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Becht Engineering Blog

In this section of the site contributing authors submit interesting articles relating to the various services, industries and research & development efforts of Becht Engineering.

When Should the Rules for Severe Cyclic Conditions (Service) in ASME B31.3 Be Used?

process_piping_ASME_B31
This posting (November 2019) is an update to an October 2013 post which reflects changes to the ASME B31.3 Code relative to severe cyclic service that have occurred since the original post. There has been a fair amount of confusion as to when the rules for severe cyclic conditions in ASME B31.3 should be used, and the rules themselves can be somewhat confusing to apply. In the 2016 edition of ASME B31.3 the definition of when the rules for severe cyclic service are applicable were changed, which may reduce the confusion.  The definition as to when the rules of severe cyclic apply is in the 300.2, Definitions.  Prior to the 2016 edition, it stated that severe cyclic conditions are: Conditions applying to specific piping components or joints in which SE computed in accordance with para. 319.4.4 exceeds 0.8SA (as defined in para. 302.3.5); and The equivalent number of cycles (N in...
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Recent Comments
Guest — Hafiz Ali Alvi

Impact on Wall thickness for C...

Dear Mr. Becht, I would like to ask what could be possible impact of cyclic service for the calculated pipe wall thickness under p... Read More
Saturday, 16 November 2019 23:59
Chuck Becht

Impact on Wall thickness for C...

Designation of a system as being in severe cyclic service does not impact the wall thickness calculations for pressure design. No... Read More
Sunday, 17 November 2019 07:40
Guest — MK

SE calculation

Dear Mr.Becht, My understanding is that the calculation of SE (for comparing to 0.8SA in the evaluation) should include only the d... Read More
Thursday, 08 August 2019 02:03
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12 Checks When Qualifying Piping Systems in Nuclear Applications

becht_nuclear_12_checks
The analysis and qualification of piping systems in nuclear power plants involves more than meeting Code stress limits. Generally, a piping system is qualified if the following criteria have been met. These various qualification criteria are typically specified in the plant FSAR, the plant design procedures, or the ASME Code. Pressure design in accordance with the design Code. This check will govern the schedule of pipes, the thickness of tubing, the schedule and pressure class of fittings, the reinforcement of openings and branch connections, the pressure rating of valves, the pressure class of flanges, and the pressure design of specialty fittings. ASME Code stress limits . This check will verify that the Code stress equations for the load combinations corresponding to Test, Design, and Service Levels A, B, C, and D loadings have been met. NRC Standard Review Plan (SRP) Section 3.6 stress limits for the postulation of high energy line...
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Evolution of Pipe Stress Equations in the ASME Nuclear Codes (and where we are today)

piping_systems
The Pre-1955 Era Until 1955, the ASME Boiler and Pressure Vessel Codes, and the ASME B31 Pressure Piping code provided rules of good design practice with quantitative criteria for pressure design.  For example, quoting from ASME VIII Rules for the Construction of Unfired Pressure Vessels Section VIII A. S. M. E. Boiler Construction Code, 1927: U-20. For Internal Pressure. The maximum allowable working pressure on the shell of a pressure vessel shall be determined by the strength of the weakest course, computed from the thickness of the plate, the efficiency of the longitudinal joint, the inside diameter of the course, and the maximum allowable unit working stress.  (S×t×E)/R = maximum allowable working pressure Where S = maximum allowable unit working stress in lb. per sq. in. = 11,000 lb. per sq. in. for steel plate stamped 55,000 lb. per sq. in., 10,000 lb. per sq. in. for steel plate stamped less...
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Capacity Reduction of a Compression Member with an Initial Deformation

piping_support_3D
A recent review of equipment installed in a power plant found a piping strut that was visibly bent. Would the bend in the strut reduce its load bearing capacity as a compression member? The answer is YES!  The load bearing capacity of a bent strut against buckling is reduced. The reduction in buckling capacity is a function of the strut’s section properties and its initial deformation. We will see here how this can be quantified analytically (closed-form solution) and numerically (FEA solution). The equation for the maximum axial load capacity of a column, before it buckles, was first formulated by Leonhard Euler in 1757. F cr  = (π 2  E I)/(K L) 2 Where E = Young’s modulus of column material; I = cross-sectional moment of inertia of the column; L = unbraced length of column; and K is a factor that depends on the degree of fixity in the ends....
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Guest — Jay Tiwari

Review

Very well explained! With the help of piping design model, the problem has been solved. The load bearing capacity of a bent strut ... Read More
Thursday, 30 November 2017 00:48
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