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]

You would normally try and match the strength of the two materials and their schedule or wall thickness.

But sometimes you can have a different schedule for the flange.

What are the specifics here in terms of the two materials and the two schedules?

It does sound like the supplier is just trying to sell you something he has on the shelf rather than get or machine what you want.

Ask another supplier first.

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

 

[0707]

You should follow the code of construction of the vessel. What the supplier says means nothing.

luis

 

[weldstan]

Agree with Little Inch; however, there will be instances where the flange rating will need to increased from the pipe schedule.

 

[XL83NL]

If your supplier is the designer of the vessel itself, he may be right. Otherwise he can’t know what you need. Do as LI said, ask another.

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

 

[1503-44]

Why is it that are we not asking the piping design engineer???

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

 

[XL83NL]

Its a a PV (OP mentioned nozzle), so the piping designer shouldn’t be involved. Also to me the piping designer, if this were a flange on a pipe spool, is not the person who makes the line class, pipe class or pipe spec, thus doesn’t necessarily have the knowledge to answer such questions.

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

 

[1503-44]

I don't think so. First, the subject is the flange ending the pipe spool that will be attached to the flange on the PV.

Secondly, my piping design engineers apparently have far more knowledge and responsibility than yours. If there are any line specs at all, my piping design engineer will determine the applicability of a particular line spec to the pipe being designed. If there are no line specs, my piping design engineer will determine the material, pressure class and wall thickness required for each pipe to be designed. Then, if needed, he/she will write the line specification for that pipe any and probably all pipes to be used on the rest of the project.

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

 

[XL83NL]

Still don’t agree on the first part, that’s not how I read the OP.

On the second I’ve gotta admit you may be right. It depends on the job description. To us, and how I’m familiar with most piping designer job descriptions (in Europe), they do the routing, occasionally the BOM, but almost never the mechanics. Maybe a lead piping engineer would, but that’s a different job description (to me).

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

 

[saplanti]

What do you mean by the nozzle neck schedule is important. Some cases the nozzle needs to be self reinfoced and the thickness is designed bt the vessel designer for the reinforcement, which is large than pipe schedules. In this scenario, the nozzle neck thickness is reduced to the required schedule (wall thickness) of the flange neck outside the reinforcement area. This is very common.

However, if the nozzle does not need to be reinforced, so the required wall thicknesses are to be the same.

Although the vessel code limit is the flange face, the process engineers give the direction on the P&ID and specifications on what schedules and materials to be used. In some countries these are not controlled adequately, and left the hired engineer’s judgement.

 

[MJCronin]

https://arvengtraining.com/en/nozzle-design-the-weak-point-of-every-equipment/

MJCronin
Sr. Process Engineer

 

[Mostafa algadi]

To make this clearly, here is a session between supplier and designer:

Supplier Say:

Schedule of flanges: the designer is insisting on having same schedule of flanges as for the nozzles necks due to mechanical and corrosion requirements.
This statement is not accurate. The higher thickness at the nozzle neck is required for the opening reinforcement. Elbow and flanges are not part of this reinforcement. Corrosion allowance and mechanical strength are checked in the relative calculation notes and found satisfactory.
It is common practice in pressure vessels to use nozzles necks with higher schedules than the weld neck flanges and fittings, many times forgings are used with thicknesses by far higher than the higher available W.N. flanges schedules.

Designer Reply:

As per our and good practice, WN Nozzle Hub thickness shall be the same as Nozzle neck to satisfy mechanical and corrosion requirements, in additioon there is no supplement calculation on the PV Elite to check flange hub thickness. Otherwise This shall be accepted only if supplier get final client approval.

Note: PV Elite is a software which has applied by supplier to get the vessel calculation and to confirm the calculation that done by the designer.

 

[LittleInch]

Both are, in theory, correct.

So then it goes down to actual.

Is it thicker than XXS?

If yes then supplier is correct, if not go with the vessel designer. IMHO.

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

 

[LittleInch]

Also why is the supplier getting so worked up about this?

What's his reason for wanting to supply presumably thinner wall flanges?

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

 

[saplanti]

One tought; they may be looking for match at internal diameters.
Second; they may be asking for long welding neck nozzle ( in this scenario, this should be indicated in the vessel spec.)

 

[saplanti]

I mistyped the second, it should be LWN ( long welding neck) flange, not nozzle.

 

[MickMc]

In my experience in piping we ask for equipment supplier to provide counter flanges for their nozzles where they are outwith ASME B16.5/16.47 scope with us providing wall thickness of connecting pipe.

 

[hacksaw]

What does the pipe stress analysis say?

Major bending stresses in the piping layout certainly affects the pressure vessel..

 

[saplanti]

It seems that the designer relies on PV Elite software only, and probably does not have access to the piping drawings/specification for the connected pipng to make decision.

I suggest you check the piping specifications of the connected pipes and ask the same wall thickness as minimum wall thickness for the nozzle flange. This wii provide the internal diameter of the nozzle as well. So the reinforcement calculation will be based on this internal diameters.

The selection of internal diameters for the nozzle connected instrumentation is governed by the instrument specification. Some instruments requıre a minimum flange class as well.

I would expect all these clear in the pressure vessel specification with nozzle tables with the required flange class and wall thicknesses inluding required flange faces etc...

Additionally the external loading on the nozzles should be noted for both vessel design as well as piping stress analysis which will guide designers to consider.

In case these are full or partially missing the hired engineer is in trouble to solve all these, and sometimes accused by not doing the job properly.

 

[curtis2004]

Hi Everyone,

I would like to discuss with some numbers for practical prospective of this discussion:

Let's assume PV has 3"x300# flanged nozzle. Let's assume PV Supplier wants nozzle neck made of 3"xSch160 pipe.
Now, let's assume Pipe Line Class specifies the line to have 3"xSch80 wall. I know that schedule of both sides shall match. However, what will happen if PV side a WN flange 3"x300# with Sch160 and connecting pipe has 3"x300# with Sch80 pipe? We will have small step in flange ID. Gasket shall have no problem.
What is downside of having this flanged connection?

Thanks,
Curtis