wind load on horizontal vessel 3

[Someone11]

I have some confusion in how Pv ELITe calculates the wind area.. on vertical vessels it was quite understandable as it multiplies the height of element and the effective wind diameter. But for the horizontal vessel,i followed the procedure given in the Moss but the result didnt match for the head part. My vessel has OD of 96". wind load multiplier 1.2, so the effective dia here becomes 115.2", then the length from top of head upto the tangent would be= 96/4 + 2"(Straight flange length is 2")=26". wind area should have been 26"*115.2" but the answer is way too far from this. Am i missing something? This calculation is for the transverse force on vessel.

 

[Jay_]

Maybe it’s something that has to do with your wind height.
Regards.

Detailing is a hobby,

 

[r6155]

@ Someone11
Your hand calculation is wrong.
Which is distance L between tangent lines. Take a paper, pencil, calculator and sketch the equipment. Then calculate the areas and check it.

Regards

 

[Someone11]

@jay if wind height was involved then wind area would have been same for all. but its not that in this case.

 

[Someone11]

@r6155

 

[Someone11]

@r6155
The snapshot that i have shown is from the report of pv elite. The ans for the second row matches my answer ( seam to seam distance is 20ft and wind dia being 9.6ft. multipying them and converting into inch generates the same ans. but the problem is for the first and last row.. what lenght have they taken here to calculate the wind area? shouldnt it be the length from top of the head to tangent line?

 

[Jay_]

Try to change wind height to 0.

Detailing is a hobby,

 

[Someone11]

@jay
im sorry but maybe i didnt get you. wind height is the height from bottom of saddle to centre of vessel. its not possible to make it zero

 

[r6155]

@ Someone11
Sorry, but you must do special training.
You must first know how to do the calculations by hand, then you can use the calculation program.

Regards

 

[BJI]

I haven't used PVE in a long time but it looks like your area is roughly equal to the projected area of a dished head, not an approximated rectangle. This would most likely exclude the straight flange, since the cylindrical element extends to the tan line.

 

[Trestala]

@r6155, I'd like to see you prove PVElite calculation is correct.

@Someone11, my observation is that PVElite uses length as "2/3(dished head height + insulation) + straight flange", then multiplied by effective diameter to get the wind area. It is far from actual cross-sectional area ellipsoidal head. Depending on how you get wind pressures, most of the time shape factor for cylinders is applied also for wind area of heads where shape factor might be lower, so there should be some multiplier when applying also to heads. Shape factor ratio between spheres (0.50) and cylinders (0.70) = 0.714 might be justifiable also instead of 0.667 as reduction factor.

It is better for someone from PVElite clarifies this.

 

[Someone11]

@RaymondN thank u so much.. it cleared my confusion

 

[r6155]

@ RaymondN
Why must I prove that the PVElite calculation is correct?

Regards

 

[Mohanlal0488]

Hi Someone11

Out of curiosity what code of practice does PVElite use to calculate wind loading?

I would suggest reviewing the code of practice that the software is using. Some of the data/equations and graphs for wind loading on cylindrical shapes can have some very funny numbers and clauses to them.

 

[saplanti]

Please note that the software that we are using is a tool to estimate our expectations as close as possible to the reality. However we can introduce loading in several optional ways in the software. Some cases the standard load application which is built in one option may not be the right choice, so we need to check other options that suitable for our application to be able to manage adequate load application.

We should not expect everything from a software, we need to engage ourselves to learn what a software can do or cannot do. Software have user guides, technical quides etc.... so we need to read them to understand the tool’s abilities and learn how to use them. Perhaps we will have more but targetted questions that can be answered by the software provider or experienced person on the software.

I understand this sometimes is difficult in busy environments, but we still need to read these guides if we work with these tools.

I write this for all the users, not particularly for the OP.

 

[Someone11]

@r6155 Please with due respect first read the questions properly then only answer.
@saplanti i am doing hand calculations and just compared it with that of Pv elite. My calculations matched in vertical vessel but in horizontal i got stuck in wind area calculations. its not that i didnt search any books or read any guides..i came here at last after going through stuffs i had..I will surely keep ur piece of advice in mind.. thank you
@Mohanlal0488 i have used Asce 2010 for the calulations..I have gone through the asce wind code too and will go through it once again thank u
my expectations from this forum was met by the answer of @Raymondn. Glad to know such people are here in this forum.
regards

 

[Someone11]

@BJI thank you for the reply

 

[r6155]

Someone11
"then the length from top of head upto the tangent would be= 96/4 + 2"(Straight flange length is 2")=26". "

Diameter of head is not 96” is 9.6 ft x 12 = 115,2”

Regards

 

[Someone11]

@r6155 goodness!!! I'm designing vessel of 96"Od and ur saying it's not 96". 96" equals 8ft.. the wind dia given there is 8*1.2 (1.2 is the wind load multiplier) which then gives 9.6ft. this is the wind diameter which is used in calculation of wind load. Wind dia is not used for calculation of depth of head..

 

[Trestala]

@r6155,
Sorry, but you must do special training. Your calculation is incorrect.