US2688315A - Heat exchanger handhole fitting - Google Patents

Description

p 7, 1954 c. H. DAVY HEAT EXCHANGER HANDHOLE FITTING Filed May 11 1951 INVENTOR FIGB U n N Patented Sept. 7, 1954 52,688,315 HEAT EXCHANGER HANDHOLE FITTING Christopher H. Davy, London, England, assignor to The Ba'bcock & Wilcox Company, Rockleigh, N. J., a corporation of New Jersey Application May 11, 1951, Serial No. 225,713

Claims priority, application Great Britain May 15, 1950 Claims.

This invention relates to tubulous forced-flow heat exchangers. In tubulous forced-flow heat exchangers having headers formed with hand holes closed by hand hole fittings difiiculty may arise in the maintenance of tight jointsubetween the hand hole fittings and their seats. Such leakage may be promoted by rapid temperature changes of the hand hole fittings due to sudden substantial variations in the temperature of the fluid in contact therewith, such temperature changes serving to efiect temporary-distortion of the fittings. Thus, in the case of steaming economisers, the inventor has observed that, when starting'up or shutting down the boiler with which the economiser is associated, pockets of steam generated in the economiser tubes can cause the ejection into an outlet header of the economiser of slugs of water which may be markedly hotter or colder thanthe prevailing temperature within the header, while such slugs of water may also be ejected in the reverse direction into the economiser inlet header, such slugs causing the inner surfaces of hand hole fittings which in the first case may be opposite the'outlet ends of economiser tubes, in the second case opposite the inlet ends of economiser tubes and opposite the outlet ends of feed water tubes, to be subjected to variations in temperature. It is an object of the invention to reduce or obviate the danger of leakage at hand hole fittings due to such fluid temperature :variations.

The present invention includes a tubulous forced-flow heat exchanger having a header formed with a hand hole, wherein screening means are adapted to impede heat transfer between a hand hole fitting and fluid within the header when such fluid has a temperature substantially diiferent from that of the hand hole fitting.

The invention also includes a tubulous forcedflow heat exchanger having headers formed with hand holes arranged to give access to the interiors of heat exchanger tubes, wherein screening means are adapted to impede heat transfer between hand hole fittings and fiuid within the headers when such fluid has a temperature substantially different from that of the hand hole fittings.

The invention furthermore includes in or for use in a tubulous forced-flow heat exchanger a hand hole fitting comprising a closure member adapted to close the hand hole at the inner face of which closure member is provided screening means covering at least the greater part of the said inner face including the central portion thereof.

Suitably in the case of the inlet and outlet headers of a steaming economiser the hand hole fittings are individually provided with screening means. The screening means for a hand hole fitting may comprise a part intended to be attached to the hand hole closure member before the installation of the fitting, but in most cases with the usual form of hand holes a substantial restriction of dimensions mustbe imposed on the part intended to be so attached, in order to permit of the manoeuvre necessary to insert the 010- sure member through the hand hole, and it may be more desirable in such cases to pass a part of larger dimensions through the hand hole separately of the closure member and attach it .to the closure element within the header. The screening means for a hand'hole fitting may comprise a mild steel plate suitably or thick centrally secured to and slightly spaced, for example by from the face of a hand hole closure member.

The invention will now be described, by way of example, with reference to the accompanying drawings, .in which:

Figure 1 is a sectional elevation of an outlet header of a steaming economiser on a plane'transverse to the axis of the header and through the centre line of a hand hole closed by a screened hand hole fitting, opposite to ya tube entering the header;

Figure 2 is an external view of a metalplate screening the hand hole closure element, and secured in place thereto, showing the side of the plate intended to face the tube end; and

Figure 3 is an external view of the header, with the hand hole fitting removed, showing the hand hole.

Referring to the drawings, a tube 1 leading a, steam and water mixture from heated tube lengths of a steaming economiser of a boiler discharges the mixture through a wall 2 of an outlet header 3 ,of the economiser, which header .is of approximately square external and internal shape. In the header wall 4 opposite to the end of the tube l is a hand hole 5, in shape square but with rounded corners (Figure '3), through which to gain access to the tube end, for the purpose, for example, of securing the tube end in the wall 2 with the application of a roller tube expander and by welding, or of introducing a tube cleaning device into the tube.

For closing the hand hole a hand hole fitting 6 is provided comprising a closure member '1 with which is formed integrally a bolt 8 which when the closure member is in position to close the hand hole extends outwardly in a direction away from the header. By means of a nut 9 .on the bolt, and a bridge 40 through which the bolt extends and which spans the hand hole .withits feet I l engaging the outer face .of the wall 4, the closure member may be urged in the direction outwardly of the header.

The closure member is in shape square but with rounded corners (Figure 2) and is formed with an outwardly directed surface l2 conforms ing to the shapeof an inwardly .directedsurface I3 formed at the periphery of 'the hand hole. When the nut 9 is tightened .on .the bolt 8 the to the interior of said surface [2 is urged towards the surface [3. Between4 the surfaces l2 and I3 is interposed a gasket I I The face I5 of the closure member facing the end of the tube I is concave and spaced therefrom is arranged a metal plate 16. The metal plate 66 is square in shape with the distance between parallel edges slightly greater than that between parallel edges of the closure member. The plate is flat except at its edges 11 which have been turned at right angles and when the plate is in position extend in a direction to enclose a Zpace between the plate and the closure mem- The plate is held in position by a stud l8 welded to the centre of the closure member face l5 so as to project therefrom towards the tube end, and the plate is retained between a nut i9 on a threaded portion 20 of the stud of smaller diameter which projects through the plate, and an annular shoulder 2| on the stud. The nut is spot welded at 22 to the stud portion 20.

During operation, if, during starting-up or shutting down of the boiler with which the economiser is associated, a pocket of steam causes a slug of hot or cold Water to be discharged by the tube i towards the opposed hand hole fitting, the water impinges mainly on the plate is rather than on the closure member 1 and, since the plate is spaced from the inner face l5 of the closure member and the metallic conductive path from the plate through the stud to the closure member is of small cross-section, the rate of heat exchange between the water and the closure member is much smaller than if the water impinged directly on the closure member over the whole inner face l5 thereof. As a result, the danger of leakage at the hand hole fitting due to distortion of the fitting as a consequence of temperature gradients in the metal thereof is largely or wholly avoided.

When installing the closure member in position, or when removing it for replacement thereof or to gain access to the tube, the closure member has to be manoeuvred through the hand hole by taking advantage of the fact that the minimum dimension A (Figure 2) between parallel edges of the closure member is less than the maximum dimension B (Figure 3) across the diagonal of the hand hole. By passing the plate H3 through the hand hole separately of the closure member, the manoeuvre can be carried out without obstruction from the plate. The securing of the plate IE to the closure member including the spot welding, or its removel from the closure member including the breaking of the spot weld 22, as the case may be, can be effected within the header by operating from the hand hole after turning the closure 'member within the header, or by operating from an adjacent hand hole, which may be a hand hole opposite to an adjacent tube end in the header or a hand hole provided for the purpose.

I claim:

1. Heat exchange apparatus comprising a header normally containing fluid and formed with a handhole through which access is afforded header, a handhole fitting closing said handhole at the inner side of said header, and screening means mounted with its periphery adjacent the inner side of said fitting and adapted to impede heat transfer between said fitting and fluid within the header when such fluid has a temperature substantially different from that of the handhole fitting, said screening means and said fitting being relatively arranged to form therebetween a clearance space which at a location adjacent said periphery is continuously open to the interior of said header.

2. Heat exchange apparatus comprising a header normally containing fluid and to which is secured a tube having a fluid flow connection with said header, said header being formed with a handhole through which access is afforded to the interior of said tube, a handhole fitting closing said handhole at the inner side of said header, and screening means mounted on said fitting in closely spaced relation'to the inner face thereof and adapted to impede heat transfer between said fitting and fluid within the header when such fluid has a temperature substantially different from that of the handhole fitting, said screening means covering at least the greater part of said inner face including the central portion thereof, said screening means and said fitting being relatively arranged to form therebetween a clearance space which at locations adjacent the periphery of said screening means is continuously open to the interior of said header, said handhole fitting and said screening means being insertable and removable through said handhole.

3. Heat exchange apparatus as defined in claim 2 wherein said screening means is formed as a plate secured to said fitting through a metallic connection of considerably smaller cross sectional area than the area of said plate at the side toward said tube.

4. Heat exchange apparatus as defined in claim 3 wherein the total periphery of said screening plate extends beyond the total periphery of said fitting and projects in a direction to enclose the space between the plate and the inner face of said fitting.

5. Heat exchange apparatus comprising a header normally containing fiuid and to which is connected a tube through which at least a portion of said fluid is supplied, said header being formed with a handhole through which access is afforded to the interior of said tube, a handhole fitting closing said handhole at the inner side of said header, and screening means mounted on said fitting in closely spaced relation to the inner face thereof and adapted to impedeheat transfer between said fitting and fluid within the header when such fluid has a temperature substantially different from that of the handhole fitting, said screening means covering at least the greater part of said inner face in- References Citedin the file of this patent UNITED STATES PATENTS Number Name Date 1,456,314 Key May 22, 1923 1,536,272 scheib .1.--. Ma 5, 1925 1,783,129 Moses etal. Nov. 25, 1930 2,053,434 Jackson Sept. 8, 1936

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