Detail of GB/T 16507.4-2022

Introduction of GB/T 16507.4-2022

Water-tube boilers - Part 4: Strength calculation of pressure parts English 1 Scope This document specifies the basic requirements for strength calculation of pressure elements of water-tube boilers, the design and calculation methods of allowable stress, calculated wall temperature, calculation pressure, weakening coefficient, element thickness, required thickness, opening reinforcement, additional thickness and maximum allowable pressure, the additional stress check, the structural restrictions and requirements, as well as the test and finite element analysis verification methods for determining the maximum allowable working pressure of elements. This document is applicable to the pressure elements defined in GB/T 16507.1, including boiler drum, start-up (steam-water) separator drum, header drum, tube, pipe, bend, elbow, circular header drum, convex head, flat end cover, cover plate and tee. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute indispensable provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. GB/T 150.3 Pressure vessels - Part 3: Design GB/T 16507.1 Water-tube boilers - Part 1: General requirements GB/T 16507.2 Water-tube boilers - Part 2: Materials GB/T 16507.3 Water-tube boilers - Part 3: Structure design GB/T 16507.5 Water-tube boilers - Part 5: Fabrication GB/T 16507.6 Water-tube boilers - Part 6: Inspection, testing and acceptance GB/T 16507.7 Water-tube boilers - Part 7: Safety appurtenances and instruments GB/T 16507.8 Water-tube boilers - Part 8: Installation and operation DL/T 695 Steel butt-welding fittings for power plant DL/T 5366 Technical code for stress calculating of steam/water piping in power plant 3 Terms and definitions For the purposes of this document, the terms and definitions given in GB/T 16507.1 as well as the following apply. 3.1 corrosion allowance thickness additional thickness required for corrosion thickness reduction of elements during the design service life 3.2 required thickness thickness of pressure element determined by theoretical calculation equation Note: If necessary, the thickness required by other loads shall also be taken into account. 3.3 design thickness sum of required thickness and additional thickness 3.4 nominal thickness thickness obtained by rounding the design thickness up to the steel standard specification Note: It is the thickness marked on the drawing. 3.5 effective thickness thickness obtained by deducting the corrosion allowance thickness, lower tolerance of thickness and process additional thickness from the nominal thickness 3.6 lower tolerance of thickness absolute value of negative lower tolerance of thickness specified in material standard Note: If no negative value is available, it shall be taken as 0. 3.7 process additional thickness maximum reduction in material thickness allowed by the manufacturing process during stamping, rolling or bending of elements 3.8 minimum required thickness minimum thickness required by elements bearing loads such as calculation pressure and calculation temperature, taking into account corrosion thickness reduction factors 3.9 hot extrusion tee straight or drum tee formed with seamless steel pipe through hot extrusion by multiple dies 3.10 straight tee tee with a straight main channel Note: Generally, the diameter of branch pipe is not greater than that of main pipe. 3.11 drum tee tee with a drum-shaped main channel Note: It is formed by forging and shrinking the main pipe section of equal straight tee, and the diameter of branch pipe thereof is usually greater than that of main pipe. 3.12 vertical section plane passing through the axis of rotation of the main pipe and the intersection between the mean diameter arc surface of the main pipe and the axis of rotation of the nozzle or opening 3.13 cross section plane perpendicular to the axis of rotation of the main pipe and passing through the intersection between the mean diameter arc surface of the main pipe and the axis of rotation of the nozzle or opening 4 Basic requirements 4.1 The structure, materials, fabrication, installation, use, repair and transformation of boiler pressure elements designed and calculated according to this document shall meet the relevant requirements of GB/T 16507.1, GB/T 16507.2, GB/T 16507.3, GB/T 16507.5, GB/T 16507.6, GB/T16507.7 and GB/T16507.8. 4.2 For boilers of units whose parameters such as peak load fluctuate greatly or frequently, the pressure elements shall be subjected to fatigue strength check. The fatigue strength check of boiler drum shall be carried out according to Annex A, and the fatigue strength check of start-up (steam-water) separator may also be carried out according to Annex A. 4.3 The maximum allowable working pressure of the special pressure elements that do not meet the applicable conditions specified in all clauses of this document or are not included in this document shall be determined according to Annex B. 5 Allowable stress 5.1 Symbols For the purpose of this clause, the following symbols apply: qmax——the maximum heat flux that the element bears, kW/m2; η——the correction coefficient; [σ]——the allowable stress, MPa. 5.2 Selection of allowable stress 5.2.1 The allowable stress ([σ]) of the pressure element material shall be selected according to GB/T 16507.2. The allowable stress of the material between the listed calculation temperatures shall be determined by the allowable stress of the adjacent calculation temperature by arithmetic interpolation, with the decimal number omitted. 5.2.2 The allowable stress ([σ]) of the boiler drum, header drum, tee and equal-diameter Y-tube with heated outer wall shall be the product of the allowable stress of the material and the correction coefficient (η) in Table 1.

Contents of GB/T 16507.4-2022

Foreword i Introduction iv 1 Scope 2 Normative references 3 Terms and definitions 4 Basic requirements 5 Allowable stress 6 Calculated wall temperature 7 Calculation pressure 8 Weakening coefficient 9 Element thickness 10 Required thickness 11 Opening reinforcement 12 Additional thickness 13 Maximum allowable pressure 14 Additional stress check 15 Structural restrictions and requirements Annex A (Normative) Calculation of low-cycle fatigue life of boiler drum Annex B (Normative) Test and finite element analysis verification methods for determining the maximum allowable working pressure of elements Annex C (Normative) Value of design additional pressure (Δpa) Annex D (Informative) Value of process additional thickness Annex E (Informative) Approximation algorithm for bending section modulus (Wx1) of opening weakened section Bibliography