Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Safe Limits

When a facility is new, the safe limits are defined by its designers. As operating experience is accumulated new safe limit values will be implemented, often through use of the hazards analysis and Management of Change processes. [Pg.29]

There are some safe limits that may have no meaningful value. For example, if a pressure vessel is designed for full vacuum operation then that vessel has no safe lower limit for pressure. [Pg.29]

The operating limit values are often quite fuzzy. As the system moves away from optimum operation it will start to exhibit symptoms of unusual operation, which will eventually lead into the troubleshooting range. [Pg.30]

The final set of values is the emergency limits. If the process parameter goes beyond one of these limits then an emergency simation has been created. [Pg.30]


The disputes that followed these events centered around interpretation of the 1938 act, which states that "The Secretary shall promulgate regulations providing for the listing of coal-tar colors which are harmless and suitable for use in food..." The FDA felt that harmless meant that a colorant must be safe regardless of the amount used, that is, harmless per se and on this basis deHsted the colorants in question. The food-color manufacturers argued that the FDA interpretation of the law was too strict, that a color additive need only be harmless when properly used, and that the FDA should estabHsh safe limits. They also contended that the conditions used for the new animal feeding tests were too severe. [Pg.432]

Saniti r is a chemical agent used on inanimate objects that reduces the number of microbial contaminants to safe limits as judged by pubHc health requirements. [Pg.121]

Is there a Safe Limit for Nitratel The two previous sections show that any safe limit for nitrate needs to be related to methaemoglobinaemia rather than... [Pg.3]

Figure 5 A surplus nitrate curve , relating the amount of nitrate left in the soil at harvest to that given in spring as fertilizer. The point at which the curve turns upwards represents the safe limit for fertilizer application. It could be described as the environmental optimum application. Fortunately, it is often close to the economic optimum. Figure 5 A surplus nitrate curve , relating the amount of nitrate left in the soil at harvest to that given in spring as fertilizer. The point at which the curve turns upwards represents the safe limit for fertilizer application. It could be described as the environmental optimum application. Fortunately, it is often close to the economic optimum.
Snubber circuii More conventional protection from high dvidi is to provide an R-C circuit across each device, as shown in Figure 6.37. The circuit provides a low impedance path to all the harmonic quantities and draws large charging currents and absorbs the energy released, Q, and in turn damps dvIdi within safe limits across each device. Now Q = C idu/di)... [Pg.132]

To contain the temperature of the electrical circuits within safe limits for a particular temperature class of the surroundings, the maximum current rating for a minimum size of a conductor is also stipulated in ICC 60079-1 I. The constructional requirements also stipulate the minimum clearances and creepage distances in air between the conducting parts of all the intrinsically safe L lectrical eirctiits. [Pg.183]

The rotor design, its cooling system or the motor size itself may have to be changed substantially for motors to be installed in fire hazard environments to limit their temperature rise in adverse operating conditions within safe limits (Table 7,6). [Pg.283]

This is the winding insulation to the body, whicli is more vulnerable to prospective voltage peaks. V,. as a result of TRVs. When the TRV exceeds the BIL of the machine, it can be dampened to a safe limit with the use of a surge arrester, say, from peak to ih, as illustrated in Figure 17.21. Details of a surge arrester and the procedure for its selection are discussed below. See also Example 17.6. The selection of the arrester w ill also depend upon the method of star (neutral) formation of the stator s... [Pg.579]

It is presumed that the protective distance (distance of the protected equipment from the arrester) is short and within safe limits. It too must be checked before a final selection of the arrester, as explained in Section 18.6.2. The above selection, however, seems to be appropriate for a distance up to 8-10 m as considered in Example 18.4. [Pg.621]

The number of thyristors in series, each selected for an impulse voltage of a little less than the impulse voltage with.stand level of the terminal equipment (Table 11.6) can effectively limit the switching overvoltages within desired safe limits. Then connecting them in anti-parallel will mean that the voltage will be forward for either of... [Pg.804]

Similar approaches are applicable in the chemical industry. For example, maleic anhydride is manufactured by partial oxidation of benzene in a fixed catalyst bed tubular reactor. There is a potential for extremely high temperatures due to thermal runaway if feed ratios are not maintained within safe limits. Catalyst geometry, heat capacity, and partial catalyst deactivation have been used to create a self-regulatory mechanism to prevent excessive temperature (Raghaven, 1992). [Pg.50]

NFPA 69 (NFPA 1997) contains information on basic design considerations, design and operating requirements, and instrumentation requirements. Appendix D presents methods for ventilation calculations, including the time required for ventilation to reduce the concentration to a safe limit, the number of air changes required for reaching a desired... [Pg.35]

Figure 13-23 suggests recommended pulse level (peak-to-peak) pressure pulsations for acceptable pipe vibration. Figure 13-24 presents allowable machinery and pipe vibration at safe limits and damage levels, and Figure 13-25 presents allowable pressure pulsations for various pipe spans between rigid supports when a 5 mil peak-to-peak vibration is allowed at the center of the pipe spans for the pipe sizes noted. [Pg.611]

The safety relief valve will protect the liquid-wetted areas of the storage vessel. The metal temperature will not significantly exceed the liquid temperature, which will be absorbing the latent heat of vaporization. However, above the liquid line no such cooling will take place. The metal temperature at the top of the vessel could therefore exceed safe limits. [Pg.305]

Torsional stresses are developed when power is transmitted through shafts. In addition, the tooth loads of gears mounted on shafts create bending stresses. Shaft design, therefore, is based on safe limits of torsion and bending. [Pg.1001]

Most packaged water chillers are large enough to have capacity control devices in the compressor. The main control thermostat will unload the compressor as the water temperature approaches a lower safe limit, so as to keep the water as cold as possible without risk of freeze damage. [Pg.145]

Many industrial processes give rise to pollutants which can present a health problem. Quantitative analysis of air, water, and in some cases soil samples, must be carried out to determine the level of pollution, and also to establish safe limits for pollutants. [Pg.4]

In a matched seal the stress is kept within safe limits by close correspondence of the two thermal expansions throughout the temperature range over which the seal has to be worked during its manufacture. [Pg.56]

The corrosion of antimony electrodes was also measured using ICP-MS (inductively coupled plasma mass spectrometry) for dissolved antimony in vivo [156], After the electrodes were inserted in the plasma, the antimony concentration showed a linear rise with time at a rate approximately of 94 j,g/L/h (r2 = 0.997). Although the projected antimony concentration is lower than the safe limit, accumulation of dissolved antimony and localized toxic effects in tissue may prevent the antimony electrode from long-term implantable applications. [Pg.315]

Applying the exchange approximation and neglecting the zero-point energy terms, we may safely limit the representation of the Hamiltonian Hsf ex within the following reduced base which accounts for the ground states of each mode and for the first (second) overtone of the fast (bending) mode ... [Pg.275]

The human taste threshold for PCP in drinking water is about 30 pg/L (USEPA 1980), a level far below the upper safe limit of 1.01 mg/L and near the no-observable-effect level of 21 pg/L (Table 23.7). Odor detection is not as sensitive as taste the odor threshold for PCP ranges from about 857 pg/L at 30°C, to 1600 pg/L at 20 to 22°C, to 12,000 pg/L at 60°C (USEPA 1980). It is not clear whether the determined organoleptic threshold values made the water undesirable or unfit for consumption (USEPA 1980). If fish and wildlife species of concern have PCP organoleptic thresholds that are similar to those of humans, or lower, will they too avoid contaminated habitats or diets ... [Pg.1223]

No-adverse-effect levels Food, upper safe limit, 70-kg adult Wood, in contact with food Drinking water Recommended Global proposed Upper safe limit Arizona California Kansas, Montana Maine New York... [Pg.1224]

Implementation Samples of the river water, sediments, and even some of the dead fish are taken to the contract lab where their chemists use GC-MS, after appropriate sample preparation, to determine that there are no toxic compounds at significant levels i.e., high enough to harm the fish. Your own results for heavy metals are also negative—nothing above safe limits was detected. [Pg.832]


See other pages where Safe Limits is mentioned: [Pg.422]    [Pg.725]    [Pg.11]    [Pg.17]    [Pg.17]    [Pg.132]    [Pg.133]    [Pg.224]    [Pg.292]    [Pg.373]    [Pg.574]    [Pg.581]    [Pg.702]    [Pg.707]    [Pg.4]    [Pg.254]    [Pg.254]    [Pg.254]    [Pg.532]    [Pg.29]    [Pg.217]    [Pg.896]    [Pg.422]    [Pg.277]    [Pg.135]    [Pg.845]    [Pg.22]    [Pg.66]   
See also in sourсe #XX -- [ Pg.19 , Pg.116 , Pg.156 ]

See also in sourсe #XX -- [ Pg.86 , Pg.87 , Pg.88 ]




SEARCH



Easy-to-Use Steam Heat Can Push Equipment beyond Safe Design Limits

Ethanol safe limits

Process Safety Management safe limits

Process controls safe operating limits

Safe Toxicity Limits for Workers

Safe biological limits

Safe operating limit

Safely explosive limits

Safety Management System safe limits

© 2024 chempedia.info