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#43575 - 07/04/11 09:06 AM Lifting vessel with sling
M Waheed Offline
Member

Registered: 03/08/07
Posts: 46
Loc: UK
Hi,

Is there any standard method for calculation of stresses in cylindrical pressure vessel being lifted by sling. In "Pressure Vessel Design Manual 3E" by Dennis Moss, there is one page (page number 413) for design of vessel for choker. However I have confusion about the terms Zin, Zout and A. Has any body used these equations?

Many thanks in advance.
M Waheed

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#43581 - 07/05/11 04:17 AM Re: Lifting vessel with sling [Re: M Waheed]
M Waheed Offline
Member

Registered: 03/08/07
Posts: 46
Loc: UK
Hi,

I would like to add following to my previous post.

The method given in "Pressure Vessel Design manual" is a combination of case 12 and 18 (Table 17) of book by R J Roark, 5th edition. I used this method and calculated stress as 6M/(t*t). It gives me very high stresses (thousands of MPa). However if I use case case 15 of table 30, I get reasonable values of stresses such as ~170MPa.

Is any body out there who have used these equation to calculate stresses in vessel lifted by sling or know any other method?

Thanks and regards

M. Waheed

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#43613 - 07/06/11 01:50 AM Re: Lifting vessel with sling [Re: M Waheed]
asd23789 Offline
Member

Registered: 06/08/11
Posts: 113
Loc: India
Hello M Waheed,

I haven't used the method described in Moss.
I studied the equations.

a) The term Zin,Zout are section modulus of the Beam at the innermost and at the outermost fiber respectively.

b) Also the A term seems to me the cross sectional area of the Beam since due to the "T" force the beam will be subjected to shear.

Hope this helps.

Regards
asd23789

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#43623 - 07/06/11 08:20 AM Re: Lifting vessel with sling [Re: M Waheed]
M Waheed Offline
Member

Registered: 03/08/07
Posts: 46
Loc: UK
Thanks ASD23789 for your response,

I used these terms you describes as well as using 6M/(t*t). This gave me very low stresses such as 1.5MPa. Whatever terms I use the stresses are not what one would expect.

Thanks

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#43632 - 07/06/11 12:43 PM Re: Lifting vessel with sling [Re: M Waheed]
asd23789 Offline
Member

Registered: 06/08/11
Posts: 113
Loc: India
Hello M Waheed

can you send me the input data you use for the calculation?
I will try it to calculate at my end?

Regards

ASD23789

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#43717 - 07/12/11 06:28 AM Re: Lifting vessel with sling [Re: M Waheed]
M Waheed Offline
Member

Registered: 03/08/07
Posts: 46
Loc: UK

Thanks asd23789,


Vessel OD = 1276

Thickness = 10 mm

Weight of the vessel to be lifted = 12300 Kg

Length of the vessel = 7 meters

Regards

M Waheed

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#43725 - 07/12/11 12:25 PM Re: Lifting vessel with sling [Re: M Waheed]
asd23789 Offline
Member

Registered: 06/08/11
Posts: 113
Loc: India

Hello M Waheed

I am doing calculations as per "Design of Vessel for Choker (Cinch) Lift at Base" in Moss. (Page 413)

As per input data provided by you, I have considered following assumptions:

1) The Sling is used on the vessel OD. Thus the properties of the base ring "A" and "Z" are now the properties of vessel. thus A=C/s area of vessel and also Z = section modulus of vessel. (Please refer Note given in Moss)

2) As per Moss angle theta = 30 deg

3) Load on tailing point T = 12300 / 2 = 6150 kg

4) Impact Factor = 1.5

5) Total Tailing Load = 6150*1.5 = 9225 kg

Output

1) uniform load = p = 9225/ (1276*0.5) = 14.459 N/mm

2) C/s area of vessel = 39772.562 mm2

3) Moment of inertia = MI = 7968711404 mm4

4) section modulus = Zout = 12490143.27 mm3 Zin = 12689030.9 mm3

5) hoop-stress deformation factor is alpha = MI / (A*R*R) for thin rings (Roarks:TABLE 9.2 Formulas for circular rings ,edition:7th)

alpha = 0.12305

6) as per table 12 of 9.2 k2 = 1-alpha = 0.87965

7) as per table 12 of 9.2 of Roarks MA (moment at A) = -1693831.59 N-mm

8) as per table 12 of 9.2 of Roarks MC (moment at C) = -2307906.80 N-mm

9) The forces TA and TC i calculate as per MOSS, since Table 18 of 9.2 of Roarks mention angle phi which moss doesn't mention.

10) the combined stress came very less approx 1 MPa.

Hope this helps.

Will let you know if other method is available.

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#43755 - 07/14/11 09:22 AM Re: Lifting vessel with sling [Re: M Waheed]
M Waheed Offline
Member

Registered: 03/08/07
Posts: 46
Loc: UK
Thanks ASD23789,

I also came with the same results. However the stresses are so low that seem unrealistic. I also have doubt about the use of Zin and Zout.

Thanks for your help

M Waheed

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#43789 - 07/16/11 05:52 AM Re: Lifting vessel with sling [Re: M Waheed]
sameercnn Offline
Member

Registered: 01/11/11
Posts: 34
Loc: Karnataka, India.
dear Mr. ASD23789,

Even i have similar problem, can you send me your email id so that i can contact you if you dont mind.

thanks,
Sameer
sameercnn@rediffmail.com

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#43791 - 07/16/11 07:30 AM Re: Lifting vessel with sling [Re: M Waheed]
asd23789 Offline
Member

Registered: 06/08/11
Posts: 113
Loc: India
Dear Sameercnn

My email Id: asd23789@asia.com

Regards

ASD23789

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