Reinforced Flathead
Reinforced Flathead
(OP)
The company I work for primary product line is the manufacturing of butterfly valves. I need to design a pressure test chamber a hi-performance, zero leakage valve we are currently building. The chamber will consist of a rolled shell and a flathead. The chamber will then be connected to the butterfly valve and valve’s disc will basically act as the other head. Due to the size, about Ø82”, the test pressure and since we are a Code shop I am designing the chamber per Section VIII, Div 1.
I reviewed UG-34 and I am connecting the flathead to the shell as shown in Fig UG-34(f). When I calculated the required thickness for the flat head, using C=0.2, it worked out to be about 1-1/2" thick. Not very particle for a test chamber I am going to use 1 time. So I decided to use a waffle/honeycomb grid to minimize the thickness required. The problem is I cannot figure out how to calculate the reinforced flathead per Code. I reviewed UG-47, but that really doesn’t apply. Can anyone point me to the correct section or offer and advice?
I reviewed UG-34 and I am connecting the flathead to the shell as shown in Fig UG-34(f). When I calculated the required thickness for the flat head, using C=0.2, it worked out to be about 1-1/2" thick. Not very particle for a test chamber I am going to use 1 time. So I decided to use a waffle/honeycomb grid to minimize the thickness required. The problem is I cannot figure out how to calculate the reinforced flathead per Code. I reviewed UG-47, but that really doesn’t apply. Can anyone point me to the correct section or offer and advice?





RE: Reinforced Flathead
RE: Reinforced Flathead
RE: Reinforced Flathead
OR
just get the 1.5" plate and add it to the scrap pile when you are done.
Seems like there are several threads on this topic in the forums here.
Good luck.
Brian
RE: Reinforced Flathead
It would seem that rib stiffened flat heads are not allowed by Div 1.
Try this post:
http://www.eng-tips.com/viewthread.cfm?qid=93914
Brian
RE: Reinforced Flathead
RE: Reinforced Flathead
@waskillywabbit: The thread really doesn't say ribs aren't allowed. It has just as many people saying "yes" as it does saying "no."
RE: Reinforced Flathead
Good luck.
Brian
RE: Reinforced Flathead
RE: Reinforced Flathead
Also you may have the option we had when we had some special valves made. We purchased the 2 Blind flanges used to test the valves, the purchaser might need the flanges.
There is an easy way out for a one time operation.
Rent one, flange that is.
This is just one of several companies that rent blind flanges.
http://www.usaindustries.com/pipe_blinds.htm
RE: Reinforced Flathead
rmw
RE: Reinforced Flathead
if you rib it, you can bring it down to 1/2 to 3/4 in.
I will try to find calcs and advise.
I may have the calcs for internal ribs only but even inside will work for your test job.
er
RE: Reinforced Flathead
Also read the "coned section with flat plate end" thread that ran several days ago.
On designing the rib-stiffened plate, you can design the plate itself as fixed-fixed beams running between the ribs (fixed due to symmetry at end). You then need enough strengh at the beam end to support the loads you're putting into it. Generally, the beams would all be parallel, not a waffle layout. Or maybe just an X-shape, then use the quarter-plate load case from Formulas For Stress and Strain to design the plate.
You can stack plates if you're careful on the design. Two= 3/4" plates do not have the same bending capacity as one- 1.5" plate, but you could stack maybe three of them, or two 1" plates, or some other combination.
Also, if designing just a single plate, check if it falls under the "large deflection" criteria of Formulas for Stress and Strain- if so, that will increase the (calculated) strength of a given plate.
Your allowable stress could be set somewhat higher than normally used for pressure vessels. Especially true if it's just a hydrotest (no signficant air volume). For example, I think AISC allows 27 KSI for bending in a 36KSI plate.
RE: Reinforced Flathead
RE: Reinforced Flathead
BTW, I am still waiting for purchasing to get pricing on the dished head.
RE: Reinforced Flathead
By the time you're done calculating & welding a dished head woulda been easier. - plus the ribbing takes up space too.
RE: Reinforced Flathead
RE: Reinforced Flathead