Some advice is given on which might be the best type of evaporator to use for a given duty. Types 1-12 refer to the twelve types listed in Section 524.

A. Vaporization

Under the heading of Vaporization are included evaporators for the revaporization of a liquefied gas and for obtaining a pure vapour from an impure liquid.

In many sectors of the industry, the vertical bayonet tube vaporiser type (2), shown in Figure 270.2 is the standard equipment for the revaporization of liquefied gases, either from ambient or sub-ambient conditions. Some manufacturers offer a range of standard designs with known capacities for many of the more common liquefied gases, such as butane, chlorine and sulphur dioxide. Note however, that if the revaporization is to take place at very low temperatures, any steam heated design may present problems with condensate freezing, and it may be necessary to resort to more specialized designs, such as indirect systems, electric heating etc. These are outside the scope of this section; advice should be sought from a specialist manufacturer.

The kettle type (1), [see Figure 270.1] is also suitable and commonly used for both liquefied gases and obtaining vapour from impure liquids, provided that in the latter case the liquid is relatively clean. The weir may be omitted for the former application, but in that case some form of level control will be necessary, as described in Section 270A.