US3838941A

US3838941A - Pumping unit

Info

Publication number: US3838941A
Application number: US00364413A
Authority: US
Inventors: S Zalkin; V Mischevich; S Skrypnik; A Fershter; V Roschupkin; S Lovchev
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-05-29
Filing date: 1973-05-29
Publication date: 1974-10-01
Anticipated expiration: 1991-10-01

Abstract

A pumping unit comprising at least two piston pumps, a first or ''''preceding'''' pump and a second or ''''succeeding'''' pump. The chambers of the pump cylinders are connected with pneumatic or hydraulic accumulators having an adjustable initial pressure. The unit comprises several shut-off devices, viz., a first shut-off device connecting the accumulators of each pump with the atmosphere; a second shut-off device interconnecting the accumulators; a third shut-off device connecting the discharge manifold of the first pump with the suction manifold of the second pump; and a one-way check valve connecting the suction manifold of the first pump with that of the second pump. Another check valve interconnects the discharge manifolds of the pumps.

Description

United States Patent [1 1 Roschupkin et a1.

1 Oct. 1,1974

I PUMPING UNIT 22 Filed: May 29,1973

21 Appl. No.1 364,413

[52] US. Cl. 417/62, 417/276 [51] Int. 1C1. F04b 23/04, F04b 49/00 [58] Field of Search 417/62, 274-277,

[56] References Cited UNITED STATES PATENTS 6/1930 Riesner 417/440 10/1940 Vickers 2/1949 Meitzler 417/274 Primary Examiner-William L. Freeh Assistant ExaminerG. P. LaPoin'te Attorney, Agent, or Firm-Waters, Roditi, Schwartz & Nissen [5 7] ABSTRACT A pumping unit comprising at least two piston pumps, a first or preceding pump and a second or succeeding pump. The chambers of the pump cylinders are connected with pneumatic or hydraulic accumulators having an adjustable initial pressure. The unit comprises several shut-off devices, viz., a first shut-off device connecting the accumulators of each pump with the atmosphere; a second shut-off device interconnecting the accumulators; a third shut-off device connecting the discharge manifold of the first pump with the suction manifold of the second pump; and a one-way check valve connecting the suction manifold of the first pump with that of the second pump. Another check valve interconnects the discharge manifolds of the pumps.

7 Claims, 5 Drawing Figures SHEET 2 [IF 5 PATENT {U GET 11974 mirl F max PATENTE'U H974 308138.841

SHEEF BM 5 l'sl lx.

PATENTEUUBT 1 3.838.941

sum u or s PATENI EU BET 4 SHEET 5 OF 5 PUMPING UNIT The present invention relates to the pump-building industry and more specifically it relates to pumping units. The invention can be utilized most successfully for handling abrasive-containing liquids in drilling deep wells.

Known in the art is a pumping unit for drilling deep wells (see, for example, A. A. llsky Calculations and designing of drilling equipment," USSR, 1957). The known pumping unit comprises two piston pumps. Each pump has two working cylinders with pistons which divide the inner space of the cylinders into two chambers. These chambers are in communication with the suction and discharge manifolds for the working fluid. The discharge manifolds of the piston pumps are combined into a common discharge line.

in the majority of cases such pumping units ensure either parallel or separate operation of the pumps, and their disadvantage lies in that the power of the pump drive converted into hydraulic power is used within strictly definite limits which depend on the maximum pump capacity and maximum permissible discharge pressure of each separate pump.

The range of power utilization of the pump drive can be widened by connecting the pumps in tandem which raises their discharge pressures.

Theoretically, tandem operation of piston pumps can be ensured only by providing them with an adjustable drive with a series characteristic (e.g. Leonard drive or a hydrodynamic transmission drive) since in a tandem connection of pumps with an inflexible characteristic the entire load would be carried by the pump whose capacity is even slightly higher than that of the other pump. It must be noted that an absolute equality of capacities of any two piston pumps is practically unattainable.

However, an inherent disadvantage of adjustable drives lies in that they reduce considerably the effective power of the pumping unit whereas heavy rotating masses and rather inflexible mechanical characteristics of the drive hinder uniform distribution of the pressure difference between the tandem pumps which, in turn, cuts down the service life of the wearing replaceable parts of the pump.

Another disadvantage lies in that the use of these types of adjustable drives fails to eliminate the irregularity of piston motion in the working cylinders of the pump, said irregularity being caused by the kinematics of the crank gear. Therefore, owing to considerable pressure fluctuations at the discharge side, piston pumps with this adjustable drive cannot render a reliable service for producing superhigh pressures during tandem operation.

An object of the present invention resides in providing a pumping unit which widens the power utilization limits of the pump drive and is capable of producing superhigh discharge pressures.

Another object of the invention resides in improving the reliability and extending the life of pump wearing parts during operation at superhigh discharge pressures.

Still another object of the invention is to produce a uniform nonpulsating flow of fluid during operation at superhigh discharge pressures.

And, finally, a further object is to distribute uniformly the transmitted power and the pressure difference between two or more tandem-operating pumps.

In accordance with these and other objects a pumping unit is provided. comprising at least two piston pumps, namely a first and a second pump, each consisting of working cylinders with a piston which divides their inner spaces into two chambers communicating hydraulically with the working-fluid suction and discharge manifolds. The discharge manifolds of the pumps are combined into a common discharge line wherein, according to the invention. at least one chamber of each working cylinder communicates with at least one pneumatic or hydraulic accumulator with and adjustable initial pressure, the accumulators of each pump being interconnected by a pipeline which communicates with the atmosphere through is first shut-off device while the accumulators of both pumps are interconnected by pipelines through a similar shut off device.

The discharge manifold of the pump being connected with the suction manifold of the succeeding pump by a pipeline through a third shut-off device which is operated by a pressure difference between the accumulators; besides, the suction manifold of the first pump is connected with the suction manifold of the second pump through a device preferably in the form of a pressure-responsive or a one-way valve whereas their discharge manifolds are interconnected through another, preferably similar device.

Owing to the use in the pumping unit according to the invention of accumulators connected to the chambers of the pump working cylinders, the delivery of fluid by each pump is uniform and nonpulsating, which improves considerably the reliability and serviceability of the unit at superhigh discharge pressures and allows the use of most economical non-adjustable electric motors or internal-combustion engines without the usual hydrodynamic transmissions which are used at present and which considerably reduce the effective power of the unit.

The use of shut-off devices in the pumping unit ensures the possibility of selective parallel and tandem operation of the pumps and. as a consequence, widens the range of utilization of the pump drive power and permits building up superhigh discharge pressures.

It is recommended that the first shut-off device be made in the form of a valve.

it is also advisable that the third shut-off device be made in the form of a cylinder with a piston which divides the inner space of the cylinder into two chambers one of which, accommodating a rod, communicates by a pipe with the hydraulic accumulators of the second pump while the other chamber is in communication with the accumulators of the first pump; the free end of the rod is provided with a cone and the body of the shut-off device has a seat. When the cone closes the seat, the working fluid does not flow from the discharge manifold of the first pump into the suction manifold of the second pump.

In a pumping unit consisting of single-acting piston pumps it is recommended that the working cylinder of each pump be divided by the piston into two chambers of which the working one is filled with being working fluid while the other, the auxiliary one, is filled with an auxiliary fluid possessing lubricating properties and being free of mechanical impurities. The auxiliary chambers of each piston pump are then connected with each other and with the accumulators by a pipeline,

communicating with hydraulic system of the entire unit with make-up pumps. Piston rods in the working chambers are preferably provided with stops, the pistons being free to slide longitudinally along the rods up to these stops. The auxiliary chambers of the second pump cylinders can be connected with the rod chamber of the cylinder of the third shut-off device; the similar chambers of the first pump can be connected with the other chamber of the same cylinder of the third device; in addition, the auxiliary chambers of the working cylinders of the pumps can be interconnected by a pipe through a valve.

Such pumping units are more convenient in servicing since they have a minimum number of replaceable parts and are more reliable in operation owing to the use of the auxiliary fluid which is characterized by lubricity and is free of mechanical impurities.

It is advisable that the rod of the second pump be made of two sealing elements separated by a shoulder of a gland body from an intermediate chamber filled with the auxiliary fluid and communicating with the axuiliary chamber of the working cylinder of the first pump.

Such a seal reduces the difference of pressures applied to individual sealing elements, thereby increasing their durability.

It is most recommended that the auxiliary chambers of the working cylinders of both pumps and the supply source of the hydraulic system be connected to a device for maintaining uniform distribution of the pressure difference between the pumps when operating in tandem.

It is also recommended that the device for maintaining uniform pressure distribution be made in the form of a slide valve with three chambers; one of these, with a rod, being connected by a pipeline with the auxiliary chambers of the second pump and with the rod chamber of the cylinder of the third shut-off device, a second chamber of the slide valve, without a rod, being connected by a pipeline with the auxiliary chambers of the first pump with the rodless chamber of the cylinder of the third shut-off device.

A middle chamber of the slide valve is then connected by a pipeline with the auxiliary chambers of both pumps and with a hydraulic makeup pump. A movable contact can be provided at one side of the slide valve, e.g. on the rod, and a fixed contact secured a slide valve body, so that the closing of these contacts starts an electric drive motor of the make-up pump.

The following description of the present invention is given with reference to the accompanying drawings, in which: a

FIG. 1 is a schematic diagram of an exemplary pumping unit according to the invention with two doubleacting piston pumps;

FIG. 2 is a diagram showing the power utilization zones of the pumping unit drive according to the inventron;

FIG. 3 is a schematic showing of the pumping unit according to the invention with two single-acting controllable pumps;

FIG. 4 is an enlarged longitudinal section of a rod seal of a supcrhigh-pressure pump according to the invention;

FIG. 5 is a schematic illustration, similar to that of HG. 3, of the pumping unit according to the invention with a device for uniform distribution of the pressure difference between the two pumps.

The pumping unit according to FIG. 1 consists of two piston pumps: a preceding or first pump 1 and a succeeding or second pump 2. Each pump accommodates piston 3 sliding in working cylinders 4 and connected to rods 5 with a driving crank gear(not shown in the drawing).

The pistons 3 divide the inner space of the cylinders 4 into two working chambers 6 and 7, each provided with a suction valve 8 and a discharge valve 9.

Besides, each working chamber 6 and 7 of the pumps 1 and 2 is connected to a pneumatic or hydraulic accumulator with an adjustable initial pressure, made in the form of a reservoir 10 filled with a compressible medium and accommodating a floating piston 11 which separates the medium from the handled fluid. The reservoirs 10 of each pump are interconnected by a pipeline 12 into a single reservoir common for all the cylinders 4, and they are connected by a pipe 13 with a source 14 of pressure of the medium (e.g. a compressor). The medium can be discharged through a valve 15 connected to the pipeline 12. The fluid is admitted into the chambers 6 and 7 of each pump through a suction manifold 16 and discharged through a discharge manifold 17.

A damper l8 installed at the discharge side of each pump eliminates pulsation during maximum-capacity operation of the unit. The rods are sealed by a conventional method.

Non-return valves

19 and 20 are installed, respectively, at the inlet'of the suction manifold 16 of the pump 2 and at the outlet of the discharge manifold 17 of the pump 1. The discharge manifolds 17 are combined into a common discharge line 21. Both valves open towards the discharge line 21 when pressure in both discharge manifolds 17 is higher than that in the discharge line 21. The discharge manifold 17 of the pump 1 is connected with the suction manifold 16 of the pump 2 by a pipeline 22 through a shut-off device 23 operated by the pressure difference between the ac cumulators 10 of the first and the second pumps 1 and 2.

A rod 24 of the shut-off device 23, connected with a piston 25 of a cylinder 26, has a cone 24 at the end, said cone being pressed by a spring 27 against a seat 28 of the shut-off device 23. A rod chamber 29 of the cylinder 26 is connected by a pipeline 30 with the pipeline 12 which interconnects the reservoirs 10 of the pump 2 with the pressure source 14 and with the outlet valve 15 of the same pump, communicating with the atmosphere.

A chamber 31 of the cylinder 26 is connected by a pipeline 32, respectively, with the pipeline 12, the source 14 and the valve 15 of the pump 1.

A valve 33 is provided for connecting or disconnecting the

pipelines

30 and 32.

The diagram in FIG. 2 shows the power utilization ranges of the pumping unit drives. The diagram illustrates Q P curves i.e., pump capacity Q vs pressure P of the working fluid. Points Q,,,,,,, Q,,,,-,,, P and P,,,,-,, denote, respectively, maximum and minimum pump capacities, and maximum and minimum pump pressures.

The straight line 1 2 gives the characteristic of the pump at maximum capacity. The straight line 3 is the pump characteristic at a maximum pressure. The curve 2 3 shows the constant power of the pump.

The straight line 5 6 gives the characteristic of the pumping unit at maximum capacity with parallel operation of the two pumps. The straightline l0 8 is the characteristic of the pumping unit at maximum pres sure with tandem-operated pumps.

The line 6 7 is the constant power curve at parallel operation of the two pumps while the line 78 is a similar curve characterizing the tandem operation of the two pumps.

During operation of one pump the power utilization zone is limited by

points

0, 1, 2, 3, 4, 0. During parallel operation of two pumps the zone is limited by

points

0, 5, 6, 7, 4, 0. During parallel and tandem operation of the pumps in the unit according to the invention, the zone is limited by

points

0, 5, 6, 8, 9, 0.

As can be seen from the chart in FIG. 2 the power utilization zone of the pumping unit is largest when parallel operation of the pumps is combined with tandem operation and this is used in the present invention.

The pumping unit shown in FIG. 3 comprises two single-acting piston pumps 1 and 2. Each pump has working cylinders 34 divided by a piston 35 into two chambers. One of these, a working chamber 36, is filled with the working fluid while another an auxiliary chamber 37 contains auxiliary fluid. The auxiliary fluid possesses lubricating properties and is free of mechanical impurities. The working chambers 36 of the cylinders 34 accommodate stops 38 secured to rods 39 of the pistons 35. The pistons 35 are free to slide longitudinally along the rods 39 to the stops 38.

The rods are provided with seals 40. Like the pumps illustrated in FIG. I the pumps shown in FIG. 3 have a suction manifold 16, a suction valve 8, a discharge valve 9, a discharge manifold 17; a damper 18 for suppressing pulsations, a non-return valve 19 installed at the inlet of the suction manifold 16 of the second pump 2; a non-return valve 20 installed at the outlet from the discharge manifold 17 of the pump 1; a discharge line 21; a pipeline 22 connecting the discharge manifold 17 of the pump 1 with the suction manifold 16 of the pump 2 through the shut-off device 23 which comprises a rod 24 with a cone 24', said rod being connected with the piston 25 of the cylinder 26 and pressed by a spring 27 against the seat 28 of the shut-off device 23.

The chamber 29 with the rod 24 of the cylinder 26 is connected by a pipeline 30 with the auxiliary chambers 37 of the pump 2 while the other chamber 31 of the cylinder 26 is connected by a pipeline 32 with the auxiliary chambers 37 of the pump 1.

The auxiliary chambers 37 of each pump are connected with each other by a pipeline 4] and with an accumulator made in the form of an adjustable-volume reservoir 42 filled with the compressible medium and provided with a diaphragm 43 which separates the medium from the auxiliary fluid.

A pipeline 44 communicates the auxiliary chambers 37 of the cylinders 34 with a make-up pump 45 of a hydraulic system, including a check valve 46 and a reservoir 47 for the auxiliary fluid. The chambers 37 of the pumps 1 and 2 are in communication through the

pipelines

30 and 32 and through a check valve 48.

The seal 40 of the rod 39 of the succeeding pump 2 has an intermediate chamber 49 (FIG. 4) which is filled with the auxiliary fluid from the reservoir 42 (FIG. 3) of the first pump I through a channel 50 drilled in the body of the hydraulic cylinder 34 of the pump 2 and through a channel SI drilled in the body of a gland 52.

The chamber 49 (FIG. 4) is a cylindrical recess in a separating shoulder53 of the body of the gland 52. Located right and left of the separating shoulder 53 are elastic sealing elements 54 with underlying plastic rings 55 pressed against the separating shoulder 53 by a nut 56 at the side of the working cylinder 34 and a bushing 57 at the drive side. The fixed joint between the body of the gland 52 and the working cylinder 34 is sealed by cups 58 to prevent fluid leaks.

Inasmuch as in the tandem-operated pumping unit (FIG. 3) the pressure of the medium in the reservoir 42 of the second pump 2 is twice the pressure in the first pump ll, each sealing element 54 (FIG. 4) is subjected only to half the total pressure built up in the pumping unit.

Shown in FIG. 5 is a schematic illustration of such a pumping unit with a device for maintaining uniform distribution of the pressure difference between the pumps 1 and 2.

The uniform distribution of pressure difference between the pumps 1 and 2 of the unit is ensured by a slide valve 59 which has three

chambers

60, 61, 62. The chamber 60 with a rod communicates through the pipeline 30 with the reservoir 42 of the pump 2 and with the chamber 29 of the shut-off device 23. The chamber 61 communicates through the pipeline 32 with the reservoir 42 of the pump 1 and with the space 31 of the device 23.

The chamber 62 of the slide valve 59 located be- I tween bands 63 of the slide valve 59 communicates with the

pipelines

30 and 32, with the reservoirs 42 of the pumps 1 and 2 and, by a pipeline 64, with the make up pump 45 of the hydraulic system. At one side, the slide valve 59 is provided with the rod 65 whose crosssectional area is twice smaller than that of the band 63 of the same slide valve 59. A movable contact 66 of the rod 65 can close a fixed contact 67 of a power supply 74 for the make-up pump 45. The fixed contact 67 is secured on the body of the slide valve 59. Besides, the rod 65 is connected with a handle 68 by a joint 69.

At the inlets of the spaces 60, 61 of the slide valve 59 are installed, respectively, throttles 70 and 71 for damping self-excited vibrations of the slide valve.

Adjustable safety valves 72 of the pumps 1 and 2 are intended to limit pressure in the reservoirs 42 of the pumps 1 and 2. A button 73 serves for starting the pump 45 during manual control of the pumping unit.

The pumping unit incorporates the source 74 of electric power for the make-up pump 45 and a reservoir 75 with auxiliary fluid.

The handle 68 is mounted on an axle 76, has a retainer 77 for stopping the slide valve in the middle position as shown in FIG. 5, and is installed on a bracket 78 connected with the body of the slide valve 59. The slide valve 59 is loaded by a spring 79.

The pumping unit shown in FIG. 1 functions as follows: the working fluid enters the suction manifolds 16 of the pumps 1 and 2, passes through the working cylinders 4 and is forced out by the pistons 3 into the dis charge manifolds 17 of the pumps 1 and 2.

The capacity of the pumping unit depends on the pressure of the compressible medium in the reservoirs 10 of the pumps 1 and 2.

If the pressure of the medium in the reservoirs 10 of the pumps 1 and 2 is the same and is higher than the 1 pressure of the working fluid in the discharge line 21,

the pistons 11 in the reservoirs 10 are in the initial positions, both pumps 1 and 2 work in parallel, i.e., their capacity is equal to the total capacity of the two pumps. in this case the shut-off device 23 is closed, because the cone 24 of the rod 24 is pressed against the seat 28 by the surplus force acting on the piston 25 in the direction of the seat 28 at equal pressures of the medium in the

chambers

29 and 31 of the cylinder 26. Both

nonreturn valves

19 and 20 are open. The valve 19 admits fluid into the suction manifold 16 of the pump 2 while the valve 20 admits fluid delivered by the pump 1 into the discharge line 21.

The pumps 1 and 2 delivering fluid into the common discharge line 21 can operate in parallel, both at a maximum capacity and at a partial controllable capacity of the pumps 1 and 2. g

The process of controlling the capacity of each of the two pumps in the pumping unit consists in the followmg.

During each discharge stroke, for example in chamber 6, part of the fluid is forced out through the discharge valve 9 while another part enters the reservoir 10 and moves the piston 11.

Then, during the suction stroke, the working fluid that has entered the reservoir 10 is again forced out by the pressure of the medium into the chamber 6 and, only after the piston 11 returns to the initial position, will the suction valve 8 open. The lower the pressure of the medium created by its source, the larger the displacement of the piston 11 and, correspondingly, the lower the pump capacity.

The capacity of the pumping unit can be controlled at will at a constant hydraulic resistance of the well where the unit is used, by changing the pressure of the medium in the reservoirs 10 of the pumps 1 and 2.

The capacity of the pumping unit can also change automatically and instantaneously as a result of changes in the hydraulic resistance of the well in which case an increase in the hydraulic resistance will cause automatic reduction of the unit capacity and vice versa.

During parallel operation with the pumps discharging fluid into a single pipeline, the hydraulic power will be evenly distributed between the two pumps 1 and 2 if the valve 33 interconnects the reservoirs 10 of the pumps 1 and 2 so that the pressures in said reservoirs are the same.

Owing to a flexible O p characteristic of the pumps, which means that their capacity changes automatically with the load (hydraulic resistance) as in centrifugal pumps, the pumps can also be used for tandem operation.

Therefore, if the pressure built up by the unit fails to satisfy the well drilling requirements, the pumps can be switched over to tandem operation For this purpose the reservoirs 10 of the pumps 1 and 2 must be disconnected by the valve 33.

It is most expedient to set a pressure of the medium in the reservoirs 10 of the first pump 1 at half the desired pressure in the discharge line 21 of the pumping unit.

Using a compressor 14, pressure of the medium in the reservoirs 10 of the second pump 2 is bulit up to the value of the total pressure in the discharge line 21. Then. owing to a pressure rise in the chamber 29 communicating with the reservoirs l0 of the pump 2, the piston 25 will overcome both the resilient force of the spring 27 and the pressure in the space 31, and will move all the way to the right, as shown in the drawings, the rod 24 admitting the fluid from the discharge manifold 17 0f the pump 1 into the suction manifold 16 of the pump 2.

Owing to the rise of pressure, the

non-return valves

19 and 20 will close automatically and the pumps 1 and 2 of the pumping unit will be switched over to tandem operation.

During tandem operation of the pumps 1 and 2 the unit capacity can also be controlled by changing the pressure of the medium in the reservoirs 10 of the pumps in a proportion of 1:2 which will ensure uniform distribution of the input power between the two pumps. On changes in the hydraulic resistance of the well the flexible Q-P curve of the pumps 1 and 2 will cause automatic changes in the capacity of the pumping unit.

Control of the pumping unit according to FIG. 1, carried out by an operator, consists in selecting and maintaining the required relation of pressures of the medium in the reservoirs 10 of the pumps 1 and 2.

The pumping unit according to FIG. 1 features the following advantages over drilling pumping units in current use:

1. Owing to the fact that the pressure of the working fluid at the inlet of the second pump 2 is half the pressure built up by the unit, the working load is distributed evenly between the two pumps 1 and 2 and the pressure difference applied to the parts of each pump (pistons 3 and valves 8, 9) is equal to half the maximum pressure; this extends considerably their service life at superhigh pressures of the discharged fluid in the well and while handling abrasive fluids.

2. Owing to the fact that both pumps 1 and 2 have reservoirs 10 filled with the medium and communicating with the chambers 6 and 7 of the pump 1 or 2, the delivery of the working fluid by each pump is uniform and nonpulsating which promotes considerably the reliability and efficiency of the pumping unit during tandem operation at superhigh discharge pressures.

3. The employment of the pumping unit according to the invention widens considerably the range of power utilization of drilling pump drives, which can be seen on the chart in FIG. 2 where the power utilization zone of the drive is as follows:

for one operating pump a zone limited by points 0, l, 2, 3, 4, 0;

for parallel operation of two pumps a zone limited by points, 0, 5, 6, 7, 4, 0;

for parallel and tandem operation of pumps in the unit according to the invention, a zone limited by

points

0, 5, 6, 8, 9, 0.

4. Owing to the use of the reservoirs l0 filled with the medium and communicating with the chambers 6 and 7 of the pumps 1 and 2, the pumping unit can be driven by the most economical non-adjustable electric motors or internal combustion engines without hydrodynamic transmissions, whose present employment reduces considerably the effective power of the unit drive.

Like the pumping unit described herein before, the pumping unit according to FIG. 3 is capable of functioning both with a parallel and a tandem connection of the pumps 1, 2.

During parallel operation the pressure of the medium in the reservoirs 42 of the pumps 1 and 2 is maintained equal because the auxiliary chambers 37 of the pumps 1 and 2 are in communication through the check valve 48.

During tandem operation of the pumps, the valve 48 disconnects the auxiliary chambers 37 and the reservoirs 42 of the pumps 1 and 2.

The volume of the auxiliary fluid filling the auxiliary chamber 37 and the reservoir 42 of the second pump 2 is increased by the make-up pump 45 which compresses the medium in the reservoir 42 and increases pressure. This raises the pressure in the chamber 29 of the cylinder 26 of the shut-off device 23 so that the pis ton 25 shifts the rod 24 all the way to the right, putting the discharge manifold 17 of the pump 1 in communication with the manifold 16 of the pump 2 through the pipeline 22. The

valves

19 and 20 close automatically.

The capacity of the pumps during both parallel and tandem operation can be controlled by changing the volume of the auxiliary fluid in the reservoirs 42 of the pumps 1 and 2 and, as a consequence, by changing the pressure of the medium in said reservoirs 42.

Inasmuch as the piston 35 is free to move longitudinally along the rod 39 to the stops 38, it will cover only a part of its complete travel in the cylinder 34, coming short of the stops 38. The travel of the piston 35 will be smaller proportionally to the valve by which the discharge pressure exceeds the initial pressure of the medium in the reservoirs 42.

If the pressure of the medium is higher than the discharge pressure, the pistons 35 will be pressed against the stops 38 and will make a complete stroke in the working cylinder 34.

The pumps of this design are more convenient to service because they have a minimum number of replaceable parts, and they are more reliable in operation due to the use of the auxiliary fluid which possesses lubricating properties and is free of mechanical impurities. These pumps are better suited to automation and remote control, which makes it possible to maintain automatically the uniform distribution of the pressure difference between the two pumps of the unit. However with equal dimensions of the pumps the capacity of this unit is lower than that of the unit shown in FIG. 1.

The pumping unit shown in FIG. 5 ensures uniform distribution of the pressure difference in the pumps 1 and 2 during their parallel and tandem operation.

The pumps 1, 2 operate in parallel when the rod of the slide valve 65 is fixed in the middle position by the handle 68 and the retainer 77. In this case the reservoirs 42 of the pumps 1 and 2 are in communication and have the same pressure of the medium.

The required discharge pressure is maintained either by the operator or automatically by the conventional methods, in this case with the aid of a contact-pressure gauge (not shown in the drawing).

The pumping unit is switched over to tandem operation as follows:

1. The safety valve 72 of the pump 1 is set to a pressure twice lower than the expected pressure in the discharge line 21.

2. The safety valve 72 of the pump 2 is set to a pressure expected in the discharge line 21.

3. The handle 68 is taken off the retainer 77.

4. The pump 45 sets automatically the preset pressures in the reservoirs 42 of the pumps I and 2.

In view of the fact that the pressure of the fluid on both faces of the slide valve is equal at the initial period of time, after taking the handle 68 off the retainer 77, and that the area of the slide valve in the chamber 60 is twice smaller than that in the chamber 61, the rod 65 of the slide valve 59 moves upward. The band 63 covers the channel 32 and the contact 66 closes the contact 67 thus starting the makeup pump 45 of the hydraulic system.

When pressure in the reservoirs 42 of the pump 2 becomes twice higher than that in the reservoirs 42 of the pump 1, the forces acting on the faces of the slide valve in the spaces 60 and 61 will be equalized and the slide valve will open the contacts 66 and 67. The springs 79 and the dampers 70 and 71 will stop the slide valve 59 in a position of equilibrium, and the band 63 will deny access of the fluid from the channel 30 into the channel 32.

At a drop of pressure in the reservoir 12 of the pump l the slide valve 59 will return to the initial position and will keep the

pipelines

30 and 32 in communication until the relation P 2P is reached where P, is the pressure in the reservoir 42 of the pump 1 and P is the pressure in the reservoir 42 of the pump 2.

The pressure in the reservoirs 42 of the pumps 1 and 2 can be increased by starting the :make-up pump 45 of the hydraulic system by means of the button 73, if this pressure is lower than that for which the safety valves 72 of the pumps 1 and 2 are set. or it can be decreased by adjusting the setting pressure of the safety valve 72 of the pumps 1 and 2.

The pumping unit shown in FIG. 5 ensures:

1. Parallel and tandem operation of the pumps.

2. Superhigh discharge pressures at a permissible pressure difference acting on all replaceable wearing parts.

3. Automatic uniform distribution of the power and the pressure difference between the two pumps.

4. Uniform flow of the discharged fluid.

The pumping unit according to the present invention will allow:

a. raising the efficiency of drilling by increasing the pressure difference used in the nozzles of jet bits while drilling wells;

b. reducing considerably the time required for auxiliary operations such as restoring the circulation of the drilling fluid and equalizing its parameters.

We claim:

I. A pumping unit comprising at least two piston pumps, namely a first or preceding pump and a second or succeeding pump; working cylinders in said pumps; pistons dividing the inner spaces of each of said cylinders into two chambers; a suction manifold admitting working fluid to said cylinders and communicating hydraulically with said chambers; discharge manifolds delivering the working fluid to consuming units and also communicating with said chambers; a common discharge line interconnecting said discharge manifolds; a hydraulic system including a supply source for the working fluid and hydraulic accumulators for said pumps, connected to said chambers, with an adjustable initial pressure, for changing the rate of fluid flow through said pumps in accordance with the prevailing discharge pressure; a first shut-off device; a pipeline interconnecting said accumulators and communicating with the atmosphere through said first shut-off device; a second shut-off device interconnecting said accumulators and being similar to said first shut-off device; a third shut-off device interconnecting said discharge manifold of the first pump with said suction manifold of the second pump and operated by a pressure difference between said accumulators; a one-way check valve interconnecting said suction manifold of the first pump with that of said second pump; and another check valve, similar to said one-way check valve, interconnecting said discharge manifolds.

2. The pumping unit as defined in claim 1, wherein said first shut-off device is made in the form of a valve.

3. The pumping unit as defined in claim 1, wherein said third shut-off device is made in the form of a cylinder with a piston which divides the inner space of said cylinder into two chambers; one of which, with a rod,

is connected by a pipeline with said accumulators of the second pump, while another chamber is connected with said accumulators of the first pump; the free end of said rod being fitted with a cone, and a body of said third shut-off device being provided with a seat so that in the closed position, when said cone closes said seat, the working fluid is prevented from flowing from said discharge manifold of the first pump into said suction manifold of the second pump.

4. The pumping unit as defined in claim 1, further comprising single-acting piston pumps with working cylinders, each divided by pistons into two chambers; one of which, a working chamber, is filled with the working fluid while the other, an auxiliary chamber, contains an auxiliary fluid with lubricating properties and free of mechanical impurities; said auxiliary chambers of the pumps communicating with each other and with said accumulators through a pipeline and being connected to said hydraulic system with make-up pumps; wherein rods of said working chambers have stops and said pistons are free to slide longitudinally along said rods up to said stops; said auxiliary chambers of the second pump are in communication with said rod-containing chamber of the cylinder of said third shut-off device, and similar chambers of said first pump are in communication with said other chamber of the same cylinderof said third shut-off device; and wherein said auxiliary chambers of the working cylinders are interconnected by a pipeline through a valve.

5. The pumping unit as defined in claim 4, wherein said second pump is provided with a seal for said rod. said seal consisting of two sealing elements separated by a shoulder of a gland body, and an intermediate chamber which is filled with the auxiliary fluid and communicates with said auxiliary chamber of the working cylinder of the first pump.

6. The pumping unit as defined in claim 4, wherein said auxiliary chambers of the working cylinders and said supply source are connected to a device for ensuring uniform distribution of the pressure difference between said pumps during tandem operation.

7. The pumping unit as defined in claim 6, wherein said device ensuring uniform pressure distribution is made in the form of a slide valve with three chambers; one of which, with a rod, communicates through a pipeline with said auxiliary chambers of the second pump and with said rod chamber of the cylinder of said third shut-off device; another chamber of said slide valve, which is without a rod, communicates through a pipeline with said auxiliary chambers of the first pump and with said rodless chamber of said cylinder of the third shut-off device, while a middle chamber of said slide valve communicates through a pipeline with said auxiliary chambers of both pumps and with a make-up pump of said hydraulic system; said rod at one side of said slide valve being provided with a movable contact while a body of said slide valve has a fixed contact which interacts with said movable contact to switch on said make-up pump.

Claims

1. A pumping unit comprising at least two piston pumps, namely a first or preceding pump and a second or succeeding pump; working cylinders in said pumps; pistons dividing the inner spaces of each of said cylinders into two chambers; a suction manifold admitting working fluid to said cylinders and communicating hydraulically with said chambers; discharge manifolds delivering the working fluid to consuming units and also communicating with said chambers; a common discharge line interconnecting said discharge manifolds; a hydraulic system including a supply source for the working fluid and hydraulic accumulators for said pumps, connected to said chambers, with an adjustable initial pressure, for changing the rate of fluid flow through said pumps in accordance with the prevailing discharge pressure; a first shutoff device; a pipeline interconnecting said accumulators and communicating with the atmosphere through said first shut-off device; a second shut-off device interconnecting said accumulators and being similar to said first shut-off device; a third shut-off device interconnecting said discharge manifold of the first pump with said suction manifold of the second pump and operated by a pressure difference between said accumulators; a one-way check valve interconnecting said suction manifold of the first pump with that of said second pump; and another check valve, similar to said one-way check valve, interconnecting said discharge manifolds.

3. The pumping unit as defined in claim 1, wherein said third shut-off device is made in the form of a cylinder with a piston which divides the inner space of said cylinder into two chambers; one of which, with a rod, is connected by a pipeline with said accumulators of the second pump, while another chamber is connected with said accumulators of the first pump; the free end of said rod being fitted with a cone, and a body of said third shut-off deVice being provided with a seat so that in the closed position, when said cone closes said seat, the working fluid is prevented from flowing from said discharge manifold of the first pump into said suction manifold of the second pump.

4. The pumping unit as defined in claim 1, further comprising single-acting piston pumps with working cylinders, each divided by pistons into two chambers; one of which, a working chamber, is filled with the working fluid while the other, an auxiliary chamber, contains an auxiliary fluid with lubricating properties and free of mechanical impurities; said auxiliary chambers of the pumps communicating with each other and with said accumulators through a pipeline and being connected to said hydraulic system with make-up pumps; wherein rods of said working chambers have stops and said pistons are free to slide longitudinally along said rods up to said stops; said auxiliary chambers of the second pump are in communication with said rod-containing chamber of the cylinder of said third shut-off device, and similar chambers of said first pump are in communication with said other chamber of the same cylinder of said third shut-off device; and wherein said auxiliary chambers of the working cylinders are interconnected by a pipeline through a valve.

5. The pumping unit as defined in claim 4, wherein said second pump is provided with a seal for said rod, said seal consisting of two sealing elements separated by a shoulder of a gland body, and an intermediate chamber which is filled with the auxiliary fluid and communicates with said auxiliary chamber of the working cylinder of the first pump.