Vent pipe, design

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 ... 

Similarly, if the vent is designed to pass liquid, it should be fitted near the edge of the roof, and its top should not be more than 8 in. above the tops of the walls. Vessels have been overpressured because their vent pipes were too long (see Figure 5-2b). Tanks in which hydrogen may be evolved should be fitted with a vent at the highest point as well as an overflow (see Section 16.2). 

The vent pipe, particularly if over 20 m in length, must be designed to minimize back pressure. Certain pressure governors have integral vent valves. 

Flame arrestors are not considered necessary on the discharge of vent pipes from drainage systems designed primarily for fire water and rain water drainage. There are a number of reasons for this ... 

Change the design of the valves and vent pipes to respond to the two-phase flow problem (which was responsible for the valves and pipes being jammed). 

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