US1462890A - Spiral casing - Google Patents

Description

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H. B. TAYLOR SPIRAL CAS ING Filed April 30 1920 2 Sheets-Sheet 2 A 50k/Wsw" Patented .July 24, i923.

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naamw amenant TAYLOR, or PHILADELPHIA, PENNSYLVANIA.

' snaai: casina. i

Application filed April 30, 1920. Serial No. 377,735.

To all whom it may concern:

Be it known that I, HAicvnY BIRGHARD TAYLOR, a citizen of the United States, residing at Philadelphia, in the county .of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Spiral Casings, of which the following is a specification. n

This invention ,relates to casings of hydraulic turbines and centrifugal pumps and particularly to casings of spiral or volute form and of cast material such as cast iron or cast steel. The object of the invention is to provide such a casin that can be economically constructed an which will be subdivided into sections which can be readily rshipped and handled, being especially adapted to turbines and pumps of large size and those subjected to high heads. n

In the construction of casings of large size and those intended for lhigh internal pres sures there are two problems of particular difficulty, namely, the staying of the walls across the internal circular opening and the attachment of the sections of the casing to each other. In order to provide the best form of water passages cast stay vanes have been used to tie the walls together .since such vanes can be properly formed to suit the How of the water. In small turbines especially when designed for small heads the stay vanes have been cast integrally with the casing. In large turbines, however, the casting of such vanes inte rally with the casing in volves the risk o shrinkage strains beino' set up during the cooling of the casting andi the use of integral vanes in large casing sections has been considered dangerous practice. The initial strains set up in casting such sections are sometimes so, serious as to cause the vanes to crack before the casings are. subjected to pressure, and in any event are indeterminate in amount and the source of serious uncertainty. In large turbines it has therefore been usual to cast the stay vanes in a separate stay vane ring bolted to the turbine casing, both the ring and the remainder of the casing being further subdivided into as man sections as are required b the limitations o shipment and handling.

he bolting of the sections of the speed ring to each other and also the bolting to connect the sections of the casing have involved dificulties of design and construction,these diiculties being increased by the necessity for bolting the speed ring to the casing. The internal pressure within the casin not only causes stresses extending circum erentially around the wall in directions contained in a radial plane passing through the axis of the casing, this stress being carried through the stay vanes, but it also causes a stress in directions perpendicular to the stress just mentioned, namely, stress tending to rupture the casing along the plane passing through the turbine axis. This latter stress must be carried from one section of the casing to anotlier and from one section of the speed ring to another through the connecting bolts and flanges. The diiiiculty of providing sufficient bolts and placing them sufficiently close to the portions of the joint subjected to load has resulted in a tendency of casings to open up at the 'oints when subjected to high pressures, an to overstrain the bolts.

In the structure of this invention a Separate stay vane ring is avoided and the stay vanes are cast integrally with the casing sections without risk of initial strains; and by the avoidance of the circular joints between the vane ring and the rest of the casing, and by a further simplification in design which will be described below, the diiiicultes in the arrangement ofthe bolting are avoided, and it becomes possible to provide ample bolting properly located with respect to the joints so that proper tightness of the joints may be obtained under pressure.l

In the embodiment of the invention illustrated in the accompanying drawings,

Fig. l is a View of an assembled casing for a hydraulic turbine taken in the direction of the turbine axis,

Fig. 2 is a sectional view to an enlarged scale on line 2 2 of Fig. l, and Figs. 3 and 4 show outlines of modified forms of casings.

The casing shown in the drawing is for the inflow to a hydraulic turbine having a runner in the space A and flow guided from the entrance B to the runner on narrowing spiral lines. The cross section of the casing decreases in the direction of flow so that while the entrance portion B may be .very large in section the end portion C is comparatively small. The casing as a whole is divided into sections between planes cutting transversely across the casing from the inside to the outside. In the specific example shown in the drawings these transverse planes r contain the axis of the casing, but it is obvious that these planes may be varied in direction to cut transversely across the casing at any desired angle.

It will be noted from the figure that no separate stay vane ring is employed. By avoiding the use of such a stay vane ring an important saving of weight becomes os-V sible iii the complete casing. The met od of subdivision used in the larger radial sections of the casing avoids the necessity for adopting such dimensions for any sect-ion as would be excessive or inconvenient for handlin and shipping.

n the casing of this invention the smaller sections 9, 10, 11, 12 of the casing contain integral stay vanes and the larger sections 5, 6, 7, 8 are constructed with separate stay vane sections 25, 26, 27, 28 without the use of a stay vane ring, by cutting the sections on diagonal planes as indicated at ab and bo in Fig. 2, so 4that each section comprises an inner part 25, 26, 27 or 28 with the corresponding stay vane (15, 16, 17 or 18) cast integral in it and an outer part 35, 36, 37, 38 bolted to the inner part. Each of the joints al thus formed has plane faces and can be readily machined by planing or other convenient means. These joints d between the inner and outer parts of each section extend from one end of the section to the other in a direction cuttino across the radial planes r and the joints fof successive sections are preferably staggered with relation to each other as shown so that each joint has its ends closed by the radial ianges of the adjacent sections and the strength of these flanges reinforces the bolting of the joints. The planes of these joints d instead of being diagonal with respect to the turbine axis, as shown in Fig. 2, can, when desired, be made vertical or parallel with the turbine axis, but they will still cut either diagonally or perpendicularly across radial planes, that is, planes containing the turbine axis such as the planes of joints r (Fig. l). It will be noted that the entrance section of the volute contains in one of its two subdivisions two stay vanes, one of which forms the -baffle or a continuation of the outer surface of the volute. l

By this subdivision of the sections into separate parts the stay vane subdivisions of these large sections can be conveniently cast separately from the other subdivisions of the sections, a method of construction which greatly simplifies the casting of the sections and provides increased assurance of sound castings being obtained for the stay vanes. l

The smaller radial sections of the casing,

which contain the vanes cast integrally, are

not too large 4to be annealed when made of cast steel, thus ensuring that any initial strains will be relieved.

incasso In order to provide greaterassurance of tightness of the radial joints r connecting'together the radial sections, particularly at their inner ends e in the portion adjacent to the central circular flanges, secondary plane Walls or webs 52 and 53 are employed in the casing of this invention, these walls extending in complete circles around the inner surfaces of the casing to form the joints with thehead cover 50 and lower cover plate 51 and being connected to the curved walls of the throat of the volute casing by radial webs 54. At each radial joint 1' it is possible in accordance with this construction to employv bolts both above and below these secondary walls at 55, 56 and 57, 58. By the use of this method the joints between successive sections of the seconda wall can be made securely tight, since eac of these joints comes midwa between two sets of bolts which effectual y joint opening up when the casing is subjected to high pressure. In casings as hererevent the tofore constructed there have been no secondary walls and the neighborhood of -'this joint has been a frequent source of weakness and leakage, which defect is securely guarded against 1n the present invention. This secondary flange or web 52, 53 also provides additional strength and stiffness for the casing, and helps to carry the circumferential stresses normal toa radial plane, thus avoiding high local stresses around the inner periphery of the casing.

This invention should not be understood to be limited to a particular method of 'subdividing the larger casing sections. Any method of subdividing the casing sections may be adopted which is convenient for shop manufacture. For example, as shown in Fig. 3, two outer radial sections 66, 67 of the casing may be bolted to a common inner casing section 68, the latter section containing vanes 17 cast integrally with it and the joints between the outer and inner sections being either planes as shown or circular joints c as shown in Fig. 4, and such as have' lto which is bolted the outer part of the hfalf casing, which may be in sections 70, 71, 72.

I claim 1. A volute casing for a turbine or pump subdivided into a plurality of separate cast sections by a series of'transverse planes, at least one of which sections is further subdivided into two smaller sections by two planes diagonal to the axis.

2. A spiral casing comprising a series o relatively small radial sections having stay lng radial end flanges, a flange extending 1nvanes cast integral tlieiewith and at least one relatively large radial section composed of separate parts with a stay vane cast 1ntegral with one ofsaid parts.

3. In a spiral casing a section divided into parts alon a plane or lanes extending from end to en of the section and cutting across radial planes containing the axis of the sp1- ral, said section havin a stay vane cast 1ntegral with one of sai parts.

4.-. In a spiral casing a cast section contained between two radial, planes and subdivided by at least one non-radial plane.

5. The combination in a spiral casing of a series of relatively small casing sections having stay vanes cast integral therewith, and relatively large casing sections having separate outer parts and inner parts bolted tpgether and having integral stay vanes 1n said inner arts.

6. he combination in a spiral casing, of a series of relatively small casing sections having stay vanes cast integral therewith, and relatively large casing sections having stay vanes integral in separate parts bolted in place in said sections.

7 In aspiral casing a series of sections having separate inner Iparts with stay vanes cast integral therewit 8. In a spiral casing a section subdivided by at least one non-radial flanged joint and an adjacent section having an integral face abutting and extending across the end of said joint.

9. In a spiral casing a section divided along a plane or planes at an angle to radial. planes containing the axis of the spiral, and adjacent sections having integral flanged faces abutting the ends of said division.

10. In a splral casing a plurality of cast sections each section being divided into parts along a plane or planes at an angle to radial planes containing the axis of the spiral, said dividing planes being at different distances from the center so that adjacent sections close the ends of said divisions.

11. In a spiral casing the combination with a casing Wall ('36, 26) having an inner edge (e) for engagement with an adjoining member (50 or 51), of a central structure (50 or 51) adjoining said edge, and a circular flange (52 or 53) extending inward from' un intermediate point between said edge and the outer portion (36) of' said casing and adapted to be connected to said central structure.

12. In a spiral casing the combination with a casing wall and a member adjoining said wall of a circular flange extending in` ward from an intermediate point thereof in a plane perpendicular to the axis of said casing and adapted to be connected to said member, and radial webs connecting said flange and said casing wall.

13. A section for a spiral casing compriswardly from an intermediate portion of the casing wall in a plane perpendicular to the axis of the casing and connecting said end flanges.

14. A spiral casin comprising a plurality of sections having anges at their ends and A a secondary circular flange extending inward and connecting said end flanges which are bolted together on both sides of said circu-l lar flange to hold'said sections securely together.

15. A volute casing Jfor a turbine or pump divided into a plurality of separate sections by transverse' planes, at least one of said sections being further subdivided into two castings bolted together, one of said castings con t aining a stay vane cast integrally therewit 16. A volute casing for a turbine or pump divided into a plurality of separate sections by transverse planes, at least one of said sections being further subdivided by at least one plane not containing the axis into twol castings bolted together, one of said castings con t aining a stay vane cast integrally therew-t 17. A volute casing for a turbine or pump divided into a lurality of' separate sections by transverse p anes, at least one of said sections being a single casting containing a stay vane cast integrally therewith, while at least one other of sai sections is further subdivided into two castings bolted together,

one of said last mentioned castings containing a Stay vane cast integrally therewith.

18. In a spiral casing a cast section having two end faces in transverse planes, and an adjacent section radially within the first section bolted thereto and having its end face-s continuous with and in the same planes as the first mentioned section.

19. A volute casing for a turbine or 'pump subdivided into a plurality of separate cast sections by a series of transverse planes, at least one of which sections is further subdivided into two smaller sections by at least one plane not containing the axis.

20. In a spiral casing a section divided into parts by at least one non-radial plane and having a stay vane cast integral with one of said parts.

21. A spiral casing comprising a plurality of sections having flanges at their ends and a secondary circular flange extending inward and connecting said end flanges which are bolted together on both sides of said circular flange to hold said sections securely to-l and a' series of relatively large casing sections having stay vanes integral in at least one separate p-art bolted to said last mentionedsections.

23. The combination with a spiral casing having a wall, the inwardly extendin rtion on one side of which is divide into two walls integral therewith and extending inward toward the axis and terminating in two parallel circular edges, of a member in the space at the center of the casing and connected toy one of said walls.

24. In aspiral casing a section bounded b two transverse planes and containing a slngle stay vane shaped to conform to the iow through said casing, said v'anes and the walls of said section forming a single casting.

25. In a spiral casing a section bounded by two non-perpendicular transverse planes and containing not more than two stay vanes cast integrally therewith.

26. In a spiral casing a section bounded by transverse planes at an angle of less than 90 to each other and containing not more thalr two stay vanes cast integrally therewit t 27. A spiral casing constructed. of cast metal subdivided by transverse planes into a plurality 'of sections, a, section in the smaller portion of the spiral containing a plurality of stay vanes cast integrally therewith and a section in the larger portion of the spiral containing a single stay vane cast integrally therewith.

28. ln a spiral casing a section bounded by transverse planes and subdivided by another plane and having a stay vane cast integral with one of the subdivisions.

HARVEY B IRCHARD TAYLOR.

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