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TOPIC: Hub on lapped flange

11 years 8 months ago #7282

  • gpsvn
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I am being asked a question, and I don't know the answer. I am posting it here and appreciate responses from the forum members.

The lapped flanges are used in companion with the stub ends. My engineer received a batch of flanges without their 'hubs'. His question is, why the lapped flanges need hubs, what are their purposes. I can only say those flanges must meet ASME B16.5, which dictates the flange and hub dimensions. I guess my answer was not a real answer, did not help him much. Any one help me out please.

Flanges 11 years 8 months ago #4494

  • Jop
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gpsvn,
I have never seen hubless Lap-joint-flanges. I would suggest that someone trace these flanges back to the source and confirm that they are not counterfeiters.

Read the related article under "I saw a good article"
Do it once and Do it Right

Hello, Well let me ask 11 years 8 months ago #4495

  • EliutBB
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Hello, Well let me ask you this, what is the difference between a Slip-on flange and a Lap-joint (without the stub end of course). If you can go out to your warehouse and check them out.

For one there is no RF...

Well I guess there is absolutley no meaning of existence for a LAp-joint flange without its stub end, tell your boss to weld them and make a statue or something... sorry for the irony

REgards

Re: Flanges 11 years 8 months ago #4496

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gpsvn,
I have never seen hubless Lap-joint-flanges. I would suggest that someone trace these flanges back to the source and confirm that they are not counterfeiters.

Read the related article under "I saw a good article"

I asked the engineer to return those flanges, that's why he asked me those questions. There is no welding on the hub, so why do we need it ?
Hello, Well let me ask you this, what is the difference between a Slip-on flange and a Lap-joint (without the stub end of course). If you can go out to your warehouse and check them out.

For one there is no RF...

A lap joint and a flat face slip on are different. Look at the corner between the flange ID and the face, the slip on has a sharp angle while the lapped flange has a rounded one. If you look close enough, the lapped flange is thicker.
Well I guess there is absolutley no meaning of existence for a LAp-joint flange without its stub end, tell your boss to weld them and make a statue or something... sorry for the irony

REgards

It's not the stub end, it's the HUB. The hub is where you weld to the pipe on the back side of a slip on flange. The lapped flange according to ASME B16.5 also has hub, that's what being discussed.

" There is no welding 11 years 8 months ago #4497

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" There is no welding on the hub, so why do we need it ? "

The hub provides stability and resistance to flexing or twisting of the flange. Consider the situation where you have a 6"NPS flange shape with no hub that is very thin, only about 1/8" (3.175 mm) thick. With your bare hands you will be able to twist the plate with ease. Now take one with a raised hub. You will find that the one with the raised hub will be resistant to the twisting effect.

So the hub helps to maintain the constant and consistent pressure against the lip of the "Stub End" piece to insure a proper joint.
Do it once and Do it Right

" There is no welding 11 years 8 months ago #4498

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" There is no welding on the hub, so why do we need it ? "

The hub provides stability and resistance to flexing or twisting of the flange. Consider the situation where you have a 6"NPS flange shape with no hub that is very thin, only about 1/8" (3.175 mm) thick. With your bare hands you will be able to twist the plate with ease. Now take one with a raised hub. You will find that the one with the raised hub will be resistant to the twisting effect.

So the hub helps to maintain the constant and consistent pressure against the lip of the "Stub End" piece to insure a proper joint.

I guess I did not express myself too well.
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