Pipe schedule vs Class rating when purchasing fittings/flanges. 2

[djdalfaro]

[edited]
Good morning,

New member here, I am new in my field and currently working on updating the pipe specs at my plant. Part of this project involves setting up new material numbers with short descriptions, which are then sent for purchasing. One of the problems I have run across is not being sure when a pipe schedule needs to be specified alongside the fitting/flange rating. It appears to my novice eyes that SCH rating is needed for BW fittings/flanges, but CLASS rating is needed for SW/THRD fittngs/flanges, with few exceptions. However I know that SCH rating changes the bore size and could cause turbulent flow if not matched. Do manufacturers take this into account? I am running across a large number of different items in the specs (just about every fitting/flange used in a commercial plant), and have access to and have read the relevant ASME, MSS standards, but would like some clarification from someone in the industry. I want to verify what is correct in practice. For example, I can specify that a coupling is 3000 CLASS rating, do I also need to specify that it will be used with SCH XS pipe? Is this information that the distributer needs to get me the correct part? Another example olets, I know that BW olets are rated by pipe schedule, while SW and THRD olets are rated by LB class. Would I need to specify that a 3000 CLASS SW Elbolet would be used on STD x XS pipe? Would it make a difference in the part I received? I have compiled the list below, and would appreciate a reply as to whether I've got it right or not. As you can see from the table below, the majority of the fittings/flanges are classified by CLASS, does this mean that the SCH rating of the pipe is not needed when ordering?​

Thank you,
Damon Alfaro


[tt]FITTING__________CLASS_____________SCH RAT
CAP______________X_________________N/A
COUPLING_________X_________________N/A
ELBOW, SW________X_________________N/A
ELBOW, THRD______X_________________N/A
BLIND FLANGE_____X_________________N/A
SLIP ON FLANGE___X_________________N/A
SW FLANGE________X_________________N/A
THRD FLANGE______X_________________N/A
WELD NECK FLANGE_X_________________X
WNORIFICE FLANGE_X_________________X
SW RED INSERT____X_________________N/A
THREADED PLUG____N/A_______________N/A
CONC RED, THRD___X_________________N/A
EQUAL TEE, SW____X_________________N/A
EQUAL TEE, THRD__X_________________N/A
RED TEE, SW______X_________________N/A
RED TEE, THRD____X_________________N/A
UNION____________X_________________N/A
ELBOLET, BW______N/A_______________X
ELBOLET, SW______X_________________N/A
ELBOLET, THRD____X_________________N/A
LATROLET, BW_____N/A_______________X
NIPOLET, BW______N/A_______________X
SOCKOLET_________X_________________N/A
THREDOLET________X_________________N/A
WELDOLET_________N/A_______________X
[/tt]

 

[BigInch]

DSB too much caffeine today?
Not Sorry Sorry ... obviously I ment to I did type "ASME" B16.5

You are free to practice any method you like, I am only saying what I have found to work extremely well in eliminating any possibility of confusion over many years ... including 2015. 2016 hasn't finished yet.

 

[XL83NL]

@ BI, thats should be ASTM A105N (as per A105 para 5.1, for flanges > Cl. 300 it's normalized per default))

 

[DSB123]

BigInch,
Sorry no Caffeine today - don't like the crap!!

I am just making the point that when designating a Flange the "correct" way is Class 600 - end of story and you cannot correct me on that score unless you can point me to where it is otherwise stated in ASME B16.5 - and you cannot. You may want to add the Lb or # but it is incorrect - and remember as engineers we should be striving for accuracy!!! You and others, by using Lb or # are just purpetuating the error. Unless you can "prove" that i am wrong in what I am stating then please consider the discussion closed. You can continue to use the incorrect way to specify flanges!!!!

 

[BigInch]

Not trying to correct you. You're not wrong.
As you like.

 

[LittleInch]

I never said it was in B16.5. I said Correct terminology is class 600, but "common" terminology is lb or #. You can't ignore how people have been calling flanges, but my post goes on to say for MTOs and orders use the correct terminology.

I use class all the time and correct those under me to do the same, but they need to know when others talk to them that, like it or not, class, lb , pound or # are interchangeable in many peoples mind and writing when referring to ASME B 16.5 flanges.

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

 

[BigInch]

Exactly. And remember that the people that buy and sell this stuff are usually not engineers anyway, which only makes the problem that much worse. 10 psi is the same to a lot of them as 1000 psig, or kph for that matter.

 

[zdas04]

Dang there is a lot of pedantic nonsense in this thread. DSB123, you come across as though you were 14 years old with nearly 20 minutes in industry. It isn't a great idea to assume that someone with as much experience as BigInch is simply wrong, and it tends to alienate the rest of us grey-hairs.

Previous versions of the code used "300 pound" quite widely to mean what is now called "300 class". It isn't in the current code, but it sure is in common usage. Just last month I told a construction superintendent that we were going to use "ASME B16.5 600 Class" flanges and he wrote it down as "ANSI 600 lb". Is it standard? No. Is it right? "Right" is so subjective. Was there communication? Hell yes, and that is the purpose of all of this stuff.

The OP got a lot of useless factoids slung in his face (and to his credit he accepted the garbage with humility, he comes across very well) when he was asking fair questions with a goal of clearing up some information that is fuzzy in many people's minds. Useful questions and the thread started out with useless answers. In my limited experience (I've only been doing this stuff for 36 years), prior to the current version of ASME B16.5, "Class" referred to "Thread pressure rating in psig". The current version of ASME B16.5 muddies that a lot. "Schedule" refers to a pipe or fitting inside diameter.

Failing to match ID of a fitting to the ID of a pipe creates fabrication problems, but it does not "create turbulence". It is fascinating to watch flow visualizations (not models, film of actual flow in a pipe with different wall thickness) of changing wall thickness. The distance from the edge of one boundary layer across the pipe to the edge of the other changes about half the change in the pipe ID and requires extreme magnification to even see.

As to non-standard pipe and fitting ID, if you are spending enough money, the foundries will make you anything you want. BigInch has worked on some jobs with a pipe budget rivaling the GNP of many countries. With that kind of purchasing power, he is careful not to waste pipe wall thickness and tries to run his design closer to real physical limits than is common in smaller projects (and he doesn't pay a premium for non-standard pipe and fittings due to the size of the orders). I would never expect to be able to get a non-standard pipe size for a project with a pipe budget under $10 million USD without paying a significant premium and waiting for a future mill run. Non standard pipe sizes should not be part of the OP's database.

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[BigInch]

Actually there are some standard "non-standard wall thicknesses" that could be put in a database, those with no schedule numbers, the heavy walls and extra heavy walls, some which have and don't have any schedule designations.

http://www.saginawpipe.com/steel_pipe_chart-2.htm