Enclosure class types

It is not unlikely that there may be some confusion in the reader s mind, after going through so many ways of area classifications, again, each class further divided according to material types. Also, these are not uniform across standards. For example, in ATEX for dust in mines, and other than mines, have different representations and ignitable fibers mentioned in the United States standard is not separately treated in other standard. In order to circumvent the situation, a small comparative study has been presented after, so the reader can understand the same properly. In order to supplement Table X/3.2.3-3, at this point some detailed comparisons of various standards have been presented in Table APII/2.2-1 and Fig. APII/2.2-1 (mainly for enclosure class) to get a better grasp on the issue about applicability (as per location/ country). 

Motor enclosures for outdoor use are NEMA weather-protected Type II, totally enclosed, fan-cooled, or drip-proof with weather protection. Motors of the latter type are widely used. Not only are they less expensive than the other types, but they also have a service factor of 1,15. The above enclosure types are all suitable for the Class I, Group D, Division 2 classifications usually encountered. 

These enclosures are designed to meet the applicable requirements of the National Electrical Code (NFPA 70) for Class I Groups A, B, C, or D hazardous locations that may be in effect. In this type of equipment, the circuit interruption occurs in air. 

Bottle systems are more varied, whether for glass, polyethylene terephtha-late (PET) or other plastic. Bottles are rinsed with oxonia solution and then sterile water prior to filling. The filler is generally of a non-contact type (it does not touch the bottles) and product is either weighed in or measured volumetrically. Caps are also chemically sterilised (unless a foil closure is used) and applied on a capper monoblocked with the filler, enclosed in a high efficiency pure air (HEPA) filtered enclosure. The filler and final rinser are in a class 100 room and file operator wears full protective clothing to prevent infection of the product. 

Motors shall be squirrel cage induction type with (totally enclosed, fan-cooled) (encapsulated) (splashproof) enclosure and roller-type bearings with NEMA Class A insulation. Motors shall be (single... 

Figure 2.5 The zone 2 concept according to VDE 0165/1991-02. Requirements for electrical apparatus with arcs or sparks in normal operation and/or temperatures exceeding a defined limit/temperature class. Two types of protection are defined here the schwadensicheres Gehause , comparable with a restricted breathing enclosure , and simple pressurization .

Classification and marking of intrinsically safe apparatus concerning explosion groups (I, IIA, IIB, IIC) and temperature classes (T1-T6) are organized in the same way as for, e.g., flameproof enclosure - d (see Tables 4.1 and 4.2, Chapter 4, and Chapter 5 for marking). Some special features, however, which are of importance for type of protection intrinsic safety - i only, will be explained in the following. 

Figs 6.72 and 6.73). Sparking components (e.g. fuses, contactors, circuit breakers) inside or parts not complying with the temperature class of the assembly are individually protected by an independent type of protection (for the most part in a flameproof housing). More recently, attempts have been made to introduce pressurized switchgear assemblies onto the market (Fig. 6.19). In the USA, the classic solution has been a flameproof enclosure with the conduit technique, see Fig. 6.83. 

Type e is also called increased safety and intended for apparatus that is to be installed in a Zone 1 area. Two of the allowable features of the type d enclosures, namely permitting sparking components and no Temperature Class hmit to the internal components, cannot be incorporated into the type e designs. The practical aspect of this is the removal of a source of ignition i.e. a spark or a hot surface. In many types of equipment e.g. luminaries, terminal boxes, junction boxes, some designs of motor control stations, telephones and public address speakers, the elimination of these two sources of ignition is not a difficult problem. 

An enclosure intended for indoor use in the atmospheres and locations defined as Class I, Group A, B, C or D in the National Electrical Code. The letters A, B, C or D, which indicate the gas or vapour atmospheres in the hazardous location must appear as a suffix to the designation Type 7, to give the complete NEMA designation. 

A special merit of this host-type is that the inclusion cavity disposed is easily to tune to the geometric and steric requirements of the guest enclosure by altering the bulk of the side arms. However, guest inclusion showing a distinct specifity against different classes of compounds, i.e. chemoselectivity control, are not feasible on a desirable scale. 

Table 3.7 provides a summary of the characteristics of the three types of Class II biosafety cabinets. Class II biosafety cabinets are intended for low- to-moderate-risk hazards. As a minimum, they should be required to meet the National Safety Foundation (NSF) Standard 49 for Class II (laminar flow) a biohazard cabinetry. The working enclosures and plenums through which air moves should be constructed of materials that are easy to decontaminate, such as staMess steel or a durable plastic. 

Cautionl U.S. NEMA class and European IP ratings are not always equivalent (NEMA 12 IP 54) Both the dust and water tests must be performed according to EN 60529 with passing results. Enclosures often fail the IP requirements, especially the dust tests. It is best to use a type-approved and marked (VDE/TUV) enclosure to ensure conformity. 

Many modern downstream processes involve the use of equipment items that are relatively compact yet possess high process capacity and are capable of remote, even pre-programmed control. Enclosure within Class III type cabinets offers a practical and reliable means of ensuring that such process steps can be carried out without risk of release of potentially hazardous products into the workplace environment. 

This paper presents Monte Carlo calculations by both the GEM 4 and KENO codes for critical arrays of 2, 3, and 4 kg plutonium metal pieces and critical arrays of lOL and 3L Dow type shipping containers of fissile solutions, These calculations indicate that the assumption of a water reflector, as specified for Class n and ro shipments in Federal and IAEA Regulations would result in a critical array of metal units three times larger than one reflected by concrete. Care, then, must be exercised when shipments that meet regulations are to be stored within concrete enclosures. 

Type 1 protection. When Type 1 protected, the equipment is damaged (i.e., SCRs are shorted) and needs to be repaired, bnt the wiring and enclosure are intact. Type 1 protection is usually given by circuit breakers and class H, K, R, and RK-5 fuses. 

Non-electrical equipment of the equipment group II, category 2 for explosive atmosphere formed from air and gases, vapours and/or mists, type of protection flame-proof enclosure, permissible explosive atmosphere of the Ex-Group IIB, T-Class T4, ambient temperature (T ) with 0°Cdiffering from the standard values -20 °C < T. -t-TO C ... 

Main motors need starter overload and short circuit protection. High rupture fuses (HRC) will protect the motor against short circuit conditions, and will interrupt the electrical supply in milliseconds of the fault occurring. It is essential that fuses of this type are always fitted. Conventional overload protection, thermal or magnetic, can offer no protection to a motor with an extended acceleration time. Thermistor overload protection is the only true protection for a motor under these conditions. A thermistor is embedded in each of the motor s three windings and connected in series. The resistance of these thermistors is designed to increase rapidly at a set temperature, depending upon the insulation class of the motor. The thermistors are connected to an electronic amplifier control unit in the starter enclosure, and will trip the starter contacts when required. The device will not reset until the motor has sufficiently cooled. 

We can, broadly speaking, discern two classes in relation to the behavior of water near surfaces nonfreezable (i.e., most tightly bound or, alternatively, confined within very small enclosures) and freezable water. This second class reflects various degrees of water-amphiphile(s) interactions and, accordingly, subsumes several types (or states ) of water. We may use the following classification of Senatra et al. [4] ... 

---