Part 2 of the standard gives the limiting values for power received by land-based and off-shore industrial-process measurement and control systems or parts of systems, during operation. Maintenance and repair conditions are not considered. Operating conditions directly related to fire and explosion hazards and conditions related to nuclear radiation are likewise not considered. The influence quantities considered in this part are limited to those which may directly affect the performance of process systems. Effects of the specific operating conditions on personnel are not within the scope of this part. Only operating conditions as such are considered; the resulting effects of these conditions on instrumentation are specifically excluded. This part establishes limit values, or sets of limit values, for the operating conditions listed. Other operating conditions, including those for which characteristics are difficult both to define and to measure, and for which adequate standards are not known to exist, will be covered in other publications. An example of an operating condition difficult to define is corrosive atmospheres, which are difficult to classify due to the wide variety and concentration of corrosive substances and combinations of substances which may be encountered. No classifications are recommended for hydraulic power supplies. In most instances, a separate hydraulic supply is provided for each operating unit, or for a small group of units. The characteristics of the supply are engineered specifically to meet the requirements of the units being operated. Certain types of pressure regulators derive their operating power from the pressure of the fluid. Similarly, certain types of temperature regulators derive pressure for valve operation from thermal expansion of the fluid in the temperature-sensing elements. The power supply for this type of "self-operated" device is not considered within the scope of this standard.