ZA200506645B - Submersible pump - Google Patents

Description

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FIELD OF THE INVENTION bos 70g 64g

This invention lies in the field of submersible pumps, pumps that are useful in ® many applications in the fields, for example, of waste water, sewerage treatment, mining activities and there are others.

BACKGROUND

Pumps of this kind have been used for a long time and in the nature of their applications are subjected to arduous conditions. South African conditions have their own particular characteristics, which require special adaptation to provide durable pumps and trouble free operation.

A particular feature distinguishing South African conditions is the vast amount of rags and textiles materials that are present in the sewage systems. To worsen this, large amounts of sand are washed in via storm water systems flushing into the sewage system. Particularly abrasive minerals are also commonly encountered.

Whereas a trend has developed from some quarters of supplying inexpensive disposable pumps, which experience has shown may have a life span of less than a year in South African conditions, the building of sturdy long lasting pumps for these conditions requires attention to special design solutions for various aspects of the pump. For example, light built pumps have exhibited “flex” under heavy pumping conditions, this is a condition in which the pump casing moves under reaction forces generated when pumping conditions are severe. Service and maintenance are an important component of the total cost of a pump over its life span. Arrangements of the components of the casing that allow easy stripping and servicing have favorable economic benefits. Design features that improve the manner in which one deals with wear of the pump casing, as occurs with abrasive substances, for example, have further economic advantages.

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THE INVENTION

_ A pump in accordance with this invention, which has a motor in a motor housing, an impeller driven from the motor shaft, a pump casing forming a pumping chamber housing the impeller, a mechanical seal providing a seal between the pump casing and the motor, comprises a back cover attached inside the pump casing and presenting a surface in proximity with the impeller, secured to the impeller casing from outside the impeller casing.

With this arrangement there is no attachment means (e.g. like bolts) in the surface of the back cover that is in proximity with the impeller, nor any hollows or cavities, which it is found would be subject to accelerated wear. Thus a preferred attachment of the back cover is bolts or screws passing through the impeller casing from outside into but not through the back cover. This provides an inexpensive and easy to reach part to replace, should replacement be required. Replacement can become necessary in order to deal with particular abrasiveness of certain materials to be pumped, e.g. sludge or sandy mediums, or when it is necessary to restore the original manufacture clearances.

In accordance with a preferred embodiment of the invention, a lower part of the mechanical seal bears and seals against a surface of the back cover, on the side of the back cover opposed to the pumping chamber.

The back cover provides the stationary seat which forms the sealing face between the rotating face and the stationary face. By removing the back cover, easy access to the mechanical seal arrangement is obtained without disturbing bearing assembly, rotary assembly or the motor casing.

Furthermore the mechanical seal is preferably housed in a cavity which is filled with oil, for lubrication and protection of the mechanical seal. A back to back type of mechanical seal is fitted in the oil filled cavity and this allows for dry running of the pump as the seal faces of the mechanical seal are oil lubricated and do not depend on water for lubrication and cooling. The back to back arrangement in the oil bath is not subject to particles clogging the spring and reducing its effectiveness, as occurs when the seal in the impeller ® housing. Abrasive wear of the sealing surface is also avoided.

A further preferred features are : - a) that the drive end bearing, located between the motor and the impeller, which carries the rotor shaft, is mounted in a housing that has a cover located on the motor side, securing the rotary assembly and bearing in place; b) the short distance overhang from the drive end bearing to the impeller.

This design allows for a sturdy, non-flexing mechanical seal alignment, which prolongs the life span of the pump.

A further preferred feature of the invention is that the motor housing is attached to the impeller housing by a substantial spigot and flange connection, which has tight tolerances. This design prevents flex during heavy pumping duty and allows for Ex-Certification. Sound in line alignment between the motor housing and the impeller housing is facilitated. Preferably this spigot incorporates the socket for the bearing and has a heavy construction. This heavy construction also contributes to a heat sink for peak temperatures of the bearing.

The preferred design of the pump also generally allows for the interchangeability of the hydraulic end to enable to use the most efficient impeller for the particular application.

The preferred design of the pump allows for ‘primary sealing” due to the double mechanical seal arrangement. The two oil seals situated in the back cover in the pumping chamber behind the impeller seals the cavity by means of sealing off the impeller neck, therefore not damaging the rotor shaft by grooving.

The preferred design of impellers is equipped with a back vane. These vanes are situated on the back of the impeller, opposite the pumping vanes of the impeller. The function of these back vanes in conjunction with the tight clearance between the impeller back vanes and the back cover forms a pumping action creating a low pressure area in front of the primary seals, ® which are situated in the back cover, sealing around the impeller neck. This at the same time removes all fines sand and sludge towards the outside away from the primary seals.

As the pump is used under water it is necessary to provide a means of lowering and connecting the pump, a method has been used in the past, which has disadvantages, in particular “blow off’. This has in the past occurred when pumping large volumes or when pumping high heads, in either case a high backpressure is generated and the pump connection to the delivery pipe tends to “blow off’.

In accordance with this invention there is provided a pedestal, which is secured down on the sump floor with guide bars to the top and a slide guide fixed to the discharge flange of the pump. Tapers are present on the pedestal and slide bracket which all face downward, assuring a definite lock when lowered onto the pedestal. Disconnecting and removal of the pump are easily done by hosting the pump upwards allowing the tapers to disengage.

When the pump is hoisted upwards the guide bars guide the pump upwards and they guide the pump downwards when it is lowered.

Preferably a seal ring is provided, which is adapted to both provide a gasket between the pump discharge flange and the slide guide and between the pump discharge flange and the outlet pipe. The seal is clamped between the pump discharge flange and the slide guide, which secures it against being accidentally dislodged when the pump is lowered into connection with the pedestal.

Once the pump is “locked on” to the pedestal the seal forms a perfect sealing face between the sliding guide and the pedestal. The advantage is that no metal faces meet, preventing wear to the pedestal, which is under water and can not be inspected and easily repaired.

THE DRAWINGS

The invention is more fully described by way of example, with reference to the drawings, in which : -

Figure 1 is a half-cross sectional elevation of a pump according to the invention,

Figure 2 is a partial front view and side view, split on line X — X, of the slide guide,

Figure 3 is a side elevation of the pedestal outlet flange,

Figure 4 is a front view onto the seal ring,

Figure 5 is a front view of the discharge flange of the pedestal,

Figure 6 is side elevation in section of the slide guide, and

Figure 7 is an elevation in section of the seal ring.

THE PREFERRED EMBODIMENTS

As shown in figure 1, the pump 1 has a motor 2 in a motor housing 3, an impeller 4 driven from the motor shaft 5, a pump casing 6 forming a pumping chamber 7 housing the impeller. Primary seals 14A located behind the impeller 4 and sealing on the impeller 4 neck, provides primary sealing and screening of particles prior to the back to back mechanical seal 8/8A — 9/9A, providing a seal between the pump casing and the motor and a back cover 10 attached inside the pump casing and presenting a surface 11 in proximity with the impeller, secured to the impeller casing from outside the impeller casing by bolts 12. There are no hollows or cavities in the surface 11 as the bolt does ® not go through the back cover. The clearance 13 between the back cover and impeller can be preserved by replacement of the back cover.

Back vane 4A on the back of the impeller 4 performs a pumping action which in its turn removes fines and slurries away from primary seals 14A, thus creating a low pressure area in front of primary seals 14A.

The part 9 of the mechanical seal seals against the surface 9A, a lower stationary seat face located on the back cover, on the side of the back cover opposed to the pumping chamber. A spring 16 keeps the parts 8 and 9 of the mechanical seal tensioned and the part 8 seals against the surface 8A of the upper mechanical seal stationary face which is located in the mechanical seal housing 15 of the pump. The mechanical seal is housed in a cavity 18 which is filled with oil, for lubrication and protection of the mechanical seal, which is a back to back type of mechanical seal.

A bearing 19 carries the motor shaft 5 and is located between the motor and the impeller, mounted in a socket 20 that has a cover 21 located on the motor side of the bearing.

The motor housing 3 is attached to the mechanical seal housing flange 22 and located by spigot 17 which has tight tolerances. The spigot 17 is unusually thick and serves as a heat sink.

As shown in figures 2 to 7 there is provided a pedestal 23, which is secured down on the sump floor (not shown) with guide bars (not shown) leading to the top, above the water surface. The pedestal carries the outlet pipe bend 24.

A slide guide 25 is fixed to the discharge flange 26 (see fig. 1) of the submersible pump.

Tapers 27, 28 and 29 on the pedestal provide a definite lock for the slide guide 25, as the tapers all face downwards, to also allow that the pump is

PY easily removed by just hoisting it upwards.

A seal ring 30 is provided, which is adapted to both provide a gasket between the pump discharge flange 26 and the slide guide 25 (see figure 6) and provides a seal between the pump discharge flange and the outlet pipe 24.

The seal is clamped between the pump discharge flange and the slide guide, which secures it against being accidentally dislodged when the pump is lowered into connection with the pedestal.

REFERENCE NUMERALS

1 submersible pump 2 motor 3 motor housing 4 impeller 4A back vane motor shaft 6 pump casing 7 pumping chamber 8 mechanical seal, upper part 8A upper stationary seal face 9 mechanical seal, lower part 9A lower stationary seat face back cover 11 back cover surface 12 bolt 13 clearance between back cover and impeller — back vane 14 low pressure area 14A primary oil seals mechanical seal housing 16 mechanical seal spring

17 locating spigot of mechanical seal/ bearing housing of motor housing 18 cavity for oil lubrication of mechanical seal 19 double angular contact ball bearing ® 20 socket for bearing 21 cover on bearing 22 flange of mechanical seal housing 23 pedestal 24 pedestal outlet slide guide 26 discharge flange of pump 27 taper 28 taper 29 taper seal ring ---mmmee=e==-000----=momeme

Claims (14)

1. CLAIMS 1 A pump, which has a motor in a motor housing, an impeller driven ® from the motor shaft, a pump casing forming a pumping chamber housing the impeller, a mechanical seal providing a seal between the pump casing and the motor, comprises a back cover attached inside the pump casing and presenting a surface in proximity with the impeller, secured to the impeller casing from outside the impeller casing.
2. 2 A pump as claimed in claim 1, in which the attachment of the back cover is bolts or screws passing through the impeller casing from outside into but not through the back cover.
3. 3 A pump as claimed in either one of claims 1 or 2, in which a lower part of the mechanical seal bears and seals against a surface of the back cover, on the side of the back cover opposed to the pumping chamber.
4. 4 A pump as claimed in any one of claims 1 to 3, in which the mechanical seal is housed in a cavity which is filled with oil, for lubrication and protection of the mechanical seal.
5. A pump as claimed in claim 4, in which a back to back type of mechanical seal is fitted in the oil filled cavity.
6. 6 A pump as claimed in any one of claims 1 to 5, in which a drive end bearing, located between the motor and the impeller, carries the rotor shaft and is mounted in a housing that has a cover located on the motor side, securing the rotary assembly and bearing in place.
7. 7 A pump as claimed in any one of claims 1 to 6, in which the motor housing is attached to the impeller housing by a substantial spigot and flange connection, which has tight tolerances.
8. 8 A pump as claimed in any one of claims 1 to 7, in which there is provided a primary seal, situated in the back cover in the pumping J chamber behind the impeller, which seals onto the impeller neck.
9. 9 A pump as claimed in any one of claims 1 to 8, in which the impeller is equipped with a back vane situated on the back of the impeller, opposite the pumping vanes of the impeller, with a tight clearance between the impeller back vane and the back cover.
10. A pump as claimed in any one of claims 1 to 9, in which there is provided a pedestal, which is secured down on the sump floor with guide bars to the top and a slide guide fixed to the discharge flange of the pump, with tapers present on the pedestal and slide bracket which all face downward, assuring a definite lock when lowered onto the pedestal.
11. 11 A pump as claimed in claim 10, in which a seal ring is provided, which is adapted to both provide a gasket between the pump discharge flange and the slide guide and between the pump discharge flange and an outlet pipe, the seal being clamped between the pump discharge flange and the slide guide.
12. 12 A pump as herein described and as illustrated in figure 1 of the drawings.
13. 13 A pedestal for a submersible pump, the pedestal as herein described and illustrated in figures 2 to 7 of the drawings.
14. 14 A pump and pedestal combination as herein described and as illustrated in figures 1 to 7 of the drawings.

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    DATED THIS 19th DAY OF AUGUST 2005 fil 3 HANN 8 Wan AFPLIGANTS AGLI