WO2000050802A1

WO2000050802A1 - Device for the separation of solid objects from a flowing fluid

Info

Publication number: WO2000050802A1
Application number: PCT/SE2000/000254
Authority: WO
Inventors: Mats Henriksson
Original assignee: Vattenfall Ab (Publ)
Priority date: 1999-02-26
Filing date: 2000-02-09
Publication date: 2000-08-31
Also published as: AU3339100A; SE9900690D0; SE513588C2; SE9900690L

Abstract

A device for the separation of solid objects (scrap) from a fluid flowing in a tube conduit (2) comprises a housing (3) mounted between separate input and output parts (2', 2') of the tube conduit, within which housing the objects may be separated and accumulated. The two tube parts (2', 2') are interconnected via at least one screw-shaped canal (10) that is formed within the housing. The tube conduit forms an outer delimiting wall (2) against which the fluid and said objects are pressed by influence of the centrifugal force during their passage through the canal. In said delimiting wall (2) are one or several openings (17) through which the objects may be flung out from the canal loop and be collected in the housing (3).

Description

DEVICE FOR THE SEPARATION OF SOLID OBJECTS FROM A FLOWING FLUID

Technical Field of the Invention

This invention relates to a device for the separation of solid objects from a fluid flowing in a conduit tube, comprising a housing mounted between separate input and output parts of the tube, within which housing the objects may be separated from the fluid and accumulated.

Prior Art

In feed water circuits to nuclear reactors of the boiler type and also in other flow circuits in nuclear power plants, there is a need of separating solid objects that accidentally have come into the feed water circuit or the flow and that may lead to problems in the nuclear power plant, e.g., clogging of gaps at the control rods of the reactor or in fuel assemblies. The objects in question may be screws, nuts, springs, chips from turning, or similar, which are of a solid nature and have a larger density than the water. In order to overcome the problems that such objects may cause, different devices called scrap traps by persons skilled in the art have been previously suggested.

A previously suggested scrap trap is based on the use of outer and inner, concentrical tubes between which is deli i- ted a ring-shaped collection space and a central body of a rotation-symmetrical basic shape placed within the inner tube, which body together with the inner tube delimits a second ring-shaped space and which at an inlet end cooperates with a first flow converting device having the purpose of transforming an arriving fluid flow into a rotating flow in the second ring space and at an outlet end cooperating with a second flow converting device having the purpose of transforming the rotating fluid flow into an outgoing, axial flow downstream of the scrap trap. By the fact that the fluid flow rotates in the second ring space, the fluid and any accompanying solid objects are submitted to influence by the centrifugal force, which involves that the objects are pressed against the inside of the collection space via holes at the downstream end of the inner tube. However, in practice, such a scrap trap has turned out to be difficult to produce because the two flow converting devices have to be given a complicated shape. The complicated shape involves that testing and producing become time-consuming and costly.

Objects and Characteristics of the Invention

The present invention aims at removing the above-mentioned inconveniences and creating an improved scrap trap or separation device. Therefore, a primary object of the invention is to create a separation device that is comparatively simple to manufacture from a technical point of view, that may not only^' be produced in a cost-effective way, but also manages to separate and keep the scrap objects in a flow in a reliable way. Another object is to create a separation device which, when passed by a main water flow in, e.g., a feed water conduit, does not cause flow disturbances such as the formation of vortices, turbulence and similar, which in turn could cause detrimental vibrations in the conduit system downstream of the separation device. Further objects of the invention is to provide a separation device that may be mounted into existing conduit tubes, and then the device shall not cause any considerable pressure drop in a fluid flow when it passes the separation device.

According to the invention, at least the primary object is achieved by the features that are defined in the characteri- zing clause of claim 1. Advantageous embodiments of the device according to the invention are further defined in the dependent claims .

Brief Further Elucidation of the Prior Art Centrifugal separation devices for general industrial purposes have been previously disclosed in, e.g., US 1931193, US 2425110, US 2512253, US 2616563, US 2986278, US 4834887, EP 0005494, EP 0162441, EP 0267285 and FR 2630658. However, no one of these separation devices is based on the use of screw-shaped canals of the type that characterizes the present invention according to the appended claims. For this reason, the previously known devices are not suited for the separation of scrap from feed water to nuclear reactors. Brief Description of the Attached Drawing

In the drawing: Fig 1 is a longitudinal section through a separation device according to the invention, and

Fig 2 is a cross-section A-A in Fig 1.

Detailed Description of a Preferred Embodiment of the Invention In the drawing, reference numeral 1 designates general- ly a separation device that is mounted in connection with a conduit tube 2 through which a fluid may be conveyed. In practice, the separation device is in first hand intended to being used in conduits for the conveyance of water, in particular feed water in nuclear power plants. The separation device is placed between first and second parts 2', 2" of the conduit tube 2. As may be seen by the arrows in the drawing, the tube part 2' is situated on an upstream side of the device and the tube part 2" on a downstream side.

The separation device comprises a housing designated 3 in its entirety, which according to the example is composed of a tubular, more specifically cylindrical outer wall 4 and two opposed gable walls 5, 5' .

To one end of the housing 3, namely the lower end, is connected an outlet 6 for the evacuation of collected scrap, e.g., in connection with a revision of a nuclear power plant.

The outlet 6 may be connected with two stop valves (not shown) , by means of which collected scrap objects may be removed from the housing under controlled conditions. It should be noted that the outlet 6 is located at the lowest point of the housing 3. The two tube parts 2' , 2" are inter-connected via a screw-shaped canal loop, which is wholly or partly built-in into the housing 3. According to the example in the drawing, the canal loop comprises four canals 10.

Between the tube conduit 2 and the cylinder wall 4 of the housing 3 is delimited a ring-shaped gap 16 that serves as a collection space for the scrap objects that are to be separated from the water or fluid flow. The tube conduit 2 serves as an outer delimiting wall in which are recessed openings 17. Within the tube conduit 2 is mounted a central, elongated core part 26 that is cylinder-shaped and has a diameter that is smaller than the inner diameter of the tube conduit 2. In this way, a ring-shaped gap 27 is formed between the core part 26 and the tube 2.

At its two opposed ends, the core part 26 has end bodies 28, 28', either of which being produced departing from an initially cylinder-shaped blank, in which are recessed four tan- gentially separated grooves 29 of a cross-sectionally slightly rounded shape and of a screw-shaped extension. Each such groove 29 has its largest cross-sectional area adjacent to a cross- ' shaped end surface 30 that extends perpendicularly to the axial extension of the tube 2. From this outer end, the individual groove has a gradually decreasing depth up to a region where the groove transposes into an individual canal 10. In said region, the groove has a depth that corresponds to the width or depth of the ring gap 27. The diameter of the individual end body corresponds to the inner diameter of the tube 2. This involves that the end body cuts off the cross-section of the tube 2. In the region where the individual groove 29 has its smallest depth, it transposes into a screw-shaped canal 10 that in its continuation is restricted by a screw-shaped partition wall 31 provided in the ring gap 27. Each partition wall may extend one or several turns along the central core part 26. The openings 17 are reces- sed in the wall of the tube 2. These are placed separately, preferably equidistantly separated along each individual canal 10.

Furthermore, in the individual canal 10 are provided one or several guiding rims 32. More specifically, according to the example, two such guiding rims 32 are provided, which are placed on the envelope surface of the core part 26 being distal from the outer delimiting wall of the canal, i.e., the tube 2. The height of the guiding rims 32 is smaller than the depth of the canal 10.

The Function of the Device According to the Invention

Presuming that the tube conduit 2 consists of a feed water conduit, water from the incoming tube part 2' will flow in with a large velocity (10 m/s) into the different canals 10 via the grooves 29 in the end body 28. When the water passes through the individual, screw-shaped canal 10, it is submitted to the influence of the centrifugal force. This involves that the water and possible, accompanying scrap objects are pressed against the inside of the outer delimiting wall that consists of the wall 2. It is true that during operation, the ring gap 16 is always filled with water, which involves that the water stream between the canals 10 and the ring gap 16 via the openings 17 becomes moderate. However, the scrap objects that usually have a consi- derably larger density than water and are pressed by the centrifugal force against the delimiting wall 2, will be flung out ' through the openings 17 and be trapped in the ring gap 16. By the fact that the housing 3 is vertical and has a lowest point at the evacuation outlet 6, the trapped scrap objects will be accumulated in the region of the outlet. The water that has been liberated from scrap objects, passes out in the outgoing tube part 2" via the grooves 29 in the end body 28', which transforms the water flow into a conventional, axial flow in the tube part 2". As seen in the stream direction, these grooves 29 have a gradually increasing depth in the direction of the free end of the end body 28' . In this context, it should be pointed out that the sum of the cross-sectional areas of the four canals 10 corresponds to the cross-sectional area of the individual tube part 2', 2". One advantage of the separation device according to the invention is that it may be manufactured in a rational way despite of comparatively complicated flow paths. Another advantage is that the device guarantees an effective and reliable separation of scrap objects from the water or the fluid, while ^~ the collected scrap objects are maintained in a reliable way in the collection space.

Claims

1. A device for the separation of solid objects from a fluid flowing in a tube conduit (2), comprising a housing (3) mounted between separate input and output tube parts (2' , 2" ) , within which housing the objects may be separated from the fluid and accumulated, c h a r a c t e r i z e d in that the two tube parts (2', 2" ) are inter-connected via an at least partly screw- shaped canal (10) that is placed inside the housing (3) and has an outer delimiting wall in the form of said tube conduit (2), against which the fluid and any present solid objects are pressed by influence of the centrifugal force during their passage through the canal, and in which there are one or several openings (17) through which the objects may be flung out of the canal and be collected in the housing, that the canal (10) extends between two end bodies (28, 28'), which are separated by a cylindrical core part (26) with a diameter that is smaller than the diameter of the tube conduit as well as of the end bodies, a ring-shaped gap (27) being delimited between the core part (26) and the tube conduit (2) , and in that, in a portion of each end body (28, 28') turned away from the core part, is provided at least one screw-shapedly extending groove (29) serving as a canal inlet and outlet, respectively, which groove transposes into a canal-forming space (10) that is delimited by at least one screw-shaped partition wall (31) provided in the ring gap (27) .

2. Device according to claim 1, c h a r a c t e r i z e d in that in the canal (10) are provided one or several guiding rims - (32) distal from the tube conduit (2), the height of these rims being smaller than the depth of the canal.

3. Device according to claim 1 or 2, c h a r a c t e r i z e d in that the individual end body (28, 28') has a cylindrical basic shape, the individual groove (29) in the same having a depth that gradually decreases from an outer end towards an inner end adjacent to the canal (10).