PIPEPROP Composite Pipe Properties Calculator

Transcription

1 PIPEPROP Composite Pipe Properties Calculator User Manual Version : Date : 10-September-2014

2 License Information PIPEPROP PIPEPROP software and source code are property of Technomak Offshore & Marine Consultancy. The software along with this user manual allows the purchaser to use the software and for non-commercial purpose only. DISCLAIMER OF WARRANTY Neither Technomak Offshore & Marine Consultancy (and its group of companies), nor the author of this program and documentation are liable or responsible to the purchaser or user for loss or damage caused, or alleged to be caused, directly or indirectly by the software and its attendant documentation, including (but not limited to) interruption on service, loss of business, or anticipatory profits. Page 2 of 19

3 Contents _ License Information... 2 About PIPEPROP... 4 Unit System... 5 PIPEPROP Inputs... 5 Pipe Properties Calculation... 8 PIPEPROP Output Limitations References Appendix Appendix Example Appendix Example Page 3 of 19

4 About PIPEPROP PIPEPROP is designed for ios platforms and available on iphone and ipads. This manual gives step by step procedure to use the software, which can be used to calculate composite moment of inertia for offshore pipelines, lift off height and bending moment capacity during lift off. You can download and install PIPEPROP from App Store. Page 4 of 19

5 Unit System Current version of PIPEPROP uses SI system of units. All the inputs for major dimension (length) are in meter and minor dimensions (diameter and thickness) are in mm. Stresses are in MPa. PIPEPROP Inputs Main input sheets for PIPEPROP is in three pages similar to the below. The user interface may vary depending on the platform and equipment (ipad or iphone). Geometry Tab Material Tab Settings Tab Page 5 of 19

6 Pipe OD Steel Outer Diameter in mm. Wall thickness Steel wall thickness in mm. Corr. coating Thickness Thickness of corrosion coating applied external to the pipeline in mm. This can be left blank. Default value is zero. CWC Thickness Thickness of concrete coating external to the corrosion coating in mm. This can be left blank. Default value is zero. Field Joint Thickness Thickness of field joint coating in mm. Anode / Misc weight Weight of anode, miscellaneous weight in kg, to be added while calculating the weight of each joint. Joint Length Length of each pipe joint in meter. Default is m (40 feet). Concrete cutback Length of concrete cutback from each end in mm. Bevel Base Length Bevel base length for concrete. Page 6 of 19

7 Pipe yield stress Yield stress of the pipe steel material in MPa. Concrete sp.gravity Specific gravity of concrete weight coating external to the corrosion coating. Corr. Coating sp.gravity Specific gravity of corrosion coating external to the steel pipe. Field Joint Coating sp.gravity Specific gravity of field joint coating. Concrete compressive strength 28 days compressive strength of concrete. If the value is zero or left blank, composite moment of inertia will not take into account the effect of concrete in stiffness properties. Bond Stress Bond stress in MPa between the steel and concrete. Default is 0.1 MPa. Water absorption Percentage of water absorption for concrete. Steel sp.gravity Specific Gravity of steel. Default is Seawater sp.gravity Specific gravity of seawater. Default is Steel Young's Mod. Young's modulus of steel in MPa. Default is MPa. Page 7 of 19

8 Pipe Properties Calculation Steel Pipe Properties Pipe steel weight, steel cross section area and steel moment of inertia are calculated using basic equations below. A = π (OD 2 - ID 2 ) / 4 MI = π (OD 4 - ID 4 ) / 64 Steel Weight, W steel = ρ steel x A x Length where, OD - Outer diameter ID - Inner Diameter Concrete Properties Modulus of Elasticity for concrete can be calculated as per American Concrete Institute (ACI) as below. E c = 33 x w 1.5 c x f c psi (in USCS units) where, w c - Weight density of concrete in pounds per cubic feet (90 w c 160) f c - 28 day compressive strength for concrete in psi. Other concrete properties such as weight, cross section area are calculated similar to the steel properties above. Correction for concrete cutback and beveling at the ends is applied before arriving the final value. Page 8 of 19

9 Shift in Neutral Axis Shift in neutral axis due to concrete thickness is calculated based on the assumption that the concrete does not take any tensile stress and effective only in compressive stress. The shift in neutral axis (p) is calculated through iterative method such that the composite area of steel+concrete in compression is equal to the area of steel in tension. Page 9 of 19

10 Length of Pipe Influenced by Field Joint Theoretically, length of pipe influenced by field joint is the length required to develop the effect of concrete coating. Figure below [Ref. 1] is used to develop the length of pipe affected by field joint. Below figure is based on concrete of 5000 psi. The value obtained is corrected for the actual concrete strength. Current version of PIPEPROP uses mean curve (close to 20in pipe) for estimating the length of pipe affected by field joint. To calculate the effective stiffness of pipe, an expression developed by Wilhoit and Merwin [Ref. 2] is used. In this computation, the length over which the influence of the joint is significant is regarded as having a stiffness equal to the average of the bare pipe and coated pipe stiffness. EEEE = EEEEEE 2 LLLL + EEEEEE LLLL LLLLLLLLLL Page 10 of 19

11 where, EIj = Average stiffness of bare pipe and coated pipe EIa = Composite pipe stiffness Lpipe = Length of pipe PIPEPROP Output PIPEPEOP output is displayed as soon as calculations are done. The results can be ed in pdf format, if your device supports functionality. Limitations 1. Current version of PIPEPROP uses mean curve for calculating the length of pipe affected by field joint. This however causes a difference of less than 3% in effective moment of inertia and considered negligible. 2. The effective moment of inertia calculated by PIPEPROP can be used only when the stress and strain is within elastic limits. Cases beyond elastic limits are not generally used in offshore pipelaying. 3. Only external concrete and corrosion coating allowed in current version. 4. Input Unit system is limited to SI system. References 1 "Effect of Concrete Coating on the Behavior of Line-Pipe", by Nathan C. Mogbo, Rice University, Ph.D., "Pipe Stresses Induced in Laying Offshore Pipeline", by Wilhoit Jr., J.C and Merwin, J.C., ASME Feb 1967 Page 11 of 19

12 Appendix Page 12 of 19

13 Appendix Example 1 Page 13 of 19

14 This example illustrates pipe properties of bare pipe of outer diameter 457.2mm and wall thickness of 23.6mm. Input data for the pipe is as below. Geometry Tab Material Tab Settings Tab Upon pressing Calculate, output similar to the below is obtained. Page 14 of 19

15 Output of Example-1 Page 15 of 19

16 Appendix Example 2 Page 16 of 19

17 A generic case of pipeline with concrete coating is presented here. The below test data of an offshore pipeline is used as input. The snapshot of input is presented below. Output results indicate that the effective stiffness (EI) from PIPEPROP is 2.367E+09 N.m 2, which differs by 2.3% from the stiffness presented below (2.314E+09). Page 17 of 19

18 Screenshot of input is as below. Geometry Tab Material Tab Settings Tab Results similar to the below will be generated. Page 18 of 19

19 Output of Example-2 Page 19 of 19