B16.5 Reducing Flange - Length Through Hub Dimension

[marty007]

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):
[ul]
[li]Table II-11: tf = 2.69"[/li]
[li]Para 6.4.1: facing = 0.06"[/li]
[/ul]

Per paragraph 6.8.2.2: The hub dimensions shall be the same as those of the standard flange of the size to which the reduction is being made (NPS10):
[ul]
[li]Table II-11: hub height = Y-tf = 4.56" - 1.81" = 2.75"[/li]
[/ul]

From this, I interpret that the flange should have a total length of:
[ul]
[li]Total length: tf + facing + hub height = 2.69" + 0.06" + 2.75" = 5.5"[/li]
[/ul]

The supplier interprets that the overall length of a B16.5 reducing flange should be the same as the length of the larger size being reduced from (NPS24). The flanges we received match the length through hub of a NPS24 300# flange: 6.56". The total length is 6.56" + facing height (0.06") = 6.625"

Am I out to lunch?

 

[pennpiper]

I agree with the suppliers interpretation.
I also wonder, why are you question this since you have already received the flanges?

prognosis: Lead or Lag

 

[marty007]

I am questioning it because this reducing flange is welding directly to an elbow with no straight pipe length. Our designs and drawings are all based on a 5.5" reducing flange length, so this would push our clients entire piping design out by 1.125" (may or may not be an issue, I don't know).

 

[marty007]

Pennpiper, could you explain why you agree with the supplier?

 

[pennpiper]

It is simply a matter of deduction.
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

 

[marty007]

pennpiper:

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.

 

[pennpiper]

Come on folks, it is not important where I got the data I used (I tried but I cannot find it).
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

 

[marty007]

pennpiper,

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,

 

[pennpiper]

I do not recommend you unilaterally modify these flanges until you have a discussion with the supplier.
Even tho there are no working parts inside the flange there could be a Warranty issue later.

prognosis: Lead or Lag

 

[doct9960]

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"

Per paragraph 6.8.2.2: The hub dimensions shall be the same as those of the standard flange of the size to which the reduction is being made (NPS10):

Table II-11: hub height = Y-tf = 4.56" - 1.81" = 2.75"

From this, I interpret that the flange should have a total length of:

Total length: tf + facing + hub height = 2.69" + 0.06" + 2.75" = 5.5"

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?

 

[marty007]

doct9960 - The reducing flange is acting as a blind flange with a small pipe extension to a 10" flange, the code of construction is ASME VIII-1. Our fitters noted the discrepancy when they started to handle the material, so nothing has been welded.

 

[rumandcola]

I am looking at table II-6 example (1) it seems to indicate that the hub height is based on the larger flange size.

 

[doct9960]

rumandcola,

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-questions.html

My old Taylor Forge catalog also says the same thing for a reducing weld neck flange.