The invention relates to an eccentric screw pump for delivering liquid and/or granular media and the use of such an eccentric screw pump.
Eccentric screw pumps are pumps for delivering a plurality of media, in particular viscous, highly viscous and abrasive media such as for example sludges, manure, crude oil and greases. Eccentric screw pumps known from the prior art comprise a rotor and a stator, wherein the rotor is accommodated in the stator and moves eccentrically in the stator. The stator is constituted by a housing with a helically coiled inner side. As a result of the motion of the rotor and mutual contact, meandering delivery spaces are formed between stator and rotor, by means of which liquid media can be transported along the stator. The rotor performs an eccentric rotary motion around the stator axis or around the longitudinal axis of the eccentric screw pump. The outer screw, i.e. the stator, has the form of a double thread, whilst the rotor screw is only single thread. Eccentric screw pumps are particularly well suited for the delivery of water, crude oil and a plurality of other liquids. The shape of the delivery spaces is constant during the motion of the rotor inside the stator, so that the delivered medium is not squashed. With a suitable design, not only fluids but also solids can be delivered with eccentric screw pumps.
An excess pressure may arise in the eccentric screw pump during the delivery of certain media. For this application, eccentric screw pumps require at least one safety device against excess pressure. This is solved in the prior art by disposing a connection line between the inlet flange of the suction side of the pump body and the discharge flange of the pressure side. The connection line is an external pipeline and/or hose line into which an overflow or safety valve is integrated.
A drawback with the described prior art is that the connection line represents an external attachment to the eccentric screw pump. On account of the necessary design height, therefore, the space requirement for the eccentric screw pump is increased. In addition, there is an increased risk of external attachments being damaged by moving loads. The requirement for safety devices against excess pressure has hitherto prevented the use of eccentric screw pumps in certain areas of application. For example, the use of eccentric screw pumps in boreholes could be advantageous. However, the space is limited here by the diameter of the borehole. In addition, there is the risk of an external pipeline on the eccentric screw pump being damaged when the eccentric screw pump is inserted into the borehole.
The problem of the invention, therefore, is to make available an eccentric screw pump with at least one safety device against excess pressure, which is characterised by a simple and uncomplicated design and in particular does not exhibit the aforementioned drawbacks of the prior art.
The above problem is solved by an eccentric screw in accordance with the invention.
The invention relates to an eccentric screw pump for delivering fluids and/or granular media, in particular viscous, highly viscous and abrasive media. An eccentric screw pump comprises a pump body and a drive unit. The pump body is split up into an inlet region with an inlet connecting piece, a pump unit and an outlet region with an outlet connecting piece. The inlet connecting piece and the outlet connecting piece comprise standardised flanges for connection with further pipe sections for delivering the pumped medium.
The pump unit is constituted by a rotor and a stator. The stator is constituted by a housing with a helically coiled inner side. The rotor is constituted as a kind of round threaded screw and moves eccentrically in the interior of the stator, as a result of which the delivery chambers constituted between the rotor and the stator are mobile in the delivery direction.
The inlet region of the eccentric screw pump forms the suction side and the outlet region of the eccentric screw pump forms the pressure side. A bypass connection with at least one safety valve is disposed between the pressure side and the suction side. Said bypass line serves for the uptake and return of back-flowing medium between the pressure side and the suction side of the eccentric screw pump, in order to prevent an uncontrolled excess pressure from building up inside the eccentric screw pump. An excess pressure has to be reduced in a controlled manner in order to hinder or prevent damage to the eccentric screw pump.
According to the invention, the bypass connection and the safety valve are integrated into the pump body of the eccentric screw pump. In particular, the bypass connection and the safety valve are integrated in the region of the pump unit into the pump body of the eccentric screw pump.
According to a first preferred embodiment of the invention, the stator comprises an additional casing. In particular, the stator is disposed in a casing tube, wherein the stator has an outer circumference which is smaller than the inner circumference of the casing tube, so that an intermediate space is formed between the stator and the casing tube. Said intermediate space is in fluidic connection with the respective internal spaces of the inlet region and the outlet region and constitutes the bypass connection. Furthermore, at least one safety valve is assigned to the intermediate space. When an excess pressure builds up on the pressure side of the eccentric screw pump, part of the delivered medium is conveyed as a return flow via the intermediate space back into the inlet region of the pump body and the excess pressure is thus reduced.
According to a second preferred embodiment of the invention, the stator is disposed in a stator sleeve. The inner circumference of the stator sleeve broadly corresponds to the outer circumference of the stator, so that the stator sleeve lies with its inner circumference extensively over its surface area against the outer circumference of the stator. At least one connection line parallel to the longitudinal axis of the eccentric screw pump is constituted between the stator and the stator sleeve. The connection line is in fluidic connection via first and second connections with the respective internal spaces of the inlet region and the outlet region and constitutes the bypass connection. The first and second connections are in particular bores in the housing of the pump body, in particular in the regions in which the outlet and inlet region each border on the pump unit. Furthermore, at least one safety valve is assigned to the at least one connection line. When an excess pressure builds up on the pressure side of the eccentric screw pump, part of the delivered medium is conveyed as a return flow via the at least one connection line back into the inlet region of the pump body.
The at least one connection line between the stator and the stator sleeve is constituted for example by a continuous recess in the external lateral surface of the stator parallel to the longitudinal axis of the eccentric screw pump. For example, a continuous groove is constituted on the external lateral surface. The recess extends along a length of the stator, in particular along the entire length of the stator.
According to a third preferred embodiment of the invention, the rotor comprises a hollow space along its rotor longitudinal axis. The hollow space can for example be a through-bore through the rotor along the rotor longitudinal axis. Alternatively, the hollow space can already be integrated into the rotor during production, whereby the latter is already cast correspondingly hollow or is moulded hollow by means of another suitable process. The hollow space of the rotor is in fluidic connection with the respective internal spaces of the inlet region and the outlet region and constitutes the bypass connection. At least one safety valve is assigned to the hollow space. When an excess pressure builds up on the pressure side of the eccentric screw pump, part of the delivered medium is conveyed as a return flow via the internal hollow space of the rotor back into the inlet region of the pump body.
According to a fourth preferred embodiment of the invention, the eccentric screw pump comprises a stator with at least one return flow channel. The return flow channel is constituted parallel to the longitudinal axis of the eccentric screw pump along the stator length. The at least one return flow channel is in fluidic connection with the respective internal spaces of the inlet region and the outlet region and constitutes the bypass connection.
The return flow channel is constituted in particular in a region between an inner thread pitch of the stator and the external lateral surface of the stator. The return flow channel does not comprise any open connection to the inner thread pitch of the stator and/or to the external lateral surface of the stator. This means that the return flow channel is constituted in the stator material.
At least one safety valve is assigned to the return flow channel. When an excess pressure builds up on the pressure side of the eccentric screw pump, part of the delivered medium is conveyed as a return flow via the at least one return flow channel of the stator back into the inlet region of the pump body. The at least one return flow channel is preferably cast in the stator during production. Alternatively, the at least one return flow channel can also be formed subsequently after the production of the stator.
According to an embodiment of the invention, the safety valve is disposed inside the return flow channel, preferably in a region between the inlet region and the pump unit. According to an alternative embodiment, the safety valve is integrated into the outlet region of the pump body. Provision is made here such that an outlet opening of the safety valve emerges into a return flow channel via a first connection. A plurality of return flow channels and a plurality of correspondingly disposed safety valves can also be used in this embodiment. When an excess pressure builds up on the pressure side of the eccentric screw pump, part of the delivered medium is conveyed as a return flow via the at least one return flow channel of the stator back into the inlet region of the pump body.
The safety valve for preventing an inadmissible pressure rise inside the eccentric screw pump can be a spring-loaded safety valve, a weight-loaded safety valve or a medium-loaded safety valve. Preferably, the safety valve is an overflow valve for releasing pressure from the interior of the eccentric screw pump when inadmissible excess pressure occurs inside the closed system.
A previously described eccentric screw pump according to the invention can be used in particular for the delivery of fluid and/or granular media in a borehole. Such an eccentric screw pump can generally be used whenever the development of excess pressure is to be expected, for example on account of the medium to be delivered.
As a result of the integration of the return flow circuit with the safety or overflow valve in the pump body of the eccentric screw pump, its structure remains compact. In particular, the integrated return flow circuit generally does not lead to an increase in the size of the pump body of the eccentric screw pump.
The integration of a return flow circuit is possible not only for eccentric screw pumps with a stator made from an elastomer. It is just as conceivable to integrate, in a comparable way, a return flow circuit in a so-called stepwise vortex pump. A stepwise vortex pump is described for example in US 2008/0050249 A1. In contrast with the eccentric screw pump, this pump does not comprise a stator made of rubber, which can be attacked by the delivered medium, for example during the pumping of petroleum or suchlike. Instead, the pump is constituted stepwise, comprises only corrosion-resistant metal components and operates in a centralized manner. Vibrations in the system can thus be eliminated, the pump can operate at raised temperatures and can be constituted smaller.
Examples of embodiment of the invention and its advantages are explained in greater detail below with the aid of the appended figures. The size ratios of the individual elements with respect to one another in the figures do not always correspond to the actual size ratios, since some forms are represented simplified and other forms magnified compared to other elements for the sake of better clarity.
Identical reference numbers are used for identical or identically acting elements of the invention. Furthermore, for the sake of clarity, only reference numbers that are required for the description of the given figure are represented in the individual figures. The represented embodiments only represent examples as to how the device according to the invention can be constituted and do not represent a conclusive limitation.
Medium M to be delivered passes via inlet flange 15 of inlet region 4 into eccentric screw pump 1, is transported by meandering delivery spaces 14 in delivery direction Fr through the pump unit and is pumped out of eccentric screw pump 1 via outlet flange 16 of outlet region 6. Bypass line 2 with a safety valve 20, for example with an overflow valve 21, is disposed between outlet flange 16 and inlet flange 15 by means of suitable connection means 17, 18. In particular, overflow valve 21 is disposed directly on a connection means 17 which is assigned to outlet flange 16. Bypass line 2 extends parallel to pump body 3 between overflow valve 21 and connection means 18 which is assigned to inlet flange 15.
With the represented safety circuit, when an excess pressure builds up on the pressure side of eccentric screw pump 1, part of delivered medium M is conveyed as return flow M
One or more overflow valves 40 for limiting the delivery pressure of eccentric screw pump 30-1 are also disposed in hollow space 43 or in the two connections 47 between hollow space 43 and the interior of pump body 3 in inlet region 4, the outlet of said overflow valves emerging into the interior of pump body 3 in inlet region 4. The arrangement of overflow valve 40 in hollow space 43 is represented in detail in
One or more overflow valves 40 for limiting the delivery pressure are disposed inside connection line 52 or between connection line 52 and second connection 56 on suction side S of eccentric screw pump 30-2.
Overflow valve 40 can also be integrated and disposed in the pump body in such a way that medium M
The invention has been described by reference to a preferred embodiment. A person skilled in the art can however imagine that modifications or changes to the invention can be made without thereby departing from the scope of protection of the following claims.
Number | Date | Country | Kind |
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102013111716.3 | Oct 2013 | DE | national |