Open bowl for a vertical turbine pump

An open bowl for a vertical turbine pump, includes a bowl body having an inner wall and an outer wall, both walls being of substantially constant optimum thickness, surrounding a vertical axis and connected by diffuser vanes which define hydraulically optimized diffuser passages through the bowl body extending from a bottom end to a top end, the diffuser vanes being radially hollow and providing open paths through the inner and outer walls to a cavity surrounded by the inner wall; a flange at the top end of the outer wall for attachment of a discharge conduit for the pumped fluid; provision on the bottom end of the outer wall for attaching to a flange of a suction bell; further provision on an inner surface at the top of the inner wall for providing sealing engagement with an upper end of a separable substantially cylindrical bearing housing; and provision at the bottom end of the inner wall for attaching to a flange of the bearing housing. The open bowl concept provides a light weight pump which provides better metal flow, solidification control, and cooling during casting by elimination of drastic section thickness variations in the bowl body.

BACKGROUND OF THE INVENTION 
This invention relates generally to vertical turbine pumps and more 
particularly to vertical turbine pumps having a low number of appropriate 
thick diffuser vanes and minimal bowl diameter and weight for pumping both 
single phase and multiphase fluids, more particularly fluids containing 
fibrous materials and other solids. 
The traditional design of a bowl for both a wet pit and dry pit 
solids-handling vertical turbine pump with few vanes, in order to allow 
passage of solid particles with relatively large diameter, results in a 
bowl with large masses of metal between the vanes which contribute nothing 
to the function of the pump. In addition, transition passage area control, 
required for hydraulic parameter optimization, leads to very large 
thicknesses for most of the extent of the vanes, which makes casting of 
such bowls very difficult due to radical changes of section thickness and 
mass which makes uniform cooling very difficult to achieve and often 
causes cracking. Pump bowls of traditional design have each hydraulic 
passage near to the next and separated from the next by a vane whose 
thickness is dictated by castability constraints and pattern and core 
requirements. Therefore, the hydraulic passages are overly constrained and 
negatively affected. This results in poor diffusion and strong vortical 
turbulent flows which lower the efficiency of the pump and increase the 
risk of poor reliability due to high vibration. Such pumps, in spite of 
their less than optimal efficiency, are very heavy and, because of the 
casting difficulties described, unnecessarily expensive. 
The foregoing illustrates limitations known to exist in present bowls for 
turbine pumps, and it would be advantageous to provide an alternative 
directed to overcoming one or more of those limitations. Accordingly, a 
suitable alternative is provided including features more fully disclosed 
hereinafter. 
SUMMARY OF THE INVENTION 
In one aspect of the present invention, a bowl for a vertical turbine pump 
is provided, including a bowl body having an inner wall and an outer wall, 
both said walls being of substantially constant thickness, surrounding a 
vertical axis and connected by diffuser vanes which define diffuser 
passages through said bowl body extending from a bottom end to a top end, 
said diffuser vanes being radially hollow and providing open paths through 
said inner and outer walls to a cavity surrounded by said inner wall; a 
flange at the top end of said outer wall for attachment of a discharge 
conduit for the pumped fluid; means on the bottom end of said outer wall 
for attaching to a flange of a suction bell; means on an inner surface at 
the top of said inner wall for providing sealing engagement with an upper 
end of a separable substantially cylindrical bearing housing; and means at 
the bottom end of said inner wall for attaching to a flange of said 
bearing housing. 
The foregoing and other aspects of the invention will become apparent from 
the following detailed description, when considered in conjunction with 
the accompanying drawings.

DETAILED DESCRIPTION 
The views in FIGS. 1 and, 3a, and 3b illustrate a single stage pump 10 of 
the invention and reveal the meaning of the term "open bowl". The pump 10 
includes as a key component an open bowl 11, formed as a single piece, 
preferably as a casting, which preferably has a bulbous bowl body 15 with 
interior inner and outer walls 14, 16, respectively, which are of 
substantially constant thickness and are connected by vanes 20, above a 
pumping chamber 49, as seen in FIGS. 3a and 3b. 
The pump 10 includes the open bowl 11, the suction bell 40, and all the 
separable components, including the impeller 30, the impeller drive shaft 
29, and the bearing housing 25, all of which are shown in FIG. 3a. The 
open paths 12 through the bowl body 15 reveal the inside surface of an 
inner cavity 13, which is also preferably bulbous, surrounded by the inner 
wall 14 of the bowl body and, to the left side of the separable bearing 
housing 25, visible through the open path 12, is the open path on the 
opposite side of the bowl body 15. These features are further illustrated 
in FIG. 3b, in which part of the outer wall 16 of the bowl body 15 has 
been removed. This reveals the radially hollow vanes 20, containing the 
radial open paths 12, and hydraulic passages I and II which are separated 
by the vanes and which spiral about the inner wall 14, containing the 
inner cavity 13, of the bowl body above the pumping chamber 49 in which 
the impeller 30 rotates. 
It is not necessary that the bowl body 15 and the inner cavity have a 
bulbous shape in every case, depending on the service for which the bowl 
is designed; however, in many cases, such a shape may enhance hydraulic 
efficiency. The bowl illustrated has only two vanes 20 and two diffuser 
hydraulic passages I, II for ease of illustration. There may, however, be 
three or more passages, as appropriate for the pump application and the 
particle sizes of solids, if any, in the pumped fluid. In any case, the 
hydraulic passages are optimized for the intended service to optimize 
performance and reduce weight. The hydraulic passages I, II are best 
described as appropriately divergent, if required, channels with 
cross-sections of optimal shapes (curvilinear rectangles or other 
polygonal shapes) which each twist approximately three-fourths of the way 
around the bowl in their paths from the bottom end to the top end of the 
bowl 11. The hydraulic passages, thus, increase, as appropriate, in 
cross-section for most of the lengths of the passages from the bottom 
nearly to the top of the bowl and blend in shape and cross-sectional area 
to match the column pipe above the bowl. Vertical wet-pit solids-handling 
pumps typically have two, three, four or more hydraulic passages, with a 
corresponding number of open paths 12, depending on pump size and design 
optimization for the service intended. 
A suction bell 40 is attached at its flange 41 by bolts 42 or other 
fastening means to the bottom end a of the outer wall of the bowl body 15. 
Flange 45 is provided at the top b of the outer wall 16 of the bowl body 
15 for attaching a column pipe (not shown) for discharge of the pumped 
fluid. The bearing housing 25 is fastened by threaded fasteners 27' 
through its flange 27, to seal the bottom end of the inner wall 14, and 
extends upward through the bulbous inner cavity 13, at the top of which 
its circumferential sealing surface 26 engages a resilient sealing ring 33 
in a groove 33' in a mating surface of the inner wall 14 to prevent 
passage of pumped fluid from the inner cavity 13 into the bearing housing 
25. The bearing housing 25 is described in detail in a co-pending patent 
application filed Sep. 5, 1997 under Ser. No. 08/924,744, which is 
commonly assigned herewith; and the description of the design and function 
of that application is incorporated herein by reference. 
The plan view in FIG. 2 shows the splitter vanes 50, at the top end of the 
bowl 11. These are the top ends of vanes 20 which connect the inner wall 
14 to the outer wall 16 and which separate the hydraulic passages I and 
II. The splitter vanes 50 direct the flow of fluid into the column pipe. 
The flange 45 extends outward from the outer wall 16 to a diameter 
compatible with that of the flange (not shown) of the mating column pipe. 
Depending on the size of the pump, the open bowl 11, can reduce the weight 
and cost of a turbine pump by a significant portion, while permitting 
enhancement of the hydraulic performance. This improves efficiency and 
reliability and permits smooth operation over a wide range of pump 
capacities. In fact, each hydraulic passage I, II is first optimized for 
optimum diffusion rate and highly efficient pressure recovery in the bowl 
along with the lowest tendency to flow separation and thus vortical 
turbulent flows. Then the metal thickness of the envelopes of the 
hydraulic passages is optimized by design to meet pressure containment 
needs while minimizing weight and facilitating the manufacturing process. 
This includes improving castability by reducing problems in liquid metal 
flow, solidification, cooling, and cracking during the casting process. 
All these steps lead to the open bowl design of the invention. 
In addition to the material savings, the casting process is simplified by 
the large opening at the bottom of the inner cavity 13 which permits use 
of large sturdy cores rather than the thin fragile cores needed for 
traditional bowl designs. Further the ability to minimize thickness 
variation in the inner wall 14, the outer wall 16, and the vanes 20 
improves uniformity of metal flow during casting and reduces the 
likelihood of cracking during solidification and cooling of the bowl 
casting. The multiple cores of the open bowl design are more difficult to 
set than are those of traditional bowl designs. However, the improved 
pumping performance provided by optimization of the hydraulic channels, 
together with the reduction of scrap losses due to cracking during casting 
of the bowls, easily justifies this increased core setting difficulty.