US2366617A - Closure head welded for pressure vessels - Google Patents

Description

Jan. 2, 1945. A. w. HARRIS CLOSURE HEAD WELbED FOR PRESSURE VESSELS Filed Feb. 10,- 1943 Patented Jan. 2, 1945 CLOSURE HEAD WELDED FOR PRESSURE VESSELS Anderson W. Harris, Chattanooga, Tenn., assignor to Combustion Engineering Company, Inc.,

New York, N. Y.

Application February 10, 1943, Serial No. 475,315

1 Claim.

This invention relates to pressure vessels.

Metallic vessels used for retaining fluids under pressure, such as drums for oil stills and steam boilers, are usually cylindrical and have the ends closed by heads formed into a full hemispherical shape; or other full formed heads are used such as semi-elliptical shape in section or a fully dished head. The stresses in elliptical and dished heads are greater than in hemispherical heads, due to their shape. Consequently hemispherical heads may be of thinner and less costly material. when necessary to put in the head an opening .that requires reinforcement, the reinforcement required in a hemispherical head is less. However, full hemispherical heads of conventional construction, when made from one plate, involve a forming operation that is difficult and costly. The dies over which the metal is bent to form the heads are costly and it has been found that the head may freeze to the male dies and is difllcult to remove.

Full elliptical and full dished heads must have a flange or straight portion around their rim to avoid excessive concentration of stresses at the point of juncture with the shells to which they are attached. Furthermore the stresses at and adjoining the joint are diflicult to properly analyze. a t

It is an object of this invention to provide an improved drum head which overcomes the difllculties of forming a conventional hemispherical head, yet provides all of the advantages of a head of that shape.

In the drawing: 1

Figure 1 is a longitudinal section of part oi a drum and its head showing the prevailing constr'uction.

Figure 2 is a similar view of a drum and its head showing the improved construction.

In Fig. i the end'of the drum shell I, being thicker than the head is machined down in thickness to provide a reduced portion 2 of the same thickness as the formed head 3. The drum end and the head are fastened together by a weld l. The head shown has been formed to a full hemisphere in shape but it may be of other equivalent full formed heads, such as a head of semi-elliptical section or a full dished head. In order to overcome the difficulties mentioned above as involved in the forming of a full hemispherical head, I form a head as disclosed in Fig.2.

' Before machining, the end or the drum shell l0 extends in full thickness as shown bythe dotted line H. The end metal is then machined off inside and outside to suitable arced surfaces The inside surface I! is substantially that of a sphere and is a, continuation of the inside spherical surface of the head iii. For convenience in machining, the part of interior surface 12 beyond the hemisphere may be made conical; 0b viously the inside surface I2 may be a substantiafcontinuation of other shaped heads, such as an inside elliptical surface in section. By so shaping the drum end, the joint I between the drum and the head may be located to one side of the plane in which the diameter of the semicircle for generation of the spherically shaped head is located. Consequently the head itself is less than a hemisphere with proportionately less material to be worked; it may be formed relatively easily from a plate by pressing it between dies without becoming frozen onto the male die because that portion of the full spherical head, which seizes the male die upon shrinking, is not present but has been incorporated in the shell. Furthermore, the location of joint It, being within the spherical limits of the head, is subject to known spherical stresses while the stresses adjoining the joint of the full spherical head to the main body as shown in Fig. l are "of doubtful analysis.

What I claim is:

In a metallic pressure vessel; a concavo-convex, monolithic head portion constituting less than a semi-ovoid, hemisphere or the like; a hollow body portion of annular cross-section of metal thicker than that of the head having an 40 integral end portion abutting the latter, said end portion being reduced to a corresponding thickness with its interior and exterior surfaces having radii corresponding to those for the head and constituting continuations thereof over a distance back from the end edge of the body portion suflicient to complement the head in forming a semi-Ovid or hemispherical end portion for the vessel; and a weld joint between the body portion and head lying outside the plane containing the diameter of the semicircle for generation ,of the spherical surfaces of said head.

ANDERSON W.,HARRIS.

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