US1603998A - Manhole closure - Google Patents

Description

Get. 19 1926. 7 1,603,998

P. THOMSEN ET AL MANHOLE CLOSURE Filed. Oct. 24, 1921 Igl a WITNESS. INVENTORS IQLJWM A TTORNE VS Patented Oct. 19, 1926.

UNITED" STATES PETER THOMSEN, OF QASSEL, AND OTTO HERMANN HARTMANN,

PATENT OFFICE.

OF OASSEL-WIL- HELMSHOHE, GERMANY, ASSIGNORS TO SGHMIDTSCHE HEISSDAMPF-GESELL SCHAFT M. B. 11, OF CASSEL-WILHELMSHOHE, GERMANY, A CORPORATION OF GER- MANY.

MANHOLE CLOSURE.

Application filed October 24, 1921, Serial No. 510,125, and in Germany October 25, 1920.

Our invention relates to the securing of tight joints at manhole openings, which are normally closed by covers or the 1ike,and the invention is esigned particularly for use in connection with receptacles containing fiuids under high pressure.

In the case of wrought-iron steam or water drums of high pressure steam boilers it has been found very difficult to obtain tight joints at the manholes. In order to obtain the requisite strength, such'drums must be made without any longitudinal seams and of relatively small diameter. Since the dimensions of manholes must not fall below a certain minimum, the relatively large openings will greatly weaken the walls of the drums, and such weakening cannot be compensated for sufiiciently by the customary expedients of either bending the walls to form flanges at the edges of the openings or riveting reinforcing rings on such walls. Owing to such weakening, the drums are deformed, thus throwing the joint surfaces of the manhole and of its cover out of true and making it impossible to preserve the tightness of the joints. This is particularly disagreeable and dangerous in the case of Steam boilers, as it gives rise to much dreaded breakdowns and shut-downs, Another difficulty experienced hitherto is due to the fact that the customary thick manhole packings, which will compensate for inequalities in the Surfaces of the joints, are not serviceable in the case of high pressures, since they will not be able to resist such pressure but will rather be forced from their seats or blown out.

By means of our present invention we overcome the drawbacks explained above.

For this purpose we produce around the opening of the drum a reinforcement integral with the wall of the drum and having, on the pressure side, a smooth, plane surface forming a seat for the manhole cover. The location and size of the manhole and the reinforcement of said manhole are so arranged that a substantial portion 'of the reinforcement extends to and merges with side wall portions of the boiler which portions are substantially parallel with the effective forces which are exerted by the boiler pressure upon the manhole cover, that is to .out of the material of the say, those components of the outwardly exerted forces which extend perpendicular to the plane of the seating surface of the cover. This reinforcement, which may be located either on the inner side of the drum or on the outer side thereof, may be produced in various Ways; for instance, it may be worked drum by operations such as hammering, pressing, and the like, or it maybe obtained by welding a suitable body to the wall of the drum so that the Welded body Wlll be integral with the said wall.

This reinforcement, formed around the manhole, particularly when it is worked out of the material of the drum, will prevent distortion of the drum and the resulting bending and warping of the seating surface,

so that a permanently tight fit of the man hole cover is assured even at the highest operating pressures up to one hundred atmospheres and over. In order to obtain a tight joint it is necessary, however, that the cover should admit of having its seating surface worked to a tight fit by grinding, scraping, or the like. It is preferable, therefore, that even when the opening is oval, circularlyflattened or rectangular, the joint surface should be so arranged as to permit of regrinding. The joint may be purely metallic; for greater convenience of manufacture, we provide the joint, in many cases, with a thin packing (from to 1 millimeter) of suit able packing material, for instance, klingerite.

When the drums are of relatively considerable length, it is desirable, for the sake of easier manufacture, to make separately the drum portion containing the manhole and connect it subsequently with the other portions of the drum. The connection may be effected by circumferential rows of rivets or by welding. In this case, it is advisable to carry out at least the smoothing or finishing of the seating surface of the manhole cover after the, completion of the drum in order to counteract or correct any distortion which'may possibly occur at the time of connecting the several portions of the drumas well as the effect of such distortion on the joint surface.

The accompanying drawing illustrates, as

tral portion 0 is provided-with a flange or reinforcement e surrounding the manhole opening and projecting toward the interior of said collector. The upper or inner end surface m forms a seat for the manhole cover 7 which is held in position by screws 71 and arms or bows h. Rotation of the cover 7 is preferably prevented as by a ring or StIlK g projecting into the manhole opening. packing ring of metal, klingerite or other suitable material may be placed at the joint. The seat surface a: and the companion lower surface of the cover f are finished to obtain a tight fit, the cover being made to conform accurately to the seat by grinding, scraping or otherwise fashioning the two contact surfaces, preferably by mutual attrition in situ, similarly to the procedure often employed in grinding valves and valve seats of automobile engines. The particular drum illustrated by Figs. 1 and 2 comprises three separately made portions 6, 0 and d respectively. The reinforcement e is made from the same piece as the portion a by pressing, hammering, or the like. However, the reinforcing ring or flange 6 might originally be a separate piece subsequently made integral with the drum portion a by welding it thereto. Preferably, the seat surface w and the co-ope'rating surface of the manhole cover 7 are roughly finished before the drum portion 0 is connected with the end portions b, d. The accurate fitting of the cover f to its seat at, however, takes place only after the portions 6, 0 and d have been connected with each other.

Another example of our invention is shown in Figs. 3 and 4. Here the steam collector drum of a high-pressure steam boiler consists of the central portion 70 and of two lateral or end portions m, 'n respectively, connected with said central portion by circumferential rows of rivets. The reinforcement 0 is here shown applied to the outer surface of the wall of the central portion k. The seat surface w, of course, is on the inside, and ismade circular so that, notwithstanding the oval' shape of the manhole cover, such surface may be turned and ground smooth. The water tubes of the boiler are indicated at w. The seat surface-m maybe recessed relatively to the inner surface of the drum portion is; see

. Fig. 3.

In the construction illustrated by Figs.

in our resent invention Fi s. 1 -3 5 and 6, the central portion 23 of the drum has no manhole, but such manholes are provided on one or both of the lateral or end portions 1) and u. The manhole cover (shown in connection with the end portion u) is a double covercoi'n 'irising an inner cover a and an outer cover 1' pressed toward cach other by bolts and nuts, indicated at against the seat 01:, which may be 111 a recess, as in the second form of our invention. The outer cover 1- not only takes the place of the bows h, but assists in preserving a tight joint. Should any leakage occur between the inner cover 8 and its seat, the outer cover 1' will prevent the high-pressure steam from rushing out immediately under full pressure, which might lead to the ser ous injury of any person near by. If desired, we may provide, on the outer cover 1", a small tube Z communicating with the space between the two covers 1*, 8 to carry off to a place where it may do no harm, any steam which may leak past the joint between the inner cover 8 and the seat w. The water tubes of the boiler are indicated at ea.

In each of the constructions illustrated herein, the reinforcement on which the cover (or s) is seated is of a thickness greater than the thickness of the shell of the boiler or other article, both in the direction in which said cover is pressed against its seat, and in a direction at right angless to the first. Thus, for example, in Fig. 1, the flange e is of a thickness or height (direction parallel to axes of screws 11) greater than the thickness of the boiler shell, and

said flange also exceeds the boiler shell in thickness when measuring the thickness of said flange in a direction at right angles to the first, that is to say, between the two vertical lines of the flange. This flange is therefore much stronger than if it had been formed by merely bending inwardly a portion of the boiler shell at the manhole opening, in which case the radial thickness of the flange would be equal to the thickness of the boiler shell. This would result in a construction of relative weakness, particularly in the case of large openings such as manholes, where the risk of distortion is much greater than with small openings such as handholes.

In each form of the invention illustrated, it will be noted that, as shown in Figs. 2 and 4, large portions of the circumference of the reinforcement :22 extend to and merge with the side walls of the central portions which are substantially parallel with the forces exerted by the boiler pressure upon the covers 7 and g respectively. Between the side walls that portion of the circumference of the reinforcement, considered in the direction of the forces exerted on the covers, is made considerably thicker than the side 2. The inner cover 8 is thus held tightly Inn walls so that a large massof material is formed by the entire reinforcement which is directly tied to the side walls. In the example shown in Figs. and 6, the entire 5 circumference of the reinforcement merges with a side wall. It will also be noted that in all three forms of the invention the reinforcement is considerably thicker than the side walls at the points where the outward bending stress due to the forces upon the cover would be greatest. In addition to the advantages derived from tying the reinforcement to the side walls, the contacting surfaces of the covers, and the anchoring plates, with the reinforced edges of the manholes are arranged directly opposite one another, so that no bending stresses are pro- \sluced upon the drums by the tightening of these parts. The covers are also made much thicker than those usually employed and they are also thickened at their central portions so as to efiectively prevent distortion of the covers. The great thickness of the reinforcements and the covers secured thereto forms a substantially solid mass of mate rial so great that distortion between portions thereof is practically impossible and the manner in which the mass of material is tied to the side walls effectively prevents distortion of the drums.

We claiznz A wrought-iron steam or water drum for a high pressure boiler provided with a manhole to allow a person to enter the drum, the edge portion of the said manhole being materially thicker in the direction of the axis of the manhole, than the surrounding portion of that part of the drum in which the manhole is provided, there being a gradual transition of thickness from said thickened edge 40 portion to the thinner surrounding portion, an oval manhole cover in engagement with that surface of said thickened edge portion which is inside the drum, and means for holding said cover in position, the cover being of such dimensions, and the said thickened edge portion being at such a distance from the surrounding parts of the drum as to permit the said cover to be turned about the axis of the manhole for the purpose of grinding the cover to its seat.

In testimony whereof we have hereunto set our hands.

PETER THOMSEN. OTTO HERMANN HARTMANN.

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