US2406243A - Valve - Google Patents

Description

Aug. 20, 1946. I

N. 3. NEWTON ETAL VALVE Filed June 21, 1943 wz'mflgfo raf kjorm fijfmorg .Zjcfaierd Few/mama Patented Aug. 20, 1946 VALVE? Norman B.*New'ton and Richard Fennema, Chicago, Ill., assignors to Crane 00., Chicago, 111.,

a corporation of Illinois Application June 21, 1943, Serial No. 491,714

'- I V 3 Claims. (C 5 This invention relates to valves. More particularly, it pertains to a novel form of seat and clo sure member combination in valve and is especially suitable for throttling service. To those who are experienced or skilled'in'the art. it is well recognized that the latter type of service in which the valve is only partially open is one of the most severe forms of working conditions to which 'a valve may be subjected. The percentage of valve failures has accordingly been very high on this type of service.

In order to obtain a true and more complete appreciation of our invention and the nature of its accomplishments, there should exist, at the outset, an understanding of certain fundamental principles of hydraulics pertaining especially to the flow of fluid under high velocity through relatively restricted orifices.

For example, it should be understood that an elastic column held rigidly at one extremity and struck at its free extremity will tend to vibrate at its natural frequency. Further, the static pressure of any fluid decreases as the velocity increases and with liquids, as this decreasing pressure approaches the vapor pressure of the liquid, 5

vapor bubbles will form, which phenomena is termed cavitation. As these vapor bubbles pass on into a lower velocity and into higher static pressure zone, they collapse and liquid rushes in to fill their voids. Therefore very appreciable and substantial high frequency impacts are imparted to'the confining walls of the conduit or container which is an objectionable effect of cavitation.

More specifically, in the case of a throttle valve,

one of the conduit walls is the valve closure mem-,

her or disc, and in this particular application the disc is preferably attached rigidly to thevalve stem and the stem in turn supported only at its upper extremity in the stuifing box packing. The resultant eifect of cavitation is the constant striking of the disc, which causes the stem and disc assembly to vibrate at its natural frequency.

It is therefore an important object of this invention to provide a novel means for minimizing cavitation by the introduction of liquid under relatively high static pressure to that restricted zone where the high velocity and low static pressure would otherwise support the objectionable cavitational tendencies.

It will be further apparent, in connection with the following description, that the high pressure can be introduced either through the closure member or through the valve seat with substana y the same beneficial results.

It is a further important object of this inven- 2 tion'to provide means for eliminating disc or valve closure vibrations of plug type closure members used for throttling non-compressible fluids. It is a further important object of this invention to dispel the low pressure zone caused by the passing and subsequent collapsing of vapor bubbles within the zone of higher pressure thus causing the high frequency impact which creates disc vibration. Specifically, such objectionable low pressure zone is dispelled and cavitational tendencies accordingly inhibited by feeding in a fluid immediately adjacent thereto at a higher static pressure.

Other equally important objects and advantages will become apparent upon proceeding with the following specification read in light of the accompanying drawing, in which Fig. 1 is a fragmentary sectional view of a preferred embodiment of our invention.

Fig. 2 is a fragmentary sectional view of a modifiecl form of the invention.

Referring now to the drawing and particularly to Fig. 1, the numeral I is used herein to designate a conventional form of bridge wall or diaphragm of a valve body or casing (not shown) having a horizontal portion, as indicated, in which a body seat ring 2 is threadedly or otherwise attached, the line pressure being on the lower or underside of the valve diaphragm I. The body seat ring 2, tightened in place by the wrenchengaging lugs I0, is preferably provided with a tapered or frusto-conical seating portion 3 which may be either faced with a hard seating material, as indicated, or else provided with the seating surface integrally as a part of the body seat ring. Preferably, although not necessarily, just below the tapered seating portion 3, the seating member is formed with a cylindrical passage designated 4 within which the tapered or plug type closure member 5 with its cylindrical shank 6 is relatively snugly fitted. As shown in the closed position of the valve, the tapered portion I of the closure member seats on the corresponding tapered surface 3 of the body seat ring and when the valve is in its throttle position, it should be understood as being just slightly lifted or removed from such seating contact as described. A portion of a valve stem 8 is shown in the fragmentary assembly, being threadedly rigidly attached to the disc 5 as indicated at 9. The transversely positioned pin [I and the weld seal [2 serve to hold the threaded shank of the stem firmly in position against rotational and axial movements.

Thus far the description hereinabove given pertains to a conventional type of globe or angle valve. Now proceeding with the essential portion of our inventive contribution, it has been discovered that the throttling problems above referred to can be overcome by providing the lower portion of the closure member with a preferably centrally positioned apertured passage, as indicated at E3, and having a plurality of radially extending passages i i discharging therefromjhe number of passages varying with the valve size and service conditions. Thus the closure member is placed in the throttled position to form a relatively restricted passage around the seat, thereby eliminating the usual vibration which heretofore has been set up and has been foundso objectionl5 able in its damage to the valve seat and closure. member. By providing the transversely extending passages i l, means have been established whereby the usual high Velocity flow of fluid into thesaidannular opening and past the seatand closure member contacting surfaces is affected to an extent that cavitation is very substantially minimized. It. Will be apparent that this is accomplished primarily by the introduction of fluid under a relatively high static pressure to'that restricted-zone substantially transverse and immediately adjacent to the valve seat where the high velocity and the low static pressure otherwise have supported cavitational tendencies in prior valve structures. i

1 An annular groove in the closure member has been found helpful in assisting inthe elimination of cavitational tendencies in line flow by locating the same, as indicated at It, around the valve'disc portion immediately adjacent to the section entering the cylindrical orstraight part A of the body seat ring. H'oweven'relatively satisfactory results under certain conditions have been accomplished without employment of the annular groove in on the valve closure member and con 40 versely it may be applied to thefsat' ring with V V acceptable results..

Referring now to the modified form, in Fig 2,

in some cases because of structural conditions en-:: countered it may be desirable'fto introduce the high pressure cavitation minimizing flow through the valve seat-ring rather than through the clo- 1 sure member and, as indicated, thismay be easily accomplished by simply vertically drilling an an-w;

- nular portion of the body seat ring longitudinally at the'desired number of locations, as indicated at It, and having in communication with each the transversely extending horizontal passages I! which may be either drilled through, as indicated,

or else may be suitably plugged separately at the end adjacent the threads. Obviously, as shown, the seat ring threads by their-engagement with the diaphragm wall I will serve conveniently as a plug at the outer end of the passage l1. Here similarly in the instant modification the annular groove l5 either in the closure member 'or-in the v 4. body seat ring may be dispensed with, if desired, depending upon the nature of the line service conditions encountered. Also the body seat ring may be annularly chamfered at its lower or inlet portion, as indicated at 18. s V

The'particular manner in which the introductionoi high pressure flow takes place transversely adjacent to the seat openingmay. vary' quite substantially, and it is therefore the desire to be limited only within the scope of the appended claims interpreted in light of the prior art.

We claim:

1.. In a plug type valve, a valve closure member of the .throttling type, a removable seat therefor, combined annular and transverse passagesconstructed and arranged to permit communication with the inlet of the said valve for directing fluid from the inlet end of the closure member through said passages to an annular passage between the closure member and the said seatwhen the closure member is in the'throttled. position,rsaid annular passage being sealed'by the said closure member when same is in closed position, the said closure member having a .irusto-cOhical throttling lip positioned within 1 the seat 7 opening whereby upon slight opening or throttling of the said closure member the flow between the throttling lip and the inner annular walls of the said seat passes over the'japertures of the transverse 30 passages.

2. In a valve, the combination includinga valve closure member of the plug type,'a tapered seat therefor, transverse passage means having an inlet end disposed to receive line flow. from the inlet end of the closure member and communicating with the valve seating contact surface between the said closurememberand the said seat whereby upon partial opening of the valve cavitation. may be minimized V therebetween by the introduction ofa diverted portion of the line fluid under relatively high static pressure in'a direction substantially transverse tothe valve seating contact surface, the said closure member having atapered throttlinglip positioned within the seat opening and over 'whichflline fluid'fiows immediately upon placing the closure member in 'a throttled position.

3; In a plug type throttling valve, the combination withja valve seat and a plug type closure member therefor, of passage means provided in saidclosure member. for discharging line fluid di-

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