Dear all,
how do you verify nozzle loads when nozzle is on top or bottom of vertical vessel?
Do you use the resultant between axial, longitudinal and circunferential forces and moments and compared with allowable?

Thanks,
Fabiogriffo

Read this thread.

Loads and moments resolved according to nozzle local co-ordinate system (in x,y & z direction) are compared against allowables available in API-610/NEMA SM-23/etc. or allowables provided by equipment vendor. In API-610 (for pumps), provision is there for application of appendix-f1 incase of nozzle loads/moments exceeding any individual allowable in x,y or z direction. The appendix allows computing and comparing resultant for each nozzle (inlet & outlet) with relevant allowables provided, further, one has to compute resultant at pump base for all nozzles loads and compare with relevant allowable provided inorder to determine adequacy.

Err, last time I looked API 610 or NEMA didn't do local loads on vertical vessel end. i.e domed ends.
Either ask vendor for actual allowables or look in PD5500 App G, EN 13445 Part 3 and hand crank the calc. If I remember right, the PD5500 calc for a spherical shell is fairly straight forward.
Remember to apply loads at the nozzle / shell junction and that the CII "Local Element Force" report give loads in the element coordinate system, that is at right angles to the shell, if you have coded it correctly.

API 610 is applicable for pumps in petroleum industry and NEMA SM-23 for turbines. For nozzles of Non-rotary equipments such as vessels, tanks etc, allowable values provided by Rosshein & Markl can be used incase more accurate data by vendor is not available.

Mr. SkyofStars,

I'm confused by this ... The original question concerned nozzle loads on a vessel end where WRC 297 does not apply, moved on to where API 610 and NEMA also do not apply. Finally to Rossheim and Markl. Wasn't their joint work to do with gasket loads ? Or is there some more work on vessel nozzles ? If not, I don't think gasket load limits should be directly equated to nozzle limits.

Different companies have different practices. Joint work of Rossheim and Markl is being used by many for getting nozzle allowables on non-rotary equipment in case more accurate data is not available.

Interesting, Mr Sky of Stars.

In accordance with R&M, what allowable piping loads would you assign to a 16" 300# carbon steel vessel nozzle at 100 deg. C ?

It would be 10100 Kg axial, 4670 kg rectangular and 4740 Kg.m moment in all three directions.

You can use Rosschim-Markl formula for exact calculation of allowable values for nozzles on towers, drums and other pressure vessels.

You might like to point out some different practice, which i must welcome and would like to know about.

I believe the R&M formula [as shown in Kellogg]is :-
Radial force = 3.25 [D+3]^3
Shear forces at shell = 1.5 [D+3]^3
Moments = 60 [D+3]^3
D in inches and results in lb and in-lb

Now these values are usefull in SPECIFYING equipment allowables, but cannot be used with any certainty in assessing the loads on existing equipment where the allowable loads are unknown. There are many many different flavours of these formulas.
For instance Norsok requires
F = 7.5x(DN)1.2+0.1xPNx(DN)1.2[in N][for 16" 300# = 29840Nm {3042kg}]
M = 4x(DN-25)1.4+2x10-5xPNx(DN)2.7[in Nm] [for 16" 300# = 47880Nm {4880kg/m}]
PN in bar and DN in millimetres.
-Norsok at least makes an allowance for pressure, as typically a higher pressure system will have stiffer piping and thicker vessel walls, so can generate higher loads, but equipment also usually have the capacity to absorb them.

All these formulas [and there are many more] are useless in assessing loads on a vessel where the allowables are unknown. At best they are a guide. The only reasonably way to do it is to include the internal pressure, vessel wall thickness, diameter, material properties and other important factors into the assesment and that implies WRC 107/297, PD5500 App g etc etc.
Allowables loads are a two way street. They have to be specified and then they have to be designed to by the manufacturer, before they are of use.
It is easy to envisage a vessel, say 1000mm in diameter, with a design pressure of 10bar, that would only require ~4mm wall thickness for pressure retaining. Try applying a ten tonne axial force and 4.7tonne-m moments to that shell see what happens. [Hopefully any decent manufacturer would beef the wall thickness up and use re-pads around the nozzles to acheive reeasonable allowable loads.[

Availability of exact data regarding vessel internal pressure, wall thickness, diameter, material properties and other important factors do provide accurate value for allowables on nozzle after calculations by equipment manufacturer.

I must reemphasize for clarity, Joint work of Rossheim and Markl can be used for specifying reasonable nozzle allowables on non-rotary equipment for manufacturer to design for it and for piping stress analysts to assess adequacy of piping loads for the system.

In case, equipment manufacturer has already provided allowables, No one would recommend use of approximate reasonable values in place of exact values.

Capn Kenny, I wonder if you are using an actual pressure in your calc. Strictly the presure in Norsok is 'Nominal Pressure' or the flange rating, i.e. for 300# flange it is PN50 or 50 bars. with DN=400 it equates to an axial force of 16.57kN.

I agree that Norsok R-001 is a good guide. It is really a math model which gives similar results to tabulations held by many companies, traditionally based on something like 6000psi bending stress in schedule 40 pipe.

As Capn Kenny says, none can be used on unknown existing equipment. Any agreed limits are better than none during fast track parallel design, where vessel fabrication may be completed whilst piping design is still in action. It is a double edged sword however. Allowable loads that are too high mean excessive reinforcement of nozzles or heavier shell than needed. Equally, loads that are too low score brownie points for the vessel designer in terms of lighter weight, but cause piping to be routed with more flexibility and thus cost. The R&M axial load above of 99kN compares to a Norsok allowable for 300# flange of 16.6kN ..... draw your own conclusions.

Oops my mistake - I read the 900# values instead of the 300# values off my spreadsheet. I used the equivalent PN value of the ANSI flange. i.e 300# = PN50. The values you quote are correct MoverZ.
I've been lucky enough to have been on both sides of the fence, as a piping guy and as a vessel design engineer for a manufacturer and there is a hugh gulf between the two in the way nozzle loads are approached.

Agreed that none can be used on unknown existing equipment.

Higher R&M axial allowable of about 99kN comparing with lower Norsok allowable 16.6 KN for 300# flange donot instate correctness or wrongness of any value.

This however signify the importance of aspect that with R&M allowables used for specifications, lesser flexible piping would do; therefore would reduce piping cost, this however also mean more reinforcement of nozzles or heavier equipment shell.

With approximately 5~6 times lower allowable of NORSOK, one would be saving pennies at the cost of highly flexible piping needed.

Economics decide here which value to go for when both equipment and piping design are to be carried by single company; vessel design/manufacturing companies would however like to go for lower nozzle allowables,for example as provided by NORSOK, to score points.

MoverZ and Captain Kenny, many thanks for introducing Norsok R-001 to me which facilitated yet another basis different from R&M provided values.

Those not having it can download The Norsok R-001 from http://www.standard.no/pronorm-3/data/f/0/01/43/6_10704_0/R-001.pdf

MoverZ and CK, you must have noted that Norsok R-001 drives all the equipments (pumps, turbines, compressors, tanks, pressure vessels) with single yard stick. As such it is very generic in application for both rotary and non-rotary equipment when comparing with specific applications of API-610, NEMA SM-23 for some rotary and R&M for non rotary equipments. Probably thats why Norsok R-001 provides 5-6 times lower nozzle allowables for Pressure vessel.

SoS, you are quite wrong.

Norsok quotes regarding pumps .... " 5.2.1.4 Alignment: Minimum twice the forces and moments in API 610, Table 2 at maximum deck deflection shall
apply, but the design's additional capability shall be stated."

Norsok quotes regarding compressors .... " 5.3.2 External forces and moments: The following additional requirements apply: Each nozzle shall withstand 4 x NEMA SM23 forces and moments within the alignment tolerances."

This thread seems to have gone full circle. The original question was regarding nozzle loads on vessel ends, moved inexplicably to rotating equipment loads, back to vessels, and now to equipment again. Wait a moment, that's not just full circle, thats two laps of the circle.

My copy of Kellogg (p. 84) says that the moment reactions for the Rossheim-Markl criteria are in foot-pounds.

"With approximately 5~6 times lower allowable of NORSOK, one would be saving pennies at the cost of highly flexible piping needed"

Conclusion from SkyofStarts is ok?

The OP vanished long ago (no wonder)

In real terms, one should not (IMHO) be doing any hand calcs or rules of thumb to validate nozzles etc. At the Purchasing stage, the vendor should clearly indicate REASONABLE nozzles forces (or design codes) allowed on his equipment.

The Stress Engineer then has to validate the resultant forces with Ceaser and Job done.

Anything alse is accepting risk of failure from the vendor and is not best practice