Plate thickness at the end of pipe. 1

[Squaric]

I'm struggling to find the plate thickness that I need to hold 10 bar in a 304l 2mm thick pipe. The plate will be welded on.

Can anyone pass on an equation to find the plate thickness?

Thanks,

Pete Hunt

 

[pennpiper]

Why don't you just use a Weld Cap of the same wall schedule as the pipe?

 

[Squaric]

Thank you for your reply. The overall component needs to be pressure rated to at least 10 bar and so I need a calculation to show that the thickness of the plate has been taken in to consideration.

I'm currently searching though the companion guide to ASME, boiler and pressure code, but I can't seem to find any solution to my problem without it seems having to over complicate matters with flanges and the like.

 

[metengr]

ASME B31.1 or 3 depending on fluid service. You should be using one of the piping codes for this application anyways to understand welding and inspection requirements.

 

[Squaric]

Thank you for your reply metengr. Yes I understand what you are saying, but I'm currently just after a quick fix. Is there even an equation to find out the thickness I require?

The part is needed for a prototype. Once this proof of concept has been made, the professionals will be brought in.

 

[metengr]

Squaric;
Instead of proof, go to ASME B16.9 "Factory-Made Wrought Butt Welding Fittings" and purchase an SA 182 or SA 240 Grade 304L stainless steel butt welded hemi-head pipe cap. The cap should be for Class 300lb service or it could be lower rating if you know the design conditions - pressure and temperature.

 

[Squaric]

Again thank you for your reply Metengr. I'll be sure to look up that section tomorrow in work.

If it makes a difference to your suggestions the item is at a pressure of 150PSI, at a temp of 300K, (25degsC)?

 

[racookpe1978]

2 mm wall thickness for 150 psi rated system?

No, that's not right unless you have an impervium-coated impossibloadenum crystal vessel. Regardless of pipe (pressure vessel) OD.

 

[AllHandlesTaken]

If you must go with the flat end - have a look at UG-34; ASME VIII-1

 

[Squaric]

racookpe1978 - Unfortunately we couldn't get in contact with the death star manufacturers to get hold of the impervium-coated 304l .

After looking through ASME B16.9, I'm right in thinking I need a 6mm plate?

It's to be welded to a 2mm thickness 304l, 8inch OD pipe, needing to hold 10bar/140PSI.

 

[boilerone]

Why can't you use commercially available 304L welded pipe end caps just like pennpiper says? You can find a product that is rated for your pressure and temperature then you can avoid calculations. Besides end caps are always better than flat end plates (welds are on the straight parts, no bending stress).

 

[AllHandlesTaken]

Squaric - How did you infer that you need a thickness of 6mm for a flate plate from B16.9?!?!?

 

[Squaric]

Sorry, I should have said, after looking through ASME B16.9 and calling a supplier they suggested that 6mm is the thickness needed.

They're suggestion was a 6mm thick flat 304l end plate, to hold the 150PSI. As they don't stock pressure rated end caps. (I presume there end caps are a miss match of quality/suppliers so they don't offer a rating on them.)I presume from your reaction this is totally wrong? Too thin?

So basically, I'm looking for what ever would be cheapest to produce in the long run. Welding would be in house, and everything has been sourced apart from the part in discussion. End cap or flat plate?

Would a SA 182 or SA 240 cap hold 150 PSI? I'm struggling to find any suppliers online that have a pressure rating in PSI/KSI/BAR on their website.

 

[jmiles]

Ok somethign is not adding up here,

you said your using NPS 8" pipe? 304L?

Well fromt he tables ive found schedule 5 pipe in 8" size has a wall thickness of 2.77 mm which is greater than what you say you have (by about 38%)

So i guess my first question is have you fabricated your own pressure pipe from rolled plate here? if so who did the initial calculations ont he pipe itself? im just thinking that your bigger problem si you have pipe here that was not designed to any standard specification, which understadably does make it harder to do the calculations.

All that being said though B31.3 has the necessary calculations to determine the correct wall thickness of pipe andassuming the pipe will hold the pressure you need then a standard fitting will work.

I am a bit concerned though that you are looking at a 2mm WT pipe and thinking 6 mm end caps might be too thin here... yes pipe can be thinner than a flat plate, but still...

 

[AllHandlesTaken]

Sorry, my exaggerated disbelief was due to the fact you concluded a flat plate at all from B16.9, not so much as the 6mm thickness (that sounds like a reasonable number - BUT check with UG-34 from ASME VIII-1!! It is a REAL simple calculation, it only gets slightly more difficult if you are bolting the plate on)

B16.9 fittings are rated as per the straight pipe they have been designated as - that is, you will not find an explicit pressure-temperature rating. Rather you will find them marked with a schedule number that means they will have the same capabilities of the equivalent straight pipe.

 

[Squaric]

The thing that isn't adding up is that I'm a Chemist and so this is new to me.

I realise the standard for 8" is 2.77mm, (The 2mm has been arranged for us and is pressure rated above the needed 150 KSI, it's also cheaper and lighter then the 2.77mm) which was why I was asking for the equation to do my own calculations in the first place as I realise using non standards will complicate things.

'I am a bit concerned though that you are looking at a 2mm WT pipe and thinking 6 mm end caps might be too thin here... yes pipe can be thinner than a flat plate, but still...'

I'm still not sure from both your comment and the previous one wether 6mm is too thick or too thin? As mentioned the 6mm was quoted from a suppiler.

 

[AllHandlesTaken]

I WILL REPEAT!!!!!!

SEE UG-34 from Section VIII Division 1 of ASME BPVC for the calculation!!!!!

Besides, you will HAVE TO go with this flat plate because there is no standard fitting for an OD of 8"

 

[SnTMan]

Squaric, no one is clear on whether you have pipe (8 5/8 OD) or tubing (8 OD) and this is kind of complicating the discussion.

It is also unclear whether this is to be a Coded application, in which case you will have to use a pressure vessel Code, such as Sec VIII, Div 1, or perhaps a piping Code such as B31.3, or a non-Coded application, in which you can use whatever design methods you like.

As AllHandlesTaken says, UG-34 is usable for a Code application, if not Code, you could look at Roarke, Table 24, Case 2.

Regards,

Mike

 

[IFRs]

You could weld a standard blind flange or a plate of equal thickness to the end of the pipe.

 

[jte]

...after checking that the 2mm thick wall can handle the moment imposed by such a connection. This type of connection does not equal a weld neck flange.

jt