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17 Sep, 2021 All articles , Case study , ATEX Industries
How A2S temperature detectors help prevent risk at Air Liquide
The context: Risk of fire and gas explosions
For many companies, limiting the risk of fire and gas explosions is a real issue. The use and storage of flammable products in the workplace considerably increases these risks.
What is fire?
A fire is an uncontrolled fire, neither in time nor in space. It is a chemical reaction of oxidation of a fuel by an oxidizer. A fire is the result of the interaction of three elements, which together form the "fire triangle":
- the fuel (wood, cloth, gasoline...),
- the oxidizer (oxygen, nitric acid, chlorine...),
- an energy source (electricity, flame, lightning...).
To stop a fire or avoid the formation of a fire, it is enough to eliminate one of these elements.
There are different classes of fire, depending on the type of fuel.
- Class A involves fuel such as wood, paper, plastic...
- Class B involves flammable liquids such as gasoline, diesel, white spirit...
- Class B involves another category of flammable liquids: polar solvents (hydrogen, ethanol, propane...)
- Class C involves electrical fires
- Class D involves flammable metal fires (aluminum, titanium, magnesium...)
- Class F involves edible oil fires
The knowledge of the fire classes allows to set up the adequate prevention and fight measures.
What is an explosion?
An explosion is an oxidation or decomposition reaction accompanied by a sudden rise in temperature and/or pressure. In the first case, it can occur in a flammable gas or dust mixture with oxygen in the air or in an explosive product. In the second case, the explosion usually occurs in a container and causes a burst.
Unlike a fire, an explosion causes a protective effect accompanied by thermal and overpressure effects.
For an explosion to occur, several elements must be present. The causes of an explosion are the same as those of a fire: the presence of the "fire triangle". The difference is that three other elements are added:
- containment,
- the presence of products in suspension (gas, dust, fog...)
- the explosive range.
Six elements are therefore involved in an explosion. To remove the risk of fire and explosion, it is sufficient to remove one of the components of the fire triangle. If one of the three remaining elements is removed, the explosion risk is eliminated, but the fire risk remains.
The problem: Preventive measures
Regardless of the type of company, the employer must put in place preventive measures against the risks of fire and explosion on his site. He must provide adequate safety equipment.
Prevention of fire-related risks
Fire risk prevention consists of :
detecting and evaluating risks in order to limit their extent
- eliminating the factors that can trigger a fire and spread the fire by implementing technical and organizational measures
- planning evacuations for the personnel and the people present
- facilitate the intervention of the emergency services
To achieve this, several measures can be adopted. They can concern the construction aspect, by the choice of fire resistant materials or by the multiplication of emergency exits for example. The measures can also be technical (alarm, smoke detector, signalling, fire extinguisher...) or active (training, awareness, safety instructions...).
The aim of fire prevention is to ensure the safety of workers and equipment and to respond effectively to the danger.
What are the potentially flammable or explosive products?
Flammable products are products that can catch fire easily and quickly. They are liquids, solids, gases or vapors that can ignite or explode when in contact with air and a source of energy.
Among the flammable or explosive products that we encounter daily, we find gasoline, methylated spirits, white spirit or paint. They are generally recognizable by the flammable pictogram (GHS02). Each flammable product is characterized by a flammability range between a lower and an upper limit.
The lower explosive limit (LEL) is the minimum concentration at which a combustible gas or vapor in air can catch fire. It is expressed in % of volume in air. Below this threshold, the risk of fire or explosion is low.
The upper explosive limit (UEL), also expressed in %, is the maximum threshold above which the product can ignite. Above this limit, ignition or explosion cannot take place because the concentration of the product is higher than the oxygen content.
In an ATEX zone, control of the concentration of combustible gas or vapor outside the LEL and UEL must be careful. The risk of fire and explosion is greater.
Our solution
Air Liquide est un groupe industriel mondialement connu, leader dans son domaine, qui évolue sur le secteur des gaz, technologies et services pour l’industrie et la santé. Oxygène, Azote et Hydrogène sont le cœur de métier du groupe. Il n’est donc pas surprenant que ce groupe doive faire face à des défis en termes de sécurité industrielle liée à la nature des produits utilisés.
Nous avons sélectionné pour ce client un capteur de température performant pour protéger ses armoires gaz.
Our approach
To meet the customer's expectations as closely as possible, we began by listening to the customer's requirements and defining the customer's constraints. We then selected our TSDC Series Ex d temperature sensor range that best met the application.
We adapted the product to offer a customized technological solution dedicated to the specific needs expressed: dual-blade detection/transmission technology, low temperature trip point, armored cable, 316L stainless steel design and special mounting kit
This requirement does not correspond to the standards usually found on the market and given the vital importance of these sensors for the safety of the installations. It is easy to imagine what the impact of a faulty sensor could be!
We therefore developed prototypes so that Air Liquide's design office could carry out tests to validate the product technically and then reference it.
Product strengths
The TSDC-BTS Series ATEX sensor is a temperature detection and control sensor. It consists of an explosion-proof enclosure and high temperature resistant cables. The TSDC-BTS Series ATEX sensor is configured from a switch located in the explosion-proof housing. The switch consists of two heat-sensitive metal elements.
This thermal sensor protects a machine from overheating by cutting off its circuit when the nominal switching temperature is reached. As soon as the machine cools down to its reset temperature, the switch returns to its initial state and the circuit is completed.
The TSDC-BTS Series ATEX sensor is available in two sizes: 35 mm and 65 mm (inside dimension). For better pressure resistance and sealing, its tube and body have been assembled. This type of sensor is suitable for various fields such as pharmaceutical, petrochemical or refinery. It can be used in zones 1/21 and 2/22.
A2s' ability to listen and react was once again demonstrated in this request from Air Liquide, which put our design office to great use in order to deliver a safe and durable solution. Responding to challenges of this type is part of our DNA. We can thus express our full involvement alongside our customers to find solutions.
