Branch charts for large diameter piping

[jonesey]

I am in the process of expanding a couple of our piping material specifications from 24" NB up to 42" NB. Regarding branch charts, previous companies here have specified use of reinforcing pads and not used weldolets or reducing tees (they had cheap welders from italy). As i would like to standardise our branch charts, anybody have any advice as to when to choose weldolets over butt weld reducing tees and re-pads ? My initial reaction is to drop the use of re-pads totally, use butt weld reducing tees in the sizes they are commericially available and for the rest use weldolets.

 

[FIF99]

Hi,
It's difficult to say, and it's very much depending on other components specified and the applicable service.

For low pressure pipe classes (ASME class 300# and lower) I would allow the use of pipe to pipe connections. Internal pressure as well as external loadings are the parameters whether a reinforcing pad is required or not. Normally this will be assessed by pipe stress engineers.

Small bore branches could be specified by using weldolets/nipolets. For reducing tees we normally specify maximum two size reductions, e.g. 24"x20"; 20"x18".
Other size combinations (24"x16" and lower) RTE and Reducers, which is often more commercial than specifying RTE's with smaller branch sizes.

Hope this serves you.
Regards.

 

[DSB123]

Weldolets are O.K. provided they are welded out correctly. On large bore lines that are relatively thin the amount of weld required to fully weld out a weldolet is significant and the fabricator will not generally do this correctly due to problems with distortion. The consequence is that the resulting branch does not have the correct strength.