<P> Propylene is used in production welding and cutting . It cuts similarly to propane . When propylene is used, the torch rarely needs tip cleaning . There is often a substantial advantage to cutting with an injector torch (see the propane section) rather than an equal - pressure torch when using propylene . Quite a few North American suppliers have begun selling propylene under proprietary trademarks such as FG2 and Fuel - Max . </P> <P> Butane, like propane, is a saturated hydrocarbon . Butane and propane do not react with each other and are regularly mixed . Butane boils at 0.6 ° C. Propane is more volatile, with a boiling point of - 42 ° C. Vaporization is rapid at temperatures above the boiling points . The calorific (heat) values of both are almost equal . Both are thus mixed to attain the vapor pressure that is required by the end user and depending on the ambient conditions . If the ambient temperature is very low, propane is preferred to achieve higher vapor pressure at the given temperature . </P> <P> Propane does not burn as hot as acetylene in its inner cone, and so it is rarely used for welding . Propane, however, has a very high number of BTUs per cubic foot in its outer cone, and so with the right torch (injector style) can make a faster and cleaner cut than acetylene, and is much more useful for heating and bending than acetylene . </P> <P> The maximum neutral flame temperature of propane in oxygen is 2,822 ° C (5,112 ° F). </P>

List two types of grinders used by welders