Session: CS-01-01 Structural Integrity of Pressure Components

Paper Number: 61894

Start Time: Tuesday, July 13, 2021, 09:00 AM

61894 - Investigation of Nozzle on Knuckle Region of Dished Head 

ASME Code Section VIII Division 1 [1] has rules for the shape and proportions of opening. However, the Code [1] does not impose any restriction on the location of nozzle opening(s) on dished heads. Many corporate guidelines/ user design requirements meant for pressure vessel design and specification suggest avoiding placement of any type of nozzle in knuckle area of dished head and generally state in their design specification for limiting the placement of nozzle including its reinforcement to within the crown area for both Torispherical and Ellipsoidal dished heads. Code [1] provides rules for shape of openings, size of openings, strength and design of openings, however, the existing rules does not provide any restrictions on the specific location of the nozzle on the dished head knuckle portion.

Code [1] rules UG-37(a) provides the benefit in reinforcement by reducing the required thickness (tr) of the dished head when the nozzle is in the spherical portion of the dished head for the Ellipsoidal and Torispherical dished head.

High stresses occur in the knuckle region of the dished head due to edge bending effect caused as the cylinder and head try to deform in different directions. For various reasons the user design requirements insist on placing the nozzle in the knuckle region, further compounding the complexity of the stress pattern in the knuckle area. 

The work carried out in the paper was an attempt to check whether is it safe to locate a nozzle in the knuckle region of the dished head since the knuckle portion are generally subjected to high stresses in comparison to the crown portion of a dished head and Code [1] and [2] does not impose any restrictions for the placement of nozzles in the knuckle region. Also, in this paper an attempt was made to evaluate the induced stresses when equivalent sizes of nozzles are placed in the crown as well as the knuckle portion of the dished head.

Presenting Author: Sujay Pathre LLOYD'S REGISTER ASIA

Authors:

Sujay Pathre LLOYD'S REGISTER ASIA
Ameya Mathkar LLOYD'S REGISTER ASIA
Shyam Gopalakrishnan LLOYD'S REGISTER ASIA