B16.5 Reducing Flange - Length Through Hub Dimension
B16.5 Reducing Flange - Length Through Hub Dimension
(OP)
We've received a few B16.5 reducing flanges from a supplier that have come in longer than I expected. I was hoping that someone could tell me if I'm out to lunch on my interpretation of B16.5:
First, I don't have the 2013 edition yet, my references are per the 2009 edition. If there are any changes that affect this question, please let me know.
Size: NPS10 x NPS24 300# Weld Neck Reducing Flange
Per paragraph 6.8.1: Flange thickness and facing shall be the same as those of the standard flange of the size from which the reduction is being made (NPS24):
Am I out to lunch?
First, I don't have the 2013 edition yet, my references are per the 2009 edition. If there are any changes that affect this question, please let me know.
Size: NPS10 x NPS24 300# Weld Neck Reducing Flange
Per paragraph 6.8.1: Flange thickness and facing shall be the same as those of the standard flange of the size from which the reduction is being made (NPS24):
- Table II-11: tf = 2.69"
- Para 6.4.1: facing = 0.06"
- Table II-11: hub height = Y-tf = 4.56" - 1.81" = 2.75"
- Total length: tf + facing + hub height = 2.69" + 0.06" + 2.75" = 5.5"
Am I out to lunch?





RE: B16.5 Reducing Flange - Length Through Hub Dimension
I also wonder, why are you question this since you have already received the flanges?
prognosis: Lead or Lag
RE: B16.5 Reducing Flange - Length Through Hub Dimension
RE: B16.5 Reducing Flange - Length Through Hub Dimension
RE: B16.5 Reducing Flange - Length Through Hub Dimension
a. the vendor/supplier made the flange
b. the vendor designed the flange
c. the vendor designed the flange in accordance with ASME B16.5
d. a reducing flanges would have a 'Y' dimension (length through the hub) consisting of part of the larger size dimensions and part of the smaller size dimensions.
e. the dimensions provided by the poster for the 'Y' dimension is 6.6"(+)
f. my search via Google for actual dimensions for Class 300 24" by 10" (see note) RFWN Reducing Flange produced a dimension of 6.6"(+)
(note: I was taught to always designate a Reducing Flange by the rating then the larger size then the smaller size.)
Thus I agree with the suppliers interpretation.
prognosis: Lead or Lag
RE: B16.5 Reducing Flange - Length Through Hub Dimension
d.: you say that reducing flange should consist of 'Y' dimension consisting of part of the larger size dimension and part of the smaller size dimension. So larger size part (NPS24 flange) provides 2.75", and the smaller part (NPS10 hub) provides 2.75", for a total of 5.5"
f.: Could you provide a link?
I've done some further searching myself, and found a different conclusion: Link (go to second FAQ question)
Does anyone else have experience with this?
Cheers.
RE: B16.5 Reducing Flange - Length Through Hub Dimension
What is important is for the OP to realize that he has the flanges and he needs to move on with the project.
He should also use this as a 'Lesson Learned' and contact vendors in the future if there is the possibility of a requirement for non-traditional flanges or fittings.
All of us need to recognize that some of the dimensional issues is ASME Standards are "Recommendations" not "Absolutes". I experienced a situation where we had (3) 24" x 18" Weld-O-Let (P91 material) in a complex fitting-to-fitting configuration. The Catalog had an "A" dimension of 9". When received at the shop one had an "A" dimension of 8", one at 9" and one at 10".
Enough said.
prognosis: Lead or Lag
RE: B16.5 Reducing Flange - Length Through Hub Dimension
I am trying to learn here, not just blindly accept the word of a supplier. Suppliers can be wrong sometimes, and it is my job to catch and correct anything that was not done correctly.
This potential error could lead to re-work of not only piping designs, but possibly some structural design that are already being fabricated.
Yes, you're correct, we have the flanges. Now our choice going forward is to force the redesign of the piping and structural, or to put the flanges under the CNC and re-machine them to the shorter length overall length. What I am trying to determine is the correct interpretation of the code, so that I know my options going forward.
Regardless, I have learned my lesson on reducing flanges, and will ask for drawings in the future.
Thank you,
RE: B16.5 Reducing Flange - Length Through Hub Dimension
Even tho there are no working parts inside the flange there could be a Warranty issue later.
prognosis: Lead or Lag
RE: B16.5 Reducing Flange - Length Through Hub Dimension
marty007,
You are correct in your interpretation. The paragraphs you cited, especially para. 6.8.2.2, is very clear when it comes to the dimensions of a reducing weld neck flange. I hope you have not fully paid the supplier. You can also back charge them for their error if it causes schedule delay or rework on your project. A reputable flange manufacturer would not make this mistake.
Is the reducing flange connected to a vessel? What is the Code of construction?
RE: B16.5 Reducing Flange - Length Through Hub Dimension
RE: B16.5 Reducing Flange - Length Through Hub Dimension
RE: B16.5 Reducing Flange - Length Through Hub Dimension
The example you cited is for a reducing threaded flange. It is not applicable to a reducing weld neck flange.
Refer to the FAQ below regarding reducing flanges.
http://www.texasflange.com/frequently-asked-questi...
My old Taylor Forge catalog also says the same thing for a reducing weld neck flange.