Open machines — Very few open machines are made today. Most standard motors are drip-proof and guarded, Figure 15, or at least semiguarded. To improve the protection offered by drip-proof enclosures, some manufacturers offer special processes or treatments to protect the windings and bearings.
Totally enclosed machines— Most totally enclosed machines are fancooled.However, some models in fhp ratings
are totally enclosed and nonventilated. Totally enclosed motors are more expensive, but offer better protection. Outside ventilating air and contaminants are excluded from interior parts of a totally enclosed motor. The motor is not airtight,
but usual entrances to the inte- rior, such as the conduit box, are gasketed. Clearances like those around shafts are kept as small as possible.
Explosion-proof machines — Hazardous atmospheres require special totally enclosed motors. Motors for these atmospheres are designed to standards established by Underwriters Laboratories (UL). Only after a motor has been examined and approved by UL can it be sold as an explosion- proof motor.
Washdown — For those applications that are subjected to washdowns with high-pressure liquid cleaners require
more features to protect the motor from severe conditions. These are typically encountered in such industries
as food processing plants and dairies. The motors are housed in a steel enclosure that is covered with an FDA approved epoxy paint or in a stainless-steel enclosure. Seals at every opening are selected to prevent fluids from entering the motor as well as out of the bearings. Inside, all parts are covered with epoxy paint or other material to retard corrosion
Bakery service — For the baking industry, motors similar to the white washdown motors are rated for service
according to Baking Industry Sanitation Standards Committee (BISSC) requirements. Every bend is filleted to prevent material build-up in a sharp bend, fold, or crack. Typically the same internal and external protection is provided as is supplied with washdown motors, and the final finish is a glossy, smooth white.
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