>Just a heads up - it looks like your new "header flange to pipe" (picture 5) was welded on the >outside.  I think that 'acceptable practices' state that there should only be a tack weld on the >outside and the actual structural weld should be on the inside.  What does everyone else say?   In >any event be sure to keep an eye on the welds.

>
>Ken Powell

It depends on the configuration.  Generally, if are side loads due to thermal stress, vibration, whatever; it is better to have a snug fit of tube through the flange and weld on the inside.  This reduces the stress on the weld and can increase the reliability of the weld.  The key in either case is the quality of the weld and the heat treatment after the weld.

At least that’s what I recall from my days as a practicing engineer.  Mine are welded on both sides.  I’d prefer they were welded inside only.

Al