USRE22980E - Spring hanger - Google Patents

Description

A. B. DONKERSLEY ET AL March 9, 1948.

5 PR ING HANGER Original Filed June 9, 1944 d 6 b m e "2 a ca 2 a HI F, m

Reisaued Mar. 9, 1948 SPRING HANGER Albert B. Donkersley and James R. Welshman,

Cranston, R. 1., assignors to Grinnell Corporation, Providence, R. 1., a corporation of Delaware Original No. 2,397,094, dated March 26, 1946, Se-

rial No. 539,579. June 9, 1944. Application for reissue November 8, 1947, Serial No. 784,922

2 Claims. 1

This invention relates to improvements in spring hangers. More especially it has to do with the provision of a simple, rugged hanger, using only a single direct-acting spring, which can be installed in a vertical space heretofore deemed insufficient for' available hangers having like sensitivity and load supporting ability.

Spring hangers are desirably employed where a known load supported by thehangers is sub- Ject to a moderate range of movement which can be foretold with reasonable certainty. Probably the greatest need for such hangers is for the sup- POrt of a pipe line which conducts fluid whose temperature may. vary and cause movement of certain of the pipes in the system. Most such systems comprise vertical risers at one p ace or another from which horizontal pipe lines extend. It is the expansion or contraction of the risers which causes the vertical displacement of the horizontal pipes, the magnitude of the movement being in proportion to the length of the risers. If this displacement is large, say from one to four inches, the horizontal pipes should be supported by what is known in the trade as a constant-support hanger. When the displacement is not over an inch the cost of a constantesupport hanger seems not Justified and yet the problem of properly supporting the horizontal pipe lines is nevertheless pressing.

The importance o1 providing proper support for pipe systems carrying steam is appreciated when the pressures and temperatures involved are realized. In power plants the present day pressures frequently are as high as 2000 pounds per square inch and the temperature of the steam is around 960' F. Under such conditions even a small local failure would be disastrous to personnel because, aside from the high pressure behind a leak, the escaping steam is at a temperature sumcient to impart a. dull red color to the metal of the pipe. Moreover, the performance of the metals now used in pipe lines and valves sub-- by a process of graphitizatlon. This is especially so in regions adjacent to welds, a serious fact when it is realized that welding is almost exclusively employed in the fabrication and lnstal lation of such Pipelines.

Pipe lines are seldom, if ever, of uniform weight per unit of length. Besides the different sizes of pipes used in a line there are usually fittings and valves at various locations, and occasionally a bend may be provided to absorb what would otherwise be a horizontal displacement of the line. Thus to provide proper support a hanger should be particularly adapted for the precise portion of the total weight of the line which the hanger is to carry. An ideal condition wouldbe to design a hanger for its individual load, but this is economically prohibitive. Hence in practice a spring hanger should be designed to be .used with a restricted range of loads and to so limit the working range of the spring that, any load within the load range can be supported with safety to the pipe line.

All this emphasizes the need for properly supporting pipe lines which carry fluids at high presssures and temperature and which are subject to vertical displacements. Throughout the movement of the pipe the load does not appreciably change in weightunless the fluid by chance changes from the liquid to the gaseous state or vice versabut the piping may shift its position to an extent that would make the use of a fixed hanger undesirable if not actually dangerous. Since the load does not change in weight during its contemplated movements, and since the lifting effect of a direct-acting spring does vary in accordance with its deflection, it is most desirable that a spring of such characteristics be used that its supporting eflect on the load be not extensively changed throughout the range of movement.

The desired sensitivity in a spring hanger ordinarily presupposes a hanger long enough in vertical extent to permit the spring to be extended its free length when the load is not being su-pported. This requires hangers of such vertical dimension as to be incapable of installation in many places where the space between a load and an overhead fixed support is limited. If in such a limited space a single spring hanger of the kind heretofore available on the market is installed; it means that to save space a spring having a large spring characteristic must be employed with consequent sacrifice of sensitivity. Indeed, this very fact usually rules out the use of the ordinary spring hanger because the setup of a piping system. for example, is generally such that the consequent changes in the lifting force of the spring throughout even a small range of movement of the load are prohibitive, in that unsafe stresses and reactive forces would be imposed upon either the piping itself or the fittings 1 I or'apparatus to which it is connected.

with the foregoing in mind. the primary object of the present invention is to provide a hanger, having Just a single direct-acting spring, which can be installed in a relatively small vertical space and which will nevertheless'have a desired sensitivity and avoid extreme changes in the lifting force of the spring throughout the movement of the load. We have'found that by pre-loading or pre-compressing a'spring of desired sensitivity during the assembly of the hanger, and by designedly shaping and arranging certain parts ofin the spring, a hanger of such over-all size can be provided that it can be used in'places'where heretofore the space available was deemed too small for hangers of the customary construction. More specifically, by employing a dished or recessed plate at the lower end of the hanger casing and another such plate for engagement j with the spring appreciable vertical space is I saved.' And it is a feature of the spring plate that its edge is soshaped and disposed as to serve as the indicator for a suitable scale or scales proaaoeo the hanger so as to utilize some ofthe space withi of deflection of the spring, then the intermediate- N 4' I g another scale lie have graduations representing the deflection or distance the load may move. The former scale, showing the load range, does not begin with a zero graduation but 'with one indicatingfthe minimum load which the hanger is intended to support. and the scale ends with the maximum load to be yieldingly carried by the hanger. For example, if the hanger is adapted for supporting loads from 600 pounds to 850 pounds. the topmost graduation on the load scale will be marked 600 and the lowermost graduation will be marked 850.- Between .these end,

markings the scale is provided with intermediate graduations which preferably have a relation with the spring constant of the spring used in the hanger. If this constant is 150 pounds per-inch graduations would be 650, 700, and pound increments up to 850.

The upper end plate 12 could bea simple flat plate, as indicated in dotted outline in Fig. 2, to

so on in 50 which suitable means could be attached. for convided on the outside of the hanger. One such scale has graduations'indicating the. extent of movement of the spring .plate when carrying loads as indicated on the load range scale. Ob-

viously such a marked sav ng in over-all vertical length means a corresponding saving in the amount and weight of material going into the make-up of a hanger and, what is more important, now makes it possible to employ direct,- acting single spring hangers in places where space limitations prohibited the installation of such hangers as were heretofore on the market.

The best mode in which we have contemplated applying .the'principles of our improvements is shown in the accompanying drawing, but these are to be deemed merely illustrative for it is in-' v tended that the patent shall cover by suitable expression in the appended claims what e f tures of patentable novelty exist in the invention disclosed.

In the drawing: Figure 1 is a medial sectional view of a hanger embodying our improvements, showing their relation when the hanger is partly assembled;

Figure 2 is a like medial vertical section, taken as on line 2-2 of Figure 4', showing the parts fully assembled;

Figure 3 is another like sectional view showing the relation of parts when a load is being supported; d

Figure 4 is a perspective of the improved hang-- necting the hanger with some overhead support,

but where space permitswe prefer to use a. dished plate such as is shown in full lines. The dished portion no of such a plate upstands from the plane of the top edge of the shell and thus provides space within the dished portion for a nut [8 which is secured to the inner surface of the plateby being tack welded thereto as indicated at 20. The nut is placed around an axial hole He in the plate in order that the threaded end of a supporting rod or eye bolt (see Fig. 3) may be passed through the hole and screwed into the nut I8. a

The lower plate II is designcdly of dished or recessed shape, having its rim Ma secured to the shell within the lower edge thereof and with its of the parts dished portion Ill) upstanding. within the shell. This particular arrangement is preferred for two reasons. The dished portion serves as a centering guide for a spring 22 housed within the shell with its bottom resting on the rini a of the lowerend plate, and the space within the dished portion is available to a'wrench when applied to a tubular coupling member '24.

A movable dished spring. plate 28 has its rim 26a resting on the spring 22 with its dished portion 25b downstanding within the spring. This arrangement'provides a space for the head 28a of a hanger rod 28 whose shank extends downward through an axial hole 26c in the movable plate 26 and is provided with external threads 28b at its lower end. These are engaged byv internal threads in the tubular coupling member 24 whose body normally extends downward through an axial hole llc in the lower end plate and is provided with opposed flat surfaces suitable for engagement by a wrench.

, II is welded into the shelland'then the-spring On one side of the shell, in the upper part thereof, is 'an opening Illb so arranged that a flat scale plate It may be attached to the shell overlying the said opening, If a metal or other opaque scale plate is used a vertically disposed slot |6a- (see Fig. 4) will beprovided therein, but such a slot is not necessary if the scale plate is made of transparent material. On the plate may,

be provided a scale with graduations [8b. indicating the weight of the load being supported and 22, standing at its free length, as seen in Figure l, is inserted in the shell,it's lower end being centered in the casing by the upstanding dished portion llc of the lower plate. Prior to placing the spring plate 26 on the top of the spring, the shank of the hanger rod .28 will have beenpassed through the axial hole 260 and threaded into the coupling member 24. when the latter has progressed far enough along the shank for the end of the hanger rod to be seen in the peep hole 30, the rod and coupling member are secured together. preferably bytack welding as indicated at 32.

Then the coupling member and hanger rod are engages the top of the spring. The dished portion 26b of the plate, extending into the space within the spring, serves to center the plate with v respect to the spring and thus bring the coupling member 24 into alignment with the axial hole lie in the lower end plate of the shell. The top plate I! is next applied to the spring plate, rim to rim, as shown in Figure 1, it being of course understood that prior to this the nut l8 has been secured to the underside of the topv plate. The hanger parts are now ready for the pre-loading or pre-compressing of the spring.

This step of pre-loading is readily accomplished by the use of a press which, acting on the top plate l2, forces this plate, the spring plate 26, hanger. rod 28, and coupling member 24 down-v ward, and at the same time compresses the spring 22, When the upper side of the rim Ila of the top plate is flush with the top edge of the shell ill, the plate and shell are welded together as 20 shown in Figures 2 and 3. Upon removal of. the hanger from the press the spring will be preloaded and exerting force on both end plates of the shell.

Actually the spring force is exerted upon the bottom plate and the movable plate between which plates the pre-compressed spring is confined, the latter plate being held at a limited distance from the bottom plate. This limited distance or inside height of the casing is the significant or effective height which controls the extent to which the spring is pre-compressed during the assembly of the hanger. By properly limiting this height of the casing between the bottom and movable plates the hanger cannot be used to yieldingly support a load which weighs less than the force exerted by the spring in its pre-compressed condition. To this end also there is no provision for adjustment of the spring force, thus insuring that once the hanger is fully assembled the spring will thereafter be under a. permanent, non-adjustable pre-compression.

We have found that a highly satisfactory hanger is attained by pre-compressing the spring so that it has a pre-load of not less th'an. three times its spring constant. For example, if the multiple is say 3.5, then with the hanger previously referred to as being adapted for a load range of from 600 to 850 pounds, using a spring having a spring constant of 150 pounds per inch of deflection, the spring would be pre-compressed to 525 pounds. This would be the force exerted by the spring on the movable plate 26 when the hanger is assembled. as shown in Fig. 2. If any load of less'than 525 pounds is applied to the hanger, no deflection of the spring will occur. Not until at least the minimum load of 600 pounds is being supported will the indicating edge 26d of the spring plate be opposite the uppermost graduation on the scale lGa. If a load in excess of 850 pounds is imposed on the hanger,

supported, but not yieldingly supported because it will cause no deflection of the spring, and likewise any load in excess of the maximum spring force will be supported, but not yieldingly supported because the spring will be deflected to its a the desired percentage, namely Thus they 6 solid length. But in the designed load range of the hanger any load will be yieldingly supported with a predetermined variation in supporting effect. That is, if the hanger is one adapted for a 5 loadrange of from 600 to 850 pounds, and the 10 pounds at the end of either half inch of movement. Likewise if the maximum load of 850 pounds is being carried by the hanger, then for the same assumed inch of deflection, either up or down, the variation in the spring force will be '15 pounds. Thus a hanger embodying the present improvements will yieldingly support a known load with a predetermined variation in supporting effect during movement of the load within the intended load range of the hanger.

This variation is predetermined as a selected percentage of the minimum load so that throughout the load ran'gethis selected percentage will not be exceeded. In the instant example, witha minimum load of 600 and a variation of 75 pounds per half inch of deflection, the percent- .01 the spring constant. Referring again to the hanger heretofore mentionedas an example, this multiple is found by dividing the pro-compressed load by the spring constant, that is 525- 150 gives a multiple of 3.5. If now another hanger on the 5 pipe line must be adapted to support a minimum load of 1800 pounds, and the same percentage of variation in the supporting eiiect is to be maintained, then the necessary change in spring force is found by multiplying the minimum load by 1aoo 12 2%=225 pounds Since this change is for only a /2 inch deflection, 'it is multiplied by 2 to get the spring constant of 450 pounds per inch of deflection. Having thus arrived at the proper spring constant it need only be multiplied by the multiple 3.5 to determine the pre-compressed load to be imposed on the spring, thus 450x3.5=1575 pounds. Accordingly if all the springs in a group of hangers sup-- 5 multiple arrived at as aforesaid. Having determined the proper rare-compression of the spring so that at the minimum load the percentage variation in supporting effect will be in keeping with good practice, it follows that iorany greater load in the load range of the hanger this percentage variation will'not be exceeded. Thisis because the spring constant remains constant even though the loads are larger, and therefore with such larger loads the percentage of variation in the supporting effect will actually be less than that with the minimum load.

Thus by pie-compressing springs in accord ance with the improvements herein disclosed, a

hanger of proper predetermined load range will be used for the load to be supported and upon its of safe engineering practice.

' plished as follows.

a supporting rod 34 or eye bolt is passed through the axial hole lie in the top plate and screwed into the nut II. By turning the rod or eye bolt until its inner end makes contact with the head 28a of the hanger rod a full thread engagement with the nut I8 is assured. Thereupon a jam nut 36 is turned tishtly against the top plate. locking the supporting rod or eye bolt and such top plate firmly together. The aforesaid contact of the supporting rod 34 with the head 28a of the hanger rod cannotonly be felt, but such contact is actually indicated by the novel indicator of thehanger. The rim 28a of the spring plate is beveled to provide a sharp edge 28d which, as shown in Figs. 2, 3

pling member- Ifl'o'rbymeansof theti'erodll,

is complete the coupling member 24 and lower tie rod '38 are locked together by another lam nut II, and the hanger will thereafter support the load yieldingly and permit movements of the load which may ordinarily occur.

By pre-loading or pre-compressing the spring, and by employing the dished or recessed plates at both ends of the spring, and arranging their and 4, lies close by the scale plate It. Ifthe workman, watches this indicating edge while screwing the supporting rod M into the nut II. he will observe-a slight movement of the edge immediately contact is made and the spring plate starts to move. Indeed'it is immaterial'if the scale plate ismoved downward slightly to abundantly assure a full thread engagement between the supporting rod 34 and the'nut ll, be-

cause the beginning of the scales lib and lSc with which the indicator cooperates is well below the place where such. slight movement would bring the spring plate.

The installation of the hanger may be accom- It may first be secured to dished portions as described, the o'ver-allvertical dimension of the hanger is kept reasonably small, and enables a spring of the desired sensiv tivityto be used. Because of'all this the improved hanger can now be employed in installations where heretofore, although spring supports were desirable, the available space prohibited.

the used such hangers as market.

We claim:

have been on the 1. A spring hanger for supporting a known load with a predetermined variation in supporting eflect during movement of. the load within a range, said .hanger comprising a casing having plates secured to its top and bottom ends,

some overhead support by means of the rod 34 as previously described. Then another tie rod 38, which is connected with the load, isapplied to the lower end of the coupling member 24. If this lower tie rod is rotatable, it can be -turned into the coupling member but if the rod 38 is held non-rotatable about its axis a wrench is applied to the coupling member 24 to turn the latter along the. non-rotating tie rod, preferably far enou h for the end of the rod tobe seen through the, peep hole 30a. As the coupling member turns so does the hanger rod 28, and

' possibly the spring plate 26. This is immaterial because the indicating edge 26:! extends all around the plate and is always visible regardless of how the plate may be rotated.

It is desirable that the hanger be adjusted so that when the loadis in its normal position, the spring will be compressed to an extent that will bring the indicating edge 25d somewhere in the vicinity of the load mark on the scales. Thus setting of the indicator may be accomplished when the load is in'its normal position'and being carried by the hanger. Usually the load is a. pipe which may move between what is called its "hot" position and its 'cold position. If the extent of this movement is known, and it usually is, then the hanger can beadjusted at either position. If the pipe moves upward a known amount when heated, then the setting of the hanger when the pipe is cold is with the a movable plate within the casing. a hanger rod engaging said movable plate and extending downward through the bottom end plate for connection with the load-to be supported. and a spring confined within said casing between the bottom plate thereof and the movable plate said spring having a free length greater than the height ofsaid casing and having a spring constant corresponding tothe said predetermined variation and being pre-compressed so 'as to limit its .working range to one in which the spring force exerted while yieldingly supporting the load is not less than a selected multiple of the sp i constant I 2. A spring hanger for supporting a portion of a piping system having a substantially constant weight and being subject to movement within a limited range due to changes in temperature of the system, said hanger having a casing and a plate relatively movable with respect to one another, and a pre-compressed spring confined between said-plate and a part of the said casing and connected with the said portion of the piping system for supporting said portion with a predetermined variation in supporting eflect during movement of said portion within said limited range; the said spring havindicating edge 26d the said-known distance below the eventual normal hot position. If the pipe on the other hand moves downward from its cold to its normally hot position,'.then the hanger rna'y be initiallyset with the indicating edge the known distance above theeventual normal position of. the pipe. Such adjustment of the hanger .is accomplished by means of the couconstant. e

' ALBERT B. DONKERBLEY. JAMES R. WELBHMAN.

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