【正文】 ble for the designs of fuel pipeline, fuel gas pipeline, hydrogen gas pipeline and underground straight buried pipe. Related standards quoted by this specification: Nominal diameter of the pipeline parts (3131047) Nominal pressure of the pipeline parts (3131048) Seamless steel pipe shall be used for highpressure boiler (385310) For low and mediapressure boiler, seamless steel pipe is used (GB3087) Carbon construction steel (313700) Spiral welded steel pipe (SY5036~5039) Lowpressure stream conveyance with welding steel pipe (3133092) Steel pressure vessel (GB150) Carbon steel covered electrode (GB5117) Low alloy structural steel (GB5118) Technical specifications on pipeline stress calculation of fossil fuel power plant (SDGJ6) Electric power construction and technical specification for the acceptance (pipeline section) (DJ56) Electric power construction and technical specification for the acceptance (Welding in fossil fuel power plant) (DL5007) Electric power construction and technical specification for the acceptance (Radio examination of the steel loadbearing pipeline buttjointed seams) (SD143) Metallic technical supervision specification of the fossil fuel power plant (DLA38) Supervision code for boiler of power industry (SDl67) 8 2 General policy conditions Design specifications Piping design shall be carried out according to the thermodynamic system and setup. It requires good material sources, proper setup, good indemnification, smooth drainage, smaller flow resistance, low construction cost, appropriate hanger and support, convenient installation as well as maintenance, flexible extension, and shall be tidy and nice in appearance. Hydraulic impact and resonance shall be avoided, and noise shall be reduced. Piping design shall ply with related standards and specifications of the state and the ministry. Design parameter Design pressure Piping design pressure (gauge pressure) refers to the maximal working pressure of the interior media in service. For the utility of water pipe and design pressure, the influence of water column39。s static pressure shall be considered。 when the pressure is lower than 3% of the nominal pressure, it will not be considered. The design pressure of the main pipe is applicable in the following specifications: (1) Main steam line Nominal working pressure at the boiler superheater exit or working pressure at the maximumcontinuous evaporative capacity of boiler shall be taken. When the boiler and steam turbine permits the pressure to be 5% greater (5% OP for short), 5% overpressure value shall be added. (2) Reheat steam pipeline The pressure shall be times of the pressure cylinder exhaust pressure under steam turbine39。s maximal design capacity operating condition (see note). Pressure of the high temperature reheat pipe can be reduced to the undermost setpressure of the safety valve at the reheater outlet. Note: maximal design capacity operating condition of the steam turbine refers to the valve widely open condition (VWO for short) or valve widely open condition + 5% overpressure (VWO+5%OP for short) condition. (3) Steam turbine39。s extraction line 9 Nonregulated extraction line39。s pressure shall be times of the extraction pressure of the steam turbine at maximal design capacity condition, which shall be no lower than : Regulated extraction line will use its maximum operating pressure. (4) Blowdown line of the backpressure steam turbine Its maximum operating pressure shall be adopted. (5) Steam pipe behind the reliever The maximum operating pressure shall be adopted. (6) Steam water pipeline connected to the monopipe boiler starting vessel The maximum possible operating pressure in all kinds of segregator operating conditions shall be adopted. (7) High pressure feed water pipeline For nonvariable speed feed water pump outlet pipe, from fore pump to main feed pump or from the main feed pump to boiler economizer entrance, pressures for each shall take the sum of the summit value of the performance curve with fore pump or main feed pump and the pump39。s water inlet side pressure respectively。 As for variable speed feed water pump outlet pipe, from the feed pump outlet to the stop valve, the design pressure shall take the sum of the rated speed performance curve summit value and the water inlet side pressure。 From stop valve at the pump outlet to entrance of the boiler economizer, the pressure shall take the sum of the pump water inlet side pressure and times of pump popping pressure at the pump39。s rated speed and design flow. (8)Above high pressure feed water pipeline pressure shall consider the amendment on pressure made by water pump inlet temperature. For the constantvoltage deoxidizing system, the sum of the desecrator rated pressure and the water column static pressure at the maximum water level shall be adopted. For sliding pressure operation of deaerator, the sum of times of the heated deaerator extraction pressure at steam turbine‘s maximal design capacity condition and the water column static pressure at the deaerator‘s maximal water level shall be taken. (9) Condensate pipe 10 For pipeline at the inlet side of the condensate pump, the water column static pressure (by this time, the pressure inside the condenser shall be taken as the air pressure) from the pump inlet center line to the turbine exhaust casing39。s interface section and it shall be no lower than 。 For the bypath at the outlet of the single stage pump and system pump, the pressure shall take the sum of the pump lift when the outlet valve is closed and the water inlet side pressure (the aforesaid water column static pressure)。 The pipeline at the condensate pump39。s outlet side of the twostage pump system shall adopt the same pressure as that of the corresponding single stage pump s