GB2366332A

GB2366332A - Electrically driven pump

Info

Publication number: GB2366332A
Application number: GB0021135A
Authority: GB
Inventors: Rodney Bruce Gilmour
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-08-30
Filing date: 2000-08-30
Publication date: 2002-03-06
Anticipated expiration: 2020-08-30
Also published as: GB0021135D0; GB2366332B

Abstract

An electrically driven sealess pump comprises a pump casing 1, a combined impeller 2 and electric motor rotor 2,4, and an electrical stator assembly 3. The casing is machined at two regions 1.1,1.2, which cooperate with machined surfaces of the impeller to define hydrodynamic bearings. The electrical rotor 2.4 comprises an electrically conducting inner annulus, an outer annulus and connecting bars located in a coil of low remanence steel 2.5, and is protected by a corrosion / erosion resistant baffler 2.2. A hole 2.3 allows fluid to flow through the impeller to aid positioning of the impeller in the casing and to provide a cooling flow in the gap between the electric stator and rotor. The electric stator is also protected by a barrier 3.1, and comprises U shaped conductors, arranged radially in a coil of low remanence steel and connected centrally to allow a diametric current flow and peripherally by conducting rings (3.5), which are in turn connected in a termination housing 3.4 to an external power source. Various motor speeds are allowed for and a flow inducer or a flow straightener may be provided. A multi-stage pump comprising a plurality of impellers may be provided.

Description

<Desc/Clms Page number 1> Sealess Pump with Diametric Current Drive This invention relates to a pump driven by electrical energy and constructed such that the pump impellor(s) (2) and electrical rotor (2.4), of the motor drive, are integral or connected and remain in contact with the pumped fluid. The electrical stator(s) and rotor(s) are separated from the pumped fluid by a material barrier (3.1,2.2) resistant to the corrosive properties of the fluid. The pump may be used in a wide variety of configurations, of which the centrifugal type would be common, and duties, and is particularly useful when handling hazardous fluids. Sealess centrifugal pumps are well known and fall in two broad configurations: electrically driven canned pumps and magnetically driven pumps. Both types, while having the distinct advantage of requiring only static sealing do possess two disadvantages. Firstly, they have many moving and static parts most of which can wear or fail. Secondly, a small proportion of the pumped fluid is required to follow a relatively long and complex path of close clearance in order to lubricate the bearings of the rotating assembly and in the case of the electrically driven canned pump to provide cooling to the electrical motor. Consequently, these types of pump are prone to failure or damage should a full or partial blockage occur in the lubricating or cooling pathway. The objectives of this invention include: a significant reduction in the total number of components compared to other commonly available pumps; and a simplification of the cooling flow path so allowing a more robust pump better able to handle solid material in the pumped fluid and fluids close to their boiling point. in principle, these objectives are achieved by maintaining the concept of the electrically driven canned pump and transforming the electrical stator / rotor from the traditional 6squirrel - cage' induction motor cylindrical arrangement to a disc arrangement with diametric current flow. The motor works as any induction motor: alternating motor currents flowing along the diametric conductors have an associated magnetic field and induce a current in the rotor conductor; the interaction of field and current induces a force. Because the 'top half of the conductor takes the current inward and the 'bottom half outward the forces act together to produce a driving torque that rotates the impellor. The speed of rotation can be varied from pump to pump by the conducting ring configuration varying the number of poles. Further speed variation is possible by external electronic variable speed control, Accordingly, this invention provides a pump comprising: a. an outer casing, (1, Fig 1), with an inlet, an outlet, and a machined face to mate to the electrical stator housing; these three faces provide the primary sealing of the pump and may be detailed in a number of different ways including the use of gaskets, 0 rings or for the inlet and outlet welding to the pipework to which the pump is connected; as well as the sealing faces two other areas of the casing are carefully machined, firstly as the inlet nozzle opens into the front of the casing a step (1. 1) is machined on which the front of the impellor floats hydrodynamically, secondly, the circumferential surface at the back of the casing which also provides a hydraulic bearing surface for the impellor (1,2);

b. a fluid impellor (2), comprising, in the single stage centrifugal pump configuration, on one side a plurality of impellor vanes, (2. 1), shrouded or not, and on the other a corrosion resistant barrier which may have a profiled fluid side to promote radial fluid flow, (2.2); between lies an electrically insulated electrical rotor(2.4), comprising an inner and outer annulus connected by a plurality of radial conductors, in a coil of low remanence steel (2.5); a hole (2.3) or holes allow a proportion of the pumped fluid to pass from the front of the impellor to the back to provide a cooling flow between the rotor / stator motor gap and contribute to the axial positioning of the impellor within the casing when the pump is running; the profiles of the corrosion resistant barrier of both the impellor and the electrical stator are parallel, however, the profiles themselves may be flat, concave or convex; the clearances between the impellor and the casing, together with number of holes in the impellor regulates the position of the impellor within the casing; c. an electrical stator casing and electrical termination assembly, (3), comprising an outer casing, a corrosion resistant barrier on the fluid side, (3. 1), a plurality of electrical stator conductors, (3.2, Fig 1, Fig 3) arranged radially in a coil of low remanence steel, (3.3), connected centrally to allow a diametric current flow, and connected peripherally by conducting rings (3.5) to allow a multiphase, multipole motor, further connected to electrical terminals within a termination housing, (3.4).

The single stage centrifugal pump may be enhanced by the addition of a flow inducer or a flow straightener in the inlet or become a multistage pump through the addition of more impellors without the electrical rotor. Another configuration is the axial flow pump in which case an electrical rotor may be fitted to both sides of the impellor, the fluid vanes being peripheral and the electrical stator drive being fitted to both sides also. Further cooling of the electrical stator conductors may be provided externally through cooling jackets or independent heat exchanger(s).

The pump may be made of any material capable of withstanding the pressure of the pumping system and corrosive and erosive nature of the fluid pumped; it may be constructed of an inexpensive casing material lined with exotic metal or plastic material. The hydraulic bearing surfaces of the casing may be fitted with bearing material such as silicon carbide, as may the corresponding surfaces of the impellor. The pump may have mounting feet or brackets to locate or anchor the pump or may simply be fixed by its inlet and outlet connections,

Description The single stage centrifugal pump embodiment of this invention will now be described with reference to Figures 1, 2, 1 Figure I shows a cross section of the complete pump Figure 2 shows the electrical rotor Figure 3 shows the electrical stator The fluid side pump casing, (1, Figure 1), is here shown with flanged, bolted, raised face inlet and outlet connections and a shape typical of centrifugal pumps that are common. Within the casing two areas are machined, (1. 1, 1.2), so that, together with the machined surfaces of the impellor (2), two hydrodynamic bearings are created that allow the smooth running of the impellor. The rear of the casing is machined to mate and form a seal with the electrical stator casing, (3).

The impellor, (2), is shown as a closed vane impellor on the pumping side. Fitted within the body of the impellor on the motor side is a coil of low remanence steel (2.5); radial and inner and outer annular grooves in the coil accommodate the motor rotor, (2.4, Fig 1, 2). The rotor is a one piece unit, comprising an inner annulus, radial conducting spokes and an outer annulus, all made of electrically conducting material and insulated electrically from both the steel coil and the protective barrier, (2.2). The protective barrier (2.2) is welded to the main body of the impellor at the periphery and at the centre around the cooling and balance hole, (2.3). The cooling and balance hole(s) allow a proportion of the pumped fluid behind the impellor subsequently to flow radially and take away beat generated by the motor, also to govern the axial position of the impellor within the casing. The electrical stator assembly is shown in Figure I and diagrammatically in Figure 3. The outer casing (3) mates on one side to the pump casing, on the other to the termination housing (3.4). The stator windings are protected from the pumped fluid by a corrosion erosion resistant barrier (3. 1) which is welded to the outer casing (3). Within the casing lies the shaped coil of low remanence steel (3.3) to carry the stator conductors (3,2), Figure 3, The conductors are essentially U shaped, their individual profile depending on the electrical drive size, hence the motor current, for larger motors being laminated. The inner annulus of conductor ends are connected so that the current in an individual conductor flows diametrically; the connection may be made by a unit made up of a sandwich of tabbed conducting discs separated by electrically insulating material, the disc being of sufficient diameter and thickness to carry the motor current. Electrically insulated conducting rings (3.5) so connected to provide the required number of poles and phases connect the outer annulus of the conductor ends. These rings are in turn connected to the termination housing (3.4) by cables and thus to the power supply. Further connection for thermistor and other protective or diagnostic means are provided in the termination housing.

Claims

CLAIMS 1. A sealess electrically driven pump comprising: a. an outer casing with an inlet, an outlet, and a machined face to mate to the electrical stator housing; two other areas of the casing are machined, firstly as the inlet nozzle opens into the front of the casing a step is machined on which the front of the impellor floats hydrodynamically, secondly, the circumferential surface at the back of the casing which also provides a hydraulic bearing surface for the impellor; b. a fluid impellor comprising, in the single stage centrifugal pump configuration, on one side a plurality of impellor vanes, shrouded or not, and on the other a corrosion resistant barrier which may have a profiled fluid side to promote radial fluid flow-, between lies an electrically insulated electrical rotor, comprising an inner and an outer electrically conducting annulus connected by a plurality of radial conductors, in a coil of low remanence steel; a hole or holes allow a proportion of the pumped fluid to pass from the front of the impeilor to the back to provide a cooling flow between the rotor stator motor gap; the hole(s) together with the clearances between the impellor and the casing regulates the position of the impellor within the casing when it is running-, c. an electrical stator casing and electrical termination assembly comprising an outer casing, a corrosion resistant barrier on the fluid side, a plurality of electrical stator conductors arranged radially in a coil of low remanence steel, connected centrally to allow a diametric current flow, connected peripherally to allow a multiphase, multipole motor, further connected to electrical terminals within a termination housing. 2. A pump as claimed in claim I where a flow inducer is fitted to the impellor. 3. A pump as claimed in any preceding claim where a flow straightener is created in the inlet nozzle of the pump. 4. A pump as claimed in any preceding claim where the front casing is modified to allow the addition of more rings of impellor vanes so creating a multistage pump. S. A pump as claimed in any preceding claim where wear rings are fitted to the bearing surfaces of the casing. 6. A pump as claimed in any preceding claim where wear rings are fitted to the bearing surfaces of the impellor. 7. A pump as claimed in any preceding claim where the electrical stator casing is fitted with connections to permit the use of external heat exchangers, 8. A pump as claimed in any preceding claim where the electrical stator casing is fitted with a jacket to permit external cooling. 9. A pump as claimed in any preceding claim which is made from metal, plastics material, or a combination of these materials. 10. A pump substantially as herein described and illustrated in the accompanying drawings.