Problem
On the customer's production line, the sugar is conveyed to the collector using a pneumatic conveying system. In the process, a cloud of icing sugar forms, which combines with air to form an explosive mixture. Due to the dusty sugars, the pneumatic conveying section and the collection system have been classified as ZONE_20 in accordance with ATEX.
For reference. Explosive Zone 20 is an area in which combustible dust in the form of a cloud is present continuously or partially during normal operation of equipment, in an amount capable of producing a concentration sufficient to produce an explosion of combustible or flammable dust in mixtures with air; and/or where layers of dust of arbitrary or excessive thickness may form. This may be clouds within the dust content area where dust can form explosive mixtures frequently or for long periods of time.
The aspiration system installed at the customer's site was not able to cope with the sugar dust cloud. Sucrose has a tendency to stick together and due to insufficient ventilation capacity it was partially clogging the filters.
Task
The customer commissioned us to provide explosion protection for the sugar collector and to upgrade the aspiration system. The project was carried out on a turnkey basis.
Solution
We carried out the following work for the customer:
- Preparation of the technology project for the explosion protection system and modernisation of the aspiration system;
- Supply of equipment from the manufacturer;
- Installation and commissioning of the explosion protection system and the industrial aspiration system;
- Commissioning of the equipment and putting it into operation.
All work was carried out in accordance with ATEX standards.
The result
To protect against the explosion, we applied two methods:
- Flameless release of explosion energy, as there were people working near the sugar collector all the time;
- Cutting off the explosion.
We installed two FLEX R3 flame arresters. These are flameless explosion release devices, rectangular in shape and with a curved surface. Due to their design, they are suitable for rooms with complex geometry and small dimensions.
The FLEX R3 flame arrestor consists of two main elements:
- Explosion protection panel. Used to release the energy of an explosion in the equipment to be protected into the surrounding area. In the event of an accident, the panel opens and releases the shock wave to the outside. As a result the pressure in the equipment drops to safe values and the structure is not destroyed. The "open/closed" position of the explosion panel is monitored by an alarm device.
- External casing with scattering surface. This is a construction of special meshes which cool the blast wave and prevent the spread of open flames and burning particles. It is used to protect people and adjacent equipment when an explosion is released in enclosed spaces.
Additionally, we have installed an HRD barrier in the pneumatic conveying system. This is a technical device to limit the spread of an explosion, it isolates the sugar collector from the associated equipment. .
Special sensors in its design detect changes in pressure and temperature rise when sugar dust ignites. They transmit a signal to the controller, which in turn sends a command to the HRD to activate the sugar canisters. The entire process takes no more than 60 ms.
We also replaced the customer's aspiration system with industrial equipment of higher productivity.
The combination of two explosion protection methods and a ventilation retrofit allowed us to reliably protect people and operating equipment against possible explosions of the dust/air mixture in the sugar collector..