Reinforcement for conical reducer

[Davide94]

Good morning,

i've some problems with the design of eccentric conical reducer, particulary:
i define the reducers's conical thickness using the ASME SEC.VIII div 1 UG-32 (f). This paragraph says to calculate the reinforcement when require by the rule in 1-5(d) and 1-5(e): these statement at (a) that their use it's possible for the design of rinforcement, if needed, at the large and small ends for conical reducers sections and conical heads where all elements have a common axis so, if i have an eccentric reducer could i use this chapter?
Moreover, if i can use this chapter, i don't understand why the lower is design pressure, the higher is the allowable stress of cylinder material, the lower is the delta value and consequently i have to use a reinforcement while i haven't got to use it if the design pressure is higher and the lower is the allowable stress of cylinder material.

Thanks in advance,
Regards

 

[pennpiper]

Davide94 (Civil/Environmental)
Your question is very confusing, it sounds a lot like a class project.
I was in the piping field for more than 45 years and never had to add any reinforcement.
What is the material of the Reducer?
What is the Pipe Class (wall thickness of the connected pipe)?
What is the Design Pressure and Temperature of this system?
What is the Commodity in this system?
Where is this Reducer being used (ie: Pump suction/Discharge, PSV Inlet, PSV Outlet, etc.)?
Can you supply a sketch or Isometric of the line?

Better questions = better answers

Sometimes its possible to do all the right things and still get bad results

 

[Davide94]

Hi pennpiper,

thanks for your intersting. I try to explain better my problem: i've got to design a scraper trap with a design pressure of 18.75 bar at ambient temperature. The material reducer is ASTM A 234 WPS with a costant thickness of 9.53 mm, while the connected pipes are 36" API 5L Grade B t=12.70 mm and 32" API 5L X70 t=11.12 mm.
I'd only like to understand if i could use the formulas present in ASME SEC.VIII 1-5(d) and 1-5(e), because 1-5(a) says to use it only for all element have a common axis, but i have an eccentric reducer.
Moreover i'd like to understand the consequences of delta values in Table 1-5.1 and 1-5.2: in fact the lower is design pressure, the higher is the allowable stress of cylinder material, the lower is the delta value and consequently i have to use a reinforcement while i haven't got to use it if the design pressure is higher and the lower is the allowable stress of cylinder material. N.B.: i don't have to use reinforcement but i'd like to understand this.

Thanks in advance,
Regards

 

[KevinNZ]

If this is a purchased reducer made to B16.5. Then all you will know about it is the size of the weld prep at end and that has the same pressure capacity as seamless pipe of the same nominal thickness. The actual thickness should be thicker than the nominal thickness.

If the nominal thickness in pipe is OK for your design pressure, then you can just model the reducer in your piping stress software with he appropriate SIF.

 

[LittleInch]

I really don't understand why you're doing this?

If it's a oig trap then just buy one from a vendor well used to making this sort of thing.

Incidentally, pig traps are not designed to ASME VIII so I'm not sure why you're suing this or what you're trying to do? Is this a conical reducer? i.e. flat sides?

Why are you fixed with three different material grades and thicknesses? Doesn't make sense.

Any manner of suppliers will sell you an eccentric conical reducer

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Davide94]

Thank you all. I decided to not calculate reinforcement for the conical eccentric reducer because this case isn't covered by ASME.
Thank you again