Am asking for the common practice r 9

[Mostafa algadi]

Am asking for the common practice regarding the flange schedule that attached to the nozzle in the pressure vessels, the designer insists that the flange should have the same schedule of the nozzle neck as per his common practice, but the supplier says it is not necessary to be same as his common practice, please what is a correct?

 

[LittleInch]

What is downside of having this flanged connection?

There isn't one IMHO.

I have occasionally seen this with the inside bore at the face end machined at 1:1 or 1:2 to avoid any turbulence, but I think that's a bit OTT.

I think the supplier is playing silly buggers here for some reason. It's no skin off his nose if someone wants a bit more metal so I'm at a loss as to why we're having this conversation...



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

 

[curtis2004]

LitteInch,

The concern is a turbulence introduced by mismatch of ID of corresponding flanges in flanged connection. This may or may not be an issue, because there are may be hundred of valves, elbows, tees, instrumentation, etc. inside of this line and all of it will cause a bit of extra turbulence.

There is another solution to match wall thickness in this situation. If PV supplier doesn't budge we can machine companion flange (face or tail, depending on increasing or decreasing wall of pipe).

Thanks,
Curtis

 

[LittleInch]

This is why we need data - sch 80 to 160 is 4mm step change.

Welds could be a bigger "bump" than that.

Still don't know why the supplier is having this argument.

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

 

[XL83NL]

It makes no sense to match the PV flange its schedule size with that if the line class that attached to the flange. Both flanges are governed by different codes/rules, so why look at it from that point of view?

Huub
- You never get what you expect, you only get what you inspect.

 

[curtis2004]

Hi XL83NL,

Yes, I think everyone knows both are constructed to different codes, and not necessarily pipe schedules would match. Both parties can be right. If piping and PV nozzle schedules don't much how do you deal with this issue? Or is there any issue at all? That is what we are arguing about.

Thanks,
Curtis

 

[saplanti]

In case the schedules (wall thicknesses) do not match the internal diameters will have a step as LittleInch has indicated.

If the PV nozzle flange has low internal diameter the process (process equipment) will suffer due to additional losses. Sometimes this can be a major issue. If it has high internal diameter it will be a strengthwise weak point.

Therefore reputable companies have procedures to match those to eliminate problems at the design and tender documentation. So ıt is not left to the pleasure of manufacturer.

 

[saplanti]

Additionally, it could be a corrosion location depending on the accumulation of process liquid and flow direction.

 

[1503-44]

Unmatched wall thickness has nothing to do with turbulence. It is a welding issue. The thicker wall must be beveled at 1:3 slope whenever the difference between wall thicknesses is greater than 3/32 inch. Of course the thiner wall must meet pressure requirements.

3/32 inch and 1:3 slope values might differ, depending on welding procedure and code used.

Welding steel fittings with different wall thicknesses
thread378-176732


“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[saplanti]

Ax1e,

You are correct for the manufacture and welding points of view, however incorrect for the others. I do not want to get involve to explain the reasons, they are fluid fundamentals and process requirements. The code rules are minimum, clients can ask more than the code rules for the purpose unless they are against the rules. In this case the client is asking the process requirement, there is nothing wrong with that.

I have worked for EPC, EPCM consultant companies in steam power, oil&gas, refinery, hydro-electric power industries, all have same requirements in contract/tender documents for vessels and piping.

We do not discuss the welding wall thickness mismatch tolerances, they are subject to totally different discussion.

But, I agree whatever is done may be acceptable, but it requires involvement of all engineering parties for acceptance, which may require additional calculation, which may be totally waste of time in case one party do not accept it. You need to get client’s approval for the change as well. Additional process run, stress analysis run will be costly, none would like to pay from their budget in the consultant offices.

 

[1503-44]

It should not be such a complicated mess as this thread is leading it to be, or nothing would ever have been built in the last 50 years.

I'm still wondering where the 29 replies and 9 stars came from.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[curtis2004]

Hi Ax1e,

I think, OP was about flanged nozzle of Pressure Vessel being thicker than wall thickness of line being thinner specified by Line Class. It is flanged connection, not welded. Depending on your reasoning, there are can be only three theoretical routes you can take:
1. Do nothing. In this case you would have a small step inside of your flanged connection corresponding to a difference of pipe wall thicknesses.
2. Ask PV supplier to provide "machined" flange face to match ID of your pipe. You still will have a step, but smooth machined one.
3. Provide "machined" tail flange to match ID of your pipe. You still will have a step, but it is machined one

What would you do and why?

Thanks,
Curtis

 

[XL83NL]

I think we scared the s*^% out of the OP with so many and such diverse replies. Let’s wait for him to return and provide some guidance on what he’s actually looking for.

Huub
- You never get what you expect, you only get what you inspect.

 

[1503-44]

Exactly. PV NOZZLE flange is what is.
Piping to PV may be different schedule than PV's nozzle flange.
Simply match the pipe run's flange face to the nozzle's pressure ff or rf or rtj face and CLASS and Weldneck wt can be whatever is required by pipe code, probably less than PV.
If pipe run's weldneck flange has wt difference to pipe run <= max allowed by code, do nothing.
If wt difference > max allowed, counterbore to match pipe run schd, if the WN length allows.
If Weldneck is too short for counterboring, weld a short length pup with equal schedule to the flange and counterbore the pup's other end to match pipe run's schedule.
IMO that's the end of discussion.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[Ramil Abbaszade]

Ideally, Nozzle neck thickness should match to the schedule or neck thickness of WN flange.Because nozzle min calculated neck thickness should match to vessel code's minimum nozzle thickness req. and and it is better to have flange schedule matching to that as well. This will also save fabricator from making Taper bore from thicker one to thinner one.

 

[1503-44]

Better yes you might say so, however... Assuming the same material is used and similar stresses exist. Generally true, but it need not be so. Pipe is made to a different specification and design code and conditions, plus pipe stresses can be entirely different as well. It is not so unusual to have such differences across a code break.