MAXIMUM NOZZLE WALL THICKNESS
MAXIMUM NOZZLE WALL THICKNESS
(OP)
Is there an ASME or BS or EN code limit to the maximum thickness that a nozzle can be? (apart from the obvious reinforcement limits)
e.g. A 150mm thick fitted with a DN600 (24” NB) nozzle – what maximum thickness would be permitted for the self reinforced forging?
I tend to use a maximum of 2 to 2.5 x shell wall thickness as the maximum nozzle thickness
e.g. A 150mm thick fitted with a DN600 (24” NB) nozzle – what maximum thickness would be permitted for the self reinforced forging?
I tend to use a maximum of 2 to 2.5 x shell wall thickness as the maximum nozzle thickness





RE: MAXIMUM NOZZLE WALL THICKNESS
RE: MAXIMUM NOZZLE WALL THICKNESS
RE: MAXIMUM NOZZLE WALL THICKNESS
This is a little off topic, but IMHO, there are cases where the tank/vessel designer wants very thick nozzles.
The discharge nozzle on horizontal tanks containing hydrofluoric or sulfuric acid are examples.
Thickened nozzles are recommended by process industry standards and practices
-MJC
RE: MAXIMUM NOZZLE WALL THICKNESS
Thanks for that.
For my info:
1. Why and when would you want very thick nozzles in tank and vessel design?
2. Why would discharge nozzle on horizontal tanks containing hydrofluoric or sulfuric acid need to be very thick? - due to brick lining weight?
Thanks
RE: MAXIMUM NOZZLE WALL THICKNESS
it is almost a neccessity when dealing with special services, where all welds, including nozzle attachment welds must be fully radiographed. This requires self reinforced "Q-lip" nozzles.
have a look at this site, may explain some of it, at least some of the economics.
http://www.ameriforgegroup.com/fvc/
RE: MAXIMUM NOZZLE WALL THICKNESS
However when 2 major oil companies (one USA and one European) state in their PV specs that self reinforced nozzles shall not be thicker than 2 x shell thickness then there is something in it.
I am trying to find out why.
RE: MAXIMUM NOZZLE WALL THICKNESS
I could not resist to join in. My experience and surely yours, is in the evaluation of the nozzle reinforcement for local and external loads, when the standard pipe thickness would lead you to increased the shell thickness, or to a local insert, a thicker strake, or sometimes even change the head type to cope with additional thickness requirements. Thickening the shell atracts PWHT, extra welding, extra costs, all the known miseries in addition to what you quoted originally. Take a thicker nozzle and most of your problems are solved, putting as much as possible reinforcement, per the Code geometric limits, into the nozzle neck (another issue is how to get the nozzle in time..).
I found that playing the geometric limits and the nozzle thickness, it could / may get me the most economical nozzle vs. costs of increased shell thickness. That's where I can see the limits of nozzle thickness, obviously within the mentioned Code limits. By the way, I'm unable to recall any specific clause in ASME, AS or EN restricting the nozzle neck thickness to a specific size, as noted above by the boys.
howzat,
gr2vessels
RE: MAXIMUM NOZZLE WALL THICKNESS
The vessels where this is applicable are thick wall vessels.
CS vessels will require PWHT no matter how you juggle the nozzle dimensions as they will be above the normal code limit of 1.5" for PWHT requirements.
The end users have obviously found issues during operation with very thick forgings - just cos the code doesn't say anything does not mean that it is correct
RE: MAXIMUM NOZZLE WALL THICKNESS
I have not run across that spec yet and I work for all the majors, every day. Is it in a general spec or specific spec for materials and/or services.
I will say, some materials do not lend themselves to this type of connection.
I know inconel 800H does not like these joints and I am sure others are in the same range of problems.
However, I have not run across any problems in P1 materials, our main product line, in either PWHT or non-PWHT vessels and we UT all or nozzle attachment joints.
In some services, there is no other choice, that I am aware of, where attachment welds must be 100% interpretable radiographs must be obtained. No right angle attachments, means no pads. That forces to self reinforced necks and thick nozzle necks.
RE: MAXIMUM NOZZLE WALL THICKNESS
When integral reinforcement is provided on nozzles 150 mm (6 in) and greater, the ratio of nozzle wall thickness-to-shell wall thickness shall not be greater than 2.
From European Oil Company:
Add to AD-540 of ASME VIII Div 2:
The required thickness of an integrally reinforced branch shall not be greater than twice the
vessel wall thickness at the location of the attachment.
RE: MAXIMUM NOZZLE WALL THICKNESS
You are talking of special services, like cyclic, criogenic or other services where a significant stress will be present at the transition (thick nozzls and thinner shell), don't you? Those very good instructions were written perhaps before the FEA could predict the level of stress in the joint. Unless good engineering calculations and stress analysis can be performed on such combination (excessive thick nozzle wall vs much thinner shell thickness), the specified limits should be followed, for additional safety. However, you are user of PV Elite and I think NozzlePRO also, so what's stopping you to run the calculation and tell us how would stack-up the 2x limitation.
cheers,
gr2vessels
RE: MAXIMUM NOZZLE WALL THICKNESS
These are client specs and requirements - so no amount of FEA will overcome them.
I am not a user of either PVElite or Vessel Pro - if I had a choice I would be using Compress
RE: MAXIMUM NOZZLE WALL THICKNESS
RE: MAXIMUM NOZZLE WALL THICKNESS
ASME VIII: same as vesselfab's reply...NONE
BS EN 13445-3: YES. See paragraph 9.4.6 (Limitations on thickness).
RE: MAXIMUM NOZZLE WALL THICKNESS
what problems do you foresee?
RE: MAXIMUM NOZZLE WALL THICKNESS
getting require reinforcement within prescribed limits
how have you handled this?