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Explosion protection for elevators

ATEX.CENTER is an official distributor of RSBP. We supply products from a manufacturer of explosion protection systems with 30 years' experience. Its mission: "Safety first".
ATEX.CENTER has been an official RSBP partner since 2019. We provide a complete service for the explosion protection of elevators: we carry out explosion safety audits, supply and install technical devices and provide service.

Explosion hazard of elevators

There are 400-500 accidents each year at plant processing and storage facilities around the world. Of these, approximately a quarter are caused by nori explosions. The statistics vary slightly from facility to facility.
Elevators are the source of primary explosions in 22% of accidents, in 24% of accidents at flour mills, and in 29% of accidents at feed mills.

This is despite the fact that such facilities are classified as hazardous, so there are increased requirements in different countries to prevent accidents. Nevertheless, elevators do explode.

The main cause is combustible dust that forms when transporting grain and other bulk materials. Combined with air it forms an explosive mixture. A single spark causes it to ignite with detonation. Due to the design of the elevator, a primary explosion is usually followed by a series of secondary explosions - devastating in effect and dangerous to people.

According to research data, each batch of harvested grain is moved by bucket elevators an average of 4-5 times. And already after the third lift the content of traumatised grains of dry wheat, barley, oats increases almost by 2,5 times. The concentration of combustible dust increases proportionally.

Sources of ignition initiation

EN 1127-1-2014 classifies 13 active ignition sources which, in contact with a combustible dust/air mixture, may lead to an accident.

In elevators, the cause of the fire may be

Sparks from a broken elevator belt;
Heating of individual pipe sections due to friction of the bucket;
Hot particles in the material to be conveyed;
Sparks from contact between the edges of the metal bucket and the pipe;
Static electricity;
Sparks from the elevator drive;
Bearing friction, etc.

The list of hazardous situations in nories is quite long. And an explosion cannot be completely ruled out in them - the risk is related to the very process of transporting bulk goods. When the same grain is lifted and dumped, combustible dust is released into the air and forms a dangerous mixture. If it comes into contact with mechanical sparks or static electricity, it causes an accident.

Safety standards for the owner of a hazardous industrial facility

The minimum explosion protection requirements for hazardous areas can be found in Directive 99/92/EC. According to this document, elevators are classified as a hazardous industrial facility as they contain an explosive environment - a mixture of air under atmospheric conditions with flammable substances in the form of dust, in which, after ignition, combustion spreads to the entire unburned mixture.

When operating hazardous facilities, it is necessary to:

Assess the risks taking into account the likelihood of explosive atmospheres;
Classify and mark hazardous areas with combustible dusts;
Install explosion protection devices for the equipment.

General requirements of Directive 99/92/EC are specified in national legislation.

Technical solutions

Explosion protection systems are selected on the basis of the operating conditions and the nature of the material to be conveyed. We therefore first carry out a risk analysis in order to determine the explosion protection class and level of protection in accordance with IEC 60079-10-2-2011.

For this purpose, we take combustible dusts for laboratory tests under "controlled explosion conditions". As a result, we determine the explosion hazard parameters of the production facility:

Low Explosion Level / LEL
Maximum rate of explosion pressure rise / (dp/dt)max
Explosion class / Kst
Minimum explosion temperature / MIT
Minimum ignition temperature / GT
Minimum explosion energy / MIE
Oxygen concentration limit / LOC.

Based on this data, we select specific explosion protection equipment. For elevators, we offer the certified ELEVEX version in cooperation with RSBP.
It is suitable for horizontal and vertical conveyors installed inside and outside the building; applicable to equipment is already in operation without costly retrofitting.

The system is certified according to CEN/TR 16829 and the technical regulation TP 012 / 2011.
. Its individual components are also certified according to specialised equipment standards EN 14373, EN 15089, EN 16009 and EN 16447.

ELEVEX is a combination of three explosion protection methods: explosion suppression, explosion overpressure relief and explosion free release. We select the specific devices on the basis of the operating conditions of the elevator.

Explosion suppression

This method is most commonly used to protect bucket elevators, as it is suitable for both built-in and external elevators. The installation of the devices does not require costly retrofitting of existing equipment, and the devices themselves are easy to maintain.

System elements:

Pressure sensors;
HRD barriers at the bucket elevator inlet and at the outlet to adjacent process equipment units;
HRD system for high-speed release of an explosive mixture at the elevator head and in the elevator boot.

The system quickly detects an initial explosion and extinguishes it at the nucleation stage. Explosive suppressants are used for this purpose. The HRD detonation containment system reduces the explosion pressure to safe values, so that the elevator and associated equipment are not destroyed.

Special features:

Sensors detect an increase in pressure in the equipment to be protected within 1 ms;
A signal via the control centre provides an almost instantaneous command to activate the HRD cylinders with extinguishing agent;
Nozzles spray a flat plume (fan) of suppressant, which increases the protected area and effectively cuts off the ignition;
The sensitivity of the system makes it possible to suppress explosions below 0.2 bar, i.e. at the nucleation stage.

Used HRD cylinders are easy to replace. The inerted explosion suppression system, unlike standard explosion detectors, is safe for use where people are working. It also meets the strict hygiene requirements for the food and pharmaceutical industries.

Excess explosion pressure relief

This method is used most often on burrows located outside the building. The main condition for its use is to release the explosion into a safe area, i.e. one where people or adjacent equipment will not be harmed.

System elements:

Pressure sensors;
HRD barriers in the elevator head and elevator boot;
Explosion relief devices - VMP panels.

Special openings are made in the processing equipment to release the shock wave and flame in the event of an explosion. Under normal operating conditions they are sealed by bursting discs of a certain size and shape (explosion dischargers). In the event of an accident these open and release the explosion products to the outside. As a result, the pressure in the elevator falls to safe levels and there is no structural failure.

Special features:

Reduces the pressure quickly to safe values;
Low-cost design and operation;
Applicable to equipment already in operation;
The explosion relief zone is up to 30 m, so that the explosion can only be released via VMP panels in areas that are free of people;
Explosion relief devices are installed outdoors;
The static opening pressure can be regulated;
Panels are available in various shapes and sizes;
The system is effective even when the explosion hazard class of the site is high.

VMP panels are simple to install and easy to maintain during operation. After a failure, they are easy to replace. The panels are also resistant to mechanical damage and unfavourable weather conditions.

Explosion-proof membranes come in flat and convex, round and rectangular, in various sizes. Therefore, it is easy to find a suitable option even for geometrically complex pieces of equipment.

fireless explosion release

This method is well suited for elevators located in enclosed areas. Flameproof explosion protection uses FLEX flame arresters, which consist of an explosion panel and an outer casing with a diffuser surface. They prevent the spread of open flames and quickly reduce the pressure and temperature of the explosion.

Pressure sensors;
HRD barriers in the head and elevator boot;
FLEX flame arresters.

The shockwave and combustion products pass through a system of special screens. Due to the dissipation effect, the temperature of the explosion is reduced from 2600 °C to safe levels, and open flames are prevented from entering the hall with people in operation. At the same time the overpressure is reduced to values to which the elevator design is resistant. Importantly, the process is automatic - no operator is needed to operate the flame arrestor correctly.

Can be installed indoors;
The smoke hazard zone is no more than 1.5 m, which allows you to organise areas that are safe for people to work in the vicinity of the elevator;
Flame arresters are certified for explosive dusts with very low minimum ignition energies (MIE) and minimum ignition temperatures (MIT).

The explosion extinguishing system is easy to install and maintain in operation. It does not require expensive construction work or modifications to existing equipment. Most importantly, the system will reliably protect the elevator from the devastating effects of an explosion and localize the consequences of an accident.

For each type of bucket elevator, we will design a different combination of devices. The principles of explosion protection are the same, but each object requires an individual approach.

Stages of work

Step 1. Evaluate the explosion hazard of the process and equipment.
Step 2. Discuss the technical specifications with the customer.
Step 3. Selection of an explosion protection solution in accordance with the applicable industrial safety legislation, the customer's wishes and the manufacturer's recommendations.
Step 4. Preparation of the project and its approval by the supervisory authorities.
Step 5. We deliver protection systems anywhere in the country.
Step 6. We assemble equipment or provide quality control of third party installation works.
Step 7. We carry out commissioning of explosion protection systems.
Step 8. We provide service and warranty support.

ATEX.CENTER takes care of the effective explosion protection in your plant.

Guarantees

ATEX.CENTER is an official distributor of the leading European distributor of explosion protection RSBP spol. s r.o. Our specialists periodically confirm their qualifications in his commission of expertise.

In cooperation with the RSBP, we have implemented more than 20 large-scale explosion protection projects. Thanks to intelligent solutions we were able to prevent more than 1 260 000 EUR of damage and save the lives of over 600 employees in 5 companies.

We give all our customers the opportunity to visit an RSBP test facility in the Czech Republic to see explosion protection in action.