Enclosures, Cabling & Connectors

Polyester vs stainless steel enclosures

January 2014 Enclosures, Cabling & Connectors

Elen Enclosures says that one of the most common requests it gets is from customers requesting a stainless steel enclosure because it needs to be strong and survive in a corrosive environment. As it turns out however, stainless steel is not always the best choice. In fact, money can be saved by choosing a more suitable material for the application.

The use of stainless steel (ie, grades 304, 304L, 316 and 316L) in the manufacture of enclosures is intended for applications where hygiene is a consideration. This is because it is easily cleaned or disinfected and therefore provides an excellent solution in the food, beverage and pharmaceutical industries. While stainless steel is strong, once it is dented it is almost impossible to get it back to its original shape to maintain the sealing. It is also a good conductor of heat, so there is always the risk of overheating the internal components when mounted in hot areas in full sun.

When it comes to corrosion resistance, stainless is excellent for certain types of chemicals but not that great for others. Chemicals that negatively affect it include aqua regia (platinum concentrators), hydrochloric acid (20% - 100% concentrations, and dry gas), hydrofluoric acid, sulphur dioxide, sulphuric acid, chlorine water (water treatment plants) and sea water.

The enclosure material of choice for harsh corrosive industrial applications, where hygiene is not a concern, is polyester: to be more specific, sheet-mould-compound glassfibre reinforced polyester (GRP). It is high-temperature high-pressure moulded to produce a strong enclosure wall structure with impact resistance rating of IK10. Wall thickness is approximately 3-4 mm. GRP is resistant to the chemicals mentioned above as well as others, is easy to work with and is about half the price of a stainless steel equivalent.

While UV does affect the surface slightly, tests and experience show a loss of about 5 microns per year in full sun. This is insignificant with a 3-4 mm wall thickness on the enclosure. After many years in the plant the surface may look a bit rough, but nothing else in the dirty corrosive environment will be looking particularly pretty either. The mechanical strength and sealing of the enclosure is not affected by this at all.

So, for system installations at breweries, dairies or pharmaceutical factories, a grade 304L stainless steel enclosure IP66 certified and manufactured by Schneider Electric Universal Enclosures is the ideal solution. However, for an enclosure that needs to live out the rest of its days in a filthy, corrosive environment, a GRP enclosure is the solution. That is, a GRP enclosure made of one-piece-moulded base with an integral canopy over the top and bottom of the door, locks that are situated outside of the sealed area and non-rusting hinge pins. The Schneider Electric Thalassa PLM series is ideal for these applications.

For more information contact Elen Enclosures, +27 (0)11 472 2220, sarelza@mweb.co.za, www.sarel.co.za


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