GB2231126A

GB2231126A - Diaphragm valve

Info

Publication number: GB2231126A
Application number: GB9005127A
Authority: GB
Inventors: Antonio Carraro
Original assignee: Carraro SRL
Current assignee: Carraro SRL
Priority date: 1989-03-07
Filing date: 1990-03-07
Publication date: 1990-11-07
Also published as: DE9002675U1; IT215751Z2; CA2011536A1; FR2644221A3; IT8920694V0; GB9005127D0; FR2644221B3

Abstract

In a diaphragm valve, the fluid passing through the valve is bled off via pipes (9, 10) in order to act as the servofluid controlling the position of the diaphragm (3). The pressure of the servofluid is controlled by a pilot valve (13) which varies the flow rate along the pipe (9) in order to vary the pressure drop across a needle valve (12). In the closed position, the diaphragm seals against concave upper edges (5) of the walls (4) of the bottom part of the valve. The pilot valve may be responsive to liquid level. <IMAGE>

Description

DIAPHRAGM VALVE The present invention relates to a diaphragm valve.

A number of valve types are l < nown, among which, in particular, is the so-called diaphragm valve. In a diaphragm valve, the outflow port can be shut by pushing a deformable diaphragm up against a seat. In these valves the diaphragm fully separates the actuating devices, generally of mechanical type, from the fluid flowing through the valve.

In other valve types, the shutting device consists of a metal plug connected, for example, by means of a stem or a rigid spindle, to a diaphragm which actuates the plug movements to open and close the fluid passage.

In both cases, they are valves including two different devices, the closing device or plug and the actuating device or actuator. These valves, especially when they have to be automatically actuated, have the disadvantage of a construction which is complicated and bulky.

According to the present invention, there is provided a diaphragm valve comprising a diaphragm for regulating the flow of fluid through the valve and actuator means for controlling movement of the diaphragm, wherein the actuator means comprises the diaphragm.

Preferably, a chamber is provided on the side of the diaphragm remote from a passageway through the valve, movement of the diaphragm being controllable in dependence on the pressure in the chamber.

Preferably, the valve further comprises means for bleeding fluid from the passageway to control the pressure of fluid in the chamber.

Preferably, the bleed means is arranged to bleed fluid from the part of the passageway upstream of the diaphragm and is in communication with the chamber. Preferably, the bleed means includes throttle means upstream of its connection to the chamber. Preferably, the bleed means includes a pilot valve downstream of its connection to the chamber.

Preferably, the bleed means is arranged to discharge the bled off fluid back into the passageway downstream of the diaphragm.

Preferably, the wall of the passageway includes a transverse web having a concave free edge for forming a seal seat for the diaphragm.

Preferably, the wall of the passageway includes a longitudinal web having a concave free edge for forming a seal seat for the diaphragm.

Preferably, the valve further comprises biasing means for biasing the diaphragm to reduce the flow of the fluid through the valve.

The invention will now be described by way of non-limiting examples with reference to the accompanying drawings, in which: Fig. 1 shows an exploded view of a valve in accordance with the present invention; Figs. 2 and 3 schematically show a section of a valve in accordance with the invention, in open and closed positions respectively; and Figs. 4 to 13 show alternative embodiments of valves in accordance with the present invention Referring to Figs. 1 to 3, the valve includes a main body 1 which is in use inserted into a pipeline 2 and which is subdivided into two parts by a resilient diaphragm 3.

The lower part of the body 1 is shaped into a series of ribs or partition walls 4 having a curvilinear upper edge so as to allow diaphragm 3, when pushed downwards, to seal against the upper edges 5 of said walls 4.

The upper side of the valve is closed by means of a cover 6 which defines the external wall of the upper part of the valve body.

In this upper chamber there is a helical spring, or similar, 7 which, hy a lower washer 8, acts on the diaphragm 6, pushing it downwards.

An offtake 9 on the body 1 connects opposite ends of the lower chamber to each other.

A central pipe 10 connects this offtake with the upper chamber.

Along the offtake there are a strainer 11, a needle valve 12 and a pilot valve 13 of known type and which is chosen depending on the system which is intended to be adopted to pilot the valve 1.

While operating, the pilot valve opens or closes the offtake 9, causing a change in the pressure inside the upper chamber. This change consequently causes a displacement of the diaphragm 3 from the closed position, shown in Fig. 3, where the diaphragm is in contact with the edges 5 so preventing fluid flow, to an open position where the diaphragrri moves away from said walls 4.

The operation can be better explained with the following example.

Supposing that the valve is initially in its closed position, as shown in Fig. 3, with the fluid filling the upper chamber side.

In this case the diaphragm is, on the upper side, subject to a force equal to the upstream fluid pressure multiplied by the whole diaphragm surface, plus the force exerted by the spring. On the lower side, it is subjected to a force only equal to the upstream and downstream fluid pressures multiplied by the surfaces on which said pressures act.

In this case, the force which pushes the diaphragm downwards prevails, so keeping it closed.

Let us imagine that at this stage the utilization becomes active, so causing a pressure reduction downstream of the valve (on the right of Figs. 1 and 2). In this case, the pilot valve 13 opens allowing the passage of the fluid along offtake 9.

Since the narrowing in the needle valve 12 causes a pressure drop in the left branch of the offtake, the greater pressure of the fluid present in the chamber will make this fluid flow along lines 10 and 9, thus causing a decrease of the pressure in the pipe over the diaphragm, thus allowing the fluid pressure in the main line to push the diaphragm upwards, as much as necessary for the downstream required capacity.

At its maximum opening, the diaphragm reaches the position shown in Fig. 2.

When the utilization downstream of the valve is reduced, the pilot valve 13 throttles or closes the offtake 8; its upstream pressure and therefore the pressure in the upper chamber increase and tend to reach a value equal to the fluid pressure inside the valve body.

In this situation where the pressures on both sides of the diaphragm balance, the diaphragm is pushed by the force exerted by the spring 7. When the diaphragm comes into contact with the edge 5 of the wall 4, there is a reduction of the force exerted by the lower chamber pressure as the diaphragm surface, on which this pressure acts, is reduced by the area of the edge 5.

Thus, the diaphragm settles in its closed position.

During the regulating action of the valve, the needle valve 12, the choking position of which has been duly set, acts as regulator of the valve action velocity.

This makes it possible to obtain the stabilization in an intermediate regulating position or a slow and controlled closing of the valve, avoiding in such a way dangerous waterhammering.

The advantages offered by this type of valve are considerable.

Since the closing takes place between a resilient surface (the diaphragm is manufactured in soft material such as EPDM rubber or VITON) and a rigid metal seat, the dead shutoff is assured without any risk of damage in case of solid particles in the fluid.

A valve with regular flow and without turbulence is obtained and, in the case of line pressure failure, the valve closes automatically due to the spring. This prevents the pipeline from emptying and the subsequent inconvenience due to lack of the pump start-up.

From a practical point of view, the valve, which can be mounted both in horizontal and vertical positions, offers some remarkable advantages since it can be used for many different applications by only changing the pilot valve type. As a consequence, it is necessary to keep in stock only a limited number of valves, since it is enough to have some different pilot valve types to meet all the possible requirements.

Finally, the valve according to the invention acts at the same time as plug valve and actuator, being a device of simple construction consisting of few parts and which consequently offers the advantage of a cheaper cost and easier maintenance.

The special diaphragm shaping enables it to adopt any position between those of fully open and closed, the position being determined by the action of the spring and the servofluid which is the same fluid flowing in the pipeline intercepted by the valve. The servofluid acts in the upper chamber with pressure values properly determined by the pilot valve.

While the valve is opening, the diaphragm position is determined by the fluid pressure acting on the lower diaphragm surface.

The variable constant spring 7 absorbs a force more than proportional to the diaphragm lift, and therefore proportional to the dynamic forces suitable for a proportional regulation and without oscillations of the diaphragm, when the servofluid pressure changes.

The pilot valve 13, in relation to the parameters according to which the main valve opening or closing is determined, acts on the servo fluid flow so as to change the pressure on the diaphragm to let it move as it is required to conform the degree of opening of the valve to the required capacity.

When the valve reaches the degree of opening appropriate to the requested capacity, the pilot valve resets so that the control flow becomes again the same as before the regulating action.

The diaphragm valve of the embodiment of the present invention is a regulation valve with proportional and integral characteristics, wherein the shuttinq device consists of a concave diaphragm of resilient material, the position of which determines the opening of the line in which the valve is inserted, and which is controlled by a pilot valve and by a needle valve inserted along a hy-pass circuit.

Figs. 4 through 13 schematically show a number of different applications of the valve according to the invention, as examples only.

Fig. 4 shows the example of a pressure reducing valve with a solenoid for remote shutoff of the main valve; Fig. 5 shows an electrohydraulically operated valve with closing speed adjustable in order to avoid waterhammering; Fig. 6 shows an electrohydraulically operated valve with a normally closed solenoid valve; Fig. 7 shows a level control valve; Fig. 8 shows an electrohydraulically operated valve with manual test valve; Fig. 10 shows a split range pilot reducing valve for a wide pressure control range; Fig. 12 shows a level control valve; Fig. 13 shows an electropneumatically operated control valve.

Claims

1. A diaphragm valve comprising a diaphragm for regulating the flow of fluid through the valve and actuator means for controlling movement of the diaphragm, wherein the actuator means comprises the diaphragm.

2. A valve according to claim 1, wherein a chamber is provided on the side of the diaphragm remote from a passageway through the valve, movement of the diaphragm being controllable in dependence on the pressure in the chamber.

3. A valve according to claim 2, further comprising means for bleeding fluid from the passageway to control the pressure of fluid in the chamber.

4. A valve according to claim 3, wherein the bleed means is arranged to bleed fluid from the part of the passageway upstream of the diaphragm and is in communication with the chamber.

5. A valve according to claim 4, wherein the bleed means includes throttle means upstream of its connection to the chamber.

6. A valve according to claim 5, wherein the bleed means includes a pilot valve downstream of its connection to the chamber.

7. A valve according to claim 4, 5 or 6, wherein the bleed means is arranged to discharge the bled off fluid back into the passageway downstream of the diaphragm.

8. A valve according to any one of claims 2 to 7, wherein the wall of the passageway includes a transverse web having a concave free edge for forming a seal seat for the diaphragm.

9. A valve according to claim 8, wherein the wall of the passageway includes a longitudinal web having a concave free edge for forming a seal seat for the diaphragm.

10. A diaphragm according to any one of claims 1 to 9, further comprising biasing means for biasing the diaphragm to reduce the flow of the fluid through the valve.

11. A diaphragm valve substantially as herein described with reference to the accompanying drawings.

12. All novel features and combinations thereof.