Why are Class I/Division 1 and Zone 1 Induction Machines Employed less and less in Industries Today?

For installation of induction machines (motors) in Class I/Division 1 or Zone 1 hazardous locations, it is important to realize that, due to higher risk of release, Division 1 (Zone 1) requirements are much more stringent than Division 2 (Zone 2). Therefore, the equipment needs corresponding explosion protection methods. There are two types of protection widely used in these locations; they are explosionproof and pressurized enclosure.This paper summarizes those requirements and the applicable standards for the US and Canada For Class I/Division 1, explosionproof is often the most cost-effective technique as the only other alternative, pressurization, requires a significant additional ancillary equipment to support pressurization. However, the explosionproof technique is limited in size due to the physical strength limitations of a large "explosion pressure withstanding enclosure." As the testing often involves multiple samples, it is impractical for a one-off design to employ the explosionproof design.For Zone 1, a flameproof "d" motor is similar construction to an explosionproof motor, but increased safety "e" becomes a practical solution for midsize motors, with only the exceptionally large motors employing pressurization "p".In some cases, changes to the implementation of the process can result in a change to the area classification resulting in a Class I/Division 2 or Zone 2 area classification, allowing, in many cases, ordinary location machines specially in North America, with a far simpler assessment and testing regimen, and less costly installation.