Hazardous Area Weighing Load Cells from Thames Side
Equipment and products operating in hazardous areas are required to meet stringent criteria. They must be 'protected' to avoid the possibility of them becoming a source of ignition. Weighing systems are often an integral part of a process within the hazardous area and therefore must have suitable protection.
Hazardous areas are essentially designated places where the presence of certain materials, such as gases, dust or fibres make an explosion probable if a source of ignition is introduced. (Probably the best known example of a hazardous area is the petrol station.)
Three essential elements are required for an explosion to take place:
- Gas, mist, vapour or dust in sufficient proportions.
- Sufficient supply of air or oxygen.
- Source of ignition
This clarifies the reasons for implementing hazardous weighing areas.
Hazardous area apparatus is classified according to the maximum temperature produced under normal or fault conditions at an ambient temperature of 40C. It goes from T6 classification, which allows a maximum surface temperature of 85C (no known products have an ignition temperature as low as this), to T1, which allows a maximum temperature of 450C.
As with legal for trade approval, hazardous area certification requirements differ between the US and Europe. However there is growing cooperation between the US authorities and CENELEC. The 1996 edition of the National Electrical Code ANSI/NFPA No 70 has introduced article 505. This allows for an alternative area classification scheme based on the IEC three zone system and identifies the areas as Class l, Zone 0,1; Group llA. B or C as applicable. Introduction of this three zone system allows the use of protection concepts already in use in Europe.
Thames Side Sensors is a market leader in the design and manufacture of industrial Hazardous Area Weighing Load Cells. We have developed a range of load cells specifically designed for the rigours of Hazardous Area Weighing Load Cells applications.
All have certification to ATEX Ex ia IIC T6 for both dust and gas in all zones and several models have Ex nA II T6 gas only certification which allows Zone 2 use without safety barriers.