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  1. barrind

    PD5500 - Pressure Vessel Repair Proposal

    Thank you for your suggestions. Yes, PD5500 is also intended for the design of vessels rather than checking in service modifications. The weld overlay idea sounds interesting as a preventative measure. I guess you would not recommend this as a course of action after a leak has occurred, since...
  2. barrind

    PD5500 - Pressure Vessel Repair Proposal

    We have a vessel which is corroding internally. Apart from the general overall loss in wall thickness there are a few quite small areas were deeper pits have formed, and have been mapped with a corrosion mapping technique. In the past one or two of these have developed through wall thickness...
  3. barrind

    Shell thermal analysis -> Stress Analysis

    For shell models with sequentially coupled thermal-stress I have always had to create the shell section in the Property module with the temperature variation option changed from "linear through thickness" to "Piecewise linear over" and put 5 in the values box, to end up with NT11, NT12, NT13...
  4. barrind

    Minimum thickness in taper zone of hemipsherical head?

    I will be using API 579 for the FFS assessment. This document covers pitting corrosion but in terms of depth, radius and distance between pits, sounds similar to the statistical methods you refer to in 510 and 653. This will end up being a level 3 assessment however if the assessment is required...
  5. barrind

    Minimum thickness in taper zone of hemipsherical head?

    Thank you. Could you point out a reference in PD5500 or other standard where it says the taper is considered part of the head, just so I can refer to this? The image on the page I refer to has the maximum slope defined and the drawing of the vessel appears to comply with this, so I can assume...
  6. barrind

    Minimum thickness in taper zone of hemipsherical head?

    We have a vessel designed to PD5500. It has hempisherical ends which are connected to the main cylinder in a fashion identical to the bottom picture on page 3/210 (page 268 in the pdf version) of PD5500:2009, i.e. the hemispherical end is thinner than the cylinder and with the median lines of...
  7. barrind

    BS 7608 fatigue design equivalent for welded copper pipes?

    I need to do some fatigue life calcs for butt welds in copper pipework. If it was steel I would follow the guidance given in BS 7608 which contains S-N curve data for various weld configurations in steel. Is there a similar standard available for welded copper structures? If not how would the...
  8. barrind

    Weld stress analysis using axisymmetric model

    In Abaqus it is possible to display a resultant force/bending moment on a cut plane in the viewer module. Could this be used to give the same discreet force and bending moment if you did model the part as an axysymmetric with welds and chose the cut plane from the root through the throat? Then...
  9. barrind

    Weld stress analysis using axisymmetric model

    I'm after some guidance on how to analyse welds based on stresses derived from an axisymmetric model. Basically the shape I am modelling is a can under internal pressrue with top and bottom covers fixed by single sided fillet welds. The designers have asked for confirmation that the weld throat...
  10. barrind

    Best practice for modelling refractory lined pipes for stress analsis?

    Thanks for everyones comments. As a trial I did a run of my model with a steel/refractory composite and you are correct, the resulting reduction in stress did seem excessive. I would add that the stress is due mainly to local bending of the main, not differential thermal expansion. In this case...
  11. barrind

    Best practice for modelling refractory lined pipes for stress analsis?

    Would it be ok then do use the deflection results from the modified modulus model to drive another model which is reverted to the true steel modulus, i.e. using displacement control for the entire model, in order to read stresses directly?
  12. barrind

    Best practice for modelling refractory lined pipes for stress analsis?

    What is the best practice for this, or should I say, most efficient practice? Modelling the steel and refractory as either a composite shell or as a solid seems tricky to me due to getting the properties of the refractory right and how it should interact with the steel shell. I have read that...
  13. barrind

    More sophisticated wind loading on cylindrical structures?

    In the past we have applied wind loading on cylindrical structures by applying the equivalent dynamic pressure on a flat plate of the same projected area as a surface traction load on the wind facing half of the model. This pressure is derived from BS6399. We have basicaly used to standard to...
  14. barrind

    Applying displacement BCs to nodes

    Not sure if I am going to be able to explain what I want here, but here goes. I have a model, part of which I need to remesh to get a much finer mesh. Try as I might I cannot get the seeding right for the mesh to propogate properly and give me a nice coarse mesh far away from this region using...
  15. barrind

    Idiots guide to setting up Abaqus to use dual core cpu?

    We recently upgraded our FEA pcs to dual core xeons running XP64bit and Abaqus 6.6-5 64 bit version. I know there is some info in the Abaqus installation manual but to be honest it seems a bit techie jargon heavy. Given the setup I describe above can someone tell me which files to edit how to...
  16. barrind

    Simulate Dead Load due to self-weight

    I understand what corus is saying now. To me it appears the -9.81 is not an acceleration per se, but a conversion factor to convert whatever unit of mass you are using in your density to whatever unit of force you want in the output and is therefore independant of whether you are working in m...
  17. barrind

    Simulate Dead Load due to self-weight

    I should also add you need to input the density of the material in the property module, though you probably guessed that already. So in my models I have all the geometry in mm, the density in kg/mm^3 and gravity as the oddball -9.81 (m/s^2)
  18. barrind

    Simulate Dead Load due to self-weight

    Just to make you aware, we have found in Abaqus 6.5 that you have to use a value of -9.81 in the gravity dialog, even if you are working in units of mm. We found that if you converted 9.81m/s^2 into mm/s^2 you get an incorrect result. It would be a good idea to model a 1m cube block resting on a...
  19. barrind

    Force required to fracture a rail?

    Thanks for all your replies. We decided to get a second opinion on the failure from a different set of met lab guys. Lo and behold they did indeed find evidence of fatigue cracking at two of the corners of the section. Quite small but flaws none the less. They now reccomend we do three charpy...
  20. barrind

    Force required to fracture a rail?

    The exact material is BS EN 10025 1993 S355 J2G3. The coils are about 2,200Kg and a forklift about 10,000Kg. As I said though we have no way of knowing if these were dropped or what happened, that is part of the mystery. When I look at the drawing, if it was going to fail anywhere due to...

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