Pressure rating of Tee

[Spoonful]

Hi all,


one question here,

for eg, 600NB STD straight tee, will it have same pressure rating as the 600NB STD pipe?

My thought is not. but some supplier have told me the tee have the same pressure rating as the same size pipe.

If see the Tee as a pressure vessel, the branch as a nozzle, since the nozzle to body dia. ratio is so large at 1:1, obviously for a pressure vessel that nozzle need to be reinforced. Where normal Tee have the same thickness at the branch and the body, hence my thought is they can not be at same pressure rating as the pipe.

If the tee need to be have the same pressure rating at the pipe, then at the branch it have to be reinforced, or have much thicker wall thickness.


Could someone please comment my thought?


Thanks in advance.

 

[saplanti]

You are producing assumptions without looking at codes. You need to justify your thought by looking at codes. Have you?

First you need to call the tee with DN600-STD Straight Tee, so they can have the same pressure rating if the materials and conditions match.

Second, the connection wall thicknesses are the same with the piping for the weld thickness match. Non of the manufacturers will sell you the Tee body with exact pipe wall thickness, otherwise they can not justify the code requirements to comply with. If you look at the code you will see that it does not specify the thickness for the tee body. It will give the matching pipe wall thickness and overall dimensions only if we concentrate on the geometry. So manufacturers will find their own way to meet the code requirements and match the nominated thickness at ends.

Material selection is another one. You need to look at the codes for that.


Hope it helps.

Ibrahim Demir

 

[Fizza453]

Spoonful,

Please see UG-44 opening paragraph. It says B16.9 fittings (it includes butt welded tee) shall be calculated by assuming it just as a straight seamless pipe.
You will use joint efficiency E=1 even if fitting is welded and whatever the degree of NDE because paragraph says "seamless pipe".
You should the basic material of the fitting, if it is made from a pipe you will add 12.5% extra thickness.
Any further comment(s) awaited.


Nasir
Welding Engineer
DESCON ENGINEERING LIMITED
PAKISTAN

 

[Spoonful]

Thanks Ibrahim and Nasir,

What I have got here to fabricate a 1200NB Tee. to used at design pressure of 2.8Mpa.

say for my case a 1200NB wall 19.05mm straight tee rolled and welded from boiler plate, from what you saying is this Tee would have same pressure rating at a 1200NB Sch19.05 pipe, made from same material, and the both wall and branch thickness of this tee are the same as the pipe,@19.05mm. I had a look in B16.9, it does not specify the wall thickness or ID, all it gives is the outside diameter at bevel and NB size.

Section 2.1 of B16.9 states " The allowable pressure rating for fittings designed in accordance with this standard may be calculated as for straight seamless pipe of equivalent material per B31"


BUT, I still couldn't understand, if see it as a pressure vessel, branch as a nozzle, with such 1:1 opening ratio, with given design pressure, shouldn't this be using Appendix 1-10 of ASME VIII Div. 1?


Logically, on the body pipe such large area is removed, so the strength of the pipe is weakened, hence reinforcement of the nozzle is needed or much thicker pipe to be used to compensate the missing material. I just couldn’t logically figure it out why same thickness but with such large opening still have the same pressure rating. Could someone please correct me if I am wrong?

Thanks for all the comments.


Spoonful

 

[SnTMan]

Spoonful, have you identified which Code or Standard you are working to?

 

[Duwe6]

Design this fabricated tee using ASME VIII Div 1. An opening this large -- the 'odd' side of the tee -- will require a LOT of reinforcement. That's why forged tees are so thick and heavy - they are integrally reinforced.

When your calculated repad size maks you gasp, recalc using pipe one or two schedules thicker -- gives some integral reinforcement.

 

[Spoonful]

Thanks for all the comments, much more clear picture now. Cheers.

 

[saplanti]

If you are making the Tee, check what you are going to do with Paulin's NozzlePro if available. So you do not get surprises or disappointment.