Design considerations Venting

Design Considerations for Injection Molded Parts (Parting lines, draft angles, wall thickness, fillets and radii, bosses, ribs, opening formations, shrinkage, gating, vents, potential knit lines)... 

L. J. Updyke, Emergency Vent Scrubbers—Design Considerations, 5th Chlorine Plant Operations Workshop, Houston, TX (1990). 

Explosion relief for vapor-air combustion within a closed top low-pressure tank cannot be accomplished by customary tank conservation vents or other Ught-weight protection. A well-written brief description of safety features of low-pressure tanks can be found in Volume 32 of the Institution of Chemical Engineers Loss Prevention Bulletin [5]. An excellent understanding of design considerations of the weak roof can be found under in section 1.3.5, from which the following paragraphs are quoted ... 

Great care is needed in the design of autoclaves and sterilization cycles because of the requirement for the presence of moisture. The autoclave must be loaded to allow complete steam penetration to occur in all parts of the load before timing of the sterilization cycle commences. The time required for complete penetration, the so-called heat-up time, varies with different autoclave constmction and different types of loads and packaging materials. The time may not exceed specific limits in order to guarantee reproducibility and, for porous loads, saturated steam. The volume of each container has a considerable effect on the heatup time whenever fluids are sterilized. Thermocouples led into the chamber through a special connector are often employed to determine heatup times and peak temperatures. The pressure is refleved at the end of each sterilization cycle. Either vented containers must be used or... 

Safety Considerations Design and location of storage tanks, vents, piping, and connections are specified by state fire marshals, underwriters codes, and local ordinances. In NFPA 30, Flammable and Combustible Liquids Code, 1993 (published by the National Fire Protection Association, Quincy, Mass.), liquid petroleum fuels are classified as follows for safety in handhng ... 

Designs and systems should minimize potential harmful exposures in both normal and emergency operations. This consideration affects the location of normal and emergency drains and vents. 

Flame arrester pressure drops mnst he taken into consideration when selecting and specifying them, especially when they are installed on vent systems of low pressure storage tanks, snch as API-type tanks. If the total system pressure drop exceeds the design pressure of the tank, the tank will he overpressnred and may he strnctnrally damaged. Refer to Section 6.1 for additional discnssion of this topic. 

When in-line detonation flame arresters are installed in single or manifolded vent systems, consideration mnst be given to the design of the system (flame arrester and piping). The following design practices shonld be considered ... 

In a particular application, therefore, careful consideration should be given to the relative importance of smoke and flame, including creating designs favoring the rapid elimination of smoke by venting, for fending off smoke, and other approaches. 

The density of air saturated with a chemical vapour may not differ significantly from that of air itself Refer to Table 4.2. This is an important consideration when designing ventilation systems, i.e. both high- and low-level extract vents may be desirable. 

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