted air flow into the detector.
The height of the gas detector installation must be considered also as many gases are heavier than air and therefore if the gas detector is installed too high up, gases such as refrigerant or Freon gases will settle lower in the room and not be readable by the gas detector.
Gas detectors should be fully calibrated upon initial installation and then checked annually under a routine maintenance schedule. Some gases are sensitive to different conditions such as altitudes and therefore require calibration before use in a new environment.
Without adequate calibration, gas detector devices do not provide the protection and alert users as they should. Calibration is effectively a product reset against a known concentration of target gas, in a balance of synthetic air or nitrogen and is required for a number of reasons.
If the detector has been subjected to adverse conditions such as a change in temperature, sensor poisoning through exposure to contaminants like silicone and solvents, or exposure to high gas concentrations this can result in a change to which the detector responds to certain gases. In addition, mechanical shock or stress and sensor age can affect performance.
The calibration is a two step procedure:
Calibration is not required as frequently as bump testing which should be carried out before each use.
Routine maintenance of gas detectors can be classified as a full calibration, bump testing and a general inspection of the devices. The frequency of when each should be carried out varies.
Bump testing of gas detectors should be carried out regularly and ideally before each use. The bump test is a much shorter test than the full calibration and ensures the gas detection device is functioning as expected.
The OSHA defines the bump test as: “a qualitative function check in which a challenge gas is passed over the sensor(s) at a concentration and exposure time sufficient to activate all alarm settings.”
Put simply, this test verifies the performance of the of the gas detector and ensures the sensors are responding to their target gas as expected. The OSHA also confirms that the bump test should be carried out “before each day’s use in accordance with the manufacturer’s instructions”.
As portable gas detectors are an important part of a workers’ daily safety equipment, bump testing ensures that equipment is safe for use and performing at the standards expected. Only fully functioning gas detectors can provide detection and protection against deadly gases.
Eventually, all gas detector sensors will come to the end of their life and some can reach this point suddenly. The product longevity depends upon the application conditions and environmental influences.
Reliable equipment, safe user behaviour and adequate training are the three components needed for effective gas detection. Staff training is just as important to gas detection as having the appropriate equipment. If staff are unaware of how to effectively and safely operate and calibrate their gas detection equipment then they put their own lives and colleagues well-being at risk.
Effective staff training is a key part of effective gas detector usage and maintenance which can often be overlooked. As a minimum, staff should have basic training and understanding of the nature of any likely gas hazards and how to minimise the chances of an encounter with these gases.
Gas monitors display information about the type of gas present and the levels of that gas. It is vital that personnel working around gases understand the information being shown, how to access it and what to do if a gas alert sounds.
Staff must also know the benefits of bump testing and calibration and how to carry out such servicing. Similarly, employees should be trained on how to fully service and maintain gas detectors and should always be carried out by someone who fully understands gas detection equipment and how to ensure safe operation in hazardous areas.
The effectiveness of any gas detection equipment is significantly impaired if it is not maintained properly and without adequate staff training the protection of personnel is always likely to be compromised.
The Three Elements Required For Effective Gas Detection
Many industrial processes and environments frequently involve flammable substances and particles including gases and vapours. For prevention purposes these areas are classified as Ex-areas or zones and are graded by the likelihood of gas being present.
ATEX European Hazardous Area Certifications
Only gas detection equipment that has been certified as suitable for use and is equipped with explosion protection in hazardous areas can be used. Explosion protection is regulated globally and the basic standards are are:
The ATEX 95 European directive is mandatory in the European Union and has been since 2003. This directive sets out the standards that equipment and protective systems for use in potentially explosive atmospheres need to fulfil in order to meet Essential Health and Safety Requirements (EHSR).
Hazardous area industries including offshore oil/gas platforms and FPSOs, onshore oil refineries, processing plants, pipelines, storage farms and LPG/LNG plants all utilise or produce a wide range of hazardous flammable liquids and gases that can be detected using correctly specified flame and gas detectors.
Detecting toxic and flammable gases requires the detectors to be classified and certified according to the specific IECEx or ATEX standard – we distribute flame and fire detectors manufactured by Spectrex to operate in the harshest environmental conditions including self-contained stand-alone devices designed for direct connection to control and alarm systems or automatic fire extinguishing systems.
Our range of Hazardous Area Fire & Gas Detection System products also includes Explosion Proof Warning Systems & Hazardous Area Lighting – comprehensive range of intrinsically safe, flameproof and explosion proof alarm sounders, sirens, bells and horns, loudspeakers and beacons.
♦ LV Power Products | Junction Boxes & Enclosures ATEX | Plugs ATEX | Control Stations ATEX | Isolators ATEX
Thorne & Derrick | Detecting Flame | Heat | Gas
Follow our Showcase Page on LinkedIn to receive hazardous area product innovations, industry news, whitepapers, videos, technical tips and training webinars for professionals involved in the explosive atmosphere industries.
Ashcroft Pressure Gauges – 7 Steps To Choosing The Correct Pressure Gauge
When selecting a mechanical Ashcroft Pressure Gauge with no external power input, there are a number of criteria that must be considered prior to choice and installation.
The 7 points below set out the key steps that must be considered, however there are also further points that must also be considered including the environmental issues, workplace location (safe or hazardous area) and mounting requirements. When considering the main points below and selecting the correct gauge product longevity, performance and reliability will be significantly improved.
The 7 main points to consider when selecting a pressure gauge are:
The accuracy of mechanical pressure gauges is described as a percentage of the full-scale range and while requirements differ between industries, the general guidelines are:
Pressure gauge dials range in size from less than 1″ to 16″ in diameter and readability requirements, space limitations and required gauge accuracy will determine the dial size chosen. Any accuracies of 0.25% to 0.5% will generally have dial size of 4½” or larger as more dial graduations are required.
Prior to choosing and installing a pressure gauge, there are many environmental considerations such as ambient temperature, condensation, humidity, water, chemicals and air-borne particulate.
The ambient temperature can affect the accuracy and integrity of the pressure gauges which are available either temperature compensated or non-temperature compensated and the ambient temperature may require the gauge to be isolated from extreme temperatures.
Where ambient conditions are corrosive and contain a large amount of particulate or if the gauge will be exposed to a wet or humid environment, then a gauge should be specified that is weatherproof/hermetically sealed or liquid filled. The correct case material can prevent corrosion and leaks which will in turn prevent leaks and safety incidents occurring.
The gauge process and the wetted parts of the pressure gauge are typically the bourdon tube and socket which must be compatible with the process media. If this not the case, then rust or corrosion can occur and will eventually lead to parts of the gauge failing and potentially cause safety issues.
The type of connection and size of connection are available in many varieties including NPT, DIN, JIS, BSP & SAE. Process pressure gauges with 4½” dials or larger are most often supplied with a ½” NPT connection to best support the gauge.
Other factors to consider when selecting a pressure gauge connection include process pressures, gauge size and weight, space limitations, leak integrity, and past experience. In addition, when mounting the pressure gauge, there are a number of options that should be considered including:
The location of the gauge connection is a key consideration as there a number of elements that must be considered prior to installation. These include the stem mount lower connection, wall/surface mount lower connect, panel mount back connect U-clamp and front flange flush mount back connection.
The American Society of Mechanical Engineers (ASME) recommends that normal operating pressure of the gauge should be confined to 25%-75% of the scale. If pulsation is present in the process, maximum operating gauge pressure should not exceed 50% of the full-scale range.
To properly select and specify a pressure gauge prior to purchase the user must consider the pressure gauge process, range, environment, accuracy, dial size, connection and mounting requirements – if in doubt, call T&D.
To prevent misapplication, pressure gauges must be selected considering media and ambient operating conditions. Improper application can be detrimental to the gauge, causing failure and possible personal injury, property damage or death.
The information contained here is offered as a guide to enable the safe and proper selection of a pressure gauge.
Users should become familiar with ASME B40.100 (Gauges – Pressure Indicating Dial Type – Elastic Element) before specifying pressure gauges. The document contains essential information regarding pressure gauge construction, accuracy, safety, selection and testing.
Should you require any further information, technical details or selection support to choose the correct pressure gauge, please do not hesitate to contact us.
Thorne & Derrick are inviting you to join LinkedIn’s fastest growing Discussion Group – Process & Hazardous Area Industries : Heat Tracing, Gas Detection, Fluid Control & Flow Measurement. News, projects, videos, promotions, whitepapers, jobs, webinars, press plus much more.
ABOUT US
Thorne & Derrick International are your single-source supplier of Electrical, Mechanical, Process & Instrumentation Equipment. T&D provide an outstanding service to UK and international customers – we are highly customer responsive and absolutely committed to providing a world-class service.
T&D supply utilities, power, renewable energy, construction, rail, manufacturing, food/beverage, mining, oil, gas and petrochemical industries – distributing 100,000+ products from 100+ manufacturers from multi-million pound stocks. Since 1985 we have established a solid reputation based on service, integrity and trust.
Published 13 Mar 2020
Press Release Date: 02.04.2020 uploaded by Chris Dodds (T&D Sales + Marketing Manager) World’s First Fully Certified ATEX Doors Thorne & Derrick International, the Experts in Equipment for Explosive Atmospheres, today announce the signing of a Commercial Distribution Agreement...
Published 04 Jul 2019
Press Release Date: 04.07.2019 uploaded by Chris Dodds (T&D Sales + Marketing Manager) Category: Stockist Distributor Agreement Announcement Thorne & Derrick International announce that they have signed a Preferred Distributor Agreement with Raytec, the world leading manufacturer of LED...
