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Explosion protection for dryers

Our company, ATEX.CENTER,
specialises in expert technical solutions for production facilities with explosive dust/air mixtures. Since 2019, we have been an official partner of the European manufacturer of explosion protection systems RSBP spol. s. r. o.

Explosion hazard of dryers

A large number of modern dryers are available on the market with automation to prevent fires. Legislators impose stringent requirements on the production control as well as on the qualifications of the personnel in the storage and processing facilities for plant raw materials. The aim of all measures is to ensure the safe operation of the equipment.

Nevertheless, dryers burn and explode. Every year 400-500 explosions occur in grain processing facilities worldwide. The most frequent accidents occur in equipment: elevators, dryers, crushers, conveyors and fans (about 50%).

The main source of explosion hazard in storage and processing facilities is combustible dust. Its explosiveness depends directly on the type of plant material and the presence of fine combustible impurities in it.

A primary explosion occurs, from which the shock wave propagates the flame and dust-air mixture further. This is followed by a secondary explosion, or even a much more destructive series of explosions.

The storage and processing facilities for plant materials are classified as hazardous industrial facilities (HIFs).

Sources of explosion initiation

In Europe, Russia and Ukraine, the EN 1127-1-2014 standard is in force. It lists 13 active ignition sources which, in contact with a combustible dust/air mixture, can initiate an explosion.

In dryers, ignition may be caused by:

electrical sparks, e.g. caused by friction between the dirty fan blades and the cover;
static electricity;
overheated coolant or surfaces;
spontaneous combustion of grain;
sparks from burning fuel;
short-circuiting;
sparks during engine start-up;
sparks from a cigarette when personnel do not follow the safety instructions.

Very often fires and explosions occur due to worn equipment, "human error" and failure to enclose hazardous areas.

Explosion and fire hazards in dryers are virtually unrelated to their design if the equipment is operated correctly and timely maintenance is carried out. It is the drying process in which combustible dust meets the source of initiation that poses the risk.

Safety standards for the owner of a HIF

The minimum explosion protection requirements for hazardous areas, including grain dryers, are laid down in Directive 99/92/EC. This defines an "explosive environment" as a mixture of air under atmospheric conditions with flammable substances in the form of gases, vapours, mists or dusts in which, after ignition, combustion spreads to the entire unburned mixture.

The owner of a HIF must:

carry out a risk assessment taking into account the probability of occurrence of explosive atmospheres;
classify and mark hazardous areas with combustible dusts;
install explosion protection devices on equipment.

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

Technical solutions

We will carry out a risk analysis to select a suitable explosion protection option. We will take combustible dusts for laboratory tests under "controlled explosion" conditions to determine their explosion hazard parameters:

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

Knowing these parameters and the location of the dryer, we will design an explosion protection system and select suitable equipment.

ATEX.CENTER is an official distributor of RSBP spol. s r.o. We supply products from a manufacturer of explosion protection systems with 30 years' experience. Its mission: "Safety comes first".
For spray dryers, we offer, in cooperation with RSBP, two basic options of explosion protection, depending on the location of the facility.

Explosion suppression + explosion venting

This option is suitable for dryers located inside knowledge where it is not possible to vent the explosion to the outside. It is also used where there is handling of toxic materials.

The explosion protection system consists of HRD barriers and an HRD system for high velocity venting of an explosive mixture. It quickly detects an initial explosion and extinguishes it before the negative effects spread in the protected area. Explosion suppressants are used for this purpose.

The three key elements of the HRD system are the pressure sensor, the HRD container with valve and the CONEX control unit which is connected with the main control system

Special features:

HRD system actuation from detection to isolation of the dangerous process segment from the rest of the equipment in milliseconds;
continuous monitoring and archiving of sensor data;
variability in the location of sensors and HRD containers;
easy replacement of used HRDs;
safe use in enclosed and open areas;
full compliance with sanitary regulations in the food and pharmaceutical industry.

The equipment is certified in accordance with the standards and technical regulations of TR CU 012/2011, TR CU 032/2013, TR CU 004/2011, TR CU 020/2011 and EN 14373.

The HRD barrier consists of the same components as the HRD system. In it, nozzles of special geometry distribute the explosive suppressant in a flat plume (fan). It cuts off the ignition and blocks the shock wave.
Flameproof venting is another system for installation inside buildings. We offer flame arresters FLEX, consisting of an explosion-proof panel and an outer casing with a diffuser surface.

When triggered, the released explosion products pass through the grid system. This ensures that the flame front does not affect the factory floor. The temperature of the blast wave reaches up to 2600 °C, and thanks to the dissipation device, the flame and combustion products are cooled down to a level that is safe for both machinery and personnel. No operator is needed to operate the flame arrester correctly.

Special features:

Possibility of indoor installation;
Effective flame arrestor and temperature reduction;
Creation of a safety zone for process equipment, buildings and people;
Up to 1.5 m smoke hazard zone;
Suitable for the food and pharmaceutical industry;
Easy installation and replacement;
Certified for explosive dusts with very low minimum ignition energy (MIE) and minimum ignition temperature (MIT) values.

Certified in accordance with EN 16009 and the technical regulation TP 012/2011.

VMP panels for explosion pressure relief

Suitable for spray dryers where the explosion can be vented outside the building using so-called baffles, or for cyclone separators and filters located outside the equipment, within the safety zone.

This option uses bursting discs of a specific size and shape. When the operating pressure inside the equipment exceeds the operating level, they open, releasing the pressure and flame from the hazardous area to the outside. In this way, the pressure does not exceed the stability limit of the structure and destruction does not occur. Explosions can only be released into safe areas.

Special features:

flame drop zone - up to 30 m;
outdoor installation;
easy installation and after-sales service;
adjustable static opening pressure;
large range of shapes and sizes;
resistance to mechanical damage and weather conditions;
high efficiency at high Kst.

Certified in accordance with EN 14797 and technical regulation TP 012/2011.

We will design our own version for other types of dryers. The principles of explosion protection are the same, but each facility requires an individual approach. The choice of explosion protection equipment depends on the type of dryer and its operating conditions.

Work stages

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 will take care of the effective explosion protection of your production.

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.