GB2085128A - Valves - Google Patents

Abstract

A slant or "Y" valve has a valve body (1) defining within the stem and one branch of the "Y" and between an inlet to an outlet a fluid flow passage 7-7a and has a poppet (2) movable in the other branch (1a) toward and away from a seat (1 b) in the passage, the branches diverging in the preferred direction of fluid flow. The poppet (2) carries a shoe (2a) which is received by the said other branch (1a) when the valve is open and which defines with the valve body (1) a streamline fluid flow path which has a venturi form progressively reducing from the inlet to the seat and progressively increasing from the seat to the outlet. A mechanism for operating the valve is described. <IMAGE>

Description

SPECIFICATION Improvements in and relating to valves This invention relates to improvements in slant or "Y" valves, especially in the larger sizes and subject to high pressures and temperatures, whereby they may be smaller, lighter, stronger and easier to operate, transport and maintain.

In "Y" valves of the known art, where the valve actuating member or "poppet" is fully withdrawn an empty space remains below it causing a sudden widening of the fluid passage, and resultant turbulence, which in order to obtain adequate flow, necessitates a "full bore" construction with resultant weight and bulk.

According to the present invention there is provided a "Y" valve, the stem and one branch of which are formed by a valve body defining a fluid passage from an inlet to an outlet and the other branch of which extends at an angle to the direction in which fluid will flow through said passage, a valve seat surrounding said passage and transversely of the axis of said other branch and a poppet valve movable along the said other branch towards and away from said seat to close and open the valve, said poppet when in the fully open condition being received in the said other branch with a shoe carried by the poppet occupying the region of the said other branch on the fluid side of the poppet and defining with said one branch and the stem a continuous streamline flow passage for the fluid which will have a venturi characteristic being progressively restricted from the inlet to the sea. and progressively returned to full bore between the seat and the outlet.

The axis of the poppet is preferably at about 45" to the stem axis, and this results in the travel of the poppet, to give full flow to the fluid, being approximately equal to its diameter, so that a reduction of the seat area and poppet will reduce the size of the whole valve and, for a given pressure, the thickness of its walls, and the size and weight of the operating mechanism.

In a "Y" valve no force is required to close it for the first 75% of the travel, and not much for the next 10%, so that only during the last 15% ofthevalve's movement need a heavy force be exerted.

In order to compensate for this a toggle action is employed of the known art, whereby the leverage from full open to full closed may increase 8 or 10 fold.

Since weight reduction is an important aspect of this invention, the following equation is submitted,.

where B is the bore of the pipe line and T the travel of the poppet: If the seat diameter is reduced to 80% of B then T = B - 20% and the height of a valve body extension in which the poppet travels is reduced by the like amount. In any valve the height of the operating mechanism is a function of T and so this will also be reduced by 20%. Therefore overall height of the valve is reduced by at least 40% of B.

In a toggle mechanism, for a given angular movement of the toggle links, the width of the unit will vary as 2T so that, by reducing T by 20% the width is reduced by 40% of B.

The smaller diameter of seat and co-acting parts also reduces the overall length of the valve.

These reductions are augmented by a 36% reduction in the poppet area, and therefore, for a given pressure, in the strength of the operating mechanism and so, putting all these factors together a "Venturi" stream-lined "Y" valve with a 20% reduction in seat diameter will be not less than 30% lighter than a full bore "Y" valve of the known art.

This reduction in weight affects not only raw material and handling at the plant, but also transportation costs which, with increasingly centralised production, may involve a substantial outlay.

It is the practice in smaller valves to have three kinds of pipe connections, namely screwed, flanged or welded; this involves complication of production, inventory and correspondence with users. Flanges in small valves are disproportionately heavy and screwed ends are difficult to disengage for servicing the valve. There is therefore provided a "one design" valve end having an internal recess to receive the end of the pipe for welding and an external screwthread for engaging a union coupling nut.

Bn a toggle mechanism of the known art the actuating screw and nuts are exposed to the atmosphere which causes corrosion and the adhesion of grit.

Accordingly in an embodiment of this invention the toggle unit is enclosed in a hollow yoke attached at its lower extremity to the valve body, its upper end providing a flat surface upon which, through rollers, the thrust in closing the valve may be taken without undue friction.

In any valve the force required to close it depends upon a known element, namely the fluid pressure and upon an unknown element, namely the force that the operator may exert upon the mechanism and so, for safety and for weight and cost saving the yoke and the links of the toggle gear are preferably of sheet metal stamped to shape, the yoke being attached to the valve body by screws in shear, as opposed to studs screwed into said body or body cover.

Because of its downwardly projecting shoe the poppet must be prevented from rotating and a convenient method of achieving this is to attach it rotationally fast relative to the valve stem which, at its upper extremity, may be attached in like manner to the toggle mechanism which in turn is attached to the yoke.

In larger valves of the known art it is usually expedientto manufacture the valve body of ferrous metal and to provide a false seat of superior metal upon which the poppet closes. In normal practice such a seat is held in place by a fine thread which is often difficult to disengage when the time comes to renew said seat.

According to a preferred embodiment of this invention a false cylinder is provided by which the poppet is guided, said cylinder at its lower extremity holding the false seat in place, and at its upper extremity being in turn held in place by the valve body cover. This means that the valve body may be welded to the pipes because when the body cover is removed, seat and cylinder may readily be withdrawn.

While moving machinery is normally housed in protected and accessible places, valves are often less conveniently located and when it comes to renewing the packing in the stem gland this may prove difficult As a further feature of this invention, to facilitate such maintenance said packing is housed in a separate member attached to the valve body cover by a screw or screws and readily withdrawable for servicing.

This invention will be better understood from the following description of a preferred embodiment thereof reference being made to the accompanying drawings in which the like numerals denote like parts throughout, and in which: Figure 1 is a longitudinal section of a "Y"valve of the known art, having a full bore seat S and a vacant space A below the poppet when full open.Arrows F F' show the turbulence caused by this sudden widening of the fluid passage; Figure 2 shows a similar section drawn to the same scale of a reduced area "Venturi" "Y" valve in accordance with the preferred embodiment of this invention; Figure 3 is a part section on line XX of Figure 2 showingthetoggle mechanism omitted from Figure 2, poppet being omitted from this illustration; Figure 4 is a part elevation on line W of Figure 3, Figure 5 is an enlarged part section on line W of Figure 3; Figure 6 shows a removable gland unit; Figure 7 shows a section of valve to pipe connection.

The valve ofthis embodiment includes a body 1 having a cylindrical extension la which lies at approximately 45"to the axis of a pipe line in which the valve is to be inserted. Valve seat ib is of sub stantiallysmallerdiameterthan pipebore7-7a.

Co-acting with said seat is poppet valve 2 which has a downwardly depending shoe 2a filling the equivalent of space A of Figure 1 and so shaped as to furnish with the bore 7 -7a a continuous streamline passage forthe fluid as indicated by arrows F', F'.

With the axis of part la at 45"to the pipe axis, travel T of poppet 2 to open fully will be equal to the diameter of seat ib and will therefore be less than that of the travel of the valve poppet shown in Figure 1.

Body 1 and shoe 2a are so shaped as to provide a continuous reduction in flow area from inlet7 to seat 1b and then a continuous increase in said area to outlet7a thus providing a "Venturi" effect which, provided that the restriction at ib is not excessive, will not impede the fluid flow.

Body extension la is sealed by cover 3 and gland unit4through which passes stem 5 which is rotationally fast with and endwise connected to poppet 2 by pin 6.

The toggle design which is now to be described not only prevents rotation of poppet 2 but imparts no rotary force to it, whereas such force is inherent in any vertical stem mechanism of the known art.

Body 1 may have end 7, 7a adapted to be welded to pipe 8 at point 9 or attached to it by union nut 9a (Figure 7).

In Figure 3 cover3 is shown attached to body extension la by bolts 3a. Part 1a has a false liner 10 to guide poppet 2 (not shown in this figure), said liner being integral with or bearing upon a false seat 11, which in turn rests on an annular ledge id in body 1. Liner 10 is held in place by cover 3 and has port 1 0a conforming to that in body 1. Crosshead 5a is connected to stem 5 by pin 6a and has trunions 5b which actasfulcrumsto links 12,12 which, atthis upper extremity engagetrunions 13a on nuts 13. As in the known art nuts 13 are drawn together or pulled apart bythe rotation of spindle 14 which has right and left hand threads and which may be rotated by crank 15 or by a motor (not shown).The upward thrust of links 12 is taken by rollers 13b which track on plate 17 which in turn is supported on yoke 16.

Yoke 16 is attached to body extension la by screws 16a which, as will be seen are in shear and not in tension. Yoke 16 substantially surrounds the mechanism 12,13, 14to protect it from atmospheric contamination, but may have opening 16b for access to gland 4 and to show the position of crosshead 5a and thus of poppet 2.

For strength and to save weight and cost, yoke 16 is made in two halves abutting at 1 sic and may be stamped from sheet metal. As already stated, if the travel of the poppet is reduced by say 20% ofthe pipe bore, dimensions H and Win Figure 3 will be reduced by double that amount as compared to a full bore "V" valve of the known art.

As an example of proportions of the valve described, a reduction of seat diameter of 20% relative to the valve bore can give a venturi flow of 100% at valve inlet and outlet and 64% at the throat.

It will be appreciated that while in the foregoing end 7 of body 1 has been referred to as the inlet and end 7a as the outlet flow may be reversed so that end 7a is the inlet and end 7 is the outlet.

Claims (10)

1. A "Y" valve, the stem and one branch of which are formed by a valve body defining a fluid passage from an inlet to an outlet and the other branch of which extends at an angle to the direction in which fluid will flow through said passage, a valve seat surrounding said passage and transversely of the axis of said other branch and a poppet valve movable along the said other branch towards and away from said seat to close and open the valve, said poppet when in the fully open condition being received in the said other branch with a shoe carried by the poppet occupying the region of the said other branch on the fluid side of the poppet and defining with said one branch and the stem a continuous streamline flow passage for the fluid which will have a venturi characteristic being progressively restricted from the inlet to the seat and progressively returned to full bore between the seat and the outlet.

2. Avalve according to claim 1 in which means are provided to prevent the poppet and its associated shoe turning about the axis of said other branch.

3. A valve according to claim 2 in which the seat is formed by an insert received by said other branch and held by a cover.

4. A valve according to claim 3 in which the poppet is actuated by a stem received in a gland set in a chamber removably located in the cover.

5. A valve according to any of the preceding claims in which the poppet is movable by actuator means to which each one of a pair of toggle arms is pivoted each arm being coupled at a drive connection remote from its pivot connection to the actuator means to drive means operable to move the drive connections toward and away from one another, thrust generated by the drive means on the actuator being carried by rollers bearing on thrust surface.

6. A valve according to claim 5 in which the drive means comprise a drive shaft with opposite threads and the drive connections are nuts on said shaft, the nuts being supported by said rollers.

7. A valve according to claim 5 or claim 6 in which the bearing surface is carried by a sheet metal yoke secured to said other branch by bolts.

8. A valve according to any of the preceding claims in which at the inlet and outlet said valve body is adapted to receive a pipe end for welding to the valve body and is externally threaded for connection in the alternative by a union nut to a pipe end.

9. A valve according to any of the preceding claims in which the reduction in seat diameter is substantially 20% of the pipe line bore at the inlet, giving a "Venturi" flow area of 100% at inlet, 64% at "throat" and 100% at outlet.

10. A "slant" or "Y" valve substantially as herein described with reference to the accompanying drawings.