Pressure switches are affected by the temperature and by the nature of the measured fuel in addition to the working pressure. This standard includes specific requirements for pressure switches for the fluids mentioned in the title (e.g. fuel oil or LPG in the liquid state) for a pressure up to 400 bar and a temperature up to 350 ? From this specific requirements are resulting concerning materials and those threads which are used for connections. The sufficent strength can be proved either by calculation or by means of a dynamic strength test which is to be performed in addition to the usual endurance test.