Vapor lock effect

The extent of flashing depends upon the fluid being pumped, but flashing has two basic effects. First, it creates a vapor-lock situation where vapor generation prevents head buildup and causes cavitation, and the pump cannot be started up. Second, in the case of light liquefied products (both hydrocarbon and nonhydrocarbon), flashing within the pump can create very low temperatures and cause auto-refrigeration. 

Figure 13.3 The effect of vapor lock is to promote condensate backup and...

Vaporizing liquid halogen agents are electrically non-conductive and are effective on a wide range of combustibles, particularly flammable liquids and electrical fires. A lock-off system is required on fixed installations to protect personnel, the normal extinguishing concentration being 5% by volume. 

Animal data are available for intermediate exposures by the inhalation and dermal routes of exposure. No animal data were located by the oral route. Most of these studies found no evidence of toxicity in any of the exposure conditions used in each (Carpenter et al. 1976 Bruner 1984 Lock et al. 1984 NTP/NIH 1986). However, the lack of toxicity in these studies has not been verified by more than one study using the same fuel oil, species, and/or route of exposure. In one aerosol inhalation study (Dalbey et al. 1987) there were positive findings for respiratory, hematological, and body weight effects at higher doses than those used in the studies by Carpenter et al. (vapor) (1979) and Lock et al. (aerosol) (1984). However, MRLs cannot be derived from these data because the Dalbey et al. study was not designed to test for a dose-response relationship, and therefore, the exact LOAEL(s) could not be determined for these effects. 

The effects of capillary condensation were included in the network model, by calculating the critical radius below which capillary condensation occurs based on the vapor composition in each pore using the multicomponent Kelvin Equation (23.2). Then the pore radius was compared with the calculated critical radius to determine whether the pore is liquid- or vapor-filled. As a significant fraction of pores become filled with capillary condensate, regions of vapor-filled pores may become locked off from the vapor at the network surface by condensate clusters. A Hoshen and Kopelman [30] algorithm is used to identify vapor-filled pores connected to the network surface, in which diffusion and reaction continue to take place after other parts of the network filled with liquid. It was assumed that, due to the low hydrogen solubility in the liquid, most of the reaction takes place in the gas-filled pores. The diffusion/reaction simulation is repeated, including only vapor-filled pores connected to the network surface by a pathway of other vapor-filled pores. 

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