Neck weld or flat flange to manhole

[mw87]

Hey Guys,
when I have design temperature about 300 C grade for vessel pressure then
I have to use weld neck flanges for nozzles,
is that guideline applies to manhole as well? What you thing about this?

 

[BJI]

It would also apply to manholes. Any shock loading would likely be less severe but the same reasons apply.

 

[SnTMan]

mw87, WHY do you have to use weld necks? And, for your manway, weld neck as opposed to what?

BJI, shock loading on a manway? How so?

Regards,

Mike



The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[mw87]

SnTMan, it's NoBo guiteline, of course.

 

[XL83NL]

NoBo guideline? Is this for work under the PED? Not sure how else a nobo would play a matter in this..

 

[BJI]

SnTMan, I believe the OP is referring using a weld neck rather than slip-on when operating at elevated temperatures. Even if not mandated, a lot of specifications will limit the maximum temperature for slip-on flanges. Thermal stress caused by temperature differentials can lead to cracking at SO fillet welds when operating at elevated temperatures. I would think it would be worse for process nozzles since the thermal transient would be more severe where the flow rate is higher at the flange vs a manhole flange, which is why I was suggesting the 'thermal' shock would be less severe. Under steady state conditions it makes no difference.

 

[mw87]

extracted from UDT's guidelines below.
(UDT - one of the polish NoBo)

 

[BJI]

Not very helpful without the figures but the rough translation appears to be orifice flanges, is this the case? You wouldn't have an orifice flange on a manhole so the P-T limit would not be applicable to this case. Might be best to clarify your question.

 

[mw87]

Kołnierz_kryzowy - sketch in attachment

 

[mw87]

Kołnierz_kryzowy - sketch in attachment

 

[r6155]

PD 5500 -2015 Fillet welded pipework flanges shall not be used for design temperatures above 370 °C
EN 13445 Flange construction . Fillet welds shall not be used for design temperatures above 370 °C.

Regards
r6155

 

[marty007]

mw87,

In the future, when asking a question in this forum please provide as much information as possible. In particular, please indicate the code of construction that is relevant to the question. Otherwise, we are left guessing, which is what has led to half of the responses so far to your question.

Cheers,
Marty

 

[SnTMan]

...I believe the OP is referring using a weld neck rather than slip-on...

Exactly, your belief, nobody knows. marty007's last post is very much to point.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[BJI]

I was going off the title, weld neck or flat flange.. not too much of a leap.