Protection of gas cabinets by anti-flagrant temperature sensors - A
Context: Fire risk and gas explosions
For many companies, reducing the risks of fire and gas explosion is a real problem. The use and storage of flammable products in the workplace significantly increases these risks.
What is the 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, the whole of which forms the "fire triangle":
- fuel (wood, fabric, gasoline...),
- oxidizer (oxygen, nitric acid, chlorine...),
- a source of energy (electricity, flame, lightning...).
To stop a fire or avoid the formation of a fire, just remove one of these elements.
There are different fire classes, 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 electric lamps
- Class D involves flammable metal lamps (aluminium, titanium, magnesium...)
- Class F involves food oil fires
The knowledge of fire classes allows for adequate prevention and control measures.
What is the explosion?
An explosion is a reaction of oxidation or decomposition accompanied by a sudden rise in temperature and/or pressure. In the first case, it may occur within a flammable gas or dust mixture with air oxygen or within an explosive product. In the second, the explosion usually occurs in a container and causes a burst.
Unlike a fire, an explosion causes a protective effect accompanied by thermal effects and overpressure.
For an explosion to occur, several elements must be assembled. 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 add:
- containment,
- the presence of suspended products (gas, dust, fog...)
- the explosive field.
Six elements are thus involved in an explosion. To remove a risk of fire and explosion, just remove one of the components from the fire triangle. If one of the remaining three elements is removed, the risk of explosion is removed, but the risk of fire remains.
The problem: Prevention measures
Regardless of the type of enterprise, the employer must put in place measures to prevent the risks of fire and explosion at its site. It shall provide adequate safety equipment. Prevention of fire risk
Prevention of fire risk consists of:
- identify and assess risks in order to limit their extent
- remove factors that can trigger a fire and spread fire through technical and organisational measures
- provide evacuations for personnel and persons present
- promoting emergency response
To this end, several mechanisms can be adopted. They may concern the construction part, such as the choice of fire-resistant materials or the multiplication of emergency exits. The devices can also be technical (alarm, smoke detector, signalling, fire extinguisher...) or active (training, awareness, safety instructions...).
The aim of fire risk prevention is to ensure the safety of workers and equipment and to respond effectively to the danger.
What are potentially flammable or explosive products?
Flammable products are products that can catch fire easily and quickly. It is a liquid, solid, gas or vapour that can ignite or explode in contact with air and an energy source.
Inflammable or explosive products that occur daily include gasoline, burning alcohol, white spirit or paint. They are generally recognizable by the flammable pictogram (SGH02). Each flammable product is characterized by a range of flammability between a lower and upper limit.
- The lower explosive limit (LIE) is the minimum concentration from which a fuel gas or vapour in the air can fire. It is expressed in % volume in air. Below this threshold, the risk of fire or explosion is low.
- The upper explosive limit (ESL), also expressed in %, is the maximum threshold above which the product may ignite. Above this limit, ignition or explosion cannot take place because the concentration of the product exceeds the oxygen content.
In an ATEX area, the control of the concentration of fuel gas or vapour outside the LIE and LES shall be careful. The risks of fire and explosion are greater.
Our solution
Air Liquide is a world-renowned industry group, leader in its field, which is evolving in the sector of gases, technologies and services for industry and health. Oxygen, Azote and Hydrogen are the core business of the group. It is therefore not surprising that this group faces challenges in terms of industrial safety related to the nature of the products used.
We selected for this customer a high-performance temperature sensor to protect its gas cabinets.
Our approach
To meet the customer's expectations as closely as possible, we started with a listening and exchange phase between the Air Liquide study office and our engineers to define the specifications and constraints of the customer. We then selected our range of temperature sensor Ex d TSDC Series that best meets the application.
We have adapted the product to offer a custom-made technology solution dedicated to the specific needs expressed: bi-lame detection/transmission technology, low temperature trigger threshold, reinforced cable, 316L stainless steel design and special mounting kit.
This requirement does not correspond to the standards usually found in the market and given the vital importance of these sensors for the safety of installations. It is easy to imagine what the impact of a failed sensor could be!
We have therefore developed prototypes so that the Air Liquide study office can perform tests in order to technically validate the product and then reference it.
Product strengths
The TSDC-BTS Series ATEX sensor is a sensor for temperature detection and control. It is composed of a deflating casing and cables that are very resistant to high temperatures. The TSDC-BTS Series ATEX sensor is configured from a switch in the blast-proof housing. It consists of two thermosensitive metal elements.
This thermal sensor protects a machine from overheating by cutting its circuit when the rated switching temperature is reached. Once the machine cools 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 (inner dimension). For better resistance to pressure and sealing, its tube and body were assembled. This type of sensor is suitable for different fields such as pharmaceuticals, petrochemicals or refinery. It may be used in zones 1/21 and 2/22.
Listening and the responsiveness of A2s have once again demonstrated itself in this request by Air Liquide, which has made a major contribution to our study office in order to deliver a safe and lasting solution. Meeting such challenges is part of our DNA. We can express our full involvement with our customers in finding solutions.
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