GB2556425A

GB2556425A - Cavity pump

Info

Publication number: GB2556425A
Application number: GB1715409.7A
Authority: GB
Inventors: Mcgarian Peter
Original assignee: Seepex GmbH
Current assignee: Seepex GmbH
Priority date: 2016-09-22
Filing date: 2017-09-22
Publication date: 2018-05-30
Anticipated expiration: 2037-09-22
Also published as: DE102016117910B4; DE202016008445U1; DE102016117910A1; GB201715409D0; GB2556425B

Abstract

An eccentric screw pump comprising at least a stator 1, a rotor 2, a drive 3, a suction housing 4 attached to the stator, a connecting shaft 9 attached to the drive. The connecting shaft is sealed by means of a shaft seal 13, a connection housing (lantern) 14 is arranged between the suction housing and the drive, to which the shaft seal is attached. The connection housing is closed and liquid-tight. A barrier pressure device may be attached to the shaft seal. Preferably a pressure monitoring device 20 is arranged in or on the connection housing. The connection housing may be provided with a detachable maintenance cover 21 and /or be box or cuboid shaped and / or filled with freshwater or freshwater-glycerol mixture. The pump, may be submersible. A controller may be included and / or equipped with an automatic shut-off device connected to the monitoring device.

Description

(54) Title of the Invention: Cavity pump

Abstract Title: Eccentric screw pump with liquid-tight connection housing or lantern (57) An eccentric screw pump comprising at least a stator 1, a rotor 2, a drive 3, a suction housing 4 attached to the stator, a connecting shaft 9 attached to the drive. The connecting shaft is sealed by means of a shaft seal 13, a connection housing (lantern) 14 is arranged between the suction housing and the drive, to which the shaft seal is attached. The connection housing is closed and liquid-tight. A barrier pressure device may be attached to the shaft seal. Preferably a pressure monitoring device 20 is arranged in or on the connection housing. The connection housing may be provided with a detachable maintenance cover 21 and /or be box or cuboid shaped and I or filled with freshwater or freshwater-glycerol mixture. The pump, may be submersible. A controller may be included and I or equipped with an automatic shut-off device connected to the monitoring device.

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Eccentric screw pump

Description

The invention relates to an eccentric screw pump comprising at least a stator, a rotor that rotates in the stator, a drive for the rotor, a suction housing that is attached (on the suction side) to the stator and a connecting shaft that is attached to the drive (and projects into the suction housing), the connecting shaft being sealed by means of a shaft seal (in order to separate the suction housing from the surroundings in a liquid-tight manner), a connection housing being arranged between the suction housing and the drive, to which connection housing the shaft seal is attached.

An eccentric screw pump of this kind is a pump from the group of rotating positivedisplacement pumps which are used to convey a wide variety of media and in particular highly viscous liquids in a wide variety of industrial sectors. Typical fields of application include, for example, the conveyance of sludge, oils and fats. The liquids to be conveyed may for example have a solids content.

The stator is made of a resilient material and is in general surrounded by a single-part or multi-part stator casing or stator housing. The housing attached to the stator on the suction side is generally referred to as a suction housing, and the housing attached to the stator on the pressure side as a pressure joint, for example. In principle, there is the possibility of operating a pump of this kind in the opposite conveying direction, such that the suction housing would then be arranged on the pressure side. Within the scope of the invention, the designation of the housing parts therefore does not depend on the actual conveying direction. Conventionally, the housing part facing the drive is referred to as the suction housing, while the opposite housing part is referred to as the pressure joint. The connection between the drive and the connecting shaft on the one hand, and between the drive and the rotor on the other hand, which connection is rotating and at the same time ensures eccentricity, is usually established via a coupling rod that is arranged in the suction housing and that is, for example, connected to the connecting shaft via a first joint and to the rotor via a second joint. The drive acts on the coupling rod via the connecting shaft. The connecting shaft can in this case be directly formed by the drive shaft of the drive. Preferably, however, the connecting shaft is a shaft separate from the drive that may also be designed as a stub shaft and in effect acts as a connecting piece between the drive shaft and the forcetransmitting components of the pump. In practice, the connection housing arranged between the suction housing and the drive is also referred to as a “lantern”. Said lantern is used to receive and/or fasten and to support both the suction housing and the drive, such that said connection housing or lantern is fastened on the base plate or directly on a foundation and supports and/or carries both the drive and the suction housing. The drive may, for example, be designed as a hydraulic drive, in particular if the pump is designed for underwater operation. Alternatively, electromotive drives or other types of drive are also used in pumps of this kind.

Eccentric screw pumps of the type described at the outset are known from practice to have a transition housing referred to as a lantern. In this case, the sealing of the pump housing (e.g. of the suction housing) against the surroundings plays an important role, since the material to be conveyed (e.g. liquid media) must of course be prevented from exiting the suction housing into the surroundings. On the drive side, the sealing is achieved by means of the shaft seal already described, which is designed as an axial face seal, for example. Axial face seals of this kind may be complementarily provided with a barrier pressure device and consequently a barrier pressure system. Problems arise in known embodiments when the shaft seal and/or the corresponding barrier pressure system are damaged, or do not function properly, since in such an instance of damage, there is the risk that the media to be conveyed leaks from the pump housing into the surroundings or into the region of the drive. This situation is particularly problematic if the pump is being used in a special environment and, for example, if environmentally harmful media are being conveyed. This is where the invention takes effect.

The object of the invention is to provide an eccentric screw pump of the type described at the outset which is distinguished by high environmental compatibility and reliable protection against the egress of media into the surroundings, while also being of simple construction.

In order to achieve this object, the invention teaches, in a conventional eccentric screw pump of the type described at the outset, that the connection housing (i.e. the lantern) is designed as a closed housing to be liquid-tight. According to the invention, said connection housing is therefore designed to receive (in the event of damage) media, e.g. liquid, entering the housing interior through the shaft seal.

The invention is based on the knowledge that the escape of media into the surroundings and into the region of the drive can very easily be prevented, even in the event of damage, if the connection housing already present on the pump is installed between the suction housing and the drive in a liquid-tight manner for receiving the liquid, such that although the liquid (e.g. oils or the like) can leak out from the suction housing through the shaft seal, which may or may not be damaged, said liquid then enters the encapsulated, self-sealed connection housing so as to be securely collected therein.

Since conventional shaft seals in eccentric screw pumps frequently do not guarantee absolute leakproofness, in pumps having a high risk of leakage, e.g. in submersible pumps, which are used when decommissioning oil platforms, barrier pressure systems are used on the shaft seals in order to prevent leakage. By means of the embodiment according to the invention having an “encapsulated” and sealed lantern, in addition to the barrier pressure system and according to the invention, additional security is provided in the form of a leak buffer.

Alternative and preferred embodiments are explained in the following.

As is generally known, the shaft seal may be designed as a(n) (single-acting or doubleacting) axial face seal. The invention draws on known embodiments in this context. In addition, an axial face seal of this kind may be equipped with a barrier pressure device or a barrier pressure system. A barrier pressure device of this kind is preferably used in conjunction with a double-acting axial face seal. Barrier pressure systems of this kind are also known from practice. Alternatively, it is within the scope of the invention for gland packing to be used as the shaft seal.

Within the scope of the invention, the liquid-tight connection housing used as the leak buffer is of particular importance, in particular in the case where the barrier pressure system fails or when the shaft seal itself no longer performs its function. The medium leaking out of the suction housing then enters said leak buffer in a controlled manner. For this purpose, the invention proposes, in a preferred embodiment, for at least one monitoring device for monitoring the liquid or other flowable media entering the housing to be arranged in or on the connection housing. A monitoring device of this kind may, for example, comprise at least one pressure sensor or be designed as a pressure sensor. Furthermore, a monitoring device of this kind may be provided with a controller or be connected to the pump control system, such that an automatic shut-off device can be provided, which stops the pump, or the drive thereof, when the connection housing is completely full (or full up to a particular level) or when the internal pressure in the connection housing exceeds a (previously established) reference value or maximum value. It is understood that, in such a case, corresponding signals can also be sent to a monitoring device comprising an optical and/or acoustic display. As an alternative to pressure sensors, other sensors may also be used. Therefore, a temperature sensor, for example, may also be used in order to achieve control (e.g. shut-off) of the drive of the pump on the basis of the temperature inside the connection housing. Alternatively or additionally, a fill-level sensor or the like is also conceivable as a sensor.

Moreover, the sealed connection housing is used not only as a leak-collection space, but also as protection against external pressure. In addition, there is also the possibility of filling the connection housing with a liquid in a targeted manner, and in particular if the pump is subjected to high external pressure, for example underwater at great depths, since in this case counterpressure can be generated by means of the liquid. Preferably, liquids which are also used in conventional barrier pressure systems are used here. The use of freshwater or freshwater-glycerol mixtures, for example, has thus proven expedient. The viscosity of a liquid of this kind should be from 5 to 10 centistokes.

It is further expedient if the connection housing is provided with a maintenance opening which is closed by means of a detachable cover, with the interposition of a (liquid-tight) seal. The shaft seal remains accessible for maintenance purposes via a maintenance opening of this kind in spite of the encapsulated design. In this case, the cover can, for example, be formed by a removable housing wall of the connection housing. It is therefore within the scope of the invention to design the connection housing to be (substantially) box-shaped, e.g. substantially cuboid. In an instance such as this, the cover may for example be formed by one of the side walls of the box-shaped housing, one of said side walls being fastened to the remaining side walls (on the end face in each case) with the interposition of a seal, and specifically in a detachable manner, e.g. by means of screw connections.

The drive itself is, as already described, fastened to the connection housing. In this case, it is expedient to attach the drive to a corresponding drive through-hole in the connection housing, with the interposition of a seal, such that the connection housing is also sealed off from the drive. It is therefore possible, for example, for the drive shaft of the drive to project into the connection housing via said through-hole, a stub shaft as the connecting shaft, for example, being attached to the drive shaft. Said stub shaft is located substantially inside the connection housing and projects through a shaft through-hole in the connection housing into the region of the suction housing where it is attached to the coupling rod, for example, via a swivel joint. The shaft seal, which receives the connecting shaft, is preferably fastened to the connection housing and particularly preferably attached to the shaft through-hole in the connection housing with the interposition of a seal.

The eccentric screw pump according to the invention is preferably used to convey media in sectors in which particularly high demands are placed on leakproofness, for example for environmental protection reasons. The eccentric screw pump can therefore be used, for example, for transporting oils or oil-containing media (e.g. oil-containing sludge). Particularly preferably, the pump can be used when decommissioning oil platforms, and therefore the pump is also suitable for underwater operation. On account of the design according to the invention, the (oil-containing) media to be conveyed is reliably prevented from being released into the environment, i.e. into the water. This is because the eccentric screw pump according to the invention is preferably designed as a submersible pump for underwater use. It is usual for the components that come into contact with seawater to be designed to be corrosion-resistant, i.e. resistant to saltwater corrosion. The connection housing according to the invention also has the advantage that it also protects the drive shaft from saltwater corrosion, and therefore said drive shaft does not necessarily need to be designed to be corrosion-resistant.

The invention will be described in more detail in the following with reference to the drawings in which only one embodiment is shown. In the drawings:

Fig. 1 shows an eccentric screw pump according to the invention in a (simplified) vertical cross-section,

Fig. 2 shows a detail from the object according to Fig. 1 in the region of the connection housing (partly disassembled), and

Fig. 3 shows the object according to Fig. 2 in perspective view.

In the figures, an eccentric screw pump is shown which can be used, for example, as a submersible pump underwater for conveying (oil-containing) sludge or the like, e.g. during decommissioning of oil platforms. In its basic construction, the eccentric screw pump comprises a stator 1, a (merely indicated) rotor 2 that rotates in the stator 1, and a drive 3 for the rotor 2. On the suction side, a pump housing is attached to the stator 1, which pump housing is referred to as the suction housing 4. A housing part attached to the stator on the pressure side is referred to as the pressure joint 5. The suction housing 4 is provided with a supply opening 6 which is closed by means of a cover 7 in the state shown. The drive 3 is equipped with an integrated drive shaft 8 which is attached to a connecting shaft 9. Said connecting shaft 9 is designed as a stub shaft in the embodiment shown. The rotor 2 is connected to the connecting shaft 9 via a(n) (indicated) coupling rod 10, the coupling rod 10 being attached to the connecting shaft 9 via a first joint 11 and to the rotor 2 via a second joint 12. In order for the suction housing 4 to be separated from the surroundings and/or the drive in a liquid-tight manner, the connecting shaft 9 is sealed by means of a shaft seal 13. Said shaft seal is designed, for example, as an axial face seal. Particular details are not shown in the figures. The shaft seal 13 or axial face seal is, as is generally known, equipped with a (merely indicated) barrier pressure device 15 for proper sealing of the shaft seal 13. Moreover, it can be seen in the figures that a connection housing 14 is arranged between the suction housing 4 and the drive 3, which connection housing is also referred to as a lantern. A connection housing of this kind receives both the suction housing and the drive and supports the suction housing and the drive. In this respect, the connection housing 14 can be fastened to a base plate 24. The shaft seal 13 is attached to said connection housing 14.

According to the invention, the connection housing 14 is not only designed as mechanical protection and not only as mechanical supports for the other pump components, but said connection housing is also designed as a closed housing to be liquid-tight and is thus in particular designed to receive liquid (or other such media) entering through the shaft seal 13 into the housing interior in the event of damage. According to the invention, the connection housing 14 thus forms a completely encapsulated leak buffer. If a medium (e.g. liquid) enters the region of the connection housing 14 from the suction housing 4 via the shaft seal 13 (e.g. if the axial face seal and/or the barrier pressure system fail(s)), it is reliably ensured by means of the encapsulated connection housing 14 that no medium to be conveyed is released into the surroundings.

The connection housing 14 comprising the components attached thereto is shown in particular in Fig. 2 and 3. It can in particular be seen that the connection housing 14 comprises a drive through-hole 16 on the drive side, through which the drive shaft 8 passes into the connection housing 14. The drive 3 is attached to said drive through-hole 16 or to the connection housing 14 with the interposition of a seal 17. Furthermore, the connection housing 14 comprises a second through-hole on the suction-housing side which is referred to as the shaft through-hole 18. The connecting shaft 9 (or stub shaft) passes from the connection housing 14 through said shaft through-hole 18 into the suction housing 4, and in a manner sealed by the shaft seal 13. The shaft seal 13, which receives the connecting shaft 9, or the sealing housing thereof, is therefore attached to the shaft through-hole 18 or to the connection housing in the region of said shaft through-hole with the interposition of another seal 19. Thus, overall, the shaft seal 13 and the drive 3 are also attached to the connection housing 14 in a sealed, liquid-tight manner.

At least one monitoring device for monitoring liquid entering the housing is arranged in or on the connection housing 14. Said monitoring device comprises a (merely indicated) pressure sensor 20 in the embodiment. Said pressure sensor may, for example, be integrated in a control system, such that the pressure sensor 20 identifies when the pressure inside the connection housing 14 exceeds a previously established reference value, such that the pump or drive can be shut off by means of the control system. This is because it is optionally possible for the connection housing to be filled (beforehand) with a liquid, in particular with freshwater or a freshwater-glycerol mixture. Liquids of this kind are also used for the operation of the barrier pressure system. An increase in pressure is detected by means of the pressure sensor 20 in the event of a leak in the region of the axial face seal. As an alternative to or in addition to a pressure sensor, the monitoring device may also comprise a fill-level sensor, in particular if the connection housing is not filled with a liquid during normal operation.

For reasons of clarity, the shaft seal 13 shown in Fig. 2 and 3 and the drive 3 are shown when not fastened/when being assembled.

The connection housing 14 is designed as a box-shaped housing in the embodiment shown. In this specific embodiment, said housing is for example cuboid. The connection housing 14 is provided with a maintenance opening which is closed by means of a detachable cover 21, with the interposition of a seal 22. Said cover 21 is in this case formed by a removable housing wall of the connection housing. Fig. 2 and 3 show the housing when the cover has been removed, such that both the seal 22 and the screw connections 23 can be seen, by means of which the cover 21, i.e. said housing wall, is fastened to the remaining housing walls in a liquid-tight manner. The seal 22 is in this case inserted in a corresponding end10 face groove which surrounds the housing opening.

Claims

1. Eccentric screw pump comprising at least a stator (1), a rotor (2) that rotates in the stator (1), a drive (3) for the rotor (2), a suction housing (4) that is attached to the stator (1), a connecting shaft (9) that is attached to the drive (3), the connecting shaft (9) being sealed by means of a shaft seal (13), a connection housing (14) being arranged between the suction housing (4) and the drive (3), to which connection housing the shaft seal (13) is attached, characterised in that the connection housing (14) is designed as a closed housing to be liquid-tight.

2. Eccentric screw pump according to claim 1, characterised in that the shaft seal (13) is designed as an axial face seal, in particular as a double-acting axial face seal.

3. Eccentric screw pump according to either claim 1 or claim 2, characterised in that at least one barrier pressure device (15) is attached to the shaft seal (13).

4. Eccentric screw pump according to any of claims 1 to 3, characterised in that at least one monitoring device for monitoring media, e.g. liquid, entering the housing is arranged in or on the connection housing (14), the monitoring device in particular being designed to monitor pressure.

5. Eccentric screw pump according to claim 4, characterised in that the monitoring device comprises at least one pressure sensor (20) or is designed as such.

6. Eccentric screw pump according to any of claims 1 to 5, characterised in that the connection housing (14) is provided with a maintenance opening which is closed by means of a detachable cover (21), with the interposition of a seal (22).

7. Eccentric screw pump according to claim 6, characterised in that the cover (21) is formed by a removable housing wall of the connection housing (14).

8. Eccentric screw pump according to any of claims 1 to 7, characterised in that the drive (3) is attached to a drive through-hole (16) in the connection housing (14), with the interposition of a seal (17).

9. Eccentric screw pump according to any of claims 1 to 8, characterised in that the shaft seal (13), which receives the connecting shaft (9), or the sealing housing thereof, is attached to a shaft through-hole (18) in the connection housing (14) with the interposition of a seal (19).

10. Eccentric screw pump according to any of claims 1 to 9, characterised in that the connection housing (14) is box-shaped, for example substantially cuboid.

11. Eccentric screw pump according to any of claims 1 to 10, characterised in that the connection housing (14) is filled with a liquid (during operation), in particular with freshwater or a freshwater-glycerol mixture.

12. Eccentric screw pump according to any of claims 1 to 11, characterised in that the eccentric screw pump is designed a submersible pump for underwater use.

13. Pump system comprising an eccentric screw pump according to any of claims 1 to 12 and comprising a controller connected to the eccentric screw pump.

14. Pump system according to claim 13, characterised in that controller is equipped with an automatic shut-off device for the eccentric screw pump and is preferably connected to the drive and to a monitoring device of the eccentric screw pump.

Intellectual

Property

Office

Application No: GB1715409.7 Examiner: Mr Mat Smith