NFPA 85/B31.1 veiws on npt pipe adapters, bushings, unions - oil pipe

[USAeng]

This if for fuel oil piping on a utility boiler-

Our company works to NFPA 85 and B31.1 for fuel piping systems.

Does anyone know if nfpa or asme b31.1 has any rules or guidelines regarding the use of pipe adapters, bushings, and unions? I cant seem to find anything while reading through each book... this is for mostly small piping 1/2"-2".

I find for piping with threaded connection the pipe shall be extra strong (schedule 80)... I assume this means the fitting as well shall be schedule 80

The owner of our company has a notion that there are special guidelines though that say you can not use bushings and adapters and such... I see no reason why this cannot be used and see nothing in nfpa or B31.1 to back up his thoughts.

 

[TBP]

The fittings will only be sch 80 if you're going to butt weld them. For screwed, it'll be something like class 3000 forged steel fittings, perhaps class 300 malleable iron, etc.

 

[Canadieng]

Regarding B31.1 -

Have a look at Table 126.1, which allows ASME B16.11 fittings, which includes threaded couplings, bushings, ...

 

[Duwe6]

Not Class 3000, please. A threaded 3000# '3M' fitting body that is threaded becomes a 2M fitting. When you spec 3M threaded, you get an *extremely* heavy, Class 6M body [sutiable only for Sch 160 and XXH pipe] that has threads cut into it.

Don't ask how I know this, please.

 

[TBP]

Duwe6 - I have never ordered a class 3000 threaded fitting, and receieved anything BUT a class 3000 fitting. If I had, I would have sent it back, with instructions that I be sent what was stated on the purchase order.

If you said you needed a fitting suitable for a 3,000 PSIG service, then perhaps the correct fitting was - in fact - a class 6000.

 

[USAeng]

Anything special about fully threaded nipples? I have a guy saying you are never allowed to use fully threaded nipples... he claims to have heard it directly from asme...

I guess I am a little confused about the pipe fittings...can you use schedule 80 pipe fittings like bushings, nipples, etc? or do the threads make the fittings too thin? B31.1 says that the pipe that is to be threaded must be at least schedule 80... so it is already taking under consideration that the threads will be cut into the pipe as it calls out the schedule 80...

How do you come up with using class 3000 fittings?

I would buy this nipple as I can not find anything in b31.1 saying we cannot use it for piping with pressure less than 100 psi. It conforms to the asme threading B1.20.1 spec

Mcmastercarr part number: 7727K191


is there anything wrong with picking it that you can think of?

Thank you for your help... I am trying hard to read through the code carefully to make sure I understand this... it is a learning experience for me. Thank you.

 

[MikeHalloran]

I can't cite a specific prohibition, but I know that close nipples are definitely _not_ preferred in many industries, because they're mechanically weak, and difficult to disassemble. I tend to specify short-ish hex nipples instead.





Mike Halloran
Pembroke Pines, FL, USA

 

[USAeng]

Also, would anything be wrong with a class 300 malleable iron fitting? I see b16.3 listed in table 126.1 and I can get class 300 malleable iron elbows from mcmaster that are made to b16.3. Thanks again

 

[TBP]

I believe that the issue with close nipples is that there's nowhere on them to stamp any kind of ID, heat numbers, etc.

 

[USAeng]

This seems like it should also apply to bushings as they are fully threaded inside and outside...

 

[USAeng]

well... I guess there is the little hex area...

 

[USAeng]

ok... b31.1 says in 124.5 that there are exceptions to using malleable iron fittings in 122.7.2.

122.7.2-
A) "Seamless steel or nickel alloy piping materials shall be used in all areas where line is within 25 ft of equipment or other lines having an open flame. Seamless steel or nickel alloy pipe shall also be used for fuel oil systems located downstream of burner shutoff valves"

So this seems to rule out using any fittings made of anything but forged steel as our equipment is all within 25' of the flame and all downstream of the shutoff valves... so no brass fittings or ductile or malleable iron correct?