Pressure Temperature Rating (PT-Rating)
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Code | Design Pressure | Design Temperature |
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B31.1 | The internal design pressure shall be not less than the maximum sustained operating pressure (MSOP) within the piping system including the effects of static head. | The piping shall be designed for a metal temperature representing the maximum sustained condition expected. The design temperature shall be assumed to be the same as the fluid temperature unless calculations or tests support the use of other data, in which case the design temperature shall not be less than the average of the fluid temperature and the outside wall temperature. |
B31.3 | The design pressure of each component in a piping system shall be not less than the pressure at the most severe condition of coincident internal or external pressure and temperature expected during service, except as provided in par. 302.2.4. | The design temperature of each component in a piping system is the temperature at which, under the coincident pressure, the greatest thickness or highest component rating is required in accordance with par. 301.2 |
B31.4 | The piping component at any point in the piping system shall be designed for an internal design pressure which shall not be less than the maximum steady state operating pressure at that point, or less than the static head pressure at that point with the line in a static condition. The maximum steady state operating pressure shall be the sum of the static head pressure, pressure required to overcome friction losses and any required back pressure. | The design temperature is the metal temperature expected in normal operation. It is not necessary to vary the design stress for metal temperatures between –20 °F and 250 °F. |
B31.8 | Design pressure is the maximum operating pressure permitted by the Code, as determined by the design procedures applicable to the materials and locations involved. | No design temperature. The Code mentions only ambient temperature and ground temperature. (1975) |