Fine dust particles combine with air to form an explosive mixture. During transport or loading/unloading it accumulates on the walls of the hopper and in the hard-to-reach joints of adjacent equipment. It is impossible to visually determine when it has reached a dangerous concentration.
There may also be ignition sources in storage bins. According to EN 1127-1 these are e.g:
- Heated surfaces;
- Sparks of mechanical origin;
- Static electricity;
- Hot dust particles.
In an enclosed tank space, the combustible dust/air mixture and the ignition source lead to a local explosion. The shock wave displaces the burning dust further and a series of secondary explosions occur - dangerous to people and destructive to equipment and facilities.
As an accident cannot be completely ruled out in aspiration filters and storage hoppers, explosion protection systems are used
We were given the task of carrying out a turnkey project in an existing plant. The task was to design an explosion protection system compatible with the installed equipment, select suitable technical devices and install them on site.
The unique nature of the project was due to the limitations of the conditions of the existing plant. We had no investment margin to upgrade the customer's equipment, so cost-effective solutions were required. In the end, we were able to do without increasing the cost of the project.
Our experts carried out an audit of the customer's plant and classified the hazardous areas in accordance with EN 1127-1. Based on these results, we carried out the following work stages for the customer:
- We calculated and selected the necessary equipment;
- Supplied it from the manufacturer;
- Carried out installation and commissioning, including integration of the explosion protection system into the existing process flow;
- We have put the devices into operation and tested them.
All work was carried out in accordance with ATEX standards.
We have installed VMP steel explosion-proof panels for the explosion protection of the filters. These are passive explosion protection devices for releasing explosions into the environment.
Special openings (ducts) have been made in the process equipment, which are covered by explosion protection panels during the normal course of the process. When an explosion occurs, the pressure in the filters rises. When it reaches certain values, the panel opens and releases explosion products into an unoccupied area where no persons are present.
The advantages of explosion-proof panels:
- Five designs for various operating conditions, with a temperature range of up to 240 °C.
- Large selection of sizes and different types of design: rectangular, round, convex and flat;
- Resistance to mechanical damage due to the material
- Simple installation- assembly according to prefabricated drawings and manufacturer's instructions;
- Installation without structural modifications to the existing process equipment;
- Simplicity of maintenance - only visual inspection for cleanliness and integrity of the blast panel is required;
- Easy replacement after a failure;
- Long service interval - once a year.
We have used EX DOOR blast doors to protect bunkers. They are similar in principle to explosion panels, but are designed for repeated use.
An explosion door is a blast pressure relief device with magnetic fasteners. Under the action of the shockwave, the EX DOOR is torn away without damaging the structure. After an accident, the door simply has to be lifted and put back in place. This significantly reduces downtime due to repair work.
VMP and EX DOOR blast doors were used in this project as the most economical solutions. The customer's operating conditions allowed for this type of explosion protection.
We would like to point out that explosion dischargers cannot be used where people are working or in the vicinity of adjacent equipment. In such a case, FLEX flame arresters are additionally used. Each explosion protection project must be carried out individually.