Nozzle Loads
Nozzle Loads
(OP)
I know that I may be searching for a non-existent answer, but I have to ask. In lieu of a customer’s specification for a nozzle load, what should a vessel supplier use for this calculation?
It has been a practice for some suppliers to use nothing. I think that this is a just ignoring the problem so that it goes away. Thermal reactions, PRV shock and other loads must be considered by UG-22.
If the supplier is mounting a PRV on top a vessel, I expect that supplier to properly support the PRV to handle the side loads generated or derate the flange for this load. If I am mounting this PRV, them it is my responsibility to specify the side loads to the vessel supplier.
For other piping connections, it is not so straight forward. You can strategically place pipe supports to minimize the loads, but you can never eliminate them. That being said, what loads should be used in the calcs?
Chris Foley
Midland, TX
It has been a practice for some suppliers to use nothing. I think that this is a just ignoring the problem so that it goes away. Thermal reactions, PRV shock and other loads must be considered by UG-22.
If the supplier is mounting a PRV on top a vessel, I expect that supplier to properly support the PRV to handle the side loads generated or derate the flange for this load. If I am mounting this PRV, them it is my responsibility to specify the side loads to the vessel supplier.
For other piping connections, it is not so straight forward. You can strategically place pipe supports to minimize the loads, but you can never eliminate them. That being said, what loads should be used in the calcs?

Chris Foley
Midland, TX





RE: Nozzle Loads
Brian
Pressure Vessels and Autoclave Systems
www.mcabeeconstruction.com
The above comments/opinions are solely my own and not those of McAbee Construction.
RE: Nozzle Loads
or something like NEMA SM-23 or API-610 or Kelloggs
That way you'll get them thinking & they'll realize it's neither an anchor nor "zero"
RE: Nozzle Loads
John
RE: Nozzle Loads
API 560 section5 lists maximum allowable nozzle loads.
RE: Nozzle Loads
What has API 560 got to do with allowable nozzle loads??? Do you mean API 650???
RE: Nozzle Loads
I checked to make sure my Dyslexia haddn't kicked in, it IS API 560 Section 5 that lists allowable nozzle loads. Once in a while one of our clints will requests that our nozzles be designed to these load.
I just thought this may be of some use for jcfoley.
RE: Nozzle Loads
I have never used API 560 but we buy a lot of API 661 heat exchangers. API 661 has a listing of nozzle loads but I find these loads to be quite high.
Thanks,
Chris
RE: Nozzle Loads
API 661 applies only to Air Coolers (Fin-Fans).
NozzleTwister
Houston, Texas
RE: Nozzle Loads
Thanks for the clarity. Sorry to have queried.
RE: Nozzle Loads
There have been several discussions of nozzles and nozzle loadings within this forum...For atmospheric tanks, vessels and rotating equipment.
http://www.eng-tips.com/viewthread.cfm?qid=75687
A long time ago, when dinosaurs roamed the earth, I worked for a company in Boston Mass called "Stone & Webster Engineering". This very question came up then on the specification of design loads for new vessels and tanks. After much discussion and the review of various piping stress analyses for similar components, it was decided that an approximation based on the connected pipe diameter was about the best anyone could do....
If you use loads of about ~250D (forces in each of three directions) and ~300D (moment in each of three directions) for nozzles of 4inch to 16 inch NPS ( where D is the nozzle size in inches and forces are in lbs.; moments in ft-lbs)....you will have a reasonable design loading that will cover most cases
Example: 10 inch NPS pipe nozzle
Fx=Fy=Fz = (250)(10)= 2500 lbs
Mx=My=Mz = (300)(10)= 3000 ft-lbs
Again, this is just a general rule of thumb....if nothing else is available
Now, I know there will be objections to this rule of thumb.......so lets hear them !!!!..........
My opinion only......
MJC
RE: Nozzle Loads
I found out today, that API 537, 2003, Flare Details for General Refinery and Petrochemical Service, refers to API 560 for nozzle allowables as a default if the purcahser doesn't provide any loads to the vender.
Personally I think this is a mis-application. The nozzle table in API 560, Fired Heaters for General Refinery Service, tops out at 12" and I've had very few Flare Stack Inlets that small.
NozzleTwister
Houston, Texas
RE: Nozzle Loads
A star for your comments. This is exactly the sort of thing that I was looking for. I knew in the back of mind that it would come from someone with "years & years" of experience. But I didn't think that it would go back to the age of dinosaurs!
Just goes to show that the latest is not necessarily the greatest.
PS: Yes, my family had some deep Irish roots a very long time ago. My son & my wife have red hair so we even look Irish!
RE: Nozzle Loads
As I understand, some time back, companies specd 3X API. Then, API raised the loads by 50%, so now we call for 2X API to get them same numbers.
Edward L. Klein
Pipe Stress Engineer
Houston, Texas
"All the world is a Spring"
All opinions expressed here are my own and not my company's.
RE: Nozzle Loads
I am still very curious as to how manufacturer's say that they will comply and then still use the maximum temperature & pressure rating of a B16.5 flange. What happened to calculating the equivelent pressure and derating the flange based on these loads?
RE: Nozzle Loads
RE: Nozzle Loads
These loads are applied at the nozzle shell junction, but I have heard of instances where loading is specified at the flange face, which introduces a further moment at the shell interface due to the flange forces multiplied by the nozzle outstand.
I checked against MLC's numbers above and in comparison my forces are about 10% lighter, but moments nearly 5 times greater (if I got the conversions right).
I have found that only for vessels with lower pressure, that I may have to slacken off on the above loads so as not to overdesign. Generally though the resulting design has proven satisfactory when checked against piping loads provided when the piping stress guys catch up.
Regards,
JohnGP
RE: Nozzle Loads
Thank you for your post....
I completely agree with the statement that clients are asking for heartache by not specifying any nozzle loads.
Please understand that my earlier posting was based on a "shakey" memory from an employer long ago...I only mentioned them if the specifier had literally nothing else to use.
My intention was to apply these "design loads" at the nozzle/shell junction.
I believe that your methodology may be more useful and the larger nozzle moments a much better idea, but only for pressure vessels (MAWP>50 psi)....not for large atmospheric tanks.
I also recall some corporate "design nozzle load guidelines" where the torsional moment on the nozzle is about three times the other two.
and....I completely agree that the piping stress guys are always the last ones to the table. (sometimes they are not even invited at all !!)
I have always particularly liked the situation where you are performing a flexibility analysis on the piping as the system is being fabricated.
My opinion only
-MJC
RE: Nozzle Loads
I have not had to specify loadings for tanks, but as suggested, the above factors would be excessive. API650 now has a method to readily determine allowable loadings for tank nozzles, and I suspect it is generally easier to position pipe supports for a tank, to reduce nozzle loadings, then it is for some pressure vessels I have worked with.
I only mentioned the fact that I apply loadings at the nozzle shell interface because it does make a difference, and definition of assumed loading point of reference should be made clear to the vessel designer, and piping stress analyst, so that everyone is playing in the same ball game.
Regards,
JohnGP
PS I know all about "shakey" memories......or at least I think I used to.