RU212223U1 - Hydraulic unloader of a centrifugal sectional pump with a continuously renewable lubricant layer - Google Patents

Abstract

The utility model relates to the field of pump engineering, namely to devices for unloading the rotors of centrifugal sectional pumps from the axial force of the rotor. This utility model solves the problem of ensuring the temperature regime of the pump in accordance with regulatory requirements by preventing the contact interaction of a pair of relief rings during wear in the setting mode. The hydraulic unloading device of a centrifugal sectional pump with a continuously renewable lubricating wedge includes a housing 1, a shaft 2 with an unloading disk 3 fixed on it, a movable unloading ring 4 with a flat working surface and a fixed response ring 5, the working surface of which is divided by blind bevels at an angle to the flat working surfaces. The setting of the wedge gap between the fixed and movable parts of the device determines the creation of a lubricating layer 10 between the relief rings in the end gap 9. The lubricating layer is continuously renewed by the pump when the pumped liquid enters from the radial slot 8 between the distance sleeve 7 and the discharge sleeve 6 into the discharge chamber 11 and prevents contact the interaction of the relief rings in the mode of wear by seizure during the start of the pump by providing a hydrodynamic mode of operation of the friction pairs.

Description

The utility model relates to pump engineering, in particular to unloading devices for balancing the axial forces of the rotors of centrifugal sectional pumps for pumping oil, oil emulsion and formation water.

During the operation of a centrifugal sectional pump, an axial force acts on the rotor of the unit, which displaces the shaft with the pump impellers towards the suction pipe. To balance the axial force acting on the rotor in centrifugal sectional pumps, a hydraulic unloading device is used, which ensures the balance of the rotor. With wear of the unloading rings, the pump rotor gradually shifts towards the suction pipeline. Exceeding the maximum permissible value of the axial displacement of the rotor during operation of a centrifugal sectional pump due to high wear of the unloading rings can lead to rubbing of the impellers on the guide vanes, followed by the formation of through holes in the front disks of the impellers and a decrease in the efficiency of the pumping unit. Also, the process of starting a centrifugal sectional pump is often accompanied by overheating of the unloader assembly due to dry friction of the flat working surfaces of the unloading rings, which leads to recrystallization and embrittlement of the metal with an increase in the wear rate of the unloading rings.

To increase the wear resistance of the rings of the unloader assembly, it was proposed to manufacture unloading rings from alloyed steels, carry out heat treatment, apply wear-resistant coatings to the working surface, but these measures did not bring a significant effect and turned out to be expensive.

Known hydraulic unloading device [AS. No. 1492092 of the USSR, IPC F04D 29/04, publ., 07/07/1989], containing a pump housing with a cover, a shaft placed in the housing, a support foot fixed with radial and axial clearances relative to the housing on an elastic base made in the form of a ring. An annular protrusion is made in the cover opposite the peripheral section of the heel. An unloading disk is installed on the shaft, which forms an end slot with the fifth during pump operation. Installing the heel on an elastic base ensures the uniformity of the end gap in the circumferential direction.

The disadvantages of the known device include the impossibility of ensuring stable properties of the material of the elastic base during operation of the device at elevated temperatures, which occurs when the pump is started with an insufficient amount of pumped liquid inside the pump.

Known hydraulic unloading device with a pliable thrust ring containing a slotted gap formed by the protrusions of the discharge disk and the pump housing [A.S. No. 1569435 USSR, IPC F04D 29/04, publ. 06/07/1990]. The protrusion is formed by pairing the elastic ring with a rigid safety ring. Due to the deformation of the elastic ring, the end gap takes the form of a confuser, increasing the bearing capacity of the hydraulic unloading unit. It is assumed that the protrusion of the unloading disk can contact with a rigid safety ring in off-design modes of operation of the pump, which excludes the operation of the elastic ring in the dry friction mode.

The disadvantages of the known device include the instability of this system for balancing the axial forces of the rotor due to the presence of an elastic element in the unloading chamber, which causes the end gap to fluctuate during operation of the device.

To perceive the axial force of the rotor of a centrifugal multistage sectional pump, an unloading device of a centrifugal pump can be used to balance the axial force [US Pat. No. 2165038 RF, IPC F04D 29/04, publ. 04/10/2001]. The device comprises a thrust bearing fixed on the pump housing and a hydraulic bearing fastened to the shaft. Additional bearing surfaces in the unloading chamber and sealing surfaces of the mechanical slotted seal are placed on the hydraulic foot and on the thrust bearing. The sealing surfaces of the gap seal are separated by an annular channel from additional supporting surfaces. The ring channel is connected with the open area, as well as with open and closed channels.

At the nominal operating mode of the pump, a self-adjusting gap is formed between the hydraulic bearing and the thrust bearing. From the central part, the liquid flows through the annular channel, mainly through open and closed channels, and exits through the gap between the sealing surfaces.

During transient operating modes, the device operates as a journal bearing partially unloaded by hydrostatic force. The axial load is distributed to the sealing surfaces and to additional surfaces in the unloading chamber. The presence of open channels provides wetting of additional surfaces with the pumped liquid, which ensures their lubrication and cooling.

The disadvantage of this device is its low durability and reliability due to the absence of inclined sections on the working surface of the heel, which will not allow creating a wedge grip during transient operation of the pump and significantly reduce the friction force between the contact surfaces, minimizing the power loss due to friction, thereby ensuring , complete cooling of contact surfaces.

To balance the axial force of the rotor can be used hydraulic unloader centrifugal sectional multistage pump with inclined bearing surfaces, used as a prototype in the description of the invention [Useful model No. 204236 RF, IPC F04D 29/04, publ. May 17, 2021].

The efficiency of using this model is to reduce friction losses and to ensure the hydrodynamic mode of operation of the contact surfaces of the friction pairs of the relief rings, which makes it possible to prevent the contact interaction of the relief rings in the mode of wear by seizure during pump start-up.

The unloading device of a centrifugal multistage pump includes a housing, a rotating unloading disk fixed on the rotor with a movable unloading ring of a flat shape of the working surface, and a reciprocal unloading ring rigidly fixed to the discharge cover. The working surface of the reciprocal unloading ring is divided into segmented flat sections necessary for the perception of the axial force of the rotor, through radial grooves and through bevels at an angle to the flat surface, which create a continuously renewed lubricating layer in the support.

A lubricating wedge from a pumped oil emulsion is formed by dividing the working surface of the fixed ring with through radial grooves and bevels of its individual parts along the entire width of the ring. The formation of hydrodynamic pressure in the wedge gap occurs due to the entrainment of the oil emulsion into this gap from the radial grooves during the rotational movement of the movable relief ring relative to the stationary one, due to which the working surfaces of the relief rings will operate in the liquid friction mode, which will ensure their full lubrication and cooling.

The disadvantages of this device include the complexity of manufacturing the fixed ring, as well as increased hydraulic losses in the unloading chamber due to the presence of through radial grooves on the fixed unloading ring and separate inclined surfaces beveled across the entire width of the fixed unloading ring.

The objective of the utility model is to increase the durability and reliability of the unloading unit of a centrifugal sectional pump in the hydrodynamic mode of operation of friction pairs due to the formation of a lubricating wedge between the working surfaces of the unloading rings operating in one friction pair.

The technical result obtained by using the proposed utility model is to ensure the optimal temperature mode of operation of the unloading device and reduce friction losses of the contacting working surfaces of the unloading rings by preventing the interaction of the unloading rings in the mode of wear by setting and ensuring the hydrodynamic mode of their operation during pump start.

The task is achieved due to the fact that the hydraulic unloading device of a centrifugal sectional pump with a continuously renewable lubricating layer, including a housing installed in it, a unloading disk fixed on the rotor with a movable unloading ring of a flat shape of the working surface, and a mating unloading ring rigidly fixed on the discharge cover, according to the proposed technical solution, the end surface of the reciprocal unloading ring is made in the form of flat sections, which are supporting surfaces, and are divided by blind bevels located at an angle to the flat surface and providing a continuously renewed lubricating layer in the support with the formation of a wedge gap between the movable and fixed parts of the device.

According to the proposed utility model, the hydraulic unloading device of a centrifugal sectional pump includes a housing, a unloading disk fixed on the pump rotor with a movable unloading ring of a flat shape of the working surface, and a mating unloading ring rigidly fixed to the discharge cover. The cavity between the movable and reciprocal unloading rings forms an unloading chamber.

What is new is that the working end surface of the reciprocal unloading ring is divided by separate blind bevels at an angle to the flat surface, designed to form a continuously renewable lubricating wedge gap between the movable and reciprocal unloading ring.

The formation of a continuously renewable lubricating layer in the support is achieved by installing a wedge gap between the movable and fixed parts of the device, which makes it possible to provide full cooling and the required bearing capacity of the unloading unit.

The lubricating wedge of the pumped liquid is formed by dividing the working surface of the mating ring with blind bevels at an angle to the flat surface. The formation of hydrodynamic pressure in the wedge gap occurs due to the entrainment of the pumped liquid into this gap from the cavities formed by the space between the inclined bevels of the counter ring and the flat surface of the movable discharge ring, thereby increasing the reliability and durability of the device.

In FIG. 1 shows the unloader, Fig. 2 shows the reciprocal unloading ring.

The unloading device consists of a pump housing 1 with a shaft 2 placed in it. An unloading disk 3 is fixed on the shaft. An unloading ring 4 with a flat working surface is fixed on the unloading disk 3. On the discharge cover of the hydraulic machine, a reciprocal unloading ring 5 is fixed, the flat working surface of which is divided by blind bevels at an angle to the flat surface. Discharge sleeve 6 is installed in the discharge cover housing, forming a radial slot 8 with the distance sleeve 7 installed on the pump shaft. An end slot 9 with a continuously renewable lubricating layer 10 is formed between the working surfaces of the two discharge rings. The discharge chamber 11 is formed by an internal cavity of the annular space.

под углом α к плоской поверхности. Причем кривизна наружной стенки наклонной поверхности определяется величиной наружного диаметра наклонных участков - окружностью диаметром D_c, центр которой совпадает с центром разгрузочного кольца наружным диаметром D_н.The reciprocal unloading ring (Fig. 2), the flat surface 12 of which is divided by blind bevels 13 with a radius of curvature R, the length of each inclined section

at an angle α to a flat surface. Moreover, the curvature of the outer wall of the inclined surface is determined by the value of the outer diameter of the inclined sections - a circle with a diameter D _c , the center of which coincides with the center of the discharge ring with an outer diameter D _n .

The proposed unloading device works as follows. When the pump is running, part of the pumped liquid from the last stage enters the discharge chamber 11 through the annular gap 8 between the discharge sleeve 6 and the distance sleeve 7 (Fig. 1). When the rotating movable discharge ring 4 moves relative to the fixed counter ring 5, the incoming liquid along the inclined sections of the working surface 13 of the counter ring is entrained on a flat working surface 12 (Fig. 2), creating a hydrodynamic pressure in the liquid wedge formed to provide a continuously renewable lubricating layer 10. The pressure of the pumped liquid on the movable ring 4 and the unloading disc 3 shifts the pump rotor towards the discharge side. The end gap 9 between the rings 4 and 5 increases with the displacement of the rotor towards the discharge side, and the pressure in the unloading chamber 11 decreases until the force generated by it is balanced by the axial force acting towards the suction side. The operation of the device in this case is similar to that of the prototype.

During transient operation of the pump, when the magnitude of the axial force of the rotor exceeds the magnitude of the pressure force in the discharge chamber, the flat sections 12 of the working surface of the return ring 5 come into contact with the flat working surface of the movable ring 4, the device will be partially unloaded by the hydrostatic pressure formed by a continuously renewable lubricating layer between the interacting the surfaces of the relief rings. Due to the blind beveled sections 13, located at an angle to the flat surface 12, the flat working surfaces of the relief rings will operate in the liquid friction mode, which will ensure their full lubrication and cooling.

Claims (1)

Hydraulic unloading device of a centrifugal sectional pump with a continuously renewable lubricating layer, comprising a housing, a discharge disc fixed on the rotor with a movable discharge ring having a flat shape of the working surface, and a mating discharge ring fixed on the discharge cover, characterized in that with the formation of a wedge gap between the movable and fixed parts of the device, the end support surface of the reciprocal unloading ring is made in the form of flat sections separated by blind bevels located at an angle to the flat support surface.

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