DOES ASME SEC VIII DIV.1 ALLOW NOZZLE INSIDE PIPE MACHINING? 1

[staticmh]

Good day Folks!

Hope you doing all well.

I've been faced one case, where my vessel is having NPS-10" nozzle and coupled with pump assembly with blind flange.

Issue is that pump have the submersible assy, which outside dimension is 245mm.

We procured the pipe NPS-10" SCH-80, which ID is 242.82mm. now if we use the NPS-10" SCH-80 the pump assembly cannot be insert through the pipe due to lesser inside dia as compare to NPS-10 SCH-80 pipe.

However, Vessel is U-stamped and we intent to machine it up to sch-60 thickness (12.7mm) & Inside diameter 247.6mm as per our understanding.

Can anybody advice me whether ASME SEC VIII Div. 1 allow to machine the nozzle pipe (SA-106 Gr.B , 3.2 certification, NACE Compliance) material or not. Please refer the code clause we have to address with AI.

Thanks in advance.

 

[KevinNZ]

If a pipe has reduced wall thickness from machining or corrosion etc. it is still a pipe.

But the original design may have required S80 wall thickness for a reason.

 

[r6155]

See the required thickness in the original calculation.

Regards

 

[MJCronin]

KevinNZ...

You state: "But the original design may have required S80 wall thickness for a reason."

Please recall that the ASME Section VIII code requires "extra thickness" in either the adjacent vessel shell ORin the nozzle wall to make up for the loss of material in the hole in the shell and to provide stiffness for the nozzle. Nozzle wall thickness is not determined by pressure stresses alone ! Other International Pressure Vessel Codes have the same approach.

Nozzle walls may also must be thickened by the vessel designer in order for the nozzle to sustain external loadings (from adjoining piping). These loads may be imposed by the purchaser and contained within contract documents

Now, understand that because of commonly accepted methods of vessel fabrication, it is usually cheaper and easier to provide nozzle reiniforcement and stiffness by increasing the wall thickness of the nozzle.

Because STATICMH probably does not have any pressure vessel records, (all plant records are discarded when the plant is sold to the new owners) we cannot answer his question...

So, yes R6155..... he should review the original calculation ..... but those records are long gone

Anyone else have information or opinions on this important topic ?

MJC

MJCronin
Sr. Process Engineer

 

[r6155]

staticmh, did you check the actual inside diameter of the nozzle?

Regards

 

[saplanti]

Staticmh,

Are you an engineer?

I do not understand how these things work as you described. Is there any purpose doing the assembly like that? I would normally expect that the pump suction is connected onto the nozzle by flange or weld. The nozzle was supposed to have an insert into the vessel for the suction assembly with elbow in accordance with Hydraulic Institute standards on the vertical pressure vessels.

You say that the suction elbow pipe assy will go through the blind flange. This kind of assy will cause more problems, especially vibrations in the suction line, and blind flange connection and on the weld on the blind flange will suffer. To cut the problems you may need to weld the suction pipe close to the suction area by support members on the vessel bottom wall in the vessel as well. I am assuming that you are not the vessel manufacturer, but the installer of the equipment.

It seems that there is a mismanagement issue here. I suggest you discuss the issue first with the process engineer, second with the design engineer of the pressure vessel on the application.

 

[staticmh]

@KevinNZ,

The material of the pipe is having 3.2 certificate, with NACE compliance (Due to sour service) and with different code of specification testing compliance.

At this stage the procurement of lower schedule (i.e. 60) is an critical aspect, our vessel is under the fabrication and just came to know by the procurement & fabrication team that the pump nozzle pipe size-10" schedule is received as schedule 80 instead of schedule 60. As our requirement is schedule-60, if we dont not use the schedule-60 pipe it will make the lesser inside diameter and ultimately pump assembly will not be insert through the nozzle due to lesser inside diameter.

My main concern of query is that, does ASME SEC VIII Div. 1 allow to machine the pipe (NPS-10 ; schedule-80) from inside to reduce the thickness up to schedule 60. Please if anybody could advice me on my clarification will be appreciated. This clarification is purely for the the Mechanical design Engineers of static equipment. Other people may not understand the actual picture.

 

[staticmh]

@MJCronin

Thickness calculation already performed and qualifying the code requirement with schedule - 60 pipe and found acceptable. But unfortunately we received the schedule - 80 pipe which is creating problem.
The problem is that we selected the schedule-60 pipe (during design) only due to maintain the large inside diameter of the pipe to allow the pump assembly insert through the nozzle pipe to bottom sump boot.

we can resolve the problem by machining the NPS-10" ; schedule-80 pipe from inside because we need the inside diameter equal to schedule-60.

Our vessel is U-Stamped and we can not do at our own, ASME Inspector intervention is requested already but response is awaited, and meanwhile i thought to discuss with my eng-tip family that is anybody can advice on my case or anybody earlier had solved the same problem which i am facing now.

My main concern of query is that, does ASME SEC VIII Div. 1 allow to machine the pipe (NPS-10 ; schedule-80) from inside to reduce the thickness up to schedule 60.

Advice within ASME SEC VIII Division 1 premise.

 

[staticmh]

@saplanti

First of all Greetings from my end!
Secondly thank you for commenting with your concern on this thread. its really constructive and get more interesting when we got interaction with some different cultural and mind set personnel round the globe.
Eng-tip is quite means alot to me and always welcoming to share their thoughts , experience, lesson learnt and much more.

DONT BE STATUS QUO and judging to anybody without any information about him, every one is here to discuss the technical points and obviously we are here for some reason. For your information, I've been working since 15 year as mechanical design engineer of static equipment and I'm graduate certified engineer.

Now lets come to your first points,
1 - "I do not understand how these things work as you described. Is there any purpose doing the assembly like that? I would normally expect that the pump suction is connected onto the nozzle by flange or weld. The nozzle was supposed to have an insert into the vessel for the suction assembly with elbow in accordance with Hydraulic Institute standards on the vertical pressure vessels."

Staticmh reply: First you understand the assembly requirement and constraints, for the horizontal vessel (especially in sump drain drums) whether with boot in concrete pit or buried condition pump assembly is require for the successful suction of the sludge contamination through submersible assembly inside the vessel (boot).

See below image of pump assembly (Isometric view) [FIGURE-1]:

Similarly now see the maximum dimension of the submersible part of pump assembly, which is marked by vendor as 245mm and understand that is the limit for us to maintain the inside diameter of the nozzle. the nozzle inside diameter should be within the range of 245mm to easily insert the pump submersible assembly through nozzle pipe.

See below (blue color limit dimension) [FIGURE-2]:

But unfortunately our procurement people bought it wrongly as Schedule-80, even it was clearly mentioned on drawing to procure the schedule-60, Anyway the mistake done and being an engineer we have to solve it.

The reason why we recommended the schedule-60 was the clear gap maintain for the ease of insert the pump assy. through pipe inside.

Received pipe = NPS-10" ; schedule - 80 and ID is 242.82mm
Required Pipe = NPS-10" ; schedule - 60 and ID is 247.6mm

(Pump assy. maximum limit. is 245mm)

with NPS-10" pipe schedule - 60 , 247.6mm - 245mm = 2.6mm gap is available which is sufficient for insert through nozzle pipe.

But we have now NPS-10 , schedule-80, so it will be like that 242.82 - 245 = -2.18 mean pump cant be insert through the nozzle pipe inside diameter due to lesser diameter of pipe. now due to not having other option we intent to machine the pipe from inside to maintain the equivalent I.D of schedule-60. (i.e. 247.6mm)

My main concern of query was to get the advice and endorsement on my intention of solution (that is machine the pipe inside), now share your concurrence whether ASME SEC VIII Div. 1 allow to machine the pipe or not.

Be noted the vessel is U-Stamped and we can not do at our own, ASME Inspector intervention is requested already but response is awaited, meanwhile i thought to discuss with my eng-tip family that is anybody can advice on my case or anybody earlier had solved the same problem which i am facing now.

Now lets come to second points,

2- "You say that the suction elbow pipe assy will go through the blind flange. This kind of assy will cause more problems, especially vibrations in the suction line, and blind flange connection and on the weld on the blind flange will suffer. To cut the problems you may need to weld the suction pipe close to the suction area by support members on the vessel bottom wall in the vessel as well. I am assuming that you are not the vessel manufacturer, but the installer of the equipment."

Staticmh reply: Clear your understanding that there is not any elbow involve neither in my above post and nor any where else, only the flange assy. word used which is shown above in figure-1. Pump loading received from pump vendor and already verified the calculation in WRC / FEA at shell to nozzle junction. we're the vessel manufacturer & its EPC contractor and additionally own the U1 , U2 & R stamp. Only the pump is sourced out from some specialized vendor.


Now lets come to third points,

3- "It seems that there is a mismanagement issue here. I suggest you discuss the issue first with the process engineer, second with the design engineer of the pressure vessel on the application."

Staticmh reply: There is nothing mismanaged all the things are self explanatary and for your kind information, you need to understand the case as above depicted fully with as supportive images and explanation. And there is not any process engineer involvement require to fix this up its purely mechanical discipline clarification & case. You should understand it if you have any bit experience of static equipment design.

Hopefully all the things are clear to you and got the answer of each point wise.

Thanks!

 

[saplanti]

Thanks for the detailed reply. You should get all these in the first post, so we would not get confused. It might be everything clear for you but we cannot visualise the concept and misjudge.

It looks everything under control since you are obliged to get the inspector’s agreement on the issue.
In case you change the thickness of the nozzle, you need to modify the nozzle drawing of the vessel. You additionally cannot call the nozzle thickness Sch 80 any more, if the final thickness is within the tolerance of Sch 60 you can call it Sch 60. Otherwise you need to assign the minimum thickness on the drawing.

Beside all, you need to check the nozzle reinforcement requirements. The other thing, if I understood correctly, is the additional forces and moments that comes from the attachment on to connection of the flange on the nozzle. We do not have anything about the vessel, perhaps a sketch of the vessel with the attached pump would give us better information. You may be required to provide additional gussets to support flange and reduce moments and forces on the nozzle. This is again my imagination, you may come up with different scenario.

Hope it helps.

 

[staticmh]

@saplanti

All the statement in my earlier post is clearly understandable if any one having little engineering background. i don't think so you are from engineering background or not.

Now i re-stated only for you to demonstrate the actual case with supportive images & explanation, which is barely require for a sound technical person. Anyhow,incase of thickness change calculation already performed on Sch-60 and providing sch-80 will be fine which is higher than the 60. there is not any issue with design point of view.

Only i need to know that does code ASME SEC VIII Div. 1 allow to machine the pipe inside or not. And if allow then what inspection, testing & NDE requirement shall be followed to satify the code compliance.

 

[saplanti]

staticmh,

Please look at your original post. Can you see any statement as you described?
I can see that statement on your second post to KevinNZ now which I did not read earlier.

What you re-stated was supposed to be given in your earlier post for everyone to understand what you are doing. Perhaps you do not want answers to your problems other than concentrating one issue. If that is the case whatever we say is not going to satisfy your inspector, be ready for everything.

I understand you have already controlled every single item that needs to be considered, so you do not need our advise. Hope everything goes well on your side.

 

See the required thickness in the original calculation.

That seems like a complete answer.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[SnTMan]

Generally speaking if a thing is not prohibited, it is permitted.

Regards,

Mike

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

 

[TGS4]

And machining out a nozzle to change the ID is not specifically prohibited.

 

[r6155]

I suggest machining the 4 flanges OD 245 mm to OD 242 mm. Do nothing in the nozzle NPS 10 sch 80

Regards

 

[GD2]

Staticmh,
I don’t see an issue machining a 80 sch pipe to 60 sch pipe. If the vessel design calculated the nozzle a 60 sch pipe, go ahead and do the machining.

My only worry is that the weld joint now got converted to a joint with wide root gap. My guess is that it’s a groove joint. I suggest check with your welding engineer as it will change the WPS. He/she might advise do a RT.

It’s not uncommon to see welding with wide root gap using buttering method.

BTW, what’s the vessel design pressure?

GDD
Canada

 

[SnTMan]

See UW-13(i)

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

 

[staticmh]

@saplanti

Thanks for your valued concern, still welcoming you to write on threads but only constructive, positive, brief and solution oriented.

 

[staticmh]

@ironic metallurgist

Thank you for your valued feedback my dear, concern is not about required thickness, infact it is about the pipe inside machining.

Vessel pump vendor assembly is unable to go through the Schedule-80 pipe. so we want to utilize the schedule-80 and then machining to maintain schedule-60.