GB2059505A

GB2059505A - Centrifugal Pumps

Info

Publication number: GB2059505A
Application number: GB8028720A
Authority: GB
Original assignee: Foster Miller Inc; Foster Miller Associates Inc
Current assignee: Vencore Services and Solutions Inc
Priority date: 1979-09-24
Filing date: 1980-09-05
Publication date: 1981-04-23
Also published as: ZA805373B; DE3035257A1; GB2059505B; AU536349B2; CA1153622A; AU6207480A

Abstract

A system for transporting a slurry (41) comprises a centrifugal pump connected in a conduit (18). The pump has a helical bladed rotor (30) mounted within a housing (20) provided with a vent (38). The bladed rotor creates a fluid vortex (40) with a central air core (42), the diameter of which varies to equalize the pressure in the housing with the back pressure in the conduit. The slurry is fed into an inlet port (26) of the pump and is carried by the fluid vortex to a pump outlet port (28). <IMAGE>

Description

SPECIFICATION A Pumping Device and a Material Transport System The present invention relates to a pumping device and a material transport system.

Delivery of solids to a haulage system often has many variables such as flow rate, density and product size. Ideally, bulk solids transport systems would be continuous, never changing in flow rate or consistency. For most situations this is not the case. Accordingly, conventional haulage systems must be capable of handling randon flows and variable flow rates.

Hydraulic transport of solids has succeeded primarily where relatively steady-state flow conditions can be maintained, for example, overland transport of coal and other fine slurries.

For hydraulic haulage to be competitive with other means of transport, such as conveyor belts, rail cars, or trucks, it must be capable of handling random flows and variable flow rates. Hydraulic transport of solids under continually varying rates, concentration and density presents a monumental control problem for a system using conventional state-of-the-art pumps. Hydraulic transport lines several thousand meters long with centrifugal pumps appropriately located along the line are subject to severe water hammer and pump cavitation if the input conditions (solids concentration, solids density and solids or fluid flow rate) change. Cavitation and water hammer can occur when the system contains some sections with high concentrations of solids and others with little or no solids.These sections of fluid tend to move at different velocities due to inertia effects causing separation of the column and potential pump failure. In addition, transient effects can be particularly disastrous if the pump at the input point ventilates or cavitates due to inadequate control of sump conditions. There are many control schemes which can or have been devised to reduce these problems. Variable speed drives on the pumps and/or intermediate sumps at each pump location have been used. Both, however, require elaborate control systems to insure that the line dynamics remain within the system's capability.

According to the present invention from one aspect there is provided a pumping device comprising: (a) a housing with an internal chamber, said housing including inlet means, outlet means and vent means that communicate with said chamber, said inlet means being configured to direct a material carried in a fluid external of said housing into said chamber; and (b) rotor means mounted in said housing for rotation in said chamber, said rotor means including blade means configured to create a fluid vortex having a central ventilated core from said fluid directed into said chamber through said inlet means; and (said vortex transporting said material at said inlet means to said outlet means, said fluid constituting a carrier for said material being transported.

According to the present invention from another aspect there is provded a material transport system comprising: (a) a transport line means; (b) input station means connected to said transport line means and configured to feed a fluid mixture into said transport line means; (c) receiving station means connected to said transport line means and configured to receive said fluid mixture; and (d) at least one pump means operatively connected to said transport line means intermediate said input station means and said receiving station means, said pump means including a housing with an internal chamber, said housing including inlet means, outlet means and vent means that communicate with said chamber, said inlet means being configured to direct a material carried in a fluid external of said housing into said chamber, rotor means mounted in said housing and constrained for rotation within said chamber, said rotor means including blade means configured to create a fluid vortex having a ventilated core from said fluid directed into said chamber through said inlet means when said rotor is rotated, a mouth of said vortex being adjacent said inlet means, and drive means operatively connected to said rotor means for rotating said rotor at a sufficiently high rate to create said vortex, said inlet means and said outlet means being connected to said transport line, and said material being carried by said ventilated vortex from said inlet means to said outlet means.

The present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a pumping device; Fig. 2 is a sectional view of the pumping device of Fig.1; and Fig. 3 is a schematic diagram of a material transport system embodying the pumping device.

In the following, by way of example, a pumping device 10 is utilized as a boost pump in a material transport system 12 in which particulate solids are carried from an input station 14 to a receiving station 1 6 via a transport line 1 8.

Pump 10 includes a housing 20 having a frusto-conical nose 22 and an internal chamber 24. Nose 22 terminates in an inlet port 26 which communicates with transport line 1 8. Housing 20 is also provided with an outlet port 28 which communicates with transport line 18. A rotor 30 with one or more helical blades 32 is mounted in housing and constrained for rotation within chamber 24 at nose 22. Rotor 30 has a generally conical shape that tapers inwardly towards inlet port 26. Rotor 30 is mounted on a shaft 34 that is journaled in bearings 36, for example tapered roller bearings, which provide maximum stiffness.

Helical blade 32 has a gradually expanding diameter from inlet port 26 towards outlet port 28. A vent 38, for example a conduit which is open to the atmosphere, leads to the center of rotor 30. In an alternative embodiment, housing 20 is vented through rotor 30.

Blade 32 is configured to create a fluid vortex 40 having a ventilated core 42. In the illustrated embodiment, by way of example, a slurry 41 entering inlet port 26 flows towards chamber 24 at the leading edge of blade 32. When rotor 30 is rotated by a driver 44, blade 32 maintains fluid vortex 40 and pressurizes housing 20 at outlet port 28. Particulate solids 41 that are fed into inlet port 30 are picked up by blades 32, flung outwardly and submerged in vortex 40. The fluid level in pump 10 adjusts automatically in response to applied down-stream pressure in line 18. The inner radius of vortex 40 contracts when line pressure increases. The maximum pressure occurs when core 42 of vortex 40 has contracted to the size of atmospheric vent 38.In response to an increase in back pressure, ventilated core 42 contracts or decreases until the pressure in housing 20 is equalized to the back pressure without any decrease in flow. That is, as the back pressure increases, core 42 contracts and fluid vortex 40 expands. Blade 32 engages a greater portion of slurry 41, whereby the pressure within housing 20 increases until it balances the back pressure. Similarly, in response to a decrease in back pressure, core 42 expands and the pressure in housing 20 decreases until the pressures are equalized. The centrifugal action of slurry 41 prevents introduction of air into transport line 1 8 as long as vortex 40 is maintained within housing 20.

Rotor 30 is driven by driver 44 through a gear assembly 46 which includes a gear train 48 having three helical gears 50 mounted in a gear box 52. A shaft 54 of driver 44 is connected to gears 50 through a flexible coupling 56 and shaft 34 is connected directly to gears 50. In the illustrated embodiment, by way of example, driver 44 is an 1800 rpm, 400 horsepower motor and rotor 30 has a diameter of 31.5 inches and rotates at 1000 rpm. Solids enter rotor inlet 26 at a very low axial velocity and swirl compared to the peripheral velocity of the rotor inlet at its maximum diameter. The blade tip speed is approximately 1.8 m/sec. The blade 32 leading edge is sickle-shaped, with the tip at the forward outermost inlet diameter and the shank of the sickle attached to the rearward inner most hub of rotor 30. Blade 32 is helical and pitched at a shallow angle from a radial plane of shaft 34.The helical pitch gives a small ratio or axial flow velocity to rotor speed, so that over the entire range of flow rates, the solids have initial trajectories that hit the blade pressure surface at a shallow glancing angle. Axial impact velocity is consequently small and thus wear of the blade surface is minimized. The sickle-shaped blade 32 reduces the effect of the high relative velocity of solids to the blade leading edge. Impact near the tip is with an edge angled approximately 60 degrees from the relative velocity and thus impact velocity is half of that for the normal impact in a typical pump. Bounce energy is approximately 25 percent of that for normal impact.

Referring now to Fig. 3, there is shown material transport system 12 in which particulate solids are carried from input station 14 to receiving station 1 6. Particulate solids enter input station 14, for example a helical inducer or a slurry pump, through a line 62 and valve 64. A fluid, for example water, is fed into helical inducer 14 via a line 66 and a valve 68. The slurry discharged from helical inducer 14 is fed through a pair of ventilated boost pumps 10 to receiving station 1 6. Pumps 10 operate at a constant speed with a constant water flow rate and with variable solid flow rate. Ventilation of pumps 10 isolates each line section from the next. Also, it has been found that transport system 10 handles flows of at least thirty-five percent change in rate.

Claims

1. A pumping device comprising: (a) a housing with an internal chamber, said housing including inlet means, outlet means and vent means that communicate with said chamber, said inlet means being configured to direct a material carried in a fluid external of said housing into said chamber; and (b) rotor means mounted in said housing for rotation in said chamber, said rotor means including blade means configured to create a fluid vortex having a central ventilated core from said fluid directed into said chamber through said inlet means; and (c) said vortex transporting said material at said inlet means to said outlet means, said fluid constituting a carrier for said material being transported.

2. A pumping device as claimed in claim 1 wherein said blade means includes at least one helical blade.

3. A pumping device as claimed in claim 2 wherein said helical blade has a gradually expanding diameter from said inlet means to said outlet means.

4. A pumping device as claimed in claim 3 wherein said blade had a sickle-shaped leading edge.

5. A pumping device as claimed in any preceding claim wherein said vent means is a conduit which leads from the center of said rotor to the atmosphere about said pumping device.

6. A material transport system comprising: (a) transport line means; (b) input station means connect said transport line means and configured to feed a fluid mixture into said transport line means; (c) receiving station means connected to said transport line means and configured to receive said fluid mixture; and (d) at least one pump means operatively connected to said transport line means intermediate said input station means and said receiving station means, said pump means including a housing with an internal chamber, said housing including inlet means, outlet means and vent means that communicate with said chamber, said inlet means being configured to direct a material carried in a fluid external of said housing into said chamber, rotor means mounted in said housing and constrained for rotation within said chamber, said rotor means including blade means configured to create a fluid vortex having a ventilated core from said fluid directed into said chamber through said inlet means when said rotor is rotated, a mouth of said vortex being adjacent said inlet means, and drive means operatively connected to said rotor means for rotating said rotor at a sufficiently high rate to create said vortex, said inlet means and said outlet means being connected to said transport line, and said material being carried by said ventilated vortex from said inlet means to said outlet means.

7. A material transport system as claimed in claim 6 wherein said vent means is a conduit exending from the center of said rotor to the atmosphere about said pump means.

8. A material transport system as claimed in claim 7 wherein said blade means includes at least one helical blade.

9. A material transport system as claimed in claim 8 wherein said helical blade has a gradually expanding diameter from said inlet means to said outlet means.

10. A material transport system as claimed in claim 6 wherein said blade means is a helical blade wrapped about a cone shaped base that tapers inwardly toward said inlet means, said helical blade having a gradually expanding diameter that increases from said inlet means towards said outlet means and said vent means extending from the center of said rotor to the atmosphere about said pump means.

11. A pumping device, substantially as herein described with reference to the accompanying drawings.

12. A material transport system, substantially as herein described with reference to the accompanying drawings.