How operators not only increase production safety but also reduce costs by using groundbreaking protection against dust explosions and what part new standards play.
Spray-drying plants are an ideal application for the protective measure of “explosion venting” and they are primarily used in the chemical and food industry, e.g. to produce milk powder or soluble coffee powder. The food is finely pulverized in a drying tower using jets or rotating discs. The powder-like product is then using hot gas.
This process poses a severe explosion risk, as flammable dust swirls about in the spray-drying tower. Consequently, the atmosphere is potentially explosive. If an ignition source were then also to occur, an explosion would be unavoidable. For this reason, it is necessary to provide suitable protection systems in these plants. There are new design principles for this now according to the new VDI 2263 Sheet 7 guideline, which deals with dust fire and explosion protection in spray-drying plants (Dust fires and explosion protection – Hazards, assessments, protective measures).
The guideline now takes into account that various influential operating factors during spray drying may reduce the violence of the explosion compared to other dust plants. Product moisture, dust concentration and the working temperature play an important role in this.
New, groundbreaking methods of calculation: less volume means smaller venting areas
The KSt value, among others, is influenced considerably by the dust concentration. In terms of designing pressure relief suitable for practice, a realistic dust concentration for spray-driers is assumed. This is different to the concentration with which maximum violence of explosion is to be expected. Extensive analysis and concentration measurements by experts from the VDI working party allow for a new, groundbreaking method of calculation. This leads to significant reductions in the venting area required, de facto to smaller or a lower number of bursting discs.
As well as these safety-technical requirements, additional demands are placed on those types of protection systems that should not conflict with the product’s quality assurance.
However, since every protection system is connected to the container to be protected, the risk of undesired product contamination is a concern due to the accumulation of possible sediments. This risk should always be taken into consideration particularly when engineering plants processing food or pharmaceuticals.
To address this requirement, the flat bursting disc EX-GO-VENT-HYP has been especially developed for hygienically demanding applications found in the industries of food processing and pharmaceuticals. The smooth surfaces, in connection with the patented, full surface and tapered sealing concept, enable the implementation of these special bursting discs in previously critical plants such as spray-dryers with/without wet cleaning, fluidized bed dryers, filters and mixers. To ensure a wide-spread acceptance of the application in operational practice, the design of the EX-GO-VENT-HYP is based on the strict criteria of EHEDG (European Hygienic Engineering & Design Group).
As the EX-GO-VENT-HYP can be shaped to the plant radius and undesirable dead spots can thus be avoided, it is also ideal for use in cylindrical plants. If installed in outdoor areas, deposits caused by dropping below the dew point are avoided by the optionally available closed cell silicone cushion insulation. Loss of temperature and energy is kept to a minimum.
As a result, the EX-GO-VENT-HYP special bursting discs with their sanitary design improve product quality and at the same time protect the process against contamination and loss of production.
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The flat bursting disc EX-GO-VENT-HYP has been especially developed for hygienically demanding applications found in the industries of food processing and pharmaceuticals. If installed in outdoor areas, deposits caused by dropping below the dew point are avoided by the optionally available closed cell silicone cushion insulation.
Authors:
Roland Bunse
Head of Explosion Protection Department
REMBE® GMBH SAFETY + CONTROL
T +49 2961 74 05 – 112
epd@rembe.de
Johannes Lottermann
Head of Projects + Expansion Department
REMBE® GMBH SAFETY + CONTROL
T +49 2961 74 05 – 122
johannes.lottermann@rembe.de
