CA1172618A - Erosion resistant valve - Google Patents

Abstract

Abstract of the Disclosure A valve for use under severe throttling conditions, includes a housing with fluid inlet and outlet passages communicating with a chamber inside the housing. An abrasive-resistant throttling tube in fluid communication with the inlet passage projects into the chamber. Also, an abrasive resistant throttling plug is movably positioned inside the housing so that is can be moved between a first position wherein is end is spaced from the mouth of the throttling tube and a second position wherein is obstructs the mouth of the throttling tube. As mating surfaces of the plug and tube are eroded away by fluid flowing through the valve, the plug is advanced further and further toward the throttling tube so that unabraded surfaces of the plug and tube are presented to one another whereby maximum fluid throttling is achieved despite such wear.

Description

This inventio~ relates ~o a valve, It relates more particularly to an erosion-resistant valve. for use in severe throttling service ~pplications.

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The valves with which we are concerned here are used to thro~tle the flow of fluids maintained at very high tempera ures (e.y. 850O F) and pre~sures te.g. 2000 psi) and containing abrasive particles, a coal ash slurry for example. In these difficult service applications, the valve par~s suffer a considerable amount of erosion and wear~ The conventional way to maximize the service life of such valves is by fabricating those valve par~s which are particularly prone to erosion of. very : abrasive resistant materials and specially profiling and : ~ ~15 s~reamlining them to achieve smooth fluid flow around those parts~ ~owever, such parts made of those hard materials are .
: extremely difficult to fabricate and are therefore quite costly.
As a practical matter, then, when designing such valves there is inevitably a compromise made between valve cost and service life.
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Thus it is an objeet of the present invention to provide a valve which is particularly resistant to erosion.
Another object of the inven~ion is to provide a throttlinq 25 valve for handl ing abrasive fluids at high temperatures and pressures and which has a relatively long service 1 if e.
Another object of the invention is to provide a valve of ~7Z~ ~

this type whose parts can be replaced ~uickly and easily in the event that becomes nece~sary.
Still another objeet of the invention is to provide such a valve which is relatively economical ~o mak* and maintain.
Other objects will, in part, be obvious and will, in part, appear hereinafter.
The invention ac~ordingly comprises the fea~ures of construction, combination of elements, and arrangement of parts which wlll be exemplified in the following detailed description, lQ and the scope of the invention will be indicated in the claims.
Briefly, my valve comprises a housing which defines a relatively large, generally cylindrical chamber. An inlet port is formed in the housing and communicating therewith is a tubular throttlirlg tube which pro~ects into ~he chamber more or less }5 coaxiall~y therewith. Tha~ throttling tube, which is more or less centered in the chamber, is formed as a replaceable part. The outlet ~ort is located in the cylindrical wall of ~he housing and it is positioned appreciably radially outboard of the inner end of the throttling tube.

Th~ vaIv~ closure member comprise an elongated throttling :~: plug or rod dimensioned to be snugly received in the mouth of ~he throttling tube with minimum clearance between the two. The plug is mounted inside the chamber directly opposite the mouth of the throttl in~ tube and is movable between an extended or closed 25 position wherein i~ projects slightly into ~he ~u~e to achieve maximum throttling effect and a retracted or open position wherein it is spaced from the mouth of the tube so that it ~ t7~

throttles the fluid to a minimum extent~ Ths plug is moved to any setting between these two positions by a more or less conventional actuator mounted to the valve housing and controlled manually or by suitable elec~ric, pneumatic or hydraulic motive means. It should be understood at ~his point that throttling valves generally are never fully Glosed or fully open in the sense that the plug does not at all obs~ruct the incoming fluid.
Rather, the valve is arranged to always throttle the fluid flow to some extent between maxlmum and minimum values. Therefore, the use of the words "open" and "closed" when referring to plug position should be viewed in this context.
With the valve connected to a sour~e of fluid and the throttling plug in its open position~ fluid is free to flow through the inlet port and thro~tling tube into the valve ~hamber lS and thence to the valve outlet port~ To minimize erosion and wear due to the incoming fluid, the replaceable throttling tube may be constructed of a single piece of erosion-resistant material such as ~ool steel, cemented carbides or ~eramics, for example. Alterna~ively, it can be provided with a very hard , inser~ of such ma~erial at its inner surface which is subjected to the most wear. Likewise, the throttling plug can be made of : the same erosion-resis~an~ material or it can be pla~ed or cladded so that it is abraded ~o a minimum extent by the incoming fluid. Even though the plug and tube are composed oiL such hard material, being simple, e.g. cylindrical, shapes, they are relatively easy to fabricate.
The walls of the valve chamber are spaced an aDpreciable ~ 7~

distance from the inner end or mouth of the throttling tube 9 Fur~hermore, ~he fluid being throttled, suffers an appreciable pressure drop when entering that large chamber. Therefore, ~he walls of the valv~ chamber suffer minimum wear. ~owever, in very 5 severe service applications, a replac:eable ~all liner or baffle may be posi~ioned inside the valve chamber to protect those walls as will be described later.
To close the valve, the ac~uator is caused to advance ~he plug ~oward ~he mou~h of the throl:tling tu~e~ When the plug is lO even with or projects slightly into the mouth of the tube, maximum throttling is achieved. P~ny residual flow through the : valve may be shut off by a separate, conventional shut-off valve.
Dur ing normal use of the present valve, the mating sur faces of the throttling plug and tube are inevi~ably abraded and worn 15 by the fluid . ~owever, in the present Yalve ~ this wear is compensated for because the valve actuator is designed to advance the plug further and further toward the ~hrottling tube as 'che mating surfaces erode away. In other words, the plug is made overly long and the actuator is arranged to feed more and more of the plug length into the tube so that unabraded surfaces of the plug and tube are brought into mating engayement to achieve maximum thro~tling effect.
Further, the actuator can be arranged to rotate the pl ug as it is being advanced in order to minimize the likelihood of

2~ localized erosion of the mating plug and tube parts. Also in - some severe service applications, the plug may be provided with an axial passage through which oil or other fluid under high r~ ~ 7~6 pressure is forced to form a film over the end face of the plu~
so as to effectively prevent the abrasive particles in the incoming fluid from actually touching the plug surfaces at the point of maximum throttling.
Eventually, with repeated valve actuations, the ef~ective length of the plug will be eroded away and that part will have to be replaced. Likewise, the removable throttling tube may have to be rep~aced. However, this is accomplished simply by removing the valve housing bonnet to gain access to the valve chamber.
10` Then the plug is detached from the actuator and replaced with a new one. Also if necessary, the worn tube can be removed from the valve housing wall and substituted for by a fresh on As soon as the housing bonnet is replaced, the valve can be placed in service again. Thus, the aforesaid replacement of parts can be a~complished quickly and easily so that valve downtime is kept to a minimum.
A~cordingly, the present valve can tolerate a considerable amount of parts wear while preserving the effectiveness of ~che valve. Therefore the time between required valve shutdowns is 2~ relatively long. ~alve wear for the most part is confined to a few parts which are relatively inexpensive to make and are easily replaceable so that, when it does become necessary to service the valve, this can be done in a minimum amount of time and at minimum cost. Therefore, the present valve should find wide application in the control of the flow o~ abrasive fluids and in other heavy industrial applications presenting severe throttling problems.

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For a fuller understanding of the nature and objects of the invention, reerence should be had to the following detailed description, taken in connec~ion with the accompanying drawing, in which.
FIG. 1 is a sectional view with parts in elevation of a throttling valve embodying ~he principles of this invention with the valve shown in its open position FIG. 2 is a ~ectional view along line 2-2 of FIG. 1, and FIG. 3 is an enlarged fragmenta~y se~tional view showing the valve in its closed position.

Referring now ~o FIG. 1 of the drawing, my valve shown 15 generally at lO includes a relatively large, generally cylindrical housing 12 having a bottom wall 12a and a generally cylindrical side wall 12b which together define a relatively larse generally eylindrical chamber 13 inside the valve. The valve inlet port 14 is ormed in ~he housing bottom wall 12a and is provided with an external flange 14a. The valve outlet port 16 is formed in the housing side wall 12b and is also flanged at 15a. Us~ally the outlet port has a larger diameter than the inlet port. Circular arrays of openings 18 and 22 are provided in flanges 14a and 16a to facilitate connecting the valve to . upstream and downstream piping. Secured to the top of housing side wall 12b is a bonnet 26 which supports the valve actuator shown generally at 28.

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~ e~erring to FIGS. 1 and 2~ a throttling tube shown generally at 36 is removably secured to the housing bottom wall l~a inside chamber 13 and coaxially with ~he inlet port 14. The throttling tube includes a main tubular section 36a whose mouth or end 36b pro~ects a substantial distance into housing chamber 13 and a redu~ed diameter neck portion 36c which seats in the housing bottom wall 12a. A stepped bore 4~ is form~d in ~he housing bo tom wall 12a to snugly receive the necked down ~hrottling tube. The upper inside wall of that bore is threaded 10at 44 to mate with corresponding external thread5 46 inscribed on the ou~side of tube section 36a at the bottom thereof. Also a suitable annular seal 48 surrounds the tube neck portion 36c to provide a fluid~tight seal between the throttling tube 36 and the housing bottom wall 12a.
15The throttling tube 36 may be a single unitary piece made of an abrasive~resistant material such as tool steel or a carbide.
More preferably and as shown in FIG. 1, the tube may be composed of a main body 50 ~ade ~f a sof~-er material such as steel and a cylindrical refrac~ory inner liner 52 that forms the surfaces subjected to the most wear when the valve is in use.
Referring particularly to FIG. 1, lhe illustrated valve closure member comprises simply a cylindrical thro~tling plug or rod 54 which is disposed opposite and coaxially with the throttling sleeve 36. The diameter of the plug is slightly less 25 than that of the tube mouth 36b and its end 54a is more or less flat.
The plug 54 ext@nds up through a cylindrical bushing 58 6~

positicned in a control passage 62 in bonnet ?6 havin~ a neck 26a. The bonnet seats against the top o~ housing side wall 12b and is ~ecured thereto by a circular array of threaded studs 66 projecting up from the wall 12b through openings 68 near the edge of the bonnet. Nuts 72 turned down onto the ends of the studs clamp the bonnet to the housing flange and an annular seal 74 a~
the underside of the bonnet prevents fluid leakage between the bonnet and the housing.
An upper sec~ion 62a of ~he bonnet passage ~2 inside neck lO 26a is enlarged to receive a packinq ring 78. The ring 78 is compressed between the plug 54 and the wall of passage 62a by a packing follower 82 which is engaged around plug 54 and positioned in passage section 62a o~ the upper end of bonnet neck : 26a thereby forming a fluid-ti~ht rotary and sliding seal between : 15 the plug 54 and bonnet 26. Overlying the follower a2 is a ring 84. Threaded studs 86 projecting up rom neck 26a extend through openings in the ring and receive nuts 88 to clamp the ring to the bonnet neck 26a.
Mounted to the top of bonnet neck 26a is an enclosure 92 ~ having an opening 93 in its bottom wall which receives the neck.
The en~losure is secured to neck 26a by a nut 94 turned down onto exterior threads 95 on the neck. Plug 54 extends through bonnet 26 into enclosure 92 and its upper end 54b is threaded and pinned into a ~oupling 98 formed a~ ~he lower end of a shaft 102. Shaft 25 . 102 extends uæ throu~h the top wall of enclosure 92 into a second enclosure 104 where it is connected by a rotary coupling 106, which permits shaft 102 to rotate with respect to piston rod 108, _ g _ to one end of a pis~on rod 108 whos~ other end terminates in a piston 108a. Enclosure 104 constitutes a hydraulic or pneumatic piston cylinder having a long stroke capability. A compression spring 112 underlying pis~on 108a and reacting against an internal flange 104a in enclo~ure 104 biases the piston toward its re~racted or raised position. Fluid under pressure introduced into enclosure 104 above piston 108a via a conduit 114 causes ~he piston to move plu~ 54 toward tube 36.
Referring to FIG. 1~ when the valve 10 is conne~ted in the line, with the plug 54 in its open position as shown in that figure, fluid flows through the valve inlet port 14 into chamber 13 by way ~f the throttling ~ube 36. Then~e, ~he fluid leav~s the chamber through the outlet port 16. To achieve maximum throttling of the fluid fed ~o ~he valve, the a~uator 28 advances the plug 54 toward the thrvttling sleeve 36. ~he plug is advanced by an amount sufficien~ to posi~ion i~s end 54a more or less even with or slightly inside the mouth 36b of the : ~ throttling tube to ~he po~i~ion illustrated in FIG. 3. Typically : the stroke of the plug 54 between its fully open and closed positions is about one-fourth of the diameter of the bore or orifice in the thro~tling tube 36.
When the plug is in the closed position, the flow of fluid into the chamber is throttled to a maximum extent. With this.
general type of valve, further penetration of the plug into the tube does not result in appreciable further stoppage of fluid flow. Rather, complete stoppage of the fluid (if this is desired) is achieved by means of a completely separate shut-off ~L~'7~

valve tnot shown) positioned in the pipe in line with the valve 10~ Of course, intermediate throttling values are achieved by positioning the plug end 54a at appropriate distances from the mouth of tube 36.
As the valve performs its throttling function, erosion will occur primarily at the lower end of plug 54 and a~ the upper inner surface portion of the throttling tube 36 ~or more particularly its liner 52). Consequently, with a ~onventisnal fixed-stroke type valve, after such wear, the valve may not 1~ perform its throttling function properly. With the present valve, however, such erosion is ~ompensated ~or by making the plug several times longer than its normal operating stroke and controlling actua~or 28 so as to progressively shift the operating stroke of valve stem 58 toward tube 36. In other words, for maximum throttling, plug 54 is advanced toward the throttling sleeve 36 until a substantially unabraded, full diameter end segment of the plug intercepts a non-eroded segment of the tube liner 52. For example in a valve with a tube 36 having a two inch bore, the dis~ance traveled by plug 54 between its open and closed positions might be on the order of one-half inch. Consequently, the plug would be made, say, one inch long 50 that as the end 54a of the plug erodes away, the plug can be ~dvanced over a period of time, further and further toward the throttlin~ tube 36 much like a pencil into a pencil sharpener ~s needed to achieve maximum throttling e~fect despite such wear.
AXter prolonged valve service, the erosion of the plug 54 and the tube liner 52 may become extensive enough to require ~ 7~6 ~ ~

replacement of those parts. Such replacement is easily effected, however, simply by unscrewing the nuts 72 and removing the valve bonnet 26 from housing 12. This provides access to the hou~ing chamber 13 so that the thro~tling tube 36 can be unscrewed from the housing bottom wall 12a. Also, of course, the plug 54 can be unscrewed easily from the coupling 9~. Af~er a fresh tube and plug are ins~alled in place, the bonnet 26 can be re-secured ~o the housing 12, all of this taking a very mïnimum amount of time.
Since the replacement parts are simple cylindrical pieces, they can be formed relatively easily and inexpensively even though made of hard abrasive-resistant material.
In some applications, to minimize the erosion of plug 54, a coating of o~il can be main~ained over ~he plug end 54a. More particularly, the plu~ 54 may be provided with an axial passage ; 15 extending to its end 54a as shown in do~ted lines at 118 in FI~.
1. Oil or other fluid under high pressure can then be supplied to ~he passage 118 by way of a passage 122 in shaft 102 communica ion via a passage 124 in coupling 106 with a flexible hose 126 leading out of enclosure 104. The high pressure oil upon reaching the lower end of the passage 118 iSSU2S forth and blankets the plug end 54a, protecting it from the abrasive action -of the incoming fluid.
Preferably ~he chamber 13 in the valve housing is suf~iciently large in relation to tube 36 that the housing side 25 . wall 12b is spaced appreciably from ~he tube. That, coupled wi~h the fact that the incoming fluid suffers a pressure drop upon entering the chamber 13, means that the housing ~alls should not ~72~

be abraded to any great e~tent by the fluid. ~owever, to ev~n further minimize the effec~s of the fluid on the housing walls, a replaceable cylindrical baffle or liner indicated in dotted lines at 148 in FIG. 1 can be positioned in the chamber to bear the brunt of the fluid and direct it efficiently toward the valve ou~le~ passage 16.
In some applications, in order to minimize localized erosion of the plug end 54a and sleeve liner 52, provision may be made for rotating the plug independently of its lineal ac~uation.
With such an arrangement, the opposing or mating edges or segments of the plug and ~hrottling tube liner are shifted circumferentially relative to one another. This is accomplished in the illustrated valve by a gear drive 132 mounted in the wall of enclosure 92. It includes a ring gear 134 engaged about-shaft 102 and whose center is broached to receive splines 136 formed on that shaft. Gear 132 is mounted in the top wall of enclosure 92 between bushings 138. The gear meshes with a sprocket 142 driven by an electric motor 146 mounted to the enclosure wall. Thus the shaft 102 is ree to slide up and down relative to gear 134 in response to actua~ions of the piston 108a. ~owever, the shaft (and therefore plug 54) may also be rotated independently by mo~or 146 when that is deemed necessary. Of course, in a non-rotative valve emodiment, the gear dri~e 132 and splined rod 102 may be eliminated with the plug 5~ being coupled directly to a longer piston rod 108.
It will be seen from the foregoing then that the present valve is capable of controlling the flow of abrasive fluids such ' l1 7~

as coal slurry under high ~empera~ure and pressure conditionswithout sufferiny undue parts wear. Yet the valve is relatively inexpensive to make. Such surface erosion as does occur is confined primarily o two replaceable parts namely the throttling plug 54 and throttling tube liner 520 ~owever, as those par~s are eroded by the fluid, such erosion is compensated for by advancing the plug further and further ~oward the throttling ~ube liner thereby presenting fresh noneroded plug and lin~r surfac@s to one another to a hieve maximum hro~ling~ When substantially the entire length of the plug has been ~used up" in this fashion, ~he plug and eleeve (if need be) are easily replaceable with fresh parts. Further, even those replacement parts are rela~ively inexpensive since they are simple cylindrical shapes which can be formed relatively easily using conventional lS techniques. Resultantly~ my valve should find wide service particularly in ~hose applications involving severe throttling Gonditions.
It will aIso be seen ~hat the ob~ects set forth above, among those made apparent from the preceding description, are efficiently attained. Also, certain changes may be made in the above construction without departlng from the scope of the inventionO For example, the valve stem can be actuated manually or by hydraulic, pneumatic or other motive devic~s. Also, fluid can ke flowed through valve 10 in the opposite direction and still the valve will have a long service li~e. Therefore, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustr~tive and not in a limiti.ng serlse.
It is al30 to be under~tood that the following claims ar~.
intended to co~rer all of the generic and specific features of the inventioFl herein descr ibed .

Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A throttling valve comprising A. a valve housing defining a chamber, B. means in the housing wall defining a first fluid passage into the chamber, C. means in the housing wall defining a second fluid passage into the chamber, said second passage being spaced from said first passage, D. tubular throttling means mounted to the housing wall, said throttling means being in fluid communication with the first passage, and having a mouth projecting into the chamber, E. a throttling plug having an end, F. means for positioning the plug inside the chamber substantially in line with the throttling means, and G. means for moving the plug progressively further toward the throttling means as fluid flowing into the valve erodes the end of the plug whereby an uneroded end segment of the plug can be moved into position to obstruct the mouth of the throttling means to achieve maximum throttling effect despite such wear.

2. The valve defined in claim 1 wherein the throttling means extends appreciably into the chamber.

3. The valve defined in claim 2 wherein the housing is large in relation to the mouth of the throttling means so that the walls of the chamber are spaced appreciably from the mouth.

4. The valve defined in claim 1 wherein the opposing surfaces of the plug and throttling means are made of an abrasive resistant material.

5. The valve defined in claim 4 wherein the plug and throttling means each comprises a unitary part.

6. The valve defined in claim 4 wherein one or both of the plug and throttling means comprises a composite part which includes a support member and means defining said abrasive resistant surfaces and secured to the support member.

7. The valve defined in claim 1 wherein the throttling means is removably mounted to the housing wall.

8. The valve defined in claim 1 wherein the plug is removably connected to the positioning means.

9. The valve defined in claim 1 and further including a tubular liner positioned inside the chamber, said liner means being made of an abrasive resistant material and adapted to shield the walls of said chamber from fluid flowing through the valve.

10. The valve defined in claim 1 wherein the moving means also rotates the plug about its longitudinal axis so as to move the opposing plug and throttling means surfaces relative to one another to minimize localized fluid abrasion of those surfaces.

11. The valve defined in claim 1 and further including A. a fluid passage. extending along the plug, and B. means for injecting fluid under pressure into said plug passage so that it issues from and coats the end of the plug inside the chamber to protect the plug from erosion.

12. The valve defined in claim 1 wherein A. the tube mouth is circular, B. the plug is cylindrical with a diameter no larger than that of the tube mouth, and C. the length of the plug exceeds one-fourth the tube mouth diameter so that it exceeds the plug stroke distance between the maximum and minimum throttling positions of the plug.

13. The valve defined in claim 1 wherein A. the positioning means includes (1) a valve stem, (2) means for movably mounting the valve stem in the housing wall coaxially with the plug so that one end of the stem extends into the chamber and the other end extends out of the housing, and (3) means for removably connecting said one stem end to the plug, and B. said moving means engages the other end of the stem.