In the case of the tests described below, there has not been applied the so called explosion decoupling (or explosion isolation) which consists in an immediate closure of the pipelines connecting the apparatus with the rest of the installation. It is a common mistake frequently encountered at process plants. Tests 1-3 were in. al. to show how the effects of an explosion in one apparatus can pass through canals, transfer points and pipelines to the rest of the system (even if a system of explosion relief or suppression has been applied). Such explosion propagation may lead to a secondary explosion in neighbouring apparatus and consequences of such an event are impossible to predict. During testing, this phenomenon has been illustrated with the use of a dummy standing at the outlet of the pipe.
TEST 1 – explosion of dust tea in a filter protected with a decompression panel
In the first test, an electric spark generated inside the filter led to the ignition of a cloud of tea dust. The explosion caused a sudden increase of pressure in the apparatus and this in turn opened the decompression panel. The excessive pressure and flame were released to the environment, which protected the apparatus from damage.
It should be noted that in industrial practice, it is necessary to determine a danger zone in the area of decompression panels, where people, communication tracks and other process equipment cannot be situated. The danger zone may range from several meters to several tens of meters. The system of protection with anti-explosive panels cannot be used for toxic and harmful products.
TEST 2 – explosion of dust tea in a filter protected with a flameless explosion relief
The first phase of the demonstration proceeded in the same way as in test No. 1. The explosion of a cloud of tea dust led to a sudden increase of pressure in the filter. As a result, a flameless explosion relief was activated (the system was installed on the roof of the filter). This time, the protection system stopped the ball of fire inside the filter and only residual pressure of the explosion, posing no threat to people or equipment located in the immediate vicinity, was released to the environment.
From the technical point of view, flameless explosion relief systems are a combination of a decompression panel with an efficient, perforated heat exchanger. The latter is responsible for putting out a ball of fire and releasing gradually the explosion pressure to the environment. As a result, the solution (as opposed to decompression panels) can be used in confined spaces and within tightly mounted installations.
TEST 3 – explosion of sugar dust in a filter protected with the HRD explosion suppression system
During the first two tests, we could observe the effectiveness of passive anti-explosive systems which were activated as a result of an increase in pressure in the protected apparatus to the preset level (without participation of detection and control systems). In the third test, the HRD explosion suppression system was used as a protection. Its task is to detect immediately an explosion source (with the use of pressure sensors and/or infrared) and then to suppress it by injection of a special powder into the explosion interior. The time from detection of an explosion to explosion suppression is counted in thousandth parts of a second. Thanks to the so rapid response, the system prevents excessive pressure increase in the apparatus and protects it against possible fire.
Due to the principle of explosion suppression applied, the system is the most universal method of protection against explosion that can be used both indoors and outdoors. Furthermore, it can be used in the food industry, as well as for toxic substances.