§ 13.51. Direct and indirect fired vaporizers.

 (a)  Direct fired vaporizers shall be constructed, marked, installed, and inspected as required by § §  3.71—3.76, 3.81—3.87 and 3.131—3.136.

 (b)  Indirect fired vaporizers shall be constructed, marked, installed and inspected according to the requirements of § §  3.141—3.145 and 3.151—3.156 except vaporizers having an inside diameter of six inches or less. Such vessels shall be designed and constructed as to safely sustain a working pressure of not less than 250 pounds per square inch. These vessels need not be permanently marked except for the name of the manufacturer and the designed pressure.

 (c)  The application of direct heat to tanks and cylinders containing liquefied petroleum gas is prohibited.