PRESSURE REDUCING VALVE

Abstract: A pressure reducing valve comprises a valve body (2) with an inlet (8) and an outlet (9) and a pressure reducing assembly (4,5) providing communication therebetween. The pressure reducing assembly comprises an outer tubular guide element (4) with a plurality of axially spaced inner guide formations (13, 14, 15, 16) and an inner flow control sleeve (5) slidable on said guide formations to define within the pressure reducing assembly a plurality of axially spaced chambers (20, 21, 22). The flow control sleeve (5) has a plurality of axially spaced sets of pressure reducing orifices (24, 25, 26) positioned such that in a first position of the flow control sleeve each chamber (20, 21, 22) registers with a set of said apertures (24, 25, 26) and in a second position of the sleeve the orifices are closed by the guide formations (13, 14, 15, 16). Additionally the pressure reducing assembly has a plurality of flow transfer passageways (17, 18) arranged to allow fluid to pass serially through said sets of pressure reducing orifices and said chambers from the inlet (8) to the outlet (9), whereby pressure reduction is effected in a number of stages.

Description: PRESSURE REDUCING VALVE This invention relates to a pressure reducing valve. In flow control valves producing high pressure drops there may be problems associated with cavitation. When the pressure in a liquid is less than the vapour pressure thereof, such as might be the case after throttling of the liquid, vapour bubbles form in the liquid. Subsequent pressure recovery causes the vapour bubbles to collapse with the generation of shock waves (i.e. cavitation) which can lead to damage of the valve. In order to prevent cavitation it is known to produce valves in which the overall pressure reduction is effected in a number of successive stages so that the pressure reduction at any one stage is not sufficient to produce cavitation. It is an obJect of this invention to provide a pressure reducing valve which operates in accordance with this principle. According to the present $invention there is provided a pressure reducing valve comprising a valve body with an inlet and an outlet and a pressure reducing assembly providing communication there . X between, the pressure reducing assembly comprising an outer tubular guide element with a plurality of axially spaced inner guide formations and an inner flow control sleeve slidable on said guide formations to define within the pressure reducing assembly a plurality of axially spaced chambers, said flow control sleeve having a plurality of axially spaced sets of pressure reducing orifices positioned such that in a first position of the flow control-sleeve each chamber registers with a set of said apertures and in a second position of the sleeve the apertures are closed by the guide formations, and said pressure reducing assembly having a plurality of flow transfer passageways arranged to allow fluid to pass serially through said sets of pressure reducing orifices and said chambers from the inlet to the outlet. In a preferred embodiment the valve is structured such that fluid passes from chamber to chamber successively outwardly and inwardly through the serially arranged sets of orifices. Forthispurpose, alternate guide formations have flow transfer passageways for transfer of fluid from a chamber into which fluid has flowed outwardly of the sleeve to the next downstream chamber from which fluid will flow inwardly of the sleeve. Furthermore, internal partitioning within the sleeve allows two adjacent sets of orifices to communicate via the interior of the sleeve to allow the fluid to flow successively inwardly through the upstream of the two sets of orifices and outwardly through the downstream set into a chamber from where it is transferred via said flow transfer passageways. The invention will be further described by way of example only with reference to the accompanying drawings, in which; Fig. t. is a sectional view of one embodiment of pressure reducing valve in accordance with the invention; and Fig. 2. is a sectional view to an enlarged scale of part of the valve shown in Fig. 1. The valve 1 shown in Fig. 1 comprises a body 2 housing in a central chamber 3 thereof a pressure reducing assembly itself comprised of an outer guide element 4 and an inner apertured flow control sleeve 5 slidable within guide element 4. The body 2 of the valve 1 is itself comprised of a central section 2a and two end sections 2b and 2c mounted in position by bolts 6. Body section 2a has an integral stepped annular flange 7 which cooperates with guide element 4 tfó subdivide chamber 3 into chambers 3a and 3b, respectively to the top and bottom of the flange 7 as viewed in Fig. 1. A fluid inlet 8 provided in body section 2a communicates with chamber 3a and a fluid outlet 9 adso in body section 2a com municates wiih chamber 3b as shown. Guide element 4 is for ease of manufacture comprised of a first sleeve 10 located in chamber 3a and a coaxial second sleeve 11 extending within chamber 3b but terminating short of the lower end thereof as viewed in Fig. 1. It will be seen that the upper end of sleeve 11 is stepped and is mounted on the complementary step formation of annular flange 7 thereby isolating chambers 3a and 3b; Sleeve 10 is mounted at its upper end in body sections Ib and 1c as shown and at its lower end is located on sleeve 11 again as shown. A plurality of orifices 12 m registering with chamber 3a and arranged in axially spaced circumferential rows are provided in sleeve 10. In the illustrated embodiment, three such rows are provided but it will be appreciated that a different number may be used, if desired. The apertures of any one row are of the same diameter but the diameter of the apertures increases towards the top of the sleeve 10. Sleeve 11 is provided with a plurality, in this case four, of integral inner annular flanges which as viewed from top to bottom in the drawings are referenced as 13,14,15 and 16. Flange 13 is located in the region of flange 7 whereas flange 16 is located at the lower end of guide element 4, proJections 15 and 16 being located therebetween. The aperture defined by each of the annular flanges 13-16 is of the same inner diameter but this is slightly less than the inner diameter of sleeve 10 for reasons which will be appreciated. The annular flanges 13 and 16 each have a plurality of axailly extending flow passageways 17 and 18 respectively extending therethrough. The function of their passageways will be clear from the subsequent description. Flow control sleeve 5 extends within both sleeves 10 and 11. At its upper end and over parts of the length that it extends within sleeve 10, sleeve 5 has an enlarged head portion Sa slidable on the inner surface of sleeve 10. For the remainder of its length flow control sleeve 5 is of a diameter such that it is in sliding engagement with flanges 13 to 16 and defines an annular chamber 19 in sleeve 10. It will be noted that the flow control sleeve 5 together with the flanges 13-16 defines three annular chambers 20,21 and 22 (as numbered from top to bottom). It will also be noted that chambers 20 and 21 are in communication with each other via passageways 17 and that chamber 22 communicates with chamber 3b via passageways 18. As mentioned previously, flow control sleeve 5 is slidable within guide element 4 and as illustrated in Figs. 1 and 2 is at its extreme upper position of movement. Sleeve 5 has a plurality of sets of apertures 23, 24,25 and 26. The sets of apertures are each arranged in axially circumferential rows and are positioned such that, in postion of the flow control sleeve 5 illustrated in the drawings, apertures 23 are all in communication with apertures 12 and apertures 24,25 and 26 respectively register with chambers 20,21 and 22. In the illustrated position of sleeve 5, the lower rows of each of apertures 23, 24, 25 and 26 are respectively located just above flanges 13, 14, 15 and 16 whilst upper row of apertures 24, 25 and 26 are respectively located just below of flanges 13,14 and 15. As mentioned above, the sets of apertures 23-26 are arranged in axially spaced circumferential -rows. In each set, the apertures of any Ïne row are of the same diameter but within the set the diameter of the apertures increase from top to bottom. Apertures 23-26 function as pressure reducing aperture and and dimensioned as required to produce the desired pressure drop, in the manner well understood in this field. An. actuator rod 27 (connectable to an actuatornot shown) is mounted by its head portion 27a on flow control sleeve 5 and serves to effect the sliding movement of sleeve 5 to which reference has previously been made. The upper movement of tube 6 is limited by head portion 27a abutting against body section 2b. The head portion 27a is however shaped such that a cavity 28 is defined within sleeve 10, even at the extreme upper position of sleeve 5. Downward movement of flow control sleeve 5 is limited by its head 5a. The transition between this head 5a and the remainder of the sleeve 5 is a frustoconical face 29 and the upper row of the set of apertures 23 is spaced from the base of face 29 by a section 30 of sleeve 5. Section 30 is of a length corresponding to the depth of an annular recess 31 provided in annular flange 13 and it will be seen that face 29 effectively provides a seating face for flow sleeve 5 on flange 13. On movement of flow sleeve 5 to its extreme lower position, section 30 locates in recess 31. At this position, apertures 23,24,25 and 26 are respectively closed by flanges 13,14,15 and 16. Furthermore, apertures 12 are closed by the head 5a of flow sleeve 5. The various apertures are of course opened by upwards movement of flow control sleeve 5. On such movement, head 5a of sleeve 5 opens the lower row the set of apertures 12 before the upper row of apertures 23 is exposed beyond flange 13. This is of course attributable to the frusto-conical face 29 and section 30 which thus together provide a 'dead bandy arrangement. Within flow control sleeve 5 is a concentrically mounted balancing tube 32 extending from a supporting plug 33 closing the lower end of sleeve 5 to the head portion 27a of actuator rod 26. Balancing tube 32 communicat,es at its lower end with chamber 3b and at its upper end with cavity 28 via conduit 34 in head portion 27a. Furthermore, flow control sleeve 5 is internally partitioned into chambers 36 and 37 by an integral annular flange 35 located around balancing tube 32. The chamber 36 provides communication between apertures 23 and 24 but is isolated from chamber 37 which serves to provide communication between apertures 25 and 26. The operation of valve 1 will be described. In use of the valve inlet 8 is of course connected to a source of high pressure fluid (not shown). In the initial condition, flow sleeve 5 is at its extreme lower position so that the valve is closed. As flow sleeve 5 is moved upwardly, the lower row of apertures 12 is opened but initially the upper row of apertures 23 remains closed owing to the 'dead band' arrangement. Thus plug seating face 29 is moved outside the high velocity flow stream before holes 23 are exposed. This protects the seating face from the effects of wire drawing and erosion at low flow rates. As flow sleeve 5 is moved further upwardly, the apertures 23 are exposed beyond flange 13 and similarly apertures 24, 25 and 26 are respectively exposed beyond flanges 14, 15 and 16. Fluid can now flou through the valve, in the manner explained in more detail below, in the direction of the arrows shown in Fig. 2. Fluid entering through inlet 8 passes throughapertures 12 into chamber -19. This causes an initial pressure reduction, although the main purpose of sleeve 10 is to act as a guide for flou sleeve 5. Subsequently, fluid passes radially inwardly through apertures 23 into chamber 36 and this causes a pressure reduction depending on the number and size of apertures 23 exposed. Additionally jets of fluid passing into chamber 36 impinge upon each other, thus destrouing energy and further reducing pressure. Fluid next passes radially outwardly through apertures 24 into chamber 20, experiencing a further pressure reduction. From chamber 20 fluid passes along flow transfer passageways 14 into chamber 21 from where it passes sequentially through apertures 25 and 26 uith pressure reduction in the same usy as described for apertures 23 and 24. Fluid then passes into chamber 3b via passageways 18. In chamber 3b the direction of fluid flow is reversed and fluid finally passes through outlet 9, the required pressure drop having been achieved. Throughout the pressure reduction, the fluid encouters comparatively high pressures on its exit from the various apertures 23-26 and this gives high resistance to cavitation. It will be appreciated that advantage has been taken in thy valve design to generate a number of flu directional changes which are complimentary to the number of direct pressure reduction stages to give smooth operation of the valve. The illustrated valve construction has a number of advantages, as detailed below. Firstly, the arrangement of apertures 23-26, chambers 20-20, and chambers 36 and 37 allow a high number of pressure reduction stages in a restricted space. Secondly, the flow sleeve 5 is multi-guided along its length (ie by flanges 13-16) and this gives high resistance to vibration and noise. Thirdly, the guide element 4 and flow sleeve 5 are formed as an insertable cartridge which allows these components to be made of wear resistant materials. Fourthly, the provision of the balancing tube 32 offsets the high forces generated by the large pressure drops required.

Claims: CLAIMS; 1. A pressure reducing valve comprising a valve body (2) with an inlet (8) and an outlet (9) and a pressure reducing assembly (4,5) providing communication therebetween, the pressure reducing assembly comprising an outer tubular guide element (4) with a plurality of axially spaced inner guide formations (13,14,15,16) and an inner flow control sleeve (5) slidable on said guide formations to define within the pressure reducing assembly a plurality of axially spaced chambers (20,21,22), said flow control sleeve (5) having a plurality of axially spaced sets of pressure reducing orifices (24,25,26) positioned such that in a first position of the flow control sleeve each chamber (20,21,22) registers with a set of said apertures (24,25,26) and in a second position of the sleeve the orifices-are closed by the guide formations (13,14,15,16),and said pressure reducing assembly having a plurality of flow transfer passageways (17,18) arranged to allow fluid to pass serially through said sets of pressure reducing orifices and said chambers from the inlet (8) to the outlet (9). 2. A valve as claimed in claim 1 wherein the valve is structured such that fluid passes from chamber to chamber successively outwardly and inwardly through the serially arranged sets of orifices. 3. A valve as claimed in claim 2 wherein alternate guide formations (14,16) have flow transfer passageways (17,18) for transfer of fluid from a chamber (20) into which fluid has flowed outwardly of the sleeve to the next downstream chamber from which fluid will flow inwardly of the sleeve or to the outlet (9) and internal partitioning (35) within the sleeve allows two adjacent sets of orifices to communicate via the interior of the sleeve to allow the fluid to flow successively inwardly through the upstream of the two sets of orifices and outwardly through the downstream set into a chamber from where it is transferred via said flow transfer passageways. 4. A valve as claimed in any one of claims 1 to 3 wherein said orifices in each of said sets of orifices (24,25,26) are arranged in axially spaced circumferential rows. 5. A valve as claimed in claim 4 wherein, within any one set of orifices, the orifices of each row are of the same diameter and, within said set, the orifices increase in diameter in the direction of fluid flow through the sleeve. 6. - A valve as claimed in any one of claims 1 to 5 wherein a plurality of apertures (22) are provided in said guide element (4) adjacent said valve inlet (8), and said flow control sleeve (5) has a head (5a) adapted to open and clove said apertures (12) 7. A valve as claimed in claim 6 wherein said head (5a) has a frusto-conical surface (29) spaced from the adjacent set of orifices (23) in the flow control sleeve by a short section (30) of the sleeve, and the guide formation (13) adJacent said head has an annular recess (31) in which said short section locates when sleeve is in said second position whereby said frusto-conical surface and said short section provide a dead-b.and arrangement. 8. A valve as claimed in any one of claims 1 to 7 wherein said flow control sleeve (5) is provided with a balancing tube assembly (32,34).

Inventors: GATES, ERIC KENT PROCESS CONTROL LTD.
Applicants: KENT PROCESS CONTROL LIMITED
Application year: 1984
Main classification: F16K47
IPC codes: F16K47