Flanged connection for pressure vessel

An improved joint for removably attaching first and second members together. The first member has a circular opening and a circular wall surrounding the opening and projecting axially outwardly from the opening. A double curved second member with a circular periphery has an annular flange with an inner surface surrounding the first member wall. Transmittal of radial forces from the second member annular flange to the first member wall is effected by contact of the walls with each other or by a spacer between and in contact with the walls. Removably securing the first and second members together is effected by shear studs or other securing devices.

This invention relates to high pressure and/or high temperature vessels 
using joint structures in which at least two members are releasably 
secured together through a common interface or joint. More particularly, 
the invention is concerned with such a joint structure in which one or 
both members being joined has a double curved shell or wall. 
BACKGROUND 
In many commercial as well as experimental processing operations, it is 
necessary to join together two members by a sealing means which prevents 
the escape of liquids, gases or vapors under pressure through the joint. 
In addition to withstanding high pressures, the joint must often be able 
to withstand relatively high temperatures. The formation of joint 
structures suitable for such conditions is compounded by a need to have 
such joints periodically opened and resealed. Accordingly, to completely 
satisfy the requirements, the joint structure must not only be able to 
prevent leakage under the high pressure, and perhaps high temperature, to 
which it is subjected but must also be one which can be opened and closed 
by suitable means. 
Joint structures of different types are presently used in processing 
vessels which employ high pressures and temperatures. Such vessels 
generally contain a walled body having an opening which is closed by a 
head, cover or closure. The opening in the vessel normally has a rim or 
flange structure which mates or nests with an opposing face on the head or 
cover. Since it is often essential that there be periodic access to the 
vessel interior, the head or cover is releasably secured to the vessel. To 
prevent leakage at the interface between the cover and the vessel, various 
types of gaskets and sealing means are used. 
SUMMARY OF THE PRIOR ART 
The article by S. M. Jorgensen "Designs For Closures and Shell Joints" in 
Mechanical Engineering, pages 24 to 31, June 1969, provides a discussion 
of the problems involved in effectively sealing a closure or head over a 
pressure vessel opening and also illustrates a number of pressure vessel 
closure and seal designs, including those which employ shear studs in an 
annular interface between the closure periphery and the vessel opening. 
Jorgensen U.S. Pat. No. 3,398,853 discloses a shear stud vessel closure and 
shell joint. 
Larsen U.S. Pat. No. 3,549,186 discloses a quick opening closure using 
split shear studs. 
Although the prior art shows useful high pressure joints and seals, there 
is a need for alternative joints and seals which withstand high pressures 
without significant leaking, so that an engineer is able to select the 
joint believed most suitable for the design conditions to be satisfied. 
When the walled body or shell of a vessel in comprised of one or more 
members having a double curvature, a closure releasable joint for the 
vessel could be subjected to rotational forces which, unless resisted 
satisfactorily, would cause the closure joint to leak or fail 
structurally. As used herein, a walled body or shell has a "double 
curvature" when a straight line cannot lie in the surface of the wall or 
shell. 
A releasable joint between a closure having a double curvature and a 
circular periphery, and a circular opening in the body of a single 
curvature vessel, such as a vessel with a cylindrical body portion, or a 
circular opening in a double curvature vessel, such as a vessel having a 
body portion which is a portion of a sphere or is elliptical in section, 
must be capable of successfully withstanding the radial forces applied 
around the circular periphery of the closure as a result of pressure on 
the closure interior surface and axial forces perpendicular to the radial 
forces applied against the closure periphery, by means of bolts, shear 
studs or a breech lock structure used to releasably join the closure to 
the vessel body. There is a need for a joint structure which can be 
suitably employed to join a double curved member, such as a closure, to a 
vessel body which is adapted for use in connection with a member for 
closing large openings, and which can be fabricated by means of 
conventional techniques with acceptable tolerances. 
SUMMARY OF THE INVENTION 
According to the present invention there is provided an improved joint for 
removably attaching together two members of a high temperature and/or high 
pressure vessel. 
More specifically, the improved joint provided by the invention for 
removably attaching two members together comprises a first member having a 
circular opening and a circular wall surrounding the opening and 
projecting axially outwardly from the opening, a double curved second 
member with a circular periphery having an annular flange with an inner 
surface surrounding the first member wall, means for transmitting radial 
forces from the second member annular flange to the first member wall, and 
means at the joint for removably securing the first and second members 
together. The first member can constitute the main body of a high 
temperature and/or high pressure vessel and the second member can 
constitute a closure or removable cover for the vessel. 
The first member wall and the second member flange desirably are so 
positioned that radial forces when applied to the second member flange 
intersect the lines of force through the members at the joint and the 
lines of force through the means for removably securing the first and 
second members together. 
The first member can have either a single curvature or a double curvature 
extending from the opening therein. 
The improved joint can also include a sealing means so positioned as to 
prevent leakage through the joint when the two members are part of a 
pressure vessel. 
The means for transmitting radial forces from the second member annular 
flange to the first member wall can simply constitute substantial contact 
between those elements. Alternatively, the means for transmitting radial 
forces from the second member annular flange to the first member wall can 
constitute an adjustable spacer. 
The invention provides a further embodiment of the improved joint for 
removably attaching two members together comprising a first member having 
a circular opening and a circular trough surrounding the opening defined 
by a pair of spaced apart inner and outer walls, a double curved second 
member with a circular periphery having an annular flange with an outer 
peripheral surface adjoining and complementary to the trough outer wall 
inner surface, means for transmitting radial forces from the second member 
annular flange to the first member inner wall, and means at the joint for 
removably securing the first and second members together. 
In a more detailed embodiment, the present invention provides a joint 
improvement in a pressure vessel having a walled body, which may have a 
shape with a single or double curvature, with an opening, and a double 
curvature closure for the opening of the walled body securable in place by 
connecting means, with the improvement comprising a circular trough in the 
walled body surrounding the opening defined by a pair of spaced apart 
inner and outer walls, with said inner wall being sloped, said closure 
having an annular flange with an outer peripheral surface adjoining and 
complementary to the trough outer wall, said closure annular flange having 
an inner sloped wall spaced from the trough inner wall thereby defining a 
sealing apparatus space, a sealing ring in the sealing apparatus space, 
said sealing ring having a top surface adapted to closely approach an 
inner surface of the closure with a gasket there-between and also having a 
sloped inner surface adapted to closely approach the trough inner wall 
with a gasket there-between, means extending through the closure adapted 
to displace the ring in an axial direction to effect sealing by applying 
pressure to said gaskets, a plurality of arcuate wedges with outer sloped 
surfaces complementary to the closure flange sloped inner surface between 
the sealing ring outer surface and the flange inner surface, and means 
extending through the closure adapted to displace the arcuate wedges 
axially and independently of the ring and into contact with the ring outer 
surface and the closure flange sloped inner surface. 
The connecting means for releasably securing the closure to the vessel can 
be a plurality of shear studs positioned in shear stud receiving threaded 
holes extending partially in the closure peripheral surface and partially 
in the trough outer wall. Alternatively, the connecting means can be a 
conventional breech lock structure in which the blocks are integral with 
the vessel and the closure and with spaces between blocks permitting the 
closure to be inserted. By rotating the closure the blocks are aligned and 
locked.

DETAILED DESCRIPTION OF THE DRAWINGS 
So far as is practical, the same elements or parts which appear in the 
various view of the drawings will be identified by the same numbers. 
With reference to FIG. 1, the spherical metal vessel 10 is largely composed 
of a metal shell body 11 in the shape of a spherical zone. The circular 
opening in spherical zone 11 is closed with a removable closure 12 secured 
in place by means of a joint 15 shown in greater detail in FIG. 3. The 
removable closure 12 is also a metal shell in the form of a spherical 
zone. Both the closure 12 and vessel body 11 are doubly curved shells 
throughout, including the portions at the joint 15. 
The metal vessel 20 shown in FIG. 2 has a body composed of a vertical 
cylindrical shell portion 21 and a hemispherical shell bottom 22. The 
circular opening at the top of the vessel body is closed by a removable 
closure 24 in the form of a metal shell, having a partial elliptical 
cross-section, secured in place by joint 15. The cylindrical shell portion 
21 is a single curved structure throughout, including the portion at joint 
15. However, the closure 24 is a double-curved shell throughout, even at 
the joint 15. 
FIG. 3 illustrates in greater detail the joint 15 used on the vessels of 
FIGS. 1 and 2. However, the shell portions on joint 15 shown in FIG. 3 are 
those of the vessel 10 of FIG. 1. 
As shown in FIG. 3, circular wall 26 surrounds the opening of shell body 11 
and projects axially outwardly from the opening. Annular flange 28 is 
located around the circular periphery of closure 12 and is so dimensioned 
as to have its inner surface 29 surrounding the outer surface 30 of wall 
26 and in contact therewith, thus providing means for transmitting radial 
forces from the flange 28 to wall 26. Outer wall 27 also projects from 
shell body 11 and with inner wall 26 they defined a trough in which 
annular flange 28 securely fits. A plurality of spaced apart shear studs 
31 are threaded into holes which are one-half in outer wall 27 and 
one-half in flange 28. The shear studs serve to resist the axial force 
applied against the interior surface of closure 12. Seal 32 is provided to 
make the joint gas-tight. 
It will be readily seen that joint 15 is so designed as to have the lines 
of force intersect at that portion of the joint which minimizes moments 
which produce rotation and distortion. As shown in FIG. 3, the horizontal 
line of force A--A, the line of force B--B through the shell, and the 
vertical or axial line of force C--C intersect at point X. By taking the 
principle lines of force through a common, or close to common, point 
minimum distortion is achieved at a joint where one double curved shell 
joins another shell, which is single or double curved, while permitting 
use of thinner metal plates for the shell than would otherwise be 
permissible. 
Although the joint 15 shown in detail in FIG. 3 has shear studs 31 to hold 
the closure 12 in place, it should be recognized that other means can be 
used, including bolts, shear rings and pins. When horizontal pins are 
used, the outer wall 27 could probably be eliminated since the pins could 
extend through flange 28 into wall 26. Furthermore, while FIG. 3 shows 
shell 11 as double curved, such a shell could be replaced with single 
curved cylindrical shell 21 as shown in FIG. 2. 
As shown in FIGS. 4 and 5 of the drawings, the spherical or doubly curved 
vessel 40 has a walled body 41 which defines an opening 42 at the top. The 
walled body 41 has a circular trough 44, surrounding the opening, defined 
by an inner wall 45 and an outer wall 46. The inner wall 45 is axially 
sloped. 
The vessel 40 is covered by a removable closure 50 having an annular flange 
51 with an outer peripheral surface 52 adjoining and complementary to the 
trough outer wall 46. The closure annular flange 51 has an inner sloped 
wall 53 spaced from the trough inner wall 45 thereby defining a sealing 
apparatus space 55 therebetween. 
Sealing ring 60 is positioned in the sealing apparatus space 55. Sealing 
ring 60 has a top surface 61 adapted to closely approach inner surface 56 
of closure 50 with one or more gaskets 62 therebetween. Also, sealing ring 
60 has a sloped inner surface 64 adapted to closely approach the trough 
inner wall 45 with one or more gaskets 65 therebetween. A series of bolts 
70 arranged in a circular pattern are secured at their lower ends to 
sealing ring 60. The bolts extend upwardly through holes in the closure to 
the top where a nut 71 is located on the top of each bolt. 
A plurality of slightly spaced apart arcuate wedges 80, with outer sloped 
surfaces 81 complementary to the closure sloped inner surface 53, are 
located between the sealing ring outer surface 66 and the flange inner 
surface 53. The inner surfaces 82 of wedges 80 are axial and adapted to 
smoothly and uniformly contact outer surface 66 of the sealing ring. Bolts 
90 are arranged in a circular pattern with their lower ends secured in 
wedges 80. Generally, at least two bolts will control each wedge 80. The 
bolts 90 extend through oversized holes in the closure and project above 
the closure top surface. A nut 91 is placed on the top of each bolt 90. 
Shear stud-receiving threaded holes extend partially in the closure 
peripheral surface 52 and partially in the trough outer wall 46. These 
holes are adapted to receive shear studs 100. 
In order to close vessel 40 with closure 50, the sealing ring 60 and 
adjustable wedges 80 are positioned in place with the wedges in a downward 
position so as to permit independent movement of sealing ring 60 relative 
to the closure. In this way, tolerance for machining inaccuracy is 
accommodated. Sealing ring 60 is lowered by bolts 70 so that when the 
closure is put in place a tight seal will develop at gaskets 65. The 
closure is then placed over the vessel opening and shear studs 100 are put 
in position. Bolts 70 are then used to pull sealing ring 60 upwardly so as 
to develop a seal at gaskets 62. This movement is achieved without 
breaking the seal at gaskets 65 because there is only a slight slope to 
the mating walls 45 and 64. After the seal is positioned as described, the 
wedges 80 are moved tightly upwardly by bolts 90. Not all bolts will be 
moved upwardly the same distance since the spacing between the sealing 
ring 60 and flange inner surface 53 will vary because of machining 
tolerances. The wedges are not used to develop the seal. The function of 
the wedges 80 is to resist radial forces which develop as a result of 
pressure on the inside of the closure. The shear studs 100 resist axial 
load but not radial forces. When pressure is applied to the inside of 
closure 50 the wall 53 of flange 51 applies an inwardly directed radial 
force against the wedges which in turn transfer the load to sealing ring 
60, and ultimately to mating flange 41. 
Although the invention has been specifically described with respect to 
joining a closure on a pressure vessel, it should be understood that the 
invention also can be used to sealably join a first member to a second 
member, particularly those having circular ends to be united as, and for 
example, cylindrical bodies. 
The gaskets can be made of any suitable material including polymeric 
materials, such as rubber, or of metal such as soft steel, zinc, aluminum 
or copper. Although the drawings show two gaskets 62 and two gaskets 65, 
only one such gasket need be employed but, of course, more than two can 
also be used. 
This detailed description has been given for clearness of understanding 
only, and no unnecessary limitations should be understood therefrom, as 
modifications will be obvious to those skilled in the art.