Pipeline Wall Thickness Calculation With Example (With PDF [PDF]

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Pipeline wall thickness calculation with example (With PDF) Ad



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Written by Anup Kumar Dey ● in Pipeline,Piping Design Join us on Telegram Basics,Piping Interface



Calculation of minimum wall thickness of a given pipeline diameter and selection of actual thickness is one of the most



important basic design considerations for any pipeline projects. This is one of the basic activities that is performed at the initial stages of any detailed design project. In this article, the pipeline



wall thickness calculation methodology will be explained for a liquid pipeline of 10-inch diameter (API 5L-Gr X52, 10.75-inch OD, Design Pressure=78 Bar-g, Design Temp=60 Deg. C) with a sample example.



Criteria for Minimum Pipeline Wall Thickness Calculation The wall thickness for the CS Line pipe shall be calculated based on permissible hoop stress due to internal pressure. In



accordance with ASME B31.4, clause 403.2.1, The nominal wall thickness of straight sections of steel pipe shall be equal to or greater than tn determined in accordance with the following



Equation              :                    tn ≥ t + A Here



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A:               sum of allowances for threading, grooving, corrosion, and erosion and an increase in wall thickness if used as a protective measure tn:               nominal wall thickness satisfying requirements for pressure and allowances t:               pressure design wall thickness as calculated in inches (millimeters)



The line pipe wall thickness (t) to withstand the Join us on Telegram internal design pressure is calculated as below: t = P * D / (2 * F *S * E)



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t              :               Calculated Wall thickness (mm) P             :               Design pressure for the pipeline (kPa)=78 barg=7800 KPa Ad



D             :               Outside diameter of pipe (mm)= 273.05 mm F              :               Design factor = 0.72 S              :               Specified Minimum Yield Strength (MPa)=359870 KPa for the specified material. Ad



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E              :               Longitudinal   joint   factor = 1.0 Hence Calculated wall thickness (t, mm) = (7800*273.05)/ (2*0.72*359870*1) = 4.10 If the sum of allowances for threading, grooving, corrosion, and erosion and an increase in wall thickness if used as protective measure=0.3 mm Ad



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Then nominal wall thickness satisfying requirements for pressure and allowances= 4.1+0.3= 4.4 mm. So, any available thickness greater than 4.4 mm can be used as a Join us on Telegram selected thickness.



Pipeline Wall Thickness



Now various organizations have their own guidelines for minimum thickness selection considering pipe rigidity, supporting, handling, field bending and other aspects relating to construction and in-situ integrity of the pipeline and those need to be checked. Based on these, few checks need to be performed before deciding the final wall thickness. These are listed below: Few organizations limit the use of metallic line piping with thickness less than 4.8 mm. Hence 4.8 mm will be the selected thickness. Join us on Telegram



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The diameter to wall thickness ratio should not exceed 96 for metallic pipelines for some organizations. Here D/T=273.05/4.8=56.88.



Full Vacuum Collapse check



As per a few organizations, collapse due to vacuum conditions shall be accounted for in the design of all pipelines, even when vacuum conditions are not expected to occur in service. The calculations are carried out in accordance to pressure vessel code ASME Section VIII, DIV 1, UG-28. All vacuum collapse calculations are carried with nominal wall thickness excluding corrosion allowance.



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As per UG 28 (f) of ASME section VIII, the selected pipeline wall thickness will be safe for full vacuum, if it is capable of withstanding net external pressure of 1.01325 bar (15 psi).



Now following UG 28 equations and graphs calculate allowable external working pressure. If allowable external working pressure is more than design external pressure (i. e, 1.01325 bar) then the selected thickness is satisfactory.



Equivalent Stress check



The equivalent stresses calculations must be carried out as per ASME B31.4. The wall thickness initially derived from hoop stress considerations based on design factors, should be such that the longitudinal, shear and equivalent stresses in the pipe wall under functional and environmental loads do not exceed certain values. This is covered in ASME B31.4 Article 402 and of ASME B31.8 Article 833. Because the requirements in these various articles differ from each other, it is recommended to use a single approach for all pipelines as detailed below. The equivalent stress can be defined as follows:



Seq = (Sh 2 + SL 2 – ShSL+ 3Ss 2 ) 1/2 (Von Mises equation) Seq = equivalent stress



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Sh = hoop stress (due to pressure) SL = longitudinal stress (due to pressure, thermal expansion and bending)



Ss = combined shear stress (due to torque and shear force) The stress calculations for the operational phase shall be carried out with the nominal wall thickness excluding the corrosion allowance. The equivalent stress shall not exceed the values given below:



Allowable Equivalent Stress Limits



Pipeline



Check



Wall Thinning Criteria



Changes in direction may be made by cold bending of pipe or installing factory-made bends or elbows. The bending of the pipe will result in a significant wall thinning. Hence, the wall thickness of finished bends, considering wall thinning at the outer radius, should Join us on Telegram be not less than the calculated wall thickness for Hoop Stress. The wall thinning calculations should be carried out in accordance with BS 8010.



As per BS 8010; An indication of wall thinning as a percentage can be calculated using the following equation:



t(thin) =50/(n+1) This formula does not take into account other factors that depend on the bending process, and the bend manufacturer should be consulted where wall thinning is critical. Here, n=inner bend radius (Ri) divided by pipe outside diameter(D) for wall thinning formulae Ri=Inner bend radius=(Bend Radius*OD)-(OD/2) The value of bend thinning shall be less than 2.5%.



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Strain Check



The strain-induced in a pipeline by bending it along a radius R is= (Pipe OD)/2R (Bend Radius) the permanent bending strain should be within 2%. Ad



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Few more useful resources for you..



Comparison between Piping and Pipeline Engineering Factors Affecting Line Sizing of Piping or Pipeline Systems Corrosion Protection for Offshore Pipelines A Presentation on Pipelines – Material Selection in Oil & Gas Industry Startup and Commissioning of the Pipeline: An Article Design of Cathodic Protection for Duplex Stainless Steel (DSS) Pipeline An Article on Micro Tunneling for Pipeline Installation A short presentation on Offshore Pipeline Systems



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Anup Kumar Dey I am a Mechanical Engineer turned into a Piping Engineer. Currently, I work in a reputed MNC as a Senior Piping Stress Engineer. I am very much passionate about blogging and always tried to do unique things. This website is my first venture into the world of blogging with the aim of connecting with other piping engineers around the world.



12 thoughts on “Pipeline wall thickness calculation with example (With PDF)” Greesh Kumar says: May 12, 2020 at 10:02 pm



Hi Anup Hope you are well I have a question Join us on Telegram please can you tell me how much % of corrosion allowance will be considered during the selection of API linepipe wall thickness / designing according to ASME B31.8 Standard.



Your reply is highly appreciated Best regard, Engr. G Kumar, Karachi Reply



MUNNA RAM says: June 14, 2020 at 8:25 am



Dear Sir, 0.5 mm corrosion allowance will be considered during the selection of API line pipe wall thickness/designing according to ASME B31.8 Standard. Regards Munna Kumar Senior Engineer Pipeline Department OIL INDIA LIMITED Reply



Samson says: August 17, 2020 at 9:03 am



Thank you mr Kumar. My name is Samson a mech engr from an Join us on Telegram FMCG environment who has passion for piping design. I wanted to train to be a piping engineer from a friend but what He has been teaching me is PDMS whearas I love to be a desingner i.e to design for pressure, temperature and stress. But you are



threading the path that I want. Is PDMS a must for me to be a piping engineer. Also how can it be possible for me to switch over to piping industry without any prior job experience in piping industry. pls assist as I love to be creative and being independent which a design job/experience can offer even at old age Reply



Vinoth says: October 4, 2022 at 11:36 am



Sir,PDMS is a 3d modeling software, where it can surely assist in piping design and engineering Reply



mohamed Ismail says: February 1, 2022 at 7:32 pm



hi sir, i am mohamed ismail , what is correct thickness of pipes ( 3” ,4”,6”,8”,10”,12”,16”,18” ) recommended by safety used in for water from pump house to induction furnace in india Reply



Mark Moredo says: March 6, 2022 at 3:00 pm



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Dear All, above calculations for wall thickness applies to a single layered pipe (either Steel Pipe or PE Pipe).



How about RTP Pipes which is a 3 layered pipe designed as per API 15S (made of liner pipe, tape reinforcement, and cover pipe). Can somebody advise? Reply



Amir Alshammary says: May 15, 2022 at 12:31 pm



Pls…pdf Reply



Zoran Tunic says: July 6, 2022 at 2:16 am



One question; regarding wall thickness of the reinforcement for the pipe, what will be minimum thickness , I usually used wall thickness of the core pipe, What will be the max. wall thickness of the reinforcement . Thank you Reply



Ivan says: July 18, 2022 at 4:59 pm



Hello Anup, I would like to know if you one-on-one training? Reply



Anis Mian says: September 3, 2022 at 5:56 pm



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Hi, Have you made a Excel file for the wall thickness calculation, if yes, could you please send it to me, Thank you so much Reply



ThankGod says: November 4, 2022 at 9:24 am



Pipe length=20m Diameter=1.5m Weight=10tonnes Determine the thickness t, please how can I calculate the thickness, please someone should help me out Reply



vishnu says: November 18, 2022 at 5:36 pm



is it possible to have 0.05″ wall thickness for 3″ OD C.S pipe. please advise Reply Join us on Telegram



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