Class III equipment

Equipment shall be approved not only for the class of location but also for the explosive, combustible, or ignitable properties of the specific gas, vapor, dust, fiber, or flyings that will be present. In addition. Class I equipment shall not have any exposed surface that operates at a temperature in excess of the ignition temperature of the specific gas or vapor. Class II equipment shall not have an external temperature higher than that specified in Section 500-3(1). Class III equipment shall not exceed the maximum surface temperatures specified in Section 503-1. 

Article 503 of the NEC (National Electrical Code, USA) limits maximum temperatures for Class III equipment (suitable for ignitable fibres and flyings) to 165°C (equipment not subjected to overload) and to 120°C for equipment which may be overloaded. Thus, only temperature classes T3B, T3C, T4 and T4A, T5, T6 are applicable... 

Class III Equipment and Systems systems representing processes,... 

Equipment shock classification Class I, Class II, Class III Equipment mobility classification Hand-held, moyable, stationary, fixed ... 

Dobbie, A. K., Patient Safety—Class III Equipment Advantages, Bio-Medical Engineering, Vol. 8, No. 1,1973, pp. 125-133. 

Table 1 is condensed from Handbook 44. It Hsts the number of divisions allowed for each class, eg, a Class III scale must have between 100 and 1,200 divisions. Also, for each class it Hsts the acceptance tolerances appHcable to test load ranges expressed in divisions (d) for example, for test loads from 0 to 5,000 d, a Class II scale has an acceptance tolerance of 0.5 d. The least ambiguous way to specify the accuracy for an industrial or retail scale is to specify an accuracy class and the number of divisions, eg. Class III, 5,000 divisions. It must be noted that this is not the same as 1 part in 5,000, which is another method commonly used to specify accuracy eg, a Class III 5,000 d scale is allowed a tolerance which varies from 0.5 d at zero to 2.5 d at 5,000 divisions. CaHbration curves are typically plotted as in Figure 12, which shows a typical 5,000-division Class III scale. The error tunnel (stepped lines, top and bottom) is defined by the acceptance tolerances Hsted in Table 1. The three caHbration curves belong to the same scale tested at three different temperatures. Performance must remain within the error tunnel under the combined effect of nonlinearity, hysteresis, and temperature effect on span. Other specifications, including those for temperature effect on zero, nonrepeatabiHty, shift error, and creep may be found in Handbook 44 (5). The acceptance tolerances in Table 1 apply to new or reconditioned equipment tested within 30 days of being put into service. After that, maintenance tolerances apply they ate twice the values Hsted in Table 1.

UL 1604 ictrical Equipment for Use in Hazardous Locations, Class id II, Division 2, and Class III, Divisions 1 and 2... 

Nonincendive Circiuts. This protection technique shall be permitted for equipment in those Class I, Division 2, Class II, Division 2, and Class III locations for which it is approved. 

FPN) For further information, see Electrical Equipment for Use In Class I and II, Division 2, and Class III Hazardous (Classified) Locations, UL 1604—1988. 

Exception No. 4 Eixed dusttight equipment other than fixed lighting fixtures that are acceptable for use in Class II, Division 2 and Class III locations shall not be required to be marked with the class, group, division, or operating temperature. 

Deviations from proportionality have three principal causes I, absorption and enhancement effects, placed together because they both involve absorption II, effects traceable to heterogeneity in the samples, principally surface effects and segregation III, instability, including drifts and fluctuations, in the spectrograph and in associated equipment. Class III deviations often increase with the complexity of the electronic circuitry. 

Insulation is achieved by separating circuits and is required, for example, between user-accessible parts and live parts via insulation layers, thickness, and/or distance (creepage and clearance). There are three classes of equipment. Class I, II and III, with Class I and II products generally covered by the Low-Voltage Directive ... 

Equipment related to P3, P4 facilities such as protective suits and class III safety cabinets... 

The biosafety level (BSL) will determine the kind of personal protective equipment needed." Class I and Class II BSCs can be used at BSL 1 to BSL 3. (See Section 4.3.3 for more information about BSLs.) Specially designed Class II BSCs can be used at BSL 4 and utilize air-supplied protective suits. Class III BSCs can be used for BSL 4 work without suits. 

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. 

Class III—Marginal A condition(s) that may cause minor injury to personnel and minor damage to equipment... 

There is no inherent reason, other than cost, to locate the SA and RA cosolvent sumps into separate equipment envelopes. This arrangement is perfectly feasible, though not produced commercially. It is shown for Class III (miscible) cosolvent machines in Figure 3.33. The patent claims (described in Endnote GG) refer to a Class II cosolvent machine with separate sumps but don t specify whether they must be located in separate equipment envelopes. 

---