Torispherical dish end calculations.

Discussion in 'Chemical | Metallurgy' started by prashpan, Aug 23, 2012.

  1. prashpan

    prashpan Enthusiast

    Engineering Discipline:
    Chemical
    Can Anyone give me the formula for calculating plate size needed to make the 10 % torispherical dish ends for a reactor?
    Diameter of reactor is 3000 mm
    Height of Reactor is 3500 mm
    volume required is 25 m3
    Shell Thickness is 10 mm
    I Want to Know is what shall be the diameter of 12 mm circular plate required before it can be bent to form the dish ends?
     
    #1
  2. A.V.Ramani

    A.V.Ramani Guru

    Engineering Discipline:
    Biomedical
    I do not think that there is any formula as such.
    There is a thumb rule used in industries. It is more an internal practice.
    For shallow dishing, the diameter of the plate circle is usually the final OD of the dish plus 3 x t, where t is the thickness of the original plate. During forming a bit of the material flows from the centre towards the edges, which will give some small thickness difference over the profile.
     
    #2
  3. prashpan

    prashpan Enthusiast

    Engineering Discipline:
    Chemical
    Actually I want to calculate the weight of a reactor.
    Now the weight of the cylinder can easily be calculated by multiplying volume X Density.
    But in order to calculate the volume of top and bottom dish ends i need diameter of the plate from which they are fabricated.
    Now the approx weight of such a reactor come out to be close to 8-8.5 tons.
    But by my calculations it is coming out as only 4.5 tons. Even if we add gearbox, motor, nozzles etc. the difference should not be so large.
     
    #3
  4. A.V.Ramani

    A.V.Ramani Guru

    Engineering Discipline:
    Biomedical
    Please see section 4.3.2.3 on torispherical dished ends. The formula for approximate volume (multiply by density for weight) is given there. Calculate the outside volume and the inside volume separately; the difference is the volume of the dished end.
    (Pages 31-32) http://www.scribd.com/doc/36279206/32/Dished-Ends
     
    #4
  5. mechky

    mechky Certified CEan

    Engineering Discipline:
    Mechanical
    See if the following relations help you in computing the correct mass:

    [​IMG]

    CR = Do
    KR = 0.1Do
    SF = 3.5t
    DH = 0.1935Do – 0.455t
    THi = SF + DH

    Do = external head diameter
    SF = straight flange height
    Di = internal head diameter
    DH = depth of dishing
    CR = crown radius
    THi = total internal head height
    KR = knuckle radius
    t = wall thickness

    The external head diameter, 'Do' is usually equal to the outside diameter of cylindrical section.


    Using these relations, prepare a solid model of the torispherical end in SolidWorks or any other software. Apply the material and then you can view its mass. Add it to the mass of cylindrical section and see if the total mass is coming out to be correct or not. This will ensure that the dimensions you are using are correct.

    If the mass comes out to be correct, then only proceed with the theoretical formulae for volume calculations as they are approximate formulae and many simplified formulae give wrong answers.
     
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    #5
  6. prashpan

    prashpan Enthusiast

    Engineering Discipline:
    Chemical
    Okay, thanks for the formulae but i don't have solidworks.
     
    #6
  7. prashpan

    prashpan Enthusiast

    Engineering Discipline:
    Chemical
    Sir i did Calculated the volume by the formula given in the link. but by this calculation the weight is coming out as only 156.662 kg
    Although the height "h" is coming as 578 mm which is correct.
    Taking into consideration that R = Do for torispherical head.
     
    #7
  8. A.V.Ramani

    A.V.Ramani Guru

    Engineering Discipline:
    Biomedical
    I have not done the detailed calculations. To me it appears that 156 kg is probably one tenth. I got about 1.25 tons as the weight by another approximate order of magnitude calculation. Which makes the total reactor weight more like 4.5 tons, which is what you got independently.
    Have you considered the possibility that you are right?
     
    #8
  9. prashpan

    prashpan Enthusiast

    Engineering Discipline:
    Chemical
    Maybe but i will only find out when the reactor is fabricated, will get back when i know the answer.
     
    #9
  10. feroz khan

    feroz khan Newbie

    Engineering Discipline:
    Mechanical
    sir i want to calculate the diameter of dish to be cut for a reactor of shell having id 1000 mm & thickness 8mm.Please help me .
     
    #10

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