gusset design for nozzle 5

[PVdesigner]

Hi all

Can anybody please guide me in the design of gussets(stiffener) for a nozzle ? Any relevant papers ? Thanks in advance

 

[prex]

Gussets should be used on a nozzle only to limit deflection, when an instrument is suspended to it or a long run is required to the first support for pipe.

prex

http://www.xcalcs.com

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: Air bearing pads

 

[TGS4]

I have never been a fan of gusset stiffeners. If your vessel is operating at any temperature hotter than ambient, you are asking for differential thermal expansion troubles between the gussets and the nozzle. I have seen far too many cracks on gusset welds to believe that they are an acceptable solution.

Why do you want to add gussets to your nozzle?

 

[PVdesigner]

Nozzle extending more than 10'-0" from the vessel(Horizontal) surface vessel probably will require gussets or other type of supports.

 

[TGS4]

Egads! I would look into alternative support regimes.

What's on the end of the nozzle?

 

[PVdesigner]

Nozzle itself is 14" with blind at it;s top and a 4" nozzle on it's blind. I was wondering if this long nozzle would require supports against wind & piping loads.

 

[roca]

10'-0"? Thats not a nozzle its a pipe
What diameter is the vessel?

 

[chaulklate]

Further to what Roca said, consider a 'normal' nozzle projection, and spool to the required 10' finish dimension. Then use an alternate means of supporting the spool independent of the vessel.

 

[SnTMan]

PVdesigner, for your situation, I would assume / determine the loading, and check per WRC-107. You could also check the nozzle itself with a strength-of-materials approach.

The only nozzles I would consider gusseting are small (2" or less) pipe (not LWN) nozzles with fairly long projections. This I would do with narrrow plate gussets such that the nozzle-shell junction is well cleared by the gusset.

I agree that a 10' projection needs some external support, but I wouldn't gusset it to the shell.

Regards,

Mike

 

[MJCronin]

I would just like to add....

I also believe that nozzles should not be gusseted.

A competent vessel or piping engineer knows, of course, that some tank and pressure vessel nozzles require a more detailed analysis ( typically WRC 107/297)

There is one exception:

- Agitator nozzles on rounded heads

Chemineer (and other agitator vendors) recommend a pad-reinforced, flanged nozzle with gussets. This is in order to get the highest stiffness for the eccentric loadings on the nozzle.

-MJC

 

[roca]

Agree with MJCronin.
With the exception of the agitator support nozzle mentioned above nozzles are normally only gussetted when they are small (usually <=2"NB) and have a long outstand - these could be damaged in transport, are supporting a long level guage or other heavy instrumentation.
I have seen designers put gussetts on nozzles in order to meet nozzle load requirements which I think is not correct as you are just making the design more stiff. A certain amount of flexibility needs to inherent in the design.

 

[racookpe1978]

OK then, gussets are a poor solution for higher pressure tanks with external nozzles proturding from the tank - even those with modest external load on the nozzle.

Flip the problem around: I have a (30 plus year old) horizontal lube oil reservoir at essentially atmospheric pressure. 10 ft diameter, 30 feet long with F&D ends. Plain steel - 7/16 wall thickness.

Client has a main AC lube oil inside (suction is 3 ft above the bottom) and a backup DC lube oil pump with its suction about 16 inches above the bottom.

His shutdown AC pump is outside the tank on the pit floor, with its suction directly into the bottom of the tank. If there is a pipe break outside the tank, obviously all of the tank oil could leak out and he loses all LO pressure, because even the DC pump can't take a suction if the tank is dry.

So - can he extend the outside shutdown pump suction up into the tank by 42 inches, using gussets to reinforce the 42" stub inside the tank to prevent vibration and fatigue cracking? I would use a pad at the tank inlet itself. (There are welding, safety, access and cleanliness issues of welding inside an empty lube oil tnk, but they are straightforward relatively easily solved.)

A 42" inch stub into the tank would life his shutdown AC pump suction high above the "reserve pool" of oil inside the tank, so the DC pump could keep oil to his bearing as the plant shuts and cools down as the hypothectical original oil leak is fixed leak.