Title of Invention	SCREW PUMP OF SINGLE ENTRY, DOUBLE SHAFT CONSTRUCTION WITH TWO SCREW SHAFTS
Abstract	The invention relates to a screw pump of single-entry, double-shaft construction with an external bearing of the two screw shafts (1, 2) and a pump housing (3) enclosing the screw shafts (1, 2) by forming feed chambers (4) and externally delimiting the feed chambers (4) with its internal shell surface (3a), as well as an induction chamber (5) for the medium to be induced and a pressure chamber (6) to accommodate the medium pumped by the screw shafts (1, 2). The pump housing (3) is inserted into a pressure housing (7) and attached to the pressure housing (7), so that the pressure chamber (6) enclose the pump housing (3) at least in part.

Title of Invention

SCREW PUMP OF SINGLE ENTRY, DOUBLE SHAFT CONSTRUCTION WITH TWO SCREW SHAFTS

Abstract

The invention relates to a screw pump of single-entry, double-shaft construction with an external bearing of the two screw shafts (1, 2) and a pump housing (3) enclosing the screw shafts (1, 2) by forming feed chambers (4) and externally delimiting the feed chambers (4) with its internal shell surface (3a), as well as an induction chamber (5) for the medium to be induced and a pressure chamber (6) to accommodate the medium pumped by the screw shafts (1, 2). The pump housing (3) is inserted into a pressure housing (7) and attached to the pressure housing (7), so that the pressure chamber (6) enclose the pump housing (3) at least in part.

Full Text	FIELD OF INVENTION The present invention relates to a screw pump of single entry, double shaft construction with two screw shafts. BACKGROUND OF THE INVENTION From DE 715860 B1 a mixed-flow pump for pumped liquids is known that has a single-sided external bearing for the feed screws. The feed screws are enclosed by a housing embodied as one piece and flange-connected to a housing part in which the screw-shaped rotors are supported. This housing can be removed for servicing tasks. If the pump has to be serviced, it is necessary to take the pump out of the feed line at the inlet and outlet pipes and to install a completely new pump. Alternatively to a complete replacement, a screw pump can be dismantled and repaired on site, which is very time-consuming. Furthermore, a pump assembly from several components at the customer's location has the disadvantage that a pump test with a precise determination of the performance data is impossible, so that as a rule a complete pump replacement is necessary to meet the required performance parameters. Especially with single-well boosting there are high fluctuations in the composition of the medium to be pumped. States of pumping 100% liquid and phase of pumping 100% gas alternate in a largely unpredictable manner, whereby the phases of pumping 100% gas are particularly critical for screw pumps, since with conventional screw pumps the sealing, cooling and lubricating liquid is removed after a certain time of gas pumping. This state causes a heating of the feed screws and, associated therewith, a contact of the feed screws with one another and with the feed housing, which causes a higher wear, possibly a stoppage of the pump. The problems thus arising in terms of servicing on site have already been described. EP 0 405 160 A1 describes a screw pump with a drive shaft arranged in the internal chamber of a pump housing and at least one sealed spindle axially parallel thereto, as well as with an intake and an outlet for a flow medium to be pumped by the spindles. The spindles are enclosed by a tubular housing insert, which, together with the pump housing enveloping it, delimits at least one annular space connected to the internal chamber accommodating the spindles by at least one through hole. In addition to screw pumps, eccentric screw pumps are also used for single-well boosting, but these eccentric screw pumps are suitable only to a limited extent for pumping multiphase mixtures, as their capability of pumping 100% gas is very limited in terms of time because of the friction heat being produced. As a result of the oversizing of multi-phase pumps in a double-shaft, double-entry embodiment and for lack of suitable multi-phase pumps with lower output, thousands of oil wells all over the world are not or no longer worked, which means that valuable raw materials are not being used. OBJECT OF THE INVENTION It is therefore the object of the present invention to provide a pump that can be produced and serviced in a cost-effective manner and is basically suitable for pumping multi-phase mixtures within the scope of single-well boosting. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING Fig.1 shows a screw pump with two screw shafts in cross-sectional view. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The screw pump according to the invention in single-entry, double-shaft construction with an external bearing of the two screw shafts and a pump housing enclosing the screw shafts by forming feed chambers and externally delimiting the feed chambers with its internal shell surface, as well as an induction chamber for the medium to be induced and a pressure chamber to accommodate the medium pumped by the screw shafts, provides that the pump housing is inserted into a pressure housing and attached to the pressure housing, so that the pressure chamber enclose the pump housing at least in part. Since the pump housing can be inserted into the pressure housing and since the pump housing is attached to the pressure housing, it is possible to exchange merely the pump housing together with the screw shafts arranged therein and with the external bearing, so that a screw pump is provided in modular construction, which pump can be repaired quickly because the wearing parts can be removed completely from the pressure housing. A simple exchange of the pump housing with the screw shafts arranged therein furthermore results in a mechanical decoupling of the pressure housing and the pump housing, so that deformations caused by pressure within the pressure housing are not transferred to the pump housing at all or are transferred merely to an imperceptible extent. The position accuracy of the screw shafts to one another thus remains ensured, since the deformations of the pressure housing have no effect on the tolerances of the feed elements, seals and bearings. This reduces wear and allows the adjustment of a narrow gap size, which increases the efficiency of the pump. With a use in single-well boosting it is provided for reasons of compression to provide separation devices in the pressure chamber to separate a pumped multi-phase mixture into a gas phase and a liquid phase, so that either the separated phases can be discharged separately or a part of the separated liquid phase can be guided back from the pressure chamber to the induction chamber via a short-circuited line, in order to provide a minimum amount of liquid within the pump housing, so that the screw shafts can be cooled and the gap between the screw shafts and between the screw shafts and the pump housing can be sealed. A further development of the invention provides that the pump housing extends through the pressure housing, so that the pump housing has two mating points or end bearing points in the pressure housing. It is thereby provided for the pump housing to be attached, in particular screwed, to the pressure housing only on one side, whereas the end of the pump housing not attached to the pressure housing is supported in a guideway in the pressure housing. It is thus rendered possible for the pump housing to be supported in the pressure housing in a fixed manner on one side and in an easily moveable manner on the other side, whereby the slight clearance between the pressure housing and the pump housing is sealed by at least one seal, so that no medium to be pumped can leak from the pressure chamber through gaps in the guideway. The slight clearance within the guideway in the pressure housing ensures that the pressure prevailing in the pressure chamber does not cause any deformations within the pump housing, which deformations might alter the clearance among the screw shafts and between the screw shafts and the pump housing, so that the pump housing as a whole is slightly displaced within the pressure housing. A further advantage of the embodiment according to the invention is the simpler manufacture of the pressure housing because of the lower demands on the position accuracy of the components, so that the pressure housing can be produced in a more cost- effective manner. Furthermore, servicing is considerably simplified because of the complete removability of the pump housing together with the screw shafts and the bearing unit. In order to achieve the stiffest construction possible despite the simple structure, it is provided to attach the pump housing to the pressure housing via a base plate. Both the pressure housing and the pump housing are thus attached to the base plate, and possibly also the bearing unit in which the screw shafts are supported separated from the pumped flow. The screw shafts are supported in the bearing unit, which is in turn connected to the pump housing, so that the bearing unit can be removed completely from the pressure housing together with the pump housing and the screw shafts. The screw shafts, the pump housing and the bearing unit of the screw shafts can thus be combined to form a feed module that can be exchanged easily and subjected to a complete performance test after manufacture, so that it is possible to predict the performance parameters of the pump when the feed module is exchanged for a new or overhauled feed module. Since the pump housing is located within the pressure housing, it is possible to embody the short-circuited line within the pump housing, thus to produce a direct connection between the pump chamber and the induction chamber. The short-circuited line guides separated liquid phase back into the induction chamber in a metered manner, which entails losses in the efficiency of the pump, but renders possible a greatly extended service life when the screw pump is used to pump multi-phase mixtures. The pump housing can be arranged off-center in the pressure housing, on the one hand, in order to facilitate the separation and the return of the separated liquid phase to the induction side of the screw shafts through a short-circuited line and, on the other hand, to prevent an effect of the pressure-dependent deformations of the pressure housing on the bearing unit or on the screw shafts, or to cause this effect to produce an angular deformation of the bearing unit that counteracts a pressure-dependent deflection of the screw shafts. In addition, tie rods can be arranged in the pressure housing to prestress the pressure housing with respect to the screw shaft bearing, so that a pressure-dependent angular deformation of the bearing unit can be adjusted alternatively or in addition to a suitable positioning of the pump housing in the pressure housing and to the selection of the wall thickness and/or the use of materials. In a further integration of functions into the feed module it is provided for the induction chamber to be embodied in the pump housing, so that the induction chamber can be optimally adapted to the feed screws in terms of sizing and flow technology design. In order to simplify the embodiment of the pressure housing it is provided for the pump housing to form a part of the wall of the pressure chamber, i.e., for the insert of the pump housing to form a part of the interior wall of the pressure chamber. This requires the pump housing to be attached to the pressure housing in a sealed manner, whereby passages or flow channels for the pumped medium are provided, through which the pumped medium is guided into the pressure chamber. Connecting devices for supply lines or discharge lines are also embodied on the pressure housing, so that the pressure housing does not have to be removed from the line network when the pump is serviced, which makes it possible to prevent a considerable assembly expenditure and to avoid seal-tightness problems from installing complete pumps in or removing them from the line network. An exemplary embodiment of the invention is explained below on the basis of figure 1 representing a screw pump in cross-sectional view. Figure 1 shows a single-entry screw pump with two screw shafts 1, 2, which are composed of shafts 10, 20 coupled to one another by means of gear wheels, and rotors 11, 12 attached thereto via screws. The shafts 10, 20 are supported in a bearing housing 19 and form a bearing unit 9 sealed with respect to the medium to be pumped. The rotors 11, 12 are supported in a pump housing 3, with the shell inner surface 3a of the pump housing 3 enclosing the rotors 11, 12 so that feed chambers 4 are formed through the rotors 11, 12 meshing with one another in conjunction with the shell surface 3a, in which feed chambers the medium to be pumped is pumped via connecting channels 16 from an induction chamber 5 into a pressure chamber 6. There is a minimum clearance between the rotors 11, 12 as well as between the rotors 11, 12 and the shell surface 3a, in order to keep the leak rate of the pump to a minimum. The pressure chamber 6, here embodied as an annular space, is formed by a pressure housing 7 that delimits the pressure chamber 6 respectively on the face side on the exterior circumference. The inner delimitation of the pressure chamber 6 is realized via the exterior wall of the pump housing 3, since the pump housing 3 extends through the pressure housing 7 and thus through the pressure chamber 6. The pump housing 3 is attached to a base plate 8 by means of studs 40, to which base plate the bearing unit 9 is also attached by means of studs 41. The base plate 8 is in turn coupled to the pressure housing 7 via tie rods 42, so that the pump housing 3 is attached on one side to the pump housing 7 via the studs 40, the base plate 8 and the tie rods 42. In the area of the studs 40 the pump housing 3 is provided with an annular flange 37 that can be inserted into a correspondingly embodied recess 27 of the pump housing 7. The end 30 of the pump housing 3 facing away from the base plate 8 is supported in a recess 17 of the pump housing 7; it is not screw-connected there, however, but only sealed via a seal 27. On the face side, a further seal is sealed via the faceplate 15 that has a through hole 25 to introduce the pumped medium into the induction chamber 5. Screw threads 26 are also provided to receive connecting means or supply lines in the faceplate 15. The one-sided support of the pump housing 3 on the pressure housing 7 has the advantage that the combination, structured in a modular manner, of pump housing 3, bearing unit 9 and the feed screws 1,2 arranged therein is decoupled from the compression strains of the pressure housing 7. The pressure housing 7 can be designed for the respective system design pressure and can basically be embodied as large as desired, whereby merely the recesses 17, 27 and the connecting devices must be embodied such that the respective feed units or feed modules composed of pump housing 3 and bearing unit 9 can be mounted. The pump is completed by inserting the feed unit into the pressure housing 7, with the pump housing 3 integrated into the feed unit simultaneously forming the induction chamber 5 and ensuring the separation of induction chamber 5 from pressure chamber 6. Furthermore, flanges 14 are provided on the pressure housing 7 for the discharge lines, which can remain installed in a fixed manner. Separation devices can be provided in the pressure chamber 6 for the separation of gas phase and liquid phase when multi-phase mixtures are pumped. These devices can be baffle plates or settling zones for producing a flow speed close to zero, with a short-circuited line 13, connecting the induction chamber 5 to the pressure chamber 6, preferentially being provided at points of this type. In the embodiment shown, the short-circuited line 13 is embodied in the pump housing 3 and arranged on the bottom side, so that liquid located in the lower part of the annular pressure chamber 6, which liquid is filled up to the pressure housing 3, can be induced into the induction chamber 5 and moved through the rotors 11,12 there. This causes a heat transfer, a sealing and a lubrication of the rotors 11, 12. The embodiment shown is suitable in particular to ensure a safe functioning of the pump even with very different wellhead pressures, which can rise from quasi atmospheric pressures to over 100 bar. Pump protection filters can be integrated or arranged in the inlet opening 25 or before it, in order to hold back undesired particles and to prevent damage to the rotors 11,12. WE CLAIM 1. Screw pump of single-entry, double-shaft construction with two screw shafts (1, 2) and a pump housing (3) enclosing the screw shafts (1, 2) by forming feed chambers (4) and externally delimiting the feed chambers (4) with is internal shell surface (3a), as well as an induction chamber (5) for the medium to be induced and a pressure chamber (6) to accommodate the medium pumped by the screw shafts (1, 2), whereby the pump housing (3) is inserted into a pressure housing (7) and attached to the pressure housing (7), so that the pressure chamber (6) enclose the pump housing (3) at least in part, characterized in that the two screw shafts (1, 2) are supported with an external bearing and separation devices are provided in the pressure chamber (6) to separate a pumped multi-phase mixture into a gas phase and a liquid phase and that a short-circuited line (13) is provided from the pressure chamber (6) to the induction chamber (5), through which line separated liquid is guided back into the induction chamber (5). 2. Screw pump as claimed in claim 1, wherein the pump housing (3) extends through the pressure housing (7). 3. Screw pump as claimed in claim 1 or 2, wherein the pump housing (3) is attached, in particular screwed, to the pressure housing (7) on one side. 4. Screw pump as claimed in claim 3, wherein the pump housing (3) is attached to the pressure housing (7) via a base plate (8). 5. Screw pump as claimed in claim 3 or 4, wherein the end (30) of the pump housing (3) not attached to the pressure housing (7) is supported with clearance in a guideway (17) in the pressure housing (7), and the pump housing (3) is sealed with respect to the pressure housing (7) by means of a seal (27). 6. Screw pump as claimed in one of the preceding claims, wherein the screw shafts (1, 2) are supported in a bearing unit (9) connected to the pump housing (3). 7. Screw pump as claimed in claim 6, wherein the bearing unit (9) is attached, in particular screwed, to a base plate (8). 8. Screw pump as claimed in one of the preceding claims, wherein the screw shafts (1, 2), the pump housing (3) and a bearing unit (9) of the screw shafts (1, 2) are combined to form a feed module. 9. Screw pump as claimed in one of the preceding claims, wherein the short-circuited line (13) is embodied in the pump housing (3). 10. Screw pump as claimed in one of the preceding claims, wherein the pump housing (3) is arranged off-center in the pressure housing (7). 11. Screw pump as claimed in one of the preceding claims, wherein tie rods (42) are arranged in the pressure housing (7) to prestress the pressure housing (7) with respect to the screw shaft bearing (9). 12. Screw pump as claimed in one of the preceding claims, wherein the induction chamber (5) is embodied in the pump housing (3). 13. Screw pump as claimed in one of the preceding claims, wherein the pump housing (3) forms a part of the wall of the pressure chamber (6). 14. Screw pump as claimed in one of the preceding claims, wherein connecting devices (14) for feed lines and discharge lines are embodied on the pressure housing (7). ABSTRACT SCREW PUMP OF SINGLE ENTRY, DOUBLE SHAFT CONSTRUCTION WITH TWO SCREW SHAFTS The invention relates to a screw pump of single-entry, double-shaft construction with an external bearing of the two screw shafts (1, 2) and a pump housing (3) enclosing the screw shafts (1, 2) by forming feed chambers (4) and externally delimiting the feed chambers (4) with its internal shell surface (3a), as well as an induction chamber (5) for the medium to be induced and a pressure chamber (6) to accommodate the medium pumped by the screw shafts (1, 2). The pump housing (3) is inserted into a pressure housing (7) and attached to the pressure housing (7), so that the pressure chamber (6) enclose the pump housing (3) at least in part.

Full Text

FIELD OF INVENTION

The present invention relates to a screw pump of single entry, double shaft construction with two screw
shafts.
BACKGROUND OF THE INVENTION
From DE 715860 B1 a mixed-flow pump for pumped liquids is known that has a single-sided external
bearing for the feed screws. The feed screws are enclosed by a housing embodied as one piece and
flange-connected to a housing part in which the screw-shaped rotors are supported. This housing can be
removed for servicing tasks. If the pump has to be serviced, it is necessary to take the pump out of the
feed line at the inlet and outlet pipes and to install a completely new pump.
Alternatively to a complete replacement, a screw pump can be dismantled and repaired on site, which is
very time-consuming. Furthermore, a pump assembly from several components at the customer's
location has the disadvantage that a pump test with a precise determination of the performance data is
impossible, so that as a rule a complete pump replacement is necessary to meet the required
performance parameters.
Especially with single-well boosting there are high fluctuations in the composition of the medium to be
pumped. States of pumping 100% liquid and phase of pumping 100% gas alternate in a largely
unpredictable manner, whereby the phases of pumping 100% gas are particularly critical for screw
pumps, since with conventional screw pumps the sealing, cooling and lubricating liquid is removed after
a certain time of gas pumping. This state causes a heating of the feed screws and, associated therewith,
a contact of the feed screws with one another and with the feed housing, which causes a higher wear,
possibly a stoppage of the pump. The problems thus arising in terms of servicing on site have already
been described.
EP 0 405 160 A1 describes a screw pump with a drive shaft arranged in the internal chamber of a pump
housing and at least one sealed spindle axially parallel thereto, as well as with an intake and an outlet for
a flow medium to be pumped by the spindles.
The spindles are enclosed by a tubular housing insert, which, together with the pump housing enveloping
it, delimits at least one annular space connected to the internal chamber accommodating the spindles by
at least one through hole.

In addition to screw pumps, eccentric screw pumps are also used for single-well boosting, but
these eccentric screw pumps are suitable only to a limited extent for pumping multiphase
mixtures, as their capability of pumping 100% gas is very limited in terms of time because of
the friction heat being produced.
As a result of the oversizing of multi-phase pumps in a double-shaft, double-entry embodiment
and for lack of suitable multi-phase pumps with lower output, thousands of oil wells all over the
world are not or no longer worked, which means that valuable raw materials are not being used.
OBJECT OF THE INVENTION
It is therefore the object of the present invention to provide a pump that can be produced and
serviced in a cost-effective manner and is basically suitable for pumping multi-phase mixtures
within the scope of single-well boosting.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Fig.1 shows a screw pump with two screw shafts in cross-sectional view.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
The screw pump according to the invention in single-entry, double-shaft construction with an
external bearing of the two screw shafts and a pump housing enclosing the screw shafts by
forming feed chambers and externally delimiting the feed chambers with its internal shell
surface, as well as an induction chamber for the medium to be induced and a pressure chamber
to accommodate the medium pumped by the screw shafts, provides that the pump housing is
inserted into a pressure housing and attached to the pressure housing, so that the pressure
chamber enclose the pump housing at least in part. Since the pump housing can be inserted
into the pressure housing and since the pump housing is attached to the pressure housing, it is
possible to exchange merely the pump housing together with the screw shafts arranged therein
and with the external bearing, so that a screw pump is provided in modular construction, which
pump can be repaired quickly because the wearing parts can be removed completely from the
pressure housing. A simple exchange of the pump housing with the screw shafts arranged
therein furthermore

results in a mechanical decoupling of the pressure housing and the pump housing, so that
deformations caused by pressure within the pressure housing are not transferred to the
pump housing at all or are transferred merely to an imperceptible extent. The position
accuracy of the screw shafts to one another thus remains ensured, since the deformations
of the pressure housing have no effect on the tolerances of the feed elements, seals and
bearings. This reduces wear and allows the adjustment of a narrow gap size, which
increases the efficiency of the pump. With a use in single-well boosting it is provided for
reasons of compression to provide separation devices in the pressure chamber to separate
a pumped multi-phase mixture into a gas phase and a liquid phase, so that either the
separated phases can be discharged separately or a part of the separated liquid phase can
be guided back from the pressure chamber to the induction chamber via a short-circuited
line, in order to provide a minimum amount of liquid within the pump housing, so that
the screw shafts can be cooled and the gap between the screw shafts and between the
screw shafts and the pump housing can be sealed.
A further development of the invention provides that the pump housing extends through
the pressure housing, so that the pump housing has two mating points or end bearing
points in the pressure housing. It is thereby provided for the pump housing to be
attached, in particular screwed, to the pressure housing only on one side, whereas the end
of the pump housing not attached to the pressure housing is supported in a guideway in
the pressure housing.
It is thus rendered possible for the pump housing to be supported in the pressure housing
in a fixed manner on one side and in an easily moveable manner on the other side,
whereby the slight clearance between the pressure housing and the pump housing is
sealed by at least one seal, so that no medium to be pumped can leak from the pressure
chamber through gaps in the guideway. The slight clearance within the guideway in the
pressure housing ensures that the pressure prevailing in the pressure chamber does not
cause any deformations within the pump housing, which deformations might alter the
clearance among the screw shafts and between the screw shafts and the pump housing, so
that the pump housing as a whole is slightly displaced within the pressure housing.

A further advantage of the embodiment according to the invention is the simpler
manufacture of the pressure housing because of the lower demands on the position
accuracy of the components, so that the pressure housing can be produced in a more cost-
effective manner. Furthermore, servicing is considerably simplified because of the
complete removability of the pump housing together with the screw shafts and the
bearing unit.
In order to achieve the stiffest construction possible despite the simple structure, it is
provided to attach the pump housing to the pressure housing via a base plate. Both the
pressure housing and the pump housing are thus attached to the base plate, and possibly
also the bearing unit in which the screw shafts are supported separated from the pumped
flow. The screw shafts are supported in the bearing unit, which is in turn connected to
the pump housing, so that the bearing unit can be removed completely from the pressure
housing together with the pump housing and the screw shafts. The screw shafts, the
pump housing and the bearing unit of the screw shafts can thus be combined to form a
feed module that can be exchanged easily and subjected to a complete performance test
after manufacture, so that it is possible to predict the performance parameters of the
pump when the feed module is exchanged for a new or overhauled feed module.
Since the pump housing is located within the pressure housing, it is possible to embody
the short-circuited line within the pump housing, thus to produce a direct connection
between the pump chamber and the induction chamber.
The short-circuited line guides separated liquid phase back into the induction chamber in
a metered manner, which entails losses in the efficiency of the pump, but renders possible
a greatly extended service life when the screw pump is used to pump multi-phase
mixtures.
The pump housing can be arranged off-center in the pressure housing, on the one hand, in
order to facilitate the separation and the return of the separated liquid phase to the

induction side of the screw shafts through a short-circuited line and, on the other hand, to
prevent an effect of the pressure-dependent deformations of the pressure housing on the
bearing unit or on the screw shafts, or to cause this effect to produce an angular
deformation of the bearing unit that counteracts a pressure-dependent deflection of the
screw shafts.
In addition, tie rods can be arranged in the pressure housing to prestress the pressure
housing with respect to the screw shaft bearing, so that a pressure-dependent angular
deformation of the bearing unit can be adjusted alternatively or in addition to a suitable
positioning of the pump housing in the pressure housing and to the selection of the wall
thickness and/or the use of materials.
In a further integration of functions into the feed module it is provided for the induction
chamber to be embodied in the pump housing, so that the induction chamber can be
optimally adapted to the feed screws in terms of sizing and flow technology design.
In order to simplify the embodiment of the pressure housing it is provided for the pump
housing to form a part of the wall of the pressure chamber, i.e., for the insert of the pump
housing to form a part of the interior wall of the pressure chamber. This requires the
pump housing to be attached to the pressure housing in a sealed manner, whereby
passages or flow channels for the pumped medium are provided, through which the
pumped medium is guided into the pressure chamber.
Connecting devices for supply lines or discharge lines are also embodied on the pressure
housing, so that the pressure housing does not have to be removed from the line network
when the pump is serviced, which makes it possible to prevent a considerable assembly
expenditure and to avoid seal-tightness problems from installing complete pumps in or
removing them from the line network.

An exemplary embodiment of the invention is explained below on the basis of figure 1
representing a screw pump in cross-sectional view.
Figure 1 shows a single-entry screw pump with two screw shafts 1, 2, which are composed of
shafts 10, 20 coupled to one another by means of gear wheels, and rotors 11, 12 attached
thereto via screws. The shafts 10, 20 are supported in a bearing housing 19 and form a bearing
unit 9 sealed with respect to the medium to be pumped. The rotors 11, 12 are supported in a
pump housing 3, with the shell inner surface 3a of the pump housing 3 enclosing the rotors 11,
12 so that feed chambers 4 are formed through the rotors 11, 12 meshing with one another in
conjunction with the shell surface 3a, in which feed chambers the medium to be pumped is
pumped via connecting channels 16 from an induction chamber 5 into a pressure chamber 6.
There is a minimum clearance between the rotors 11, 12 as well as between the rotors 11, 12
and the shell surface 3a, in order to keep the leak rate of the pump to a minimum.
The pressure chamber 6, here embodied as an annular space, is formed by a pressure housing 7
that delimits the pressure chamber 6 respectively on the face side on the exterior circumference.
The inner delimitation of the pressure chamber 6 is realized via the exterior wall of the pump
housing 3, since the pump housing 3 extends through the pressure housing 7 and thus through
the pressure chamber 6. The pump housing 3 is attached to a base plate 8 by means of studs
40, to which base plate the bearing unit 9 is also attached by means of studs 41. The base plate
8 is in turn coupled to the pressure housing 7 via tie rods 42, so that the pump housing 3 is
attached on one side to the pump housing 7 via the studs 40, the base plate 8 and the tie rods
42. In the area of the studs 40 the pump housing 3 is provided with an annular flange 37 that
can be inserted into a correspondingly embodied recess 27 of the pump housing 7. The end 30
of the pump housing 3 facing away from the base plate 8 is supported in a recess 17 of the
pump housing 7; it is not screw-connected there, however, but only sealed via a seal 27. On the
face side, a further seal is sealed via the faceplate 15 that has a through hole 25 to introduce
the pumped medium into the induction chamber 5. Screw threads 26 are also provided to
receive connecting means or supply lines in the faceplate 15.

The one-sided support of the pump housing 3 on the pressure housing 7 has the advantage that the
combination, structured in a modular manner, of pump housing 3, bearing unit 9 and the feed
screws 1,2 arranged therein is decoupled from the compression strains of the pressure housing 7.
The pressure housing 7 can be designed for the respective system design pressure and can basically
be embodied as large as desired, whereby merely the recesses 17, 27 and the connecting devices
must be embodied such that the respective feed units or feed modules composed of pump housing
3 and bearing unit 9 can be mounted.
The pump is completed by inserting the feed unit into the pressure housing 7, with the pump
housing 3 integrated into the feed unit simultaneously forming the induction chamber 5 and
ensuring the separation of induction chamber 5 from pressure chamber 6.
Furthermore, flanges 14 are provided on the pressure housing 7 for the discharge lines, which can
remain installed in a fixed manner.
Separation devices can be provided in the pressure chamber 6 for the separation of gas phase and
liquid phase when multi-phase mixtures are pumped. These devices can be baffle plates or
settling zones for producing a flow speed close to zero, with a short-circuited line 13, connecting
the induction chamber 5 to the pressure chamber 6, preferentially being provided at points of this
type. In the embodiment shown, the short-circuited line 13 is embodied in the pump housing 3 and
arranged on the bottom side, so that liquid located in the lower part of the annular pressure
chamber 6, which liquid is filled up to the pressure housing 3, can be induced into the induction
chamber 5 and moved through the rotors 11,12 there. This causes a heat transfer, a sealing and a
lubrication of the rotors 11, 12. The embodiment shown is suitable in particular to ensure a safe
functioning of the pump even with very different wellhead pressures, which can rise from quasi
atmospheric pressures to over 100 bar.
Pump protection filters can be integrated or arranged in the inlet opening 25 or before it, in order to
hold back undesired particles and to prevent damage to the rotors 11,12.

WE CLAIM
1. Screw pump of single-entry, double-shaft construction with two screw shafts (1, 2) and a
pump housing (3) enclosing the screw shafts (1, 2) by forming feed chambers (4) and
externally delimiting the feed chambers (4) with is internal shell surface (3a), as well as
an induction chamber (5) for the medium to be induced and a pressure chamber (6) to
accommodate the medium pumped by the screw shafts (1, 2), whereby the pump
housing (3) is inserted into a pressure housing (7) and attached to the pressure housing
(7), so that the pressure chamber (6) enclose the pump housing (3) at least in part,
characterized in that the two screw shafts (1, 2) are supported with an external bearing
and separation devices are provided in the pressure chamber (6) to separate a pumped
multi-phase mixture into a gas phase and a liquid phase and that a short-circuited line
(13) is provided from the pressure chamber (6) to the induction chamber (5), through
which line separated liquid is guided back into the induction chamber (5).
2. Screw pump as claimed in claim 1, wherein the pump housing (3) extends through the
pressure housing (7).
3. Screw pump as claimed in claim 1 or 2, wherein the pump housing (3) is attached, in
particular screwed, to the pressure housing (7) on one side.
4. Screw pump as claimed in claim 3, wherein the pump housing (3) is attached to the
pressure housing (7) via a base plate (8).
5. Screw pump as claimed in claim 3 or 4, wherein the end (30) of the pump housing (3)
not attached to the pressure housing (7) is supported with clearance in a guideway (17)
in the pressure housing (7), and the pump housing (3) is sealed with respect to the
pressure housing (7) by means of a seal (27).

6. Screw pump as claimed in one of the preceding claims, wherein the screw shafts (1, 2)
are supported in a bearing unit (9) connected to the pump housing (3).
7. Screw pump as claimed in claim 6, wherein the bearing unit (9) is attached, in particular
screwed, to a base plate (8).
8. Screw pump as claimed in one of the preceding claims, wherein the screw shafts (1, 2),
the pump housing (3) and a bearing unit (9) of the screw shafts (1, 2) are combined to
form a feed module.
9. Screw pump as claimed in one of the preceding claims, wherein the short-circuited line
(13) is embodied in the pump housing (3).
10. Screw pump as claimed in one of the preceding claims, wherein the pump housing (3) is
arranged off-center in the pressure housing (7).
11. Screw pump as claimed in one of the preceding claims, wherein tie rods (42) are
arranged in the pressure housing (7) to prestress the pressure housing (7) with respect
to the screw shaft bearing (9).
12. Screw pump as claimed in one of the preceding claims, wherein the induction chamber
(5) is embodied in the pump housing (3).
13. Screw pump as claimed in one of the preceding claims, wherein the pump housing (3)
forms a part of the wall of the pressure chamber (6).
14. Screw pump as claimed in one of the preceding claims, wherein connecting devices (14)
for feed lines and discharge lines are embodied on the pressure housing (7).

ABSTRACT

SCREW PUMP OF SINGLE ENTRY, DOUBLE SHAFT CONSTRUCTION WITH TWO
SCREW SHAFTS
The invention relates to a screw pump of single-entry, double-shaft construction with an
external bearing of the two screw shafts (1, 2) and a pump housing (3) enclosing the screw
shafts (1, 2) by forming feed chambers (4) and externally delimiting the feed chambers (4)
with its internal shell surface (3a), as well as an induction chamber (5) for the medium to be
induced and a pressure chamber (6) to accommodate the medium pumped by the screw
shafts (1, 2). The pump housing (3) is inserted into a pressure housing (7) and attached to
the pressure housing (7), so that the pressure chamber (6) enclose the pump housing (3) at
least in part.

SCREW PUMP OF SINGLE ENTRY, DOUBLE SHAFT CONSTRUCTION WITH TWO SCREW SHAFTS

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