What to do when the code doesnÆt cover your situation? ASME B31.1 Power Piping

[Ajaxtheminor]

Currently we are designing tie-in points for a boiler house in a Kraft mill, the pipe runs (headers) we are teeing into range from 40NB (1-1/2”) to 200NB (8”), the contents range from black liquor, steam, condensate, potable water and pulp.
Company policy is to use ASME B31.1 which we have done, the tie-ins encapsulate a double block and bleed (DBB).
The conundrum is we will not be hydro testing the DBB tie in points in their entirety, isolation will be form the first block valve off the main run (header) therefore hydro will only be of the new lines.
I can’t seem to find anything in ASME B31.1 that suggests other forms of testing the DBB system for quality assurance and compliance with the code i.e. increased non-destructive testing (NDT) in lieu of hydro test, like radiography (RT), Ultrasonic testing can’t be used because thickness is too thin.
We have a solution in that the engineering design will specify extra NDT in the form of RT to compensate for the fact that we aren’t hydro testing the DBB system in full.
Have I missed something in ASME B31.1 about this situation?

 

[metengr]

No. If this is nonboiler external piping, the owner is permitted to evaluate options.

 

[Ajaxtheminor]

The Piping is part of the boiler process in the boiler house.

 

[Ajaxtheminor]

 

[metengr]

So, the piping section shown upstream of the first isolation valve are indeed part of boiler external piping. I would fabricate the boiler external piping as indicated between the header and first isolation valve as a component and perform a hydrostatic test in the shop. Once this is completed, install and RT the two connecting welds, as you mentioned. This work could be done under both the National Board Inspection Code and B31.1.

 

[Ajaxtheminor]

cheers

 

[PetieSmo]

Is the tie-in to the header intended to be a hot tap connection? Or will this be performed during an outage?

If a hot tap is required, RT seems your only alternative while the system remains at operating pressures. However, if being performed during an outage or bypass, there may be opportunity to hydrotest the tie point.

Also, what do the owner's pipe specs & testing standards require?

 

[Duwe6]

What metengr said. You are tieing into a header that has been in service. The 'new construction' rules no longer apply - thus you use NBIC [Nat'l Board] to make the tie-in.

And IMHO, using a steam code [B31.1] in a paper mill is not appropriate. B31.3 - Process Piping would have been a much better match. And also what I've seen used in *all* the mills I've worked/inspected in.