Environmental enclosures

Environmental Enclosures Enclosures for valve accessories are sometimes required to provide protection from specific environmental conditions. The National Electrical Manufacturers Association (NEMA) provides descriptions and test methods for equipment used in specific environmental conditions in NEMA 250. Protection against rain, windblown dust, hose-directed water, and external ice formation are examples of environmental conditions that are covered by NEMA standards. 

It would not be appropriate to attempt to deal in any detail here with the specialist subject of environmental enclosures and air conditioning. However, considering the relatively small coverage of apparatus in standards such as ISO 23529, it is of value to discuss briefly certain aspects of the subject. 

BS 4833, 1986. Hygrometric tables for use in the testing or operation of environmental enclosures. 

Phosgene is widely used as a chemical intermediate for the production of isocyanates used in polyurethane foams and in the synthesis of pharmaceuticals and pesticides [55]. Processes using phosgene require specialized cylinder storage, environmental enclosures, pipelines, fixtures under negative pressure... 

In situations where these conditions exist, a motor control must be mounted in a fully enclosed environmental enclosure. When installed in a sealed enclosure it is often necessary to add additional equipment to minimize or eliminate the heat generated by the motor control while it is operating. Consult the control manufacturer for recommendations. 

In this case, a high-resolution scanner is used to monitor the electrolytic cells in the tankhouse of a zinc refinery, where acres of acid-filled tanks contain pure metal anode starter plates onto which the refined metal is deposited electrolytically from unrefined cathodes in close proximity. When contact short circuits occur between electrode pairs in the tankhouse, metal production between the shorted pairs is halted, excessive current flows, and power is wasted. An IR scanner, mounted in a fiberglass environmental enclosure on the same overhead crane used to deposit and remove electrodes from the acid bath, maps the process and pinpoints the shorts, allowing service personnel to clear them with minimal exposure to toxic acid fumes. The shorts appear as hot spots on the computer-monitored thermal map. 

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