Chapter II Design PART 1 section of the system shall conform to the most sev
CONDITIONS AND CRITERIA temperature condition expected to be produced by the
101 DESIGN CONDITIONS heat exchangers in that section of the system.
101.1 General (C) For steam, feedwater, and hot water piping lead- ing from fired equipment (such as boiler, reheater, super-
These design conditions define the pressures, temper- heater, economizer, etc.), the design temperature shall
atures, and various forces applicable to the design of be based on the expected continuous operating condi-
power piping systems. Power piping systems shall be tion plus the equipment manufacturers guaranteed max-designed for the most severe condition of coincident imum temperature tolerance. For operation at pressure, temperature, and loading, except as herein temperatures in excess of this condition, the limitations
stated. The most severe condition shall be that which described in para. 102.2.4 shall apply.
results in the greatest required pipe wall thickness and (D) Accelerated creep damage, leading to excessive the highest flange rating. creep strains and potential pipe rupture, caused by
101.2 Pressure extended operation above the design temperature shall
All pressures referred to in this Code are expressed in be considered in selecting the design temperature for pounds per square inch and kilopascals above atmo- piping to be operated above 800??F (425??C).spheric pressure, i.e., psig [kPa (gage)], unless otherwise 101.4 Ambient Influences stated. 101.4.1 Cooling Effects on Pressure. Where the
101.2.2 Internal Design Pressure. The internal cooling of a fluid may reduce the pressure in the piping design pressure shall be not less than the maximum to below atmospheric, the piping shall be designed to sustained operating pressure (MSOP) within the piping withstand the external pressure or provision shall be system including the effects of static head. made to break the vacuum.
101.2.4 External Design Pressure. Piping subject to 101.4.2 Fluid Expansion Effects. Where the expan-external pressure shall be designed for the maximum sion of a fluid may increase the pressure, the piping differential pressure anticipated during operating, shut- system shall be designed to withstand the increased down, or test conditions. pressure or provision shall be made to relieve the exce
101.2.5 Pressure Cycling. This Code does not pressure.
address the contribution to fatigue in fittings and com- 101.5 Dynamic Effects
ponents caused by pressure cycling. Special consider- 101.5.1 Impact. Impact forces caused by all externalation may be necessary where systems are subjected to and internal conditions shall be considered in the piping a very high number of large pressure cycles. design. One form of internal impact force is due to the
101.3 Temperature propagation of pressure waves produced by sudden
changes in fluid momentum. This phenomena is often
101.3.1 All temperatures referred to in this Code, called water or steam ??hammer.?? It may be caused by unless otherwise stated, are the average metal tempera- the rapid opening or closing of a valve in the system. The tures of the respective materials expressed in degrees designer should be aware that this is only one example of
Fahrenheit, i.e., ??F (Celsius, i.e., ??C). this phenomena and that other causes of impact load-
101.3.2 Design Temperature ing exist.
(A) The piping shall be designed for a metal tempera- 101.5.2 Wind. Exposed piping shall be designed to ture representing the maximum sustained condition withstand wind loadings. The analysis considerations expected. The design temperature shall be assumed to and loads may be as described in ASCE/SEI 7, Minimum be the same as the fluid temperature unless calculations Design Loads for Buildings and Other Structures. or tests support the use of other data, in which case the Authoritative local meteorological data may also be
design temperature shall not be less than the average of used to define or refine the design wind forces. Where the fluid temperature and the outside wall temperature. local jurisdictional rules covering the design of building
(B) Where a fluid passes through heat exchangers in structures are in effect and specify wind loadings for series, the design temperature of the piping in each piping, these values shall be considered the minimum
ASME B31.1-2010,Download Asme B31.1 2012