SINGLE-STAGE CENTRIFUGAL PUMPING UNIT

Description

TECHNICAL FIELD

[0001] The invention relates to mechanical engineering, namely to pumping installations designed for pumping water, water solutions, as well as oil, oil products and the like through the main, process and auxiliary pipelines.

BACKGROUND ART

[0002] From the catalog "Centrifugal oil pumps for main pipelines", edited by V. A. Golovin, M., CINTIhimneftemash, 1989, p. 5, have been known centrifugal horizontal single-stage HM type pumps designed for pumping oil through main pipelines comprising a housing with a volute, and a double entry impeller disposed in the housing. Using the volute therein is directed to reducing radial forces acting on a rotor, and thus reducing vibration and improving pump reliability. However, when operating such a pump at feed rates below nominal, pressure pulsations, pump vibration are increased, which leads to substantial reduction in its efficiency and reliability. These disadvantages of the known pumps are due to their design involving use of only one volute, designed only for nominal mode, which results in loss of energy when it interacts with an impeller, which is forced to work in a different mode, i.e., at feed rates above or below nominal.

[0003] There has been known using replaceable impellers designed for corresponding reduced or increased feeding in centrifugal pumps. However despite the fact that replacement of impellers causes some change in the pattern of fluid flow and insignificant increase in pump efficiency in respective non-nominal modes, and some increase in the reliability of its operation as compared to the operation of the impeller pump in nominal mode, this measure is insufficient because the design of the pump also provides for using only one volute designed only for nominal mode, which results in loss of energy when it interacts with the impeller designed for non-nominal mode. Energy loss in this case leads to additional loss of efficiency of up to 8% with respect to optimal combination of impeller and volute.

[0004] Patent RU 57393 U1 discloses a centrifugal pump with a double entry impeller comprising a volute formed by cavities in a cover and a housing, and a replaceable guide apparatus, for which four embodiments are provided. It is noted that use of the guide apparatus in a replaceable unit with the double entry impeller provides maximum efficiency within 0,3 Q_nom - 1,25 Q_nom feed range while ensuring the requisite pressure, minimum radial forces and vibrations, since the predetermined parameters calculated for this unit provide optimum flow section. However, inlet and outlet described in each embodiment are designed for maximum feed, the inflow setting of each impeller correspond to the outflow setting, and the outflow setting of each guide apparatus correspond to setting of the same volute, which is provided in the form of cavities in the cover and the housing. This results in the same disadvantages as described above due to use of the same volute, because fluid energy conversion occurs along the entire length of the volute, which in its turn is calculated for maximum flow rather than for an optimum one. Even in case of optimal interaction of the impeller and the guide apparatus in such a pump energy losses are inevitable, since after the fluid passes through the impeller and the guide apparatus, it enters the outlet, calculated for only one mode. Moreover, if replacement of already operating pump installed on the line with a pump having other design characteristics is necessary, dismantling of the pipeline will be also necessary, which is a laborious operation requiring investing additional funds to the price of a new pump, while the need to use guide apparatuses will complicate a pump design, increase cost of its manufacture, and increase adverse noise impact on the environment.

SUMMARY

[0005] The present invention has an object of providing a single-stage centrifugal pumping unit which demonstrates peak efficiency in non-nominal modes while having a simplified design and being universal in nature.

[0006] To achieve the object, a single-stage centrifugal pumping unit comprises a centrifugal single-stage double entry pump, an electric drive motor, a coupling, connecting their shafts, a support frame for mounting the pump housing and the electric motor thereon, a housing, which consists of a base and a cover, inlet and outlet manifolds, a rotor with an impeller, the rotor being installed in support bearings, and a volute. According to the invention, the volute is configured in the form of a separate, independent component, and parts of the outside surface thereof, which are intended to be accommodated in cradles provided for this purpose in the cover and the housing, correspond to the shape of the surfaces of said cradles, the impeller and the volute are replaceable as a pair, the parameters of the impeller and the volute in each pair are calculated to provide maximum efficiency (peak efficiency) while ensuring the requisite feed and pressure. Preferably, the replaceable volutes are made as an integrated cast component and comprise a baffle separating the fluid flow during the movement.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The invention is illustrated by the following drawings.

[0008] Fig. 1 is a general view illustrating a single-stage centrifugal pumping unit; Fig. 2 is a vertical plane cross-sectional view of the pump along the pipeline axis; Fig. 3 is a vertical plane cross-sectional view illustrating schematic arrangement of a cover, a replaceable flow part and a pump housing along the pipeline axis; Fig. 4 illustrates embodiments of replaceable volutes with constant outer connecting profile and various internal hydrodynamic profile designed for optimal operation and maximum efficiency.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0009] To ensure comprehensive understanding of the essence of the present invention, its numerous specific characteristics will be described hereinafter.

[0010] According to the present invention, a single-stage centrifugal pumping unit comprises an electric drive motor 2, a centrifugal single-stage double entry pump 1 (hereinafter, the pump), a coupling 3, connecting their shafts, a pump housing 17, which consists of a base 6 and a cover 7, an inlet manifold 8 and an outlet manifold 9, a rotor 10 with an impeller 11, the rotor being installed in support bearings 12, a volute 13, and a support frame 5 for mounting the pump housing 17 and the electric motor 2 thereon. As shown in Fig. 3, the volute 13 is configured in the form of a separate, independent component, and parts of the outside surface thereof, which are intended to be accommodated in cradles 14 and 15 provided for this purpose in the housing 6 and the cover 7, correspond to the shape of the surfaces of said cradles 14 and 15. The impeller 11 and the volute 13 are replaceable as a pair, the parameters of the impeller 11 and the volute 13 in each pair are calculated to provide maximum efficiency while ensuring the requisite feed and pressure. Preferably, the replaceable volutes 13 are made casted, and they may comprise a baffle 15 for separation of the fluid flow during the movement.

[0011] The pump works in the same way as other known centrifugal single-stage double entry pumps. Upon rotation of the shaft 4 of the pump, pump medium through the inlet manifold 8 is supplied to the impeller 11, interaction of blades of which with the flow of the pumped medium causes conversion of the drive energy to the energy of flow. From the impeller 11, the pumped medium enters the volute, where the flow is smoothed out, and further through the outlet manifold it passes to the pipeline.

[0012] Possibility of using a pair of impeller and volute implemented in the pump design, which is designed and manufactured to be operated in optimal mode, minimizes the radial forces acting on the rotor, which accordingly contributes to operation of the pump with low vibrations and increases its reliability.

[0013] The advantage of the filed invention relating to the possibility of using the same housing for pumps with different characteristics is achieved by that a pump being a base member is a complicated casting of carbon steel, or stainless steel, actually consisting of a housing and a cover. Therefore, in the event of change of the pump operating conditions (reducing pressure on already existing line, or changing the flow through the already existing line) it is not necessary to use the already operating pump in ineffective way, or dismantle it and install a new one designed for new conditions. Just install a new pair of impeller and volute designed for new operating environment in already existing housing, and you will get a pump with new relative calculated characteristics. Thus, there is a significant saving of money due to no need to dismantle the old pump and manufacture a new pump in a new housing. Of particular importance is solution of providing a pump with new characteristics on the basis of the old one, as there is no need to dismantle the pipeline, on which the old pump has been installed and operated.

[0014] In addition, possibility of replacing impellers in a pump to use them in optimal mode will extend the service life of the pump itself, as impellers are rapidly wearing parts and can be manufactured from costly high wear resistant materials, such as steel 20X13, 12X18H12MZTL or similar steel and materials.

[0015] The pump housing is horizontally split, which provides for possibility to dissect, inspect, repair, and replace the parts of the pump and the entire rotor without dismantling the pipes, since the pump inlet and suction manifolds are connected to the bottom of the pump housing.

INDUSTRIAL APPLICABILITY

[0016] The present invention in proposed combination of features can be used to provide a single-stage centrifugal pumping unit which demonstrates peak efficiency in non-nominal modes while having a simplified design, and being universal in nature, durable and easy to operate.

Claims

1. A single-stage centrifugal pumping unit comprising a centrifugal single-stage double entry pump, an electric drive motor, a coupling, connecting their shafts, the said pump comprising a housing, which consists of a base and a cover, manifolds, a rotor with an impeller mounted thereon, the rotor being installed in support bearings, a volute, a support frame for mounting the pump housing and the electric motor thereon, wherein the volute is configured in the form of a separate, independent component, and parts of the outside surface thereof, which are intended to be accommodated in cradles provided for this purpose in the cover and the housing of the pump, correspond to the shape of the surfaces of said cradles, the impeller and the volute are replaceable as a pair, the parameters of the impeller and the volute in each pair are calculated to provide maximum efficiency while ensuring the requisite feed and pressure.

2. A single-stage centrifugal pumping unit according to claim 1, wherein the replaceable volutes are made as an integrated cast component and comprise a baffle separating the fluid flow during the movement.