US2546683A

US2546683A - Crown and traveling blocks and a reeving system therefor

Info

Publication number: US2546683A
Application number: US722487A
Authority: US
Inventors: Forrest J Young
Original assignee: Nat Supply Co
Current assignee: National Supply Co
Priority date: 1947-01-17
Filing date: 1947-01-17
Publication date: 1951-03-27
Anticipated expiration: 1968-03-27

Description

March 27, 1951 F. J. YOUNG 2,546,683

CROWN AND TRAVELING BLOCK AND A REEVING SYSTEM THEREFOR Filed Jan. 1'7, 1947 2 Sheets-Sheet 1 Imventor Gitomegs.

March 27, 1951 F. J. YOUNG 2,545,683

CROWN AND TRAVELING BLOCK AND A REEVING SYSTEM THEREFOR Filed Jan. 17, 1947 2 Sheets-Sheet 2 Enveutor Gtiorncgs.

Patented Mar. 27,

CROWN AND TRAVELING BLOCKS A REEVING SYSTEM THEREFOR Forrest J. Young, Los Angeles, Calif., assignor to The National Supply Company, Pittsburgh, Pa., a corporation of Pennsylvania Application January 17, 1947, Serial Ko i 22,487

ing block which is adapted to move vertically in the derrick is suspended by means of a flexible cable from a crown block position at the top of the derrick. One end of the cable which is reeved between the sheaves of the blocks extends downwardly from the crown block to a {I h0isting mechanism, and the other end extends downward1y-from.the crown block and is deadended near the base of the derrick. The drill 1 string is supported from the traveling block within the derrick.

The drill pipe, which carries the bit at its .lower end, must be withdrawn at intervals during the drilling operation fo replacing the bit, and the customary practice is to store unjointed sections of the drill pipe within the derrick, as it is being withdrawn, section by section, from the drilled hole. In a very deep drilling operations, the total amount of drill pipe to be stored within the derrickbecomes so great that the space available for movement of the traveling block within the derrick may be considerably restricted. Thus, it becomes essential to provide a traveling block of narrow width in order that adequate clearances may be maintained between .the traveling block and the pipe racked within the derrick. 1

Long strings of drill pipe require that heavy duty blocks be employed. Therefore, the requirement of narrowness'is complicated by the necessity of providing a high capacity block to handle the extremely heavy loads. In order to meet these conflicting requirements, it has been proposed to use adouble-deck travelin blockv in which two groups of sheaves'are employed, one

above the other. j capacity sheaves and bearings may be employed while maintaining a relatively narrow overall width. Accordingly, double deck traveling blocks and companion crown blocks have been used in actual operations. a conventional reeving system, in which a continuous cable is reeved progressively from right to left over adjacent sheaves, so that the high "speed sheave is .on one side of the block and the low speed sheave is .on the other side of. the

block. -Serious disadvantages result from this In this way, heavy duty, high These blocks :have employed,

' inafter.

type of reeving, however, since it causes the traveling block to cant or tilt during vertical movement in the derrick, and it causes the traveling block to turn about its vertical axis. These canting and rotating motions are objectionable since they reduce the clearance available between the moving traveling block and pipe racked in the derrick and, in severe cases, may result in fouling of the cable. v

The principalobject of my invention is to provide a crown or traveling block in whichalternate sheaves are progressively reevedwith a lead in one direction andthe remaining sheaves are progressively reeved with a lead in the other direction in order that tilting or canting of the block in operation, as well as turnin movement about its vertical. axis, may be minimized.

Another object is to provide'a crown and traveling block arrangement in which each of fthe blocks is provided I with plurality -of sheaves arranged in twofgroups 'the cable being -pro gressively reeved from' left to right around one of the groups of'sheaves andthen being progressively reeved from right to left "around the other group of sheaves, whereby the fastest and slowest speed sheaves are on one side of the block and an intermediate speed sheave is on the other side of the block.

Another object is to provide such a crown and traveling block assembly in which the sheaves in one group are of relatively large size and the sheaves in the other group are of relatively small size.

Other objects and In the drawings:

Figure 1 is a diagrammatic illustration showing a front elevation of a block assembly and reeving system, embodying my invention;

Figure 2 is a side elevation of the apparatus shown in Figure l Figure 3' is a perspective reeving diagram, showingfourteen line reeving for the traveling (block;

Figure 4 isa view similar ta-Figure 3, showing twelve line reevingfor the traveling block;

Figure 5 is a sketch employed in connection with the computation of the relative stability of a traveling block employing the reeving system embodied in my invention; and

Figure 6 is a view similar to Figure 5 relating to'a traveling block having conventional overand-over reeving.

Referring to the drawings, a crown block 20 is adapted to be supported at the top of a derrick upon beams 2|, and 22. A stationary shaft supports a primary group of relatively large, independently rotatable sheaves I, -3, Sand 1. This advantages will appear here group of sheaves is rotatable about a common axis. A. secondary group or relatively small diameter sheaves 9, II, I 3 and I is supported on a lower stationary shaft and is independently rotatable. about a common axis. 'The axis of rotation of sheaves l, 3, 5 and l is parallel to the axis of rotation of the sheaves 9, H, l3 and t5. For convenience, the primary group of relatively large sheaves will be designated 23, and the secondary group of relatively small sheaves will be designated 24.

In a similar manner, the traveling, block, 25 includes a lower stationary shaft for supportingthe primary group 26 of relatively

large diameter sheaves

2, 4 and 6 which are independently rotatable about a common axis. A secondary roup. 21 of relatively small diameter sheaves 8, l0, l2

and I4 is supported on an. upper. stationary shaft vtor rotation about a common axis. The axis of rotation of the. primary group 211 is parallel to .the axis of rotation of the secondary group 2.1.

A becket 28 is provided on the lower end, of the traveling block 25 for connection with a load carrying member, not shown.

It will, be observed that the relatively large diameter sheaves i, 3, 5 and I are disposed in alternating relation with. the relatively small diameter sheaves. 15, i3, H and 9. In a similar 'manner, the traveling block sheaves. 2, 4 and 6, .of. large diameter, are disposed, in alternating relation with the. relatively small diameter ,sheaves 8, l0, l2. and I4.

In accordance with my invention, the sheaves of one group are reeved with a. lead in one direction and the sheaves. of, the other group in each block. are reeved with a. lead in the other direction. Thus, the high speed line. 29,. of the con- ..tinuous: cable 30,. which extends to a. hoistin mechanism on. the, derrick. floor, not shown, passes first overthelarge. diameter sheave l on one side of the crown block 20., The cable then passes under the large. diameter sheave 2 on the. travel- .ing block; 25, and. the reeving progresses around ,

sheaves

3, 4, 5, 6 and Iv in that, order.

apparent that the primarygroup of sheaves in each block. is reeved progressively in a. direction It is thus from. left to right, as shown in Figure I of the drawings.

Theline. part leading, from, the sheave l on the crown block 20 then passes under the rela- ,tively small diameterv sheave 8 of. the traveling not shown. It will be understood that the reeving of: the

secondary groups

21 and 24 proceeds progressively from the. sheave 8. in a direction from right to left and that, therefore, the sheave L5 is the slowest moving sheave in the reeving system. Indeed, the sheave l5: referred to as the dead sheave, since. it. does not rotate so The high speed sheave l is thus adjacent the low speed or dead sheave 15-, while the sheave i on. the other side of the crown block 20 rotates in. an intermediate speed. In like manner the relatively high speed sheave 2 in the traveling hlOjCk is adjacent the.- relativelylow speed sheave i4, and the sheave 8 on the other side of the traveling block 25 rotates at an intermediate speed. If the sheaves were to be reeved in the conventional over-and-over system, the sheaves all, could be. of the samediameter and the reeving would proceed in the following order: I5, 14, t, 2, l3, l2, etc., and the sheave I would be the slow speed or dead sheave. The disadvantages of such over-and-over reeving is that: (1) The traveling block 25 turns about its vertical axis and hangs at an angle in the derrick; (2) the traveling block 25 is caused to tilt or cant as it is being elevated or lowered within the derrick; and (3) line clearances are diminished.

The reason for the tilt or cant is that the mechanical efiiciency of each sheave and its cooperating portion of the cable is not In other words, not all of the line tension on one side of a particular sheave is transmitted to the line on the other side of that sheave when the sheave. is rotating. The friction loss in the supporting bearing of the sheave and the friction loss due to flexing and unfiexing of the cable, as it. passes around the sheave, reduces the available tension from one side of the sheave to the other to a figure below 100%. From, considerable study and experience with this matter it has been determined that the line efficiency per sheave under operating conditions, is approximately 96%. For example, if the active end 29. of the cable 30 is being spooled on a hoisting drum, notv shown, to cause the traveling block 25 to move upwardly, the tension in that portion of the line extending between the sheaves l and 2 is. only 96% of the tension in the active end 29. Similarly, the tension in the line leading from the sheave 2 to the sheave 3 is only (.96 .96) or 92.2%. of the tension in the active, line 29. In the device shown in Figure 1, there are fourteen lines supporting the traveling blockv and, therefore, the tension in the deadline 31 when the block 25 is being raised is only about .96 or 54% of. the tension in the active. line 29. The non-uniform tension in the various parts of the line supporting the traveling block 25 is responsible for the cant or tilt of the block in operation.

A method now will be described for calculating the traveling blocks stability provided by the conventional over-and-over reevingv system, as compared to the stability provided by the reeving system embodying my invention.

In, Figure 5 the sheaves of the traveling block and sheaves of the crown block are represented by parallel straight lines. The upper portion of Figure 5 diagrammatically represents a plan view of the sheaves in, the crown block while the lower portion of. Figure, 5 diagrammatically represents a plan view of the sheaves in the traveling block. The traveling block is not illustrated directly under the crown block since this would cause confusion of the lines, It will be recognizedv at the outset that the most desirable condition, exists when, the resultant of all of the vertical forces applied to the traveling. block by the line parts passes through the geometric center of the block. If this condition were true there would be-no tilting or cantingv of the traveling block in motion.

The three

large sheaves

2, 4. and 5. on the traveling block 25 are. represented by relatively long straight lines carrying the same identifying numerals. Similarly, the four small sheaves 8, H3, I2 and M are represented by relatively short, straight lines positioned in alternate. relation with the. longer lines. Uniform lateral spacing is 'sheave.

and

sheaves ,l 2*, 3 4 5 etc., up to I5 "assumed and the letter a" is used to designate the long lines which are positioned in alternate relation are designated I, 3, 5 and 1 to correspond with the large diameter crown block sheaves. If the tension in the fast line 29 of the cable (see Figure 1) is assumed to equal P, then the tension in the line part connecting sheaves I and 2 will be Pic where k is the efiiciency of the For purposes of this analysis It will be assumed to be 96%. The tension in the line '

part connecting sheaves

2 and 3 is Pic-7c or PM.

Similarly, the tension in the line

part connecting sheaves

3 and 4 is Pk and the tension in the line

part connecting sheaves

4 and 5 is Pk etc.

"could be applied to the traveling block to have the same eiiect on the traveling block as the 'individualtensions in the line parts of the cable. :The lateral location of the point W may be established by taking moments about the straight line I4, as follows:

It can be shown that:

cti-lmP where n is the number of lines supporting the traveling block. In this case n=l4.

' Hence,

In other words, the traveling block is very nearly block are designated 2 4 6 8*, I W and M cable As'heretofore explained, the continuous is reeved progressively over adjacent sheaves with a lead in one direction only. Thus, the cable may be reeved continuously over Hence, the fast'sheave I is on one sideof the crown block and the dead sheave I is on the other side of the crown block. If the tension in the fast line from the hoist is again assumed to be P, the tension in the line part connectingsheaves' I and 2 is Pk. Similarly, the tension in the line part connecting sheaves '12 and 3 is PM,

and between

sheaves

3 and 4 is Pk etc. The

distance X to the location of the resultant forcev -:may be calculated from the equation:

invention is employed, as shown above.

which is derived from the following relationship: WX=Pa[k +k +2 (IF-Ht) +3(k' +k 4(k -i-lc +5(k +k +6m +k o 1 and since W equals 10.45P

In other words, the distance to the position of the resulting force W from the outermost sheave of the traveling block fails to correspond with the geometric center of the block where X equals 3a. The location of the resultant force W is .33a away from the center of the block with conventional over-and-over reeving. This figure compares to .0511 away from the center of the block when the reeving system embodying my From this comparison, it is to be understood that the conventional over-and-over reeving applies a resultant load on the traveling block, which is more than six times as far away from the center line of the block as is the resultant force diameter of the sheaves.

applied when the reeving system embodying my invention is employed. The canting or tilting movement of the block in operation is therefore largely overcome when my reeving system is used.

The feature which makes possible the reeving of some of the sheaves with a lead in one direction and the reeving of the other sheaves with a lead in the opposite direction is the provision of relatively large and relatively small sheaves.

Reference to Figure 2 will show that the line parts connecting

primary groups

23 and 26 are spaced from the corresponding line parts connecting the

secondary groups

24 and 21 by an amount corresponding to half the diiference in The only exception is the single line part connecting the primary sheave l with the secondary sheave 8. It will be noted that this line part is positioned at the extreme edge of the blocks and therefore the danger of fouling is minimized. The lateral spacing between adjacent sheaves provides lateral line clearance on the same order of the clearance provided between the line parts by reason of the difference in diameter of the sheaves, as shown in Figure 2.

While I have shown and described my invention in connection with a crown and traveling block organization employing fourteen lines for suspending the traveling block, it is to be understood that fewer lines may be used, if desired. As shown in Figure 4, two of the sheavesgin the secondary groups may be omitted from the system, if necessary, when it is desired to op erate fewer than twelve lines.

Having fully described my invention, it is to be understood that I do not wish to be limited to the details herein set forth, but my invention is of the full scope of the appended claims.

I claim:

1. In apparatus of t e class described having a traveling block suspended from a crown block 'by a cable rove between the blocks, the improvement comprising. in combination: a primary group of "relatively large diameter coaxial sheaves on each block, a secondary group of relatively small diameter coaxial sheaves parallel thereto on each block, the primary group of the crown block being positioned above. the secondary group thereof, and the primary group. of. the traveling block being positionedbelow the secondary group thereoi,. the cable beingv progressively reeved from a large end-sheave of the crown block around the primary group of sheaves in each block to the other large end-sheave of the crown block, and then reeved from a small end-sheave of the traveling block positioned vertically therebelow, and then around the remaining secondary group of sheaves in each block.

2. In combination, a pair of blocks, each block having a plurality of parallel sheaves, a cable progressively reeved between the blocks with a lead in one direction around alternate sheaves in each block, then from an end-sheave on one of the blocks to a sheave directly therebelow on the other of the blocks, and then reeved with a lead in the other direction around the remaining sheaves in each block, whereby in operation adjacent sheaves on one side of the block rotate at the fastest and slowest speeds and a sheave on the otherside of the block rotates at an intermediate speed.

3; In apparatus of the class described having a traveling block suspended from a crown block by a cable rove between the blocks, the improvement comprising, in combination: a plurality of relatively large diameter sheaves positioned in parallel alternating relationshi with a plurality of relatively small diameter sheaves on the same block, the sheaves being independently rotatable and laterally spaced with substantial uniformity to provide lateral clearance between line parts of the cable extending from the sheaves oi the block,

the large sheaves being interleaved with the small sheaves so that the upper portions of the. large sheaves extend above the lower portions of the small sheaves, the difference in diameter between large diam'etelsheaves and the small diameter sheaves being sufficient to provide side clearance between the line parts on the order of magnitude oi the l teral clearance so that the cable may be reeved with alead in one direction around the large diameter sheaves and in the opposite direction around the small diameter sheaves.

' 4. In a traveling block, the combination of a plurality or parallel sheaves, alternate sheaves being rotatable about two parallel axes vertically spaced, the alternate sheaves being interleaved so that the sheaves rotatable about one axis overlap the sheaves rotatable about the other axis, the diameter of the sheaves rotatable about the lower axis being. larger than the diameter of the other sheaves to establish clearance between line parts of a continuous cable supporting the block and reeved with. a lead. in one direction around the large diameter sheaves and in the opposite direction around the other sheaves.

5. In apparatus of the class described having a traveling block suspended from a crown block by a cable rove between the blocks, the improvement comprising, in combination: a primary 1 group of relatively large diameter coaxial sheaves and a secondary group of relatively small diameter coaxial sheaves parallel thereto on each block, the cable being reeved between the blocks so. that. it passes over a large end-sheave of the crown block and then around the remaining large sheaves. in each block to the other large endsheave of. the crown block, and thence to a small end-sheave of the traveling block positioned vertically therebelow, and then around the remain- "ing: small sheaves in each block to the small endslieave of the crown block adjacent the first said large end-sheave, whereby'in operation: said large end-sheave and, adjacent small end-sheave-on the sameside of the block rotate at the fastest and slowest speeds respectively, and a sheave. on the other side of the block rotates at an intermediate. speed.

6. In combination, a crown block, a traveling block, acable suspending the crown block from the traveling block, each block having a primary group'of. relatively large diameter coaxial sheaves and a secondary group of relatively small diam.- eter coaxial sheaves parallel thereto, the large sheaves of the crown block being positioned above the small sheaves thereof, the large sheaves of the traveling block being positioned below the small sheaves thereof, the two groups of sheaves in the traveling block being interleaved so that the upper portions of the large sheaves extend above the lower portions of the small sheaves,- the cable being reeved between the blocks. so that. it passes over a large end-sheave of the crown block and then around the remaining large. sheaves in each block to the other large end-sheave of the crown block, and thence to a small end-sheave of the traveling block positioned vertically thereb'elow, and then around the remaining small sheaves in each block to the small end-sheave. of the crown block adjacent the first said large endsheave, whereby the primary groups of sheaves are reeved with a lead in one direction and the secondary groups of sheaves are reeved with a lead in the other direction.

7. In combination, a crown block, atravelin block, a cablesuspendingthe crown block from the traveling block, each block having a primary group of relatively large diameter coaxial sheaves and a secondary group of relatively small diameter coaxial sheaves parallel thereto, the primary group of the crown block being positioned above the secondary group thereof, the primary group of the traveling block being positioned below the secondary group thereof, the traveling block having a greater number of sheaves in its secondary group than in its primary group, the two groups of sheaves in the traveling block being interleaved so that the upper portions of the large sheaves in the primary group extend above the lower portions of the small sheaves in the secondary group, the cable being reeved between the blocks so that it passes over an end-sheave in the primary group of the crown block and then around the remaining sheaves in the primary group in each block to the other end-sheave in the primary group of the crown block, and thence to an end-sheave in the secondary group of the traveling block positioned vertically therebelow,

and. then around the remaining sheaves. in. .the

secondary group in each block to the end-sheave inv the secondary group of the crown block adjacent the first said end-sheave, whereby the primary groups of sheaves, are reeved with a lead in. one direction and the secondary groups of sheaves are reeved with a lead in the other direction. I v FORREST J. YOUNG.

REFERENCES" CITED The following references are of record in the file of. this patent:v

UNITED STATES. PATENTS