Technical Field The present invention relates to butterfly valves. Background

Butterfly valves generally comprise a disc which is mounted for rotation about an axis from a closed position to an open condition, and vice versa. The axis of rotation usually passes vertically of the disc, and rotation may be about a single shaft or two stub shafts, one stub shaft at each of the upper and lower regions of the butterfly valve. Butterfly valves can be concentric or double eccentric, for example. A motor and gearbox is provided to drive the valve from an open condition to a closed condition and vice versa. In the event of a failure, or required service/maintenance of such a valve, it is usually required to remove the gearbox, but in order to do so, the disc needs to be locked in position. With the valve in a fully open or a fully closed position this is a fairly straightforward operation. However, in the event of a gearbox failure, the position at which the disc is located may be intermediate of the open and closed positions. This renders the process of locking the disc in position much less straightforward.

We have devised an improved apparatus and method for locking a butterfly valve in position.

Summary

According to the first aspect of the invention there is provided a butterfly valve lock device arranged to be fitted to an end portion of a shaft of a butterfly valve. The lock device may comprise a keyway and a flange, the keyway arranged to connect with the end portion of the shaft, the flange arranged to be used to connect to a housing of the valve. The flange may not be provided with drilled through-holes for securing the device to the housing. The keyway may comprise a recessed formation. The keyway is preferably arranged to substantially prevent relative rotation between the lock device and the shaft.

The keyway may comprise a square-section recess.

The keyway may extend across a protruding formation, or boss, of the lock device.

The lock device may be of stepped side cross-sectional profile. The lock device may comprise a boss, or protrusion, central of a surrounding flange.

The lock device may comprise an annular shoulder which is of intermediate height relative to the height of a central protrusion and an outer flange. The lock device may be provided with indicia which show the relative positions of recesses/bores provided in the housing structure of the valve assembly, which are used to secure a thrust bearing assembly to the housing. The indicia may comprise a plurality of spaced-apart markings, arranged in co-radial locations. The indicia may comprise circles.

According to a second aspect of the invention there is provided a kit of parts comprising the butterfly valve lock of the first aspect of the invention and a key insert arranged to be used with the lock device . According to a third aspect of the invention there is provided a method of locking a butterfly valve in position comprising removing a thrust bearing assembly at one end of a shaft of the valve and replacing the assembly with a lock device, wherein the lock device arranged to be fitted to an end portion of a shaft of the butterfly valve, the lock device comprising a keyway and a flange, the keyway arranged to connect with the end portion of the shaft, the flange arranged to be used to connect to a housing of the valve, and the method further comprising determining where through-holes should be provided in the flange and then providing through-holes in the determined locations to allow the device to be fixed to the valve housing. Other aspects of the invention relate to any combination of the above features and/or any of the features described below or shown in the drawings.

Brief description of the drawings

Various embodiments of the invention will now be described, by way of example only, with reference to the following drawings in which:

Figure 1 is a cross-sectional side-view of a butterfly valve,

Figures 2 and 3 are detailed views of a lock device in situ,

Figure 4 is a cross-sectional side view of a lock device, Figure 5 is a plan view of the lock device of Figure 4, and

Figures 6(a) to 6(h) are step sectional views which show the stepwise procedure for removing a thrust bearing of a butterfly valve, and replacing it with the lock device of Figure 4.

Detailed Description

Reference is made to Figure 1 which shows a butterfly valve 1. The butterfly valve is suitable for use in controlling the flow of fluid in pipework in which the valve is installed. The valve can be set to an open condition in which fluid is allowed to flow past the valve, and a closed condition in which fluid is prevented from flowing past the valve.

The valve 1 comprises a housing 2 which is connected to adjacent sections of pipework. The butterfly valve 1 further comprises a disc 3 which forms a closing mechanism used to isolate or regulate flow. The disc 3 is rotatably mounted to the housing by way two stub shafts 5a and 5b. The stub shaft 5a provides a connection to a gearbox (not shown), which is mounted atop the housing 2. The stub shaft 5a is provided with an elongate through-slot. In a closed condition the disc 3 is arranged to seal with an inner surface of the housing 2 by way of a 4 which is provided at the periphery of the disc. In an open condition, the disc 3 is rotated through ninety degrees to allow fluid to pass thereby. The valve 1 further comprises a stub shaft 5b, which is located at a lower region of the valve and is connected to a lock device 10. As will be described in more detail below, the lock device serves to lock the stub shaft, and therefore the disc 3, in a required position, and to ensure that substantially no rotational movement of the disc 3 occurs. Each of the stub shafts 5a and 5a is rigidly secured to the disc by way of suitable fixings such as bolts.

The lock device 1 is shown in more detail in Figures 4 and 5. The device 10 comprises a protrusion or boss 1 1 , which is located centrally of a surrounding flange 12, and is of substantially cylindrical shape. Of intermediate height (and diameter) than the boss 1 1 and the flange 12, there is provided an annular shoulder 14.

Atop the boss 1 1 there is provided a keyway 13 which extends diametrically thereof.

The keyway comprises a channel or slot of rectangular section, open at both ends.

When viewed in section it can be seen that the boss 1 1 is of the greatest height, with the shoulder 14 and the flange 12 being of lower height.

The uppermost face of the flange 12 is provided with an annular channel 15 which is arranged to receive an O-ring seal. Installation of the lock device 1 will now be explained, with reference in particular to Figures 6(a) through to 6(h). To perform a scheduled service, or because of a suspected gearbox failure, it is required to remove the gearbox from the stub shaft 5a. Before this can be done, the disc 3 needs to be locked into position to ensure that when the gearbox is removed, the disc does not rotate due to the impinging fluid pressure on said disc. Figure 6(a) shows a thrust bearing assembly 20 attached to the (lower) stub shaft 5b. The thrust bearing assembly 20 is secured to the housing 2 of the valve assembly by way of circumferentially spaced bolts 21. The assembly further comprises a mounting component 22, through which passes a mounting bolt 23, which is of two part construction with the upper part being rotatably pivotable about the lower part (and thereby allowing driven rotation of the disc). In Figures 6(a) through to 6(f), it can be seen that in that fashion, each component part of the thrust bearing assembly is disassembled, step-by-step. In Figure 6(g), the thrust bearing assembly 20 has been completely removed, and thereby allows installation of the lock device 10. In this condition, the disc is prevented from rotating due to the fluid pressure thanks to the counter reactional forces in due to the gearing in the gearbox.

The flange 12 of the lock device 10 is pre-marked to show the correct relative positions of the blind bores 25 of the housing 2 which receive fixing bolts therein to secure the lock device to the housing. These indicia are shown at 16 on the surface of the flange 12. In a stage of the installation procedure the lock device is offered up to the lower end of the valve assembly, and the keyway aligned with the stub shaft 5b. In this position, the engineer can mark the actual positions of the blind bores 25 in the housing 2 on the lock device 10, relative to the marked positions 16. The undrilled flange can then be drilled at the required positions to form through-holes to receive bolts to fix the lock device to the housing 2. In this way, it is ensured that the position of the keyway 13 will be aligned with the lower end of the stub shaft 5b.

With the through-holes formed in the flange 12 at the determined positions, the lock device, together with a key insert 9 which is provided in the keyway 13 is then urged into position. In this position the through-holes in the flange 12 will align with the blind bores 25, and so bolts 21 can be driven into position to securely attach the lock device 10 to the housing 2. The engagement between the key insert and the end of the stub shaft 5b ensures that rotation of the shaft (and therefor the disc) is prevented. With the disc now locked, and prevented from rotating, the gearbox can be safely removed from the (upper) stub shaft 5a, without risk of the disc rotating when this removal operation is performed.

As can be seen in Figure 5, the keyway 13 is offset from the series of markings 16. This is particularly advantageous when the disc 3 stops in a position which is between open and closed positions, for example due to gearbox failure, and is therefore required to be locked in that position.

It will be appreciated that regardless of the position which the disc needs to be locked in, the lock device can be used to ensure that the disc can easily be locked in this position. Figures 3 and 4 show the device locked in different positions, ninety degrees apart from each other.

It will further be appreciated that the lock device could be used for any size of butterfly valve. Conveniently, the lock device and the key insert can be provided as a kit of parts to allow the engineer to lock the valve in position as required.