NORSOK R-001, Nozzle Loads 1

[texag]

Howdy,

Recently a customer asked me to verify that our valves meet the requirements of NORSOK R-001 sec 5.1.5 for the nozzle loads. Essentially this confirms that the valve design is sufficient to support minimum moment and force loads at the nozzle to body (shell) junction that other connected equipment may impart. NORSOK gives the equations for force and the moment based on CWP and nozzle OD. What I am confused about is NORSOK's description of location and direction those loads. Below is some text from that section.

"The moment 'M' (Nm) and the force 'F' (N) shall be applied simultaneously in:
-two perpendicular directions at the right angle to the axis of pipe or in the plane tangent to the pressure retaining part at the nozzle-to-shell interface;
-direction perpendicular to the above plane.

Whenever relevant, the stress analysis shall be done both for the radial force pulling outwards together with the internal design pressure and for the same force pushing inwards with zero pressure resp. vacuum."

Can anyone with experience using this specification give me a clearer explanation of how NORSOK is wanting the forces applied?

 

[gr2vessels]

It is essentially the same as WRC 107 / WRC 297, check only for the +/- direction of the vector.
cheers,
gr2vessels

 

[texag]

I do not have a copy of that specification. Is the attached diagram a correct interpretation of the loading as described by NORSOK? Basically you have an external load causing two moments and an axial force - in addition to the other pressure and design loads. That would be a worst case scenario condition.

Is this required to allow for some flexure of the structures that the equipment may be attached to? I am not familiar with offshore engineering and am curious.

 

[gr2vessels]

Please type "WRC-107" in the search box in top of this page and select "Search Posts" in the advanced search box.
cheers,
gr2vessels

 

[narenr]

Norsok applies the nozzle forces same as WRC. Calculate the Moment/Force from the eqn given in Norsok and apply in all the 6 degrees [moment in 2 directions and torque in the 3rd, shear in 2 directions and axial force].


Narendranath R
Pipeline engineering is made easy with state of the art computer software, visit

http://www.narendranath.itgo.com.

 

[C2it]

Norsok R-001 makes life easier for the pipe stress engineer, since it nails down allowable loads on vessel nozzles that are not defined elsewhere in official documents, in the form of two equations. Note that the 'design pressure' in these equations is the flange rating (PN) and not the internal pressure. The code can be downloaded at:

http://www.standard.no/pronorm-3/data/f/0/01/43/6_10704_0/R-001.pdf

Cheers.

 

[texag]

narenr,

When I am applying my loads to calculate the 6 stresses do you mean to say that to meet NORSOK R-001 for nozzle loads I do not need to consider the stress from internal pressure in addition to the 6 loads you mentioned?

 

[C2it]

Teaxag / Narenr,

Norsok is really nothing to do with WRC 107. The equations derive a force and a moment based on pressure rating and nozzle size, to be applied in specified directions for vessel design to whatever code, suchas ASME, BS/PD or EN. The same loads are used as upper limit values in pipe stress analysis. This permits safe parallel engineering of piping and vessels and avoids submission / rejection of loads / iteration between different design groups.

 

[texag]

To start my analysis I applied the internal pressure and the loads created by the internal pressure. At the end of the nozzle I simulated remote loads to create the two momemts and the force as described in NORSOK, well, my interpretation anyway. I attached a sketch of this in a previous post. All I need to know is whether that interpretation is correct, so far I am getting different answers.

C2it, based on my diagram (which is the NORSOK forces only) did I apply the moments and force per the standard or is that incorrect? If it is incorrect could someone please sketch out the location and direction of the moments and forces on my nozzle?

 

[narenr]

See attached sketch.

F1, M1, F2, M2 = Two perpendicular directions at the right angle to the axis of pipe or in the plane tangent to the pressure retaining part at the nozzle-to-shell interface;

F3, M3 = Direction perpendicular to the above plane.

F and M are calculated from the Norsok equation which already contains the pressure. There is no need to add additional stresses due pressure.


Narendranath R
Pipeline engineering is made easy with state of the art computer software, visit www.narendranath.itgo.com.

 

[texag]

narenr,

A picture says a thousand words right?

Thank you!

 

[narenr]

It's always better in engineering to "paint the picture" than "mince the words".

For that matter, I like the BS codes and standards more than ASME.

Rgds Naren

Narendranath R
Pipeline engineering is made easy with state of the art computer software, visit

http://www.narendranath.itgo.com.

 

[C2it]

Narenr,

Surely you are not suggesting that ASME minces words, where BS codes do not ?

Fighting stuff indeed !!!!

 

[narenr]

C2it,

I am just expressing my experience. I feel ISO and BS are a lot clearer and easier to use than ASME. ASME is more like a legal code where you have ask for intrepretations. But this is off the main subject here.

Rgds Naren

Narendranath R
Pipeline engineering is made easy with state of the art computer software, visit

http://www.narendranath.itgo.com.