Valve with a structure for mitigating abrasive wear or galling of sealing surfaces between a seat ring and a closure member during their relative sliding contact with each other

A ball valve or any other type of valve in which sealing surface of the seat ring and surface of closure member keep relative sliding contact during opening and closing movement of the valves. One or more annular grooves cut into sealing surface of the seat ring around it's bore are filled with lubricant or grease used for lubricating the surfaces so as to avoid or mitigate their abrasive wear or galling caused by frictional heat.

FIELD OF THE INVENTION

The present invention is related to valves, particular to the valves in which sealing surfaces of seat rings and closure member suffer easily damage during their relative sliding contact, and the invention will protect them from abrasive wear or galling caused by frictional heat by means of a structure arranged in the sealing surface of the seat rings.

BACKGROUND OF THE INVENTION

In generally, sealing property between the sealing surfaces of the seat ring and closure member is a significant factor to affect leakage of the valve when it is in its fully closed position.

The valve in which the seat ring is made of polymer, known commonly as soft seated valve, has excellent sealing property, and the galling does not occur between the sealing surfaces of its seat ring and closure member so easy as metal seated valve does because of low friction coefficient of the polymer. The valve has long enough lifetime in general service, and is widely used.

For the fluid flowing through the valve at a higher temperature or carrying abrasive particles and/or powders, high temperature and wear resistant metal seated valve with hard facing is usually recommended to be first selected. Hard alloy and the like are normally coated, plated or welded on the surfaces of the seat ring and closure member when the metal seated valve are designed and manufactured. It is well known that the trademarks of mating coating material coated on the surfaces are different from each other generally, and their hardened hardness also varies in order to protect the sealing surface of the seat ring and the surface of the closure member against mutual abrasive wear or galling. The mating surface has to be machined precisely, too, and grinded with each other if necessary so as to increase their mutual sealing property. Therefore, not only the coating material should be resistance to high temperature, abrasion and corrosion, but it is also possessed of strong bond strength with its metallic matrix, furthermore it has low friction coefficient between the coated surfaces for lower operative torque or thrust of the valve.

In recent years, valve manufacturers in the world have diligently been searching for the materials possessing a low-friction coefficient, corrosion resistance, high hardened hardness, abrasive wear resistance and an ability being not apt to be scuffed, such as known from Node, et al., U.S. Pat. No. 5,108,813. Even so, abrasive wear or galling occurs frequently between the sealing surfaces of the seat ring and closure member of metal seated valve in actual service.

Frictional wear is a microscopic dynamic process occurred in material surface, and a complex process relating to behaviors of many subjects including mechanics, materials science, physics, chemistry and heat transfer science. According to analysis from the standpoint of physics and chemistry, wear occurs in the surfaces of two objects in relative sliding motion, and in a very thin layer of working surface. An important characteristic in the course of wear is that mechanical energy changes into heat energy, and the heating or cooling proceeds at very high velocity.

A lot of tests have shown that the abrasive wear is caused by hardness difference and galling by frictional heat. The real area of contact between mating surfaces of two bodies in relative sliding contact is far less than apparent area of contact, even though they are machined finely. The reason is that any surface has waviness and roughness whatever machining is made, and is seen microscopically as a series of asperities presenting serrated peaks, rather than the flat surface seen macroscopically, therefore the real interface of junctions between two relative sliding surfaces is only at the top of some peaks projected outwards from the surface. The softer peaks having the real interface will be sheared or microploughed by the harder peaks facing them during sliding contact relative to each other with the result that a wear fragment transfers from one surface to the other, and loss of material occurs. Meanwhile instantaneous high temperature caused by compression deformation or break at the interface will heat up the top of the peaks having small volume and tiny thermal capacity to cause their temperature to rise sharply and material of the top to become hardened, softened or phase transition. The instantaneous high temperature has the opportunity of causing the material of the interface to be risen up to melted level if the two surfaces slide quickly and repeatedly over a longer distance against each other under a bigger load, and the environment for dissipating heat around them is not so good, as a result abrasive wear or galling will occur at interface of the junctions between two surfaces.

It is also known that the abrasive wear or galling depends not only on a load exerted on sliding contact surfaces and relative sliding velocity between the two sliding surfaces, but on a distance that a smaller object slides over on a larger object, according to friction law that frictional force is proportion to contact load normal to the surfaces published by Mr. Amontons and Mr. Couloms, and the equation that material wear is proportional to load exerted on the surfaces and a distance sliding over relative to each other given by Mr. Archard.

Mr. Laitinen, et al. introduced a new parameter according to Mr. Archard's equation------lineal contact length (that is the overall sliding distance) affecting galling between the sealing surfaces of the seat ring and valve plug member in their WO patent publication No. 02/33299. Assuming static conditions and normal materials, the effect of the lineal contact length on the galling conditions can be determined from equation:
Galling factor=PVLn

In this equation, P is the surface load exerted on the sealing surfaces of the seat ring and plug member, V is the sliding velocity during their relative motion, L is the lineal contact length that is a distance slid over on the sealing surface of the seat ring by a given stationary point in the surface of the plug member from this point contacting a leading edge of the sealing surface of the seat ring to it leaving its trailing edge, and n is an exponent having a value greater than 1.

When the seat ring is sliding on the surface of the plug member relatively, the lineal contact length L along its periphery varies in sliding direction of the plug member, therefore this value has a significant effect on the distribution of the frictional heat on the surface of the plug member, particular on the sealing surface of the seat ring.

The lineal contact length must be as short as possible in order to avoid or mitigate the abrasive wear and galling caused by frictional heat between the sealing surfaces of the seat ring and plug member. The embodiment disclosed by Mr. Laitinen, et al in WO patent publication No. 02/33299 describes that the recesses, grooves or concavities slightly staggered relative to each other in the direction of movement of the plug member are arranged on the sealing surfaces of the seat ring (if possible, including the surface of the plug member) in a dense pattern but spaced apart from each other, so that a continuous contact with the valve plug member in the lineal contact length is interrupted and divided into several portions without causing leakage passageways when the valve is in its fully closed position. These recesses, grooves or concavities may provide cooling spaces of dissipating the instantaneous frictional heat, not letting the temperature at the top of the peaks in the frictional surfaces rise over high, thereby reduce the possibility of the abrasive wear and galling between the sealing surfaces of the seat ring and plug member. But the effect is unsatisfactory either because the recesses, grooves or concavities are difficult to machine or because the instantaneous high temperature accumulated at the tops cannot be timely dissipated in some cases.

The fluid transported in pipeline becomes severer than ever with the great headway and rapid development of all kinds of process industries, and operation temperature, opening or closing speed, operational frequency and sealing property requirements of the valve are also higher and higher. Abrasive wear or galling occurs frequently between the sealing surfaces of the seat ring and closure member of metal seated valve due to generation of a great deal of frictional heat or difficulty in dissipating it when the valve is used in the higher temperature and the fluid carrying harder and harder particles or powders, even though it is operated in the range of suitable temperature. The sealing surface of the seat ring made of polymer will be carbonized by instantaneous high temperature caused by frictional heat in quick opening or closing and frequent operation, with the result that movement of the valve closure member becomes sluggish or is not agile. How to find a solution to the abrasive wear or galling due to instantaneous frictional heat begins to become a subject that valve manufacturers devote much time to their research.

THE SUMMARY OF THE PRESENT INVENTION

It is therefore an object of the present invention to provide a valve able to reduce damage between the sealing surfaces of the seat ring and closure member during operation of the valve, particular a structure of the sealing surface of the seat ring which prevents the sealing surfaces of the seat ring and valve closure member from abrasive wear or galling during their relative sliding contact.

Another object of the present invention is to provide a valve able to reduce damage between the sealing surfaces of the seat ring and closure member during operation of the valve, it can avoid or mitigate abrasive wear or galling caused by their relative sliding contact by means of the structure of the sealing surface possessing the features of high efficiency, simplicity, easy processing and low manufacturing cost.

Another object of the present invention is to provide a valve able to reduce damage between the sealing surfaces of the seat ring and closure member during operation of the valve, in which the structure of the sealing surface can dramatically reduce friction coefficient between the sealing surfaces of the seat ring and closure member during their relative sliding contact, and thus reduce friction force between them.

Yet another object of the present invention is to provide a valve able to reduce damage between the sealing surfaces of the seat ring and closure member during operation of the valve, in which the structure of the sealing surface can quickly absorb and dissipate part of instantaneous high temperature caused by frictional heat between the sealing surfaces of the seat ring and closure member during their relative sliding contact.

Still another object of the present invention is to provide a valve able to reduce damage between the sealing surfaces of the seat ring and closure member during operation of the valve, in which the structure of the sealing surface can enhance the sealing property of the sealing surfaces between the seat ring and closure member.

A further object of the present invention is to provide a valve able to reduce damage between the sealing surfaces of the seat ring and closure member during operation of the valve, in which the structure of the sealing surface can reduce kinetic energy of particles or powders carried in fluid impinging on the upstream surface of the closure member so as to mitigate erosion of it.

A yet further object of the present invention is to provide a valve able to reduce damage between sealing surfaces of the seat ring and closure member during operation of the valve, in which new lubricant or grease needs not to be supplied for the structure of the sealing surface in service until scheduled maintenance, and a minimum of lubricant or grease is stored in the structure, so its pollution of the fluid in the valve is maximally reduced.

A still further object of the present invention is to provide a valve able to reduce damage between the sealing surfaces of the seat ring and closure member during operation of the valve, so that the valve according to the present invention can not only be suitable for the application of the fluid carrying abrasive particles and powders, but also the application in need of quick opening and closing or frequent operation.

The present invention relates to ball valve or any other type of valves in which sealing surface of a seat ring and surface of a closure member are always in relative sliding contact with each other. The invention has attained these objects by means of one or more annular grooves27or curved grooves36(but equivalent to part of annular groove27) which are cut in sealing surface21of seat ring14around its bore used for storing the lubricant or grease, or annular grooves27with two partitions30inserted into each of them to divide it into two groove31and32, or annular grooves27with a corrugated ring35set in each of them to divide it into many small spaces34, so that covered by the surface of closure member17, the lubricant or grease stored in grooves31,34or36would not flow away from them during opening or closing operation of the valve. The ball valve equipped with the structure of the invention will be an example of any other type of valves and be described below in detail.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

There are various kinds of valves, in which surface of a closure member of some valves always keeps relative sliding contact with part or all of sealing surface of a seat ring during their on-off or regulating operation. The principle and consequence of the sliding contact are the same as the description above. For the convenience, embodiments of the present invention are disclosed below in detail combining with the configuration of the ball valve shown inFIG. 1and the sealing surface of the seat ring shown inFIG. 2.

FIG. 1is an elevation sectional view of a prior art ball valve, which consists of a valve housing1, a ball closure member17with a regular curvature surface, a stem19and two seat rings14. Valve housing1is formed by the interconnection of a left-hand housing section2and a right-hand housing section3equipped respectively with flanges4and5on their external ends, used to be connected with pipelines by plurality of bolts and nuts (not shown) threaded through holes6and7in them, and with other flanges8and9on their internal ends, between which is disposed a gasket10used to effect a seal. One end of stud bolts11is screwed into tapped holes in flange8of housing section2, and the other end of them extended through registering holes in flange9of housing section3. Nuts12are screwed onto the free ends of stud bolts11, make flanges8and9join together. Gasket10will be compressed, and flanges8and9touch tightly when fastened together by nuts12, thereby two housing sections2and3form a whole valve housing1. A pair of annular seat rings14is held within recesses15and16of left-hand housing section2and right-hand housing section3encircling passageways13respectively, and clamped between valve housing1and ball closure member17, and their bore has the same inner diameter as the bore of passageways13of housing sections2or3adjacent to it generally. A elastic distortion will be created after two seat rings or seat seals (not shown) arranged between shoulder of recesses15and16and the back of seat rings14are compressed, so that a large sealing force is produced between the surface of ball closure member17and sealing surface21(refer toFIG. 2) of the seat rings. A cylindrical flowway18extends through ball closure member17, and its axis passes through the center of ball closure member17. The valve is opened when the axis of flowway18is aligned with the axis of passageways13of housing sections2and3. The surface of ball closure member17will completely block passageways13in fully closed position after ball closure member17is rotated 90° on its axis by stem19.

FIG. 2consists ofFIG. 2aandFIG. 2b. Radial end face20of seat ring14abuts against shoulder of annular recesses15and16in valve housings2or3, the other one 21 opposite to end face20keeps sliding contact with the surface of ball closure member17and generates a lot of instantaneous frictional heat under sealing force during on-off or regulating operation of the valve. The area of sealing surface21of seat ring14is much smaller than the surface area of ball closure member17, so sealing surface21has to slide over a long distance on the surface of ball closure member17during operation of the valve.

On the other hand, the lineal contact length varies along the periphery of sealing surface21of seat ring14in direction of their mutual sliding movement (as horizontal lines shown inFIG. 2a), in which two horizontal lines22drawn tangentially past inner edge14aof sealing surface21of seat ring14are the longest distance (the longest lineal contact length) slid across sealing surface21of seat ring14by a given stationary point in the surface of ball closure member17when ball closure member17rotates on its axis33vertical to horizontal line40inFIG. 2a. The lineal contact length decreases gradually in either direction from lines22, so that a horizontal line40passing through the centre of seat ring14and across sealing surface21of seat ring22is the second shortest sliding line23, and two horizontal lines24drawn tangentially past outer edge14bof sealing surface21of seat ring14are the shortest sliding distance, two points25in fact. Accordingly quantity or area of interface of junctions participating in sliding contact with the surface of the ball closure member17in the longest sliding length22of sealing surface21is the most, as compared with the other sliding lines, and meanwhile the same quantity or area of interface of junctions in the line equivalent to the length of line22in the surface of ball closure member17also participates in sliding contact and slides across line22, so that the interfaces around the lines22are the location of generating a great deal of frictional heat regardless of whether they are in the surface of the ball closure member or the sealing surface of the seat ring, and should also be a potential position of causing easily abrasive wear or galling tendency.

Particles or powders in fluid, which sizes are less than the clearance between face to face valleys belonging to each sliding surface, will enter into it driven by pressure differential of fluid, and they form three-body abrasive wear together with two sealing surfaces. In this case, the larger the extrusion force exerted upon junctions of the peaks, the easier loss of material from the surfaces is. At the same time the friction coefficient between the surfaces becomes very large and causes the instantaneous frictional heat to be risen greatly, the possibility of abrasive wear or galling increases sharply. If the temperature of the fluid itself is high and its heat conduction is not so good, it will be much easier to bring them about abrasive wear or galling.

Referring now toFIG. 3showing an embodiment of the present invention, wherein one or more annular grooves (two annular grooves27shown inFIG. 3) concentric with inner or outer edges of the seat ring14are cut in the sealing surface21of the seat ring14. Grooves27is filled with the lubricant or grease used for lubricating the surface of ball closure member17and sealing surface21of seat ring14in relative sliding contact referring toFIG. 1), and two surfaces will become separated from each other after the lubricant or grease is coated and firmly adhered on them. The lubricant or grease can be repeatedly coated on the surface of the closure member with it sliding continuously across grooves27, and then on the sealing surface of the seat ring keeping sliding contact with it during on-off or regulating movement of the valve, and keep holding on interfaces of the junctions in each surface and filling into the valleys around the peaks to form several layers of very thin and coriaceous molecular or fluid film. These oil films make the original dry friction between two interfaces in the prior art valve become the friction between the lubricant or grease films coated respectively on them so that the frictional coefficient of their relative sliding motion is reduced.

The lubricant or grease film is also a good endothermal body and heat conductor, the lubricant or grease filled into the valleys around the peaks and having much larger thermal capacity than the peaks will absorb not only the instantaneous high temperature generated by frictional heat between the junctions during their relative sliding contact, but also dissipate the heat not to make the temperature at the interfaces rise to the melted level bringing them to galling.

In addition, the lubricant or grease is a good sealant, too, and can be used for increasing sealing property between the surface of ball closure member17and sealing surface21of seat ring14. The lubricant or grease film can prevent the particles and powders carried in fluid from entering the clearance between the valleys. The lubricant or grease film keeps separating sealing surface21of seat ring14from surface of ball closure member17to be free them from direct contact even if the particles or powders had entered the clearance and formed three body abrasion, so that they wound not suffer abrasive wear or galling.

The lubricant or grease film can partially adsorb kinetic energy of the particles or powders impacting vertically on upstream surface of the ball closure member also, and make the particles or powders impacting on it at a sloping angle slide across it due to low frictional coefficient and not stay at the stagnation point on the impacted surface, thus the kinetic energy converted into the energy digging surface material of the ball closure member is reduced as much as possible during impingement.

In the embodiment described above, the area between upper and lower two horizontal lines22on the right side of the sealing surface of seat ring14will be partly or wholly uncovered by the surface of ball closure member17during on-off or regulating operation of the valve, except in fully open or closed position. Thus, not only the lubricant or grease stored in shorter grooves32in this area will escape, but also the lubricant or grease in the other longer covered grooves31in the rest of the area of the sealing surface on the left side will do through the opened grooves32in a short time, so that the valve will be damaged very fast after the sealing surfaces have lost the lubricant or grease coated on them.

FIG. 4is another embodiment of the present invention related toFIG. 3. Four pieces of partition30are inserted into four grooves29(part of annular grooves27) defined respectively by two segments ab and a′b′ of vertical line33and two segments be and b′c′ of horizontal lines22. One of end faces of partition30adjacent to the surface of ball closure member17has the same geometric figure and curvature as the sealing surface of the seat ring and keeps sliding contact with the surface of closure member17. The other end face and its interior and exterior circumferential surfaces are tightly abutted on the bottom face and interior and exterior circumferential surfaces of annular grooves29respectively. Partition30separates longer grooves31which are always covered by the surface of ball closure member17, from shorter uncovered grooves32, so that grooves31and32become two independent spaces and the lubricant or grease stored in them cannot flow each other. Therefore the lubricant or grease stored in grooves32will not bring the lubricant or grease stored in grooves31flowing away when it starts to escape from groove32uncovered by the surface of the closure member during on-off or regulating movement of the valve. Furthermore, even though all the lubricant or grease stored in grooves32has flowed away, the lubricant or grease stored in grooves31will still lubricate the same area in the surface of ball closure member17just like done before. Both of the surface of ball closure member17and sealing surface21of seat ring14are oiled twice during each opening and closing cycle of the valve.

In the embodiment illustrated inFIG. 5, a wavy ring35shaped from corrugated sheet or cut off from a special-shaped tube is set into an annular grooves27of sealing surface21of seat ring14. One of end faces of corrugated ring35adjacent to the surface of ball closure member17has the same geometric figure and curvature as sealing surface21of seat ring14and keeps sliding contact with the surface of the closure member in the course of their relative sliding motion. The other end face of it and its interior and exterior circumferential surface are tightly abutted on the bottom face and interior and exterior circumferential surfaces of annular groove27respectively, thus corrugated ring35divides groove27into many separate spaces34used for storing lubricant or grease individually. The lubricant or grease stored in spaces in the covered area will be not brought flowing away, with the lubricant or grease stored in whichever space in the uncovered area escaping, so this embodiment can also attain the object to still oil the same area in the surface of closure member17just like done before, as the embodiment inFIG. 4. Even though corrugated ring35can be shaped into any other shapes with wavy circumference cross-section, such as arc, triangular or rectangular, etc., they have the same principle.

FIG. 6is another embodiment of the present invention, showing two pieces of curved groove36, namely equivalent to part of annular groove27, shaped by cutting in sealing surface21around bore of the seat ring14. Two ends37and38of curved groove36are located in the areas defined by segments ab and bc, and segments a′b′ and b′c′ on the right side of sealing surface21, just like partitions30shown inFIG. 4. The arc length of curved grooves36is the same as grooves31of annular grooves27in the embodiment ofFIG. 4, and the lubricant or grease stored in grooves36is always covered by the surface of ball closure member17, so it is kept wherein and wound not escape, but the surface of the closure member will be automatically oiled with the surface sliding continuously across groove36, and then the sealing surface of the seat ring keeping sliding contact with it will be done during on-off or regulating operation of the valve. The lubricant or grease stored in grooves36in according with the embodiment will also lubricate the same area as the other embodiments described above. The benefit of the embodiment is that any type of the corrugated ring or partitions need not be inserted into annular groove27in the covered areas of sealing surface of the seat ring as the embodiments inFIG. 5andFIG. 4. The principle and functions of the lubricant are the same as the other embodiments, so not described any more.

Although the present invention was described in terms of specific embodiments, it is obvious to a person skilled in the art that various alterations and additions are possible without departing from the spirit of the invention which is set out in the appended claims, therefore the extent disclosed in the embodiments above is only for purpose of illustration and not intended to be limited by this description.