Thickness of Blind plate for Hydrotest

[kvbalu]

Hi

I am looking for some calculation or information for stiffening of Blind plates for Hydrotest. The Plates avaialable aren't sufficient for the hydrotest pressure. The diameter of the pipe is 54". the wall thickness of the Pipe is 12mm. I tried calculating the required thickness as per the Sec VIII Divn 1 code. The Plate is proposed to be welded at the end of the Pipe.

The proposal is to weld stiffeners outside on the Plate so that the hydrotest can be done. Any calculations available for determining the size of the stiffening memebers ?

Any information/calculation worksheets in this regard is solicited.
Balu

 

[eliebl]

Look at braced and stayed plates in VIII-1. That may provide a solution.

EJL

 

[MJCronin]

balu,

ASME B31.1 (Power Piping Code) has a formula for calculating the thickness of blinds and temporary blanks.

However, at 54" diameter, you are talking about a significant wall thickness for a flat plate.

Any possibility of a F&D or Elliptical head cap at the end of pipe ?

-MJC

 

[texag]

kvbalu,

You could refer to Roarks's for flat plates, table 24 case 10b, to size your end cap. As MJCronin mentioned, that likely will be a significant thickness.

texag

 

[vesselguy]

Balu,

You don't use a flat plate for this application due to the diameter. Use a dished head as a hydrotest blind.

 

[gr2vessels]

Hi balu,
Here's my two cents;- you could work out a flat plate with all sort of stiffeners on the back, as per the calculations you will be responsible for. However, by the time you finish welding miles of stiffeners on your plate, your costs will go thru the roof, let alone the time spent on design, cutting, welding, you'll be better off with the above advices from the experienced people. Buy a suitable dished end, guaranteed for the hydrotest.
For your benefit, do run those calculations in your spare time and estimate the costs / time for using the reinforced flat end. Let us know the outcome, it might be instructive to other engineers also..
cheers,
gr2vessels

 

[dcasto]

Flat Plate Skillet Calculation from B31.3 section 304.5.3


You'll be looking something near 4" thick, but you need to do the calcs.

 

[zdas04]

dcasto,
Just curious, how did you get a plate thickness when the OP never mentioned a pressure?

David

 

[FSB01]

I was asking myself same question, then I see that pipe thickness is given. If you calculate MAWP of the pipe you can get an idea of blind plate thickness. But that is just an idea, and I would not recommend anybody anything based on that.

As domed head might seem as a better solution, flat head still have some advantage (getting a domed head will take longer than just a plate) and when carbon steel is in question, material saving might be not so great.

 

[dcasto]

I used pipe thicknes, then did a calc. I just wanted the OP to know the relative size, he still needs to do calc. If he does it and comes up with 12 mm or 1200 mm they'll know something was wrong.