B31.1 vs B31.3 3

[maddocks]

I am installing a 750 HP steam boiler into an existing facility. All piping appears to be contructed to B31.3. If I continue with this, will I be in compliance with B31.1?



Jim Maddocks, P.Eng.
V.P. Engineering
jmaddocks@gasliquids.com
403-250-2950

 

[metengr]

You should review Figure 300.1.1 in ASME B31.3 - 2004 Edition, which is a diagram that illustrates the application of B31.3 piping at equipment. This diagram will answer your question regarding B31.1/ASME Section I limits.

 

[maddocks]

Thanks, the diagram is a little tough to interprete, but it appears that B31.3 can be used for boiler external piping including the steam and boiler feed water. If so, where does B31.1 come into effect?

Jim Maddocks, P.Eng.
V.P. Engineering
jmaddocks@gasliquids.com
403-250-2950

 

[metengr]

In Figure 300.1.1 and referring back to the paragraph in 300.1.1 (c), it states that the joint connecting the piping to equipment is within the scope of B31.3.

Now, if you look closely to the box in the upper right hand corner of the figure, it states Boiler External Piping that conforms to B31.1. My interpretation is that the boiler island (the box) includes external piping under B31.1. The hook-up to this island and joint (weld or flange) falls under B31.3 to the equipment.

 

[ApC2Kp]

maddocks,
The key is where the valve is located in the piping. The piping from boiler shell to first valve (second valve in blowoff piping) is in the jurisdiction of ASME B31.1 as "Boiler External Piping" or BEP. This piping has practically all the same type of documentation and AI stamp as the Section I Boiler requirements. Piping that is beyond that valve could be B31.1 Power Piping Code, but as "Non-Boiler External Piping" or NBEP, with less exam and documentation, no AI stamp. The piping beyond the valve could also be in jurisdiction of B31.3 Process Piping Code, if the Owner so chooses, as metengr has pointed out in the B31.3 diagram to illustrate.
Another way to look at the break point is to consider the extents of a boiler hydrotest. The annual boiler inspection will include a hydrotest. The piping with valves that will block in the boiler will be within B31.1 Power Piping BEP. If the boiler is in a power plant, most likely the Owner will have all the piping in the power plant designed and built to the B31.1 Code, NBEP. A process or chemical plant owner would be likely choose B31.3 process piping Code that has different design, test, and construction. You need to have Owner state what Code that is his choice for the piping beyond the boiler valves. Be careful since "Boiler External Piping" has different meaning to Authorized Inspector, than to say the piping external to system.
The B31.3 exam and test requirements will have more radiography exam than for B31.1 at moderate psi design. The pipe wall thickness of B31.1 will likely be thicker due to lower design allowable atresses of Power Piping Code.