Slurry pump valve

Abstract: Valve for application in a sludge pumping system, said valve (1) being provided with a valve body (5) which is axially movable in guide means (7), said valve body having an elastic sealing ring (12) and a metal supporting element (10) attached to it. The said valve body is provided with a valve seat (9) on which valve seat an elastic sealing ring (13) and a metal supporting element (17) are mounted, whereby the sealing rings (12) and (13) only come into mutual contact with eachother, and that the supporting elements (10) and (17) only come into mutual contact with eachother.

Description: Valve for application in a sludge pump system, as further outlined in the preambule of claim 1. Such valves are applied in pumping systems, inter alia in combination with a displacement pump. In such cases, aggressive, abrasive and corrosive liquids containing granular material, such as sand, coal, ore or, for example, mining waste, often at high temperatures, are frequently pumped over large distances under high to very high pressures. It is clear that these conditions place extremely high demands on the durability of such a system's components, among which the valve. A valve such as that mentioned in the preamble is known from Dutch patent application 8600545. The valve described herein is partially provided with a metal to metal contact-surface and partially with a metal to elastic material contact-surface. In the known valve, the metal to elastic material contact-surface is employed to allow sludge material which is present between the contact-surfaces when the valve closes, and, as a result, is under extra-high pressure, to escape via grooves provided in the metal contact-surface, without causing damage to the valve. The use of elastic sealing rings, especially under the circumstances described above, creates new problems, as is also mentioned in the Dutch patent application already cited above. It appears in practice that the elastic material wears very quickly, thereby rapidly failing in its intended function. The result is that the elastic sealing rings must be replaced by new ones at relatively short intervals, thereby requiring the system to be shut down, with all the attendant consequences. Attempts have been made to avoid having to replace the sealing rings by new ones by making the rings symmetric, in such a manner that rings which are worn on one side can be used again, before being discarded, by turning them over. However, this shows quite clearly that willingness to apply these elastic materials under such extreme circumstances is showing a considerable decline. The object of the current invention is to provide a valve which, under equivalent circumstances, has a longer life and longer maintenance-free periods than the known valve. To this end, the valve according to the invention has characterising features as outlined in claim 1. The invention makes use of the understanding that the high degree of wear of the elastic material in the known valve can largely be attributed to those particles in the sludge which, due to their presence on the contact-surface between metal and elastic material, remain on the metal part of the contact-surface during the closing of the valve and, thus, are pushed into the elastic material, resulting in heavy damage to it in a short time. In contrast to the described tendency, the invention offers a solution whereby the aforesaid particles are, on both sides, elastically embedded in the elastic contact-surface between the elastic sealing rings of the valve so that, under the same circumstances, the valve stands far less chance of sustaining damage than was previously the case. In using the common elastic materials, this already results in the life of the elastic material being prolonged, so that the periods between maintenance can be increased without any problems, thereby reducing costs. In the known sludge pump systems, it is usual to subject the solid particles in the medium to be transported to a pre-transport reduction process, with the aim of sufficiently reducing the average size of the particles. This reduction process can, by using the valve according to the invention, be shorter, without risking damage to the valve by sludge particles having a large average size, this being due to the two-sided elastic embedding of the sludge particles trapped between the elastic sealing rings of the valve during closing. The presence of the metal supporting elements in the valve according to the invention appeared, in practice, to be necessary, because the elements support the elastic material of the sealing rings on the valve body and the valve seat. The valve according to the invention has, thus, also been made suitable for working pressures in the order of 30 - 300 bar. One embodiment of the valve according to the invention is characterised in that the form of the cross-section of the sealing rings and of the supporting elements is chosen in such a way that, when the valve body is moving in the direction of the valve seat, the sealing rings are the first parts to come into contact with each other. The advantage of the embodiment is, besides the two-sided embedding of the sludge particles in the elastic contact-surface during valve closure and the coming together of the sealing rings, that just before closure of the metal supporting elements, the metal contact-surface concerned is cleaned by the sludge as it escapes from between the surfaces. In another embodiment of the valve according to the invention, the point of the contact-surface of the sealing rings furthest from the point where the contact-surfaces of the sealing rings and of the supporting elements meet has sufficient freedom to be able to move radially with respect to the motional axis of the valve body. The freedom to execute the aforementioned motion forms a basis for the further notion of making the elastic contact-surface curvilinear, hereby allowing classification according to the technical effects to be discussed below. It is preferable to have a curved contact-surface between the elastic sealing rings, particularly a contact-surface with a spherical form, whereby a somewhat crooked descent of the valve body, arising, for example, from play in the guiding media, will be very much less likely to result in an incorrect seating, so that wear will not significantly increase. As far as the wear process of the respective contact-surfaces during operation is concerned, the geometry of the contact-surfaces plays an important role, such that adopting one or more measures is characteristic for a possible embodiment according to the invention. These measures are: that the maximal external diameter of the elastic sealing ring is, at most, 1.05 times bigger than the maximal diameter of the contact-surface concerned, that the maximal external diameter of the elastic sealing ring is, at most, 1.05 times larger than the maximal diameter of an encasing element connected to the sealing ring and fixed to the high-pressure side of the valve stem, that an incision is made in the metal supporting element at the low-pressure side near the contact-surface. These measures ensure that, as the wear process of the contact-surfaces concerned progresses, the geometry of the valve according to the invention remains conserved for as long as possible, despite the fact that, in the long term, the valve body comes to rest in a progressively lower position the valve seat. In addition to the effects summarised above, it should be mentioned that, under the extreme conditions stated earlier, the lifetime of the known valves is, as a rule, never longer than a month. The current invention paves the way for embodiments of valves which possess longer average lifetimes. A further advantage pertaining to the incision is that, if the supporting element becomes somewhat worn away by the valve body, the valve body will not, as it were, partially fall between the supporting element and the valve seat. In this way, stair-like wearing-effects on the metal contact-surface are avoided. The invention and the attendant advantages thereof will be further elucidated with the aid of the accompanying figure, which shows a cross-section of a possible embodiment of the valve according to the invention. The figure shows a possible embodiment of a cross-section of a valve 1 which, for example, is used as a suction valve or a delivery valve in, for example, displacement pumps for pumping mixtures consisting of liquid and solid matter. Said pumping usually occurs at under high pressure. The valve 1 has a high-pressure side 2 and a low-pressure side 3. The low-pressure side 3 is that side of the valve 1 where, at least in the case whereby the valve 1 is closed, the pressure is lower than at the high-pressure side 2. The valve 1 is provided with a valve casing, which is not depicted, and a valve body 5 which can move in said valve casing. Attached to the valve body 5 is a valve stem 6 which is mounted in the valve casing in such a way as to be movable in a sleeve 7. The sleeve 7 is attached to the valve casing, which valve casing is not depicted, via securing media 4. If the valve 1 is of the self-working type and is moved by the pressure of the medium at the sides 2 and 3, then, in general, a spring 8, located between the valve body 5 and the sleeve 7, will be present in the valve casing. However, if the valve is not of the self-working type, then the movement of the valve body 5 will be effected by way of media which are not depicted and which can be operated from without. Located in the valve 1 is a valve seat 9 which has an essentially conical contact-surface. The valve body 5 also possesses a corresponding conical contact-surface. The valve body 5 possesses a metal supporting element 10 and the valve seat possesses a metal supporting element 17 in order to form a conically extending metal-to-metal contact-surface 11. An elastic ring 12 is mounted on the valve body 5 and an elastic ring 13 is mounted on the valve seat 9. Both rings 12 and 13 possess corresponding contact-surfaces in order to form the elastic contact-surface 14. The internal diameter and external diameter, respectively, of the rings 12 and 13 are such that, when the valve 1 closes, the rings 12 and 13 first make contact at a point 19 between the contact-surfaces 11 and 14, and only later, when the valve body 5 moves further downwards, can the metal-on-metal contact between the valve seat 9 and the metal element 10 also be effected. In the process, the elastic ring 13 in the valve seat gives way vertically and outwardly. It is desirable that the distinct contact-surfaces 11 and 14, which are preferably bordering on each other, have a curved form whereby, for example, one of the contact-surfaces is concave and the other is correspondingly convex, as appears in the figure. The sealing ring 12 is implemented in such a way that its largest diameter is larger than the diameter of the elastic contact-surface 14, whereby, under circumstances of either surface-wearing or deterioration of the elastic properties of, in particular, an uppermost lip section 15 of the the ring 13, a good seal is guaranteed at the surface 14. The largest diameter of the surface 14 is also greater than the largest diameter of an element 16 which encapsulates the ring 12 and is mounted on the valve body 5. This means that, in the event of wear of a bulging section 18 of the ring 12, the diameter will be restored to that of the encapsulating element 16, and no stair-like wear will occur. An incision has been made along the circumference of the underside of the element 10 in such a way that, if the receiving surface of element 10 becomes somewhat worn, the contact-surface 11 will not show a stair-like wear-pattern, whereby the element 10 would partially drop between the walls 21 of element 17.

Claims: Valve for application in a sludge pump system, said valve (1) being provided with a valve body (5) which is axially movable in guide means (7), said valve body having a first elastic sealing ring (12) and a first metal supporting element (10) attached to it and being provided with a valve seat (9), characterised in that, on the valve seat (9), a second elastic sealing ring (13) and a second metal supporting element (17) are mounted, located so that when the valve is closed, the first sealing ring (12) and the first supporting element of the valve body (7) only contact the valve seat (9) via the second sealing ring (13) and the second supporting element (17) respectively. Valve according to claim 1, characterised in that the respective sealing rings (12,13) and the supporting elements (10,17) come into contact with each other along essentially conical contact-surfaces (11,14). Valve according to one of the claims 1 or 2, characterised in that the form of the cross-section of the sealing rings (12,13) and the supporting elements (10,17) is chosen in such a way that, when the valve body (5) is moving in the direction of the valve seat (9), the sealing rings are the first parts to come into contact with each other. Valve according to one of the claims 2 or 3, characterised in that the point of the contact-surface (14) of the sealing rings furthest from the point where the contact-surfaces of the sealing rings (14) and of the supporting elements (11) meet has sufficient freedom to be able to move radially with respect to the motional axis of the valve body. Valve according to one of the claims 1-4, characterised in that the contact-surface (14) formed between the sealing rings (12,13) is curved. Valve according to claim 5, characterised in that the contact surface (14) of the sealing rings is curved in such a manner that the first sealing ring (12) has a convex surface and the second sealing ring (13) has a concave surface. Valve according to claim 6, characterised in that the radius of curvature of the first sealing ring (12) is different to the radius of curvature of the second sealing ring (13). Valve according to one of the claims 1-7, characterised in that the maximal external diameter of the first elastic sealing ring (12) is, at most, 1.05 times larger than the maximal diameter of the contact-surface (14) of the sealing rings. Valve according to one of the claims 1-8, characterised in that the maximal external diameter of the first elastic sealing ring (12) is, at most, 1.05 times larger than the maximal diameter of the encapsulating element (16) which is fixed to the high-pressure side (2) of the valve stem (6) and connected to the first sealing ring (12). Valve according to one of the claims 1-9, characterised in that, in the metal supporting element (10), an incision (20) is made at the low-pressure side (3) near the contact-surface (11) of the supporting elements. Valve according to one of the claims 1-10, characterised in that the sealing rings (12,13) already mentioned above are, respectively, implemented as separate clamped rings or vulcanised rings.

Inventors: DE KONING CORNELIS JOHANNES, DE KONING, CORNELIS JOHANNES
Applicants: HOLTHUIS BV, HOLTHUIS B.V.
Application year: 1991
Main classification: F04B21
IPC codes: F04B53