Many factories work with ‘hazardous’ substances. I have used the word factory rather than chemical factory as this applies equally to bakeries, sweet factories as well as factories manufacturing ‘plastic’ products. The word hazardous is in brackets, as some of the products are in our daily life not hazardous, e.g. sugar, flour, stearates etc.
The substances that are referred to are ones that have the potential to form flammable or explosive mixtures in air and under certain conditions could explode. Solvents are known to form explosive mixtures and between certain concentration levels are extremely explosive. The same applies to certain powders, e.g. sugar.
The explosion normally has two parts to it. The first is a small explosion, setting off enough energy to cause the secondary large explosion. The second explosion very often has devastating effects. The source of energy can come from various sources. In factories where these explosions are possible, certain machinery have to conform to minimum standards – they have to be e.g. explosion proof or flame proof or intrinsically safe, depending on the environment they are in.
In order to know what equipment needs to be where it is important to first classify the entire plant into zones. There are specific rules to follow in order to classify a plant or factory. Factors that affect the zoning are the products used, the distance of the product from the potential source and the integrity of the plant itself.
In terms of the Electrical Machinery Regulations Reg. 8 the owner must classify the hazardous locations and than ensure that the correct equipment is used in the specific area (zone). Every piece of electrical equipment used must (a) be issued with a certificate from the manufacturer specifying that the equipment complies with the specific rating and (b) it must be certified at least once every two years that it still conforms to the standard it was supplied under. If the equipment (including an installation) has been opened it must be re-certified once the work on it has been completed.
The re-certification of the equipment can only be done by a person who is competent to express an opinion on the safety there of (e.g. master electrician).
In these types of environments static electricity is also a major danger (they are often the initial source of energy to start the first explosion). It is therefore of utmost importance that all equipment and structures are properly earthed and that the effectiveness is tested on a regular basis by an electrician.
The effect of one of these explosions / fires is devastating. Remember they happen regularly and be aware and ensure that your factory is not a casualty!
Written by Frans Wilbrink of Wilbrink & Associates, tel. 031 – 266 9035