Problem
n food processing plants there are bulk goods which produce combustible dusts during production and transport: flour, grain, sugar dusts. Combined with air it forms an explosive mixture.
Dust settles in hard-to-reach areas of processing equipment. It can accumulate in suction filters if the ventilation system is not efficient enough. Dust is difficult to visualise, but clouds are always present in ventilation systems.
Combined with an ignition source: heated surfaces, sparks from friction, static electricity and others, a combustible dust/air mixture can cause an explosion. In production facilities where there are loose products, the possibility of such an accident cannot be completely ruled out. In accordance with EN 1127-1, explosion protection systems must be provided on them.
Task
The customer entrusted us with providing an explosion protection system for aspiration filters at an operating plant. It was necessary to integrate technical devices into the existing equipment.
Solution
We carried out a turnkey project:
- We determined the explosion hazard parameters for the dust/air mixture;
- Calculated the class of protective equipment required;
- Selected the technical devices from the manufacturer and supplied them from the manufacturer;
- Installed the explosion protection system and harmonized its operation with the existing process flow;
- Carried out commissioning and start-up of the devices.
All work stages were carried out in accordance with ATEX standards.
The result
As a way of protecting the suction filters against explosion, we have applied explosion relief by means of EX DOOR explosion-proof doors. Such devices were chosen for a number of reasons:
- This is a cost-effectivel solution. The doors are fastened on magnetic holders and can be easily detached in an explosion. After an accident, it is sufficient to lift them up and put them back, without replacing them with new ones.
- The particular characteristics of the customer's production facility made it possible to apply the blast release to the environment. Firstly, there were no people working in the area and there was no adjacent equipment that could have been damaged by the blast release. Secondly, there were no pressure surges in the customer's process, so magnetic panels could be applied.
The working principle of EX DOOR explosion-proof doors is simple. During the normal course of a production process, the panels close special openings to release the explosion. During an accident, the pressure in the equipment to be protected rises. When it reaches certain values, the door opens and releases an explosion shockwave to the outside. The pressure is reduced to values that are safe for the equipment and there is no destruction of the structure.
In addition, we have installed passive explosion protection devices -B-FLAP check valves - in the aspiration pipes. They are used to contain an explosion and prevent explosion products from penetrating into adjacent equipment.
Under normal process conditions, the B-FLAP check damper is open due to the energy of the air flow, or locked by the RPD mechanism. In the event of an explosion, it is closed by the air shock wave and locked in the closed position. This is how the mechanical check valve prevents an explosion from spreading through the pipework.
We applied these cost-effective explosion protection methods based on the operating conditions. In this project, we did not have to design the devices for pressure surges, hazardous gas environments or the presence of people. We believe that every explosion protection project must be carried out individually. Template solutions increase both the risk of an accident and the customer's costs.