Permissible Practice

FIGURE 9-19. Typical components of a powered air purifying respirator. Photo Courtesy 3M 

FIGURE 9-20. This worker is wearing respiratory protection along with a lapel badge which can be used to determine TWA worker exposures. Photo Courtesy 3M 

The employer should establish and maintain a respiratory proteetion program when respirators are required to proteet the health of the employee. The program should be in writing and eontain all of the elements speeified in the standard. If the written program has all of the required elements but the employer has not taken one or more of the aetions required, he or she ean be eited for eaeh element that has not been met. 

---

The assumption that the contraction process is ideally adiabatic, while perhaps not entirely permissible practically, seems indicated by modern theory of the behavior of molecular chains, which pictures these as undergoing, when freed of restraints, a sort of segmental diffusion, much like the adiabatic expansion of an ideal gas into a vacuum (155). In the case of the molecular chain, it diffuses to the most probable, randomly coiled configuration, which is much less asymmetric, hence shorter, than an initially extended chain. Because rubber most nearly presents this ideal behavior, those fibers which develop increased tension (a measure of the tendency toward assumption of the contracted form) when held isometrically under conditions of increasing temperature (favoring the diffusion ) are said to be rubber-like. Most normal elastic solids upon stress are strained from some stable structure and relax as the temperature is raised. 

One of the most significant laser safety standards is that developed by the Z-136 committee of the American National Standards Institute (ANSI) (55). Although it is voluntary, many organi2ations use the ANSI standard. It contains a number of items including a recommendation for maximum permissible levels of exposure to laser radiation for various wavelengths, exposure durations, and different parts of the body separation of lasers into four different classes according to the level of ha2ard they present and recommendation of safety practices for lasers in each of the classes. 

However, if air sampling estabHshes that the lead exposure concentration is excessive, engineering controls (such as improved ventilation), adrninistrative controls (such as job rotation), and work practices (such as improved personal hygiene of workers) have to be appHed to comply with the permissible exposure limit (PEL) of the OSHA standard. 

Decaffeination Regulations. Eor decaffeinated roasted coffee, EEC standards indicate the maximum content of caffeine as 0.1% db for decaffeinated instant coffee it is 0.3% db. In the United States, decaffeination usually signifies that 97% of the caffeine has been removed. Permissible solvents for decaffeination processes are defined by national legislation, eg, EDA or EEC directive. The maximum residual solvent content after decaffeination, roasting, or instant coffee processing is to be kept within good manufacturing practice, ie, very low ppm levels or below at point of sale (46). 

T - by thermometer method (only permissible if the resistance method is not practicable). 

Note To avoid uneven distribution of load on the belts when more than one belt is used the pitch length of the belts must be identical, subject to permissible tolerances. For this purpose, it is advisable to use all belts of one make only. As standard practice all belts are marked on their surfaces with their length and permissible tolerance for easy identification. 

Since it is not practical to manufacture a llameproof enclosure due to its size and bulk and the number of knockouts and openings on the doors for switches, metering, indicators, and pushbuttons (PBs) etc., it is common practice to locate the.se assemblies some distance from the affected area in a separate well-ventilated room. Depending upon the location and intensity ol contamination, it may be permissible to meet the requirement by using a pressurized enclosure by maintaining a positive pressure inside the enclosure similar to that for motors (Section 7.1.3..3). When there arc many switchgear assemblies, the room itself can be pressurized, which is safer and easier. Small enclosures, however, such as a PB station, switch or a switch fuse unit or an individual starter unit etc., which can be easily made of MS plates or cast iron, as discussed in Section 7.13, can be mounted in the hazardous area while the main MCC can be installed in the control room, away from the contaminated area and from where the process can be monitored. 

In addition, it may be necessary to limit permissible upward excursions from the TWA. In practice, concentrations of chemical agents in workplace air fluctuate frequently and to a considerable extent. The amount by which the OEL-TWA may be exceeded for short periods without impairment of health depends upon several factors, such as the nature of the substance, the frequency with which high concentrations occur, and the duration of such periods. 

The temperature of the system is proportional to the average kinetic energy (eq. (16.12), and therefore determines which parts of the energy surface the particles can exploit. Owing to the finite precision by which the atomic forces are evaluated, and the finite time step used, the total energy in practice is not constant (preservation of the energy to within a given threshold may be used to define the maximum permissible time step). 

Figure 11.3 Typical configuration for the on-line coupling of an achiral and chiral cliro-matograpliic system by means of a switching valve. The non-enantio-resolved solute is isolated on the achiral phase and then stereochemically separated on the chiral phase. Reprinted from G. Subramanian, A Practical Approach to Chiral Separation by Liquid Chromatography, 1994, pp. 357-396, with permission from Wiley-VCH.

Figure 5-3. Impeller styles and general sizes commonly in use in process industry plant. By permission, Oldshue, J. Y., Fluid Mixing Technology and Practice, Chem. Engr., June 13, 1983, p. 84 [25].

Figure 7- l4. Safety valve design operational check sheet. Adapted and added to by permission, N. E. Syivander and D. L. Kiatz, Design and Construction of Pressure Relieving Systems, Univ. of Michigan Press, Ann Arbor (1948). Six items of overpressure list above by this author and from API Rec. Practice 521 (1982). 

Contents in (J.S. gallons for one head only. This table is only approximate, but close enough for practical use. By permission, The Permutit Co., Inc., Data Book, 1953. 

Figure 10-43C. Fouling Nomograph, Part 3. Final and practical calculation for fouling factor use in conjunction with Figures 10-43A and 10-43B. (Used by permission Zanker, A., Hydrocarbon Processing. March 1978, p. 148. Gulf Publishing Company, Houston, Texas. All rights reserved.)...

Figure 11-25. Piping practices—Freon Freon-12 line sizing. (Used by permission Dresser-Rand Company.)...

---