1. Calculation of explosion relief area

If the explosion relief plate is used for the explosion relief of the dust remover, the commonly used marks for calculating the explosion relief area are: GB / t15605-2008, en14491-2012 and nfap 68-2013. At present, there are some problems in the calculation of explosion relief area in China, mainly including:

1) Instead of calculating the explosion relief area according to the relevant standards, the size of the explosion relief plate is selected according to the empirical value or the size of the dust collector. The result may be that the area of explosion relief is not large enough, which will affect the effect of explosion relief, increase the explosion relief pressure in the precipitator, and cause the deformation or damage of the precipitator;

2) Do not know the explosion characteristics of dust, such as KST, Pmax, etc.; the explosion characteristics of dust KST and Pmax are the most important and necessary parameters for the calculation of dust explosion area. The general method is to refer to the KST and Pmax values listed in the relevant standards, but there are differences between the reference dust and the actual dust in particle size, particle shape, humidity and other aspects. The most reliable method is to test the dust explosion characteristics to obtain the KST and Pmax values of the actual dust;

3) The selection of parameters for the calculation of explosion relief area is unreasonable, such as the values of Pstat and PRED; these two values will affect the calculation results of explosion relief area, such as: when the pred value is smaller, the calculated explosion relief area will be larger; when the pred value is larger, the calculated explosion relief area will be smaller. The value of PRED is related to the strength of the dust collector;

The dense distribution of filter bags or cartridges inside the precipitator significantly slows down the propagation of the explosion, which may spread along the filter bags or cartridges. In any case, because of the cooling effect of the filter bag or cartridge and no turbulence between the filter bags or cartridges, the propagation speed of the explosion will be reduced.

In the latest en14491 and NFPA 68 standards, it is allowed to select the volume of the dust remover used for the calculation of the explosion discharge area by comprehensively considering the volume of the filter bag or cartridge, the spacing between the filter bags or cartridges, the layout of the explosion discharge plate and other factors.

GB / T 15605-2008 standard 5.2.2 requirements: container volume does not include the volume of obstacles. If there are obstacles in the container (such as filter bag, envelope, filter cartridge), the volume of the container shall be less the volume occupied by the filter components or the volume surrounded by the filter medium.

It is recommended to contact a professional manufacturer or relevant personnel to calculate the area of explosion relief when selecting the explosion relief plate.

2. Arrangement position of explosion relief plate

The bursting disc can be installed on the side or top of the dust remover (depending on the mechanism of the dust remover). Please note that the filter element of the dust remover will affect the dust explosion process and hinder the venting of the venting plate!

The common mistake is the location of the relief plate. In case of dust explosion, the explosion relief piece is opened, and the explosion pressure wave flows outward. The explosion pressure wave blows the filter element or filter bag to the opening of the explosion relief piece, and the filter element or filter bag blocks the explosion relief piece, affecting the explosion relief, resulting in low explosion relief efficiency of the explosion relief piece, increasing the explosion relief pressure in the dust remover, which is greater than the design explosion relief pressure value (PRED) of the dust remover, which may cause deformation of the shell of the dust remover, or even Rupture.

5.2.2 of GB / T 15605-2008 requires that the explosion relief process shall not be blocked by obstacles, so the filter frame shall not cover the pressure relief port. If obstacles cannot be avoided to block the pressure relief port, reasonable pressure relief efficiency shall be adopted in the calculation of pressure relief area.

It is suggested in EN14491 that the bursting disc should be installed at the place where it is not easy to be blocked, which generally means that the bursting disc should be arranged at the lower part of the filter bag or the filter barrel or the filter bag or the filter barrel near the installation position of the bursting disc should be removed. According to NFPA68 standard, different discharge volume is selected according to the arrangement position of discharge plate.

3. Relief method of relief plate

When the dust remover is located outdoors, a safe place is needed for the explosion relief of the bursting disc. If there is no other production equipment and artificial channel around the relief plate and there is enough space for pressure relief, the relief plate can be used as an explosion relief device.

When the dust collector is located in the room, the explosion pressure shall be led to the outdoor safety area through the pressure relief conduit for explosion relief. When the pressure relief conduit is used for explosion relief, the length, angle, size and maximum explosion relief pressure of the pressure relief conduit shall be designed and arranged according to relevant standards. If the explosion relief conditions are not allowed, flameless vent or explosion suppression technology and equipment shall be used.