Vapor lock

This expression is known as the vapor lock index (VLI) or the front-end volatility index (EEVI). The value of n for U.S. cars is generally reported as 9 when RVP is in kPa (0.13 when pressure is in psi) (23). The maximum level of VLI is set by month and by region according to the ninetieth percentile daily maximum temperature. 

If the suction level is above the pump there is usually no problem in priming (that is, ensuring that the pump suction system is full of liquid) unless it is pumping a volatile and vapor locks when stationary. In many... 

Before startup, all systems should be properly vented. This is especially important on vertical installations where the stuffing box is the uppermost portion of the pressure-containing part of the equipment. The stuffing box area must be properly vented to avoid a vapor lock in the seal area that would cause the seal to run dry. 

The loss of large quantities of acetaldehyde is avoided by use of a spiral condenser, with sufficient heating so that a vapor lock is formed—the entrapped liquid should fill about two-thirds of the spiral. In cold weather, the tap water is usually cold enough so that any efficient long condenser, or two in series, is sufficient. 

However, cavitation may result in an even more serious condition than vapor lock. When the pressure at any point within the pump drops below the vapor pressure of the liquid, vapor bubbles will form at that point (this generally occurs on or near the impeller). These bubbles will then be transported to another region in the fluid where the pressure is greater than the vapor pressure, at which point they will collapse. This formation and collapse of bubbles occurs very rapidly and can create local shock waves, which can cause erosion and serious damage to the impeller or pump. (It is often obvious when a pump is cavitating, because it may sound as though there are rocks in the pump )... 

A critical safety issue of using diesel-ethanol blends relates to flashpoint and flammability. E-diesel blends containing 10-15% ethanol have the vapor pressure and flammability limits of ethanol. This means that ethanol concentrations in enclosed spaces such as fuel storage and vehicle fuel tanks are flammable over the temperature range 13-42 °C. Thus, there are higher risks of fire and explosion than with diesel fuel, or even gasoline. Other vehicle performance-related concerns are (a) a decreased maximum power (b) an increased incidence of fuel pump vapor lock and (c) a reduced fuel pump and fuel injector life due to the decreased lubricity of ethanol. 

First, the low boiling point (37 C) can lead to handling difficulty. We found it necessary to replace the Waters 6000A pump in the Waters Model 244 high performance liquid chromatograph (HPLC) with a Waters M45 pump to avoid an occasional interruption in flow which we assured to be caused by vapor lock. Second, there are health hazards associated with the use of HFIP, and hygenlc laboratory procedures should be followed. The system should not be used prior to consulting the HFIP Product Information and Material Safety Data Sheet from Du Pont. 

Both low-end and high-end volatility limits are established. Low-end volatility control ensures that fuel will vaporize adequately for engine starting and distribution throughout the combustion system. Upper-end volatility limits ensure that vapor locking or fuel line icing will not occur. Isopentane and certain C5 fractions are used to help control vapor pressure. 

The 10%, 20%, 50%, and 90% distillation points are specified to ensure that a properly balanced fuel is produced. Vapor pressure is also related to cold engine starting and helps limit vapor lock at high altitudes. 

Vapor locking problems can often be solved by either allowing the engine to cool or by pouring cold water over the hot fuel pump and lines. Both of these measures will allow fuel vapors to condense. 

Low-molecular-weight vapors can cause vapor locking a critical concern at high altitudes in aviation turbine fuels... 

Volatility Factor A rating of gasoline quality under environmental and operating conditions. It is a function of the Reid vapor pressure, the percent distilled at 158°F (70°C), and the percent distilled at 212°F (100°C). It can be used to help predict the vapor locking tendency of gasoline. 

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