GB2525372A

GB2525372A - Butterfly valve design and method of attaching the disc to the shaft

Info

Publication number: GB2525372A
Application number: GB1404164.4A
Authority: GB
Inventors: Terry Jones; Bruce Logan
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-03-10
Filing date: 2014-03-10
Publication date: 2015-10-28
Also published as: GB201404164D0

Abstract

A butterfly valve design 6 for increasing flow, reducing cavitation and noise comprising a method of attaching the disc to the shaft 4, 5, 3(3A), 2, using a multi sided feature on the disc 2 and shaft locking clamp 5 held in place by fixings 4. The shaft locking clamp completely covers the shaft, protecting it from being corrupted by media carried by the valve. The shaft holds the disc central in the valve body by means of this multi sided feature. It locks the disc in place through its arc of movement and applies the torque needed to close the valve. The multi sided feature 2, 3(3A), 5 evenly distributes these torque loads along the length of the feature, reducing hysteresis, also reducing stress concentrations.

Description

Page 1

BUTTERFLY VALVE DESIGN AND METHOD OF ATTACHING THE DISC TO THE SHAFT

Butterfly valves are pressure retaining andlor flow control, types of equipment. They can in some forms be safety critical equipment. These would form part of a system incorporated into pipework that allows media to flow between processes within a plant, oil or gas installation, refinery, oil platforms or sub-sea installation.

They all consist of three basic parts.

1. Body.

2. Disc.

3. Shaft.

The shaft fits through the body and the disc is connected to the shaft. The shaft acts to locate the disc in the body. The shaft then drives the disc, usually, through a 90 degree rotation. The disc carries the sealing components. The shaft also acts to lock the disc in a position within the 90 degree rotational arc, typically used on control valves.

Butterfly valves can be classified as either:-Control type.

ESD, Emergency Shut Down' type.

On-Off type.

Butterfly valves, of all types, suffer problems with flow and the method of attaching the disc to the shaft, caused by the nature of the design. As the disc is In the Line', a term used to describe something that may cause blockages in a pipeline.

The disc is a controlled blockage and this is how butterfly valves work, but this can cause a loss of flow and cavitation, which can lead to catastrophic failure.

Page 2 The invention forms two parts that work together.

The first part is a calculated feature added to the inside of the valve body.

The second is a method of attaching the disc to the shaft.

The invention will be described in detail by using examples and references to the accompanying drawings

which form part of this description.

Figure 1 Shows the main components of a butterfly valve, as described above plus the extra features and components that are the invention.

1. Body.

2. Disc.

3. Shaft plus 3A.

4. Fixings.

5. Shaft Locking Clamp. This has two methods of attachment.

Figure 2 Shows some of the components from above plus.

3. Shaft. This has a six sided feature, either symmetrical or asymmetrical that holds the disc.

6. This is the calculated feature, we will call this a Flow Relief Path' 7. Is the altemative method for the Shaft Locking Clamp' 8. Weld-overlay on seat area in body.

Figure 3 Shows some of the components from above plus.

3A. Shaft. This has an eight sided feature, either symmetrical or asymmetrical, that holds the disc.

Figure 4 Shows the method of the shaft holding the disc centrally in the valve body 9. This feature is very important as it stops the disc dropping due to gravity and / or pressure.

First part of the invention, figure 2 item 6, works by increasing the area through the valve body at the point at which the disc is thickest. The shape of the increase area is a compound arc in nature the precise dimensions are worked out by using a calculation. The change in shape and increase in area allows the media which is being carried by the valve to expand and contract, this causes changes in the pressure in these areas. The area where the media is expanding La directly in line with and perpendicular to the shaft and the thickest part of the disc. With the totally enclosed shaft and the shape of the disc together with the elliptical feature in the body, helps flow through the valve, reduces cavitation and noise and increases the Cv, 110w coefficient of the valve.

This first part of the invention, figure 2 item 6, as described above also has another effect. It allows an increased bore through the seat area 8, by allowing better access for machining. It has the effect of allowing the tooling a run-out area into which and machine tools used to finish machine the surface of the weld overlay 8 can exit after the culling is finished. This is only possible with these run-out areas.

Page 3 The second part of this invention, figure 2 items 4 fixings, 5 shaft locking clamp, 3 & 3A shaft, 2 disc, is the way in which the disc is attached to the shaft, and the shape of 5 shaft locking clamp.

The shaft locking clamp 5 can be shaped in two ways. The first shape will fit into a corresponding recess in the disc 2 this wUl be a transitional fit, controlled by tolewnces on the drawing. The second shape will fit fiat to the disc 7 and parallel to the front face of the disc 2. This also has the effect that a minimum of material is removed from the diameter of the shaft, so still maintaining the maximum strength.

The two different methods of shaping the shaft locking clamp 5 and the disc 2 will depend on the pressure being carried through the valve.

The disc and the shaft locking clamp will have either a x or eight sided symmetrical or asymmetrical feature machined into them. This would match a similar six or eight sided feature machined onto the shaft 5. The six or eight sided features would be machined such that an interference between the parts will result in a slight deformation of the shaft locking clamp 5. This will be controlled by tolerances on the drawing to ensure that a tight fit is always achieved.

This will eliminate hysteresis between the shaft 5 and,disc 2. The results of this are all the torque or load applied to the shaft is transmitted through the disc and into the sealing components of the valve.

The assembly method is shown in figure 2 and 3. The shaft would first be inserted into the body of the valve 1, the disc 2 would then fit into the corresponding feature on the shaft 3 & 3A, the shaft locking clamp 5, is then placed over the shaft 3 & 3A, and into the groove in the disc 2 of applied to a flat surface 7. It is secured by fixings 4. When the assembly is completely tightened by means of the fixings 4, it will form a tight contact with both the shaft 3 & 3A, and the mating parts 2 and S. Figure 4 item 9 shows the method by which the shaft holds the disc at the top and the bottom of the shaft locking clamp. It uses the flats on the edge of the six or eight sides feature. The dimensions of the flats on the shaft tightly match the dimensions on the shaft locking clamp and are controlled by tolerance. The shaft figure 1 item 3 is located in the body by conventional engineering means. This means that when the shaft, which is already locked in position, and disc is joined as described the disc cannot move freely or under its own weight.

Claims

Page 4CLAIMS1. A butterfly valve design comprising of a calculated feature in the valve body that improves the flow characteristics.
2. A butterfly valve deign according to claim 1 that would incorporate all types of valve bodies.
3. A butterfly valve deign according to claim 1 that would incorporate all pressure classes of valves.
4. The butterfly valve design according to claim 1 applies pressure changing areas within the media flow that lowers cavitation through the valve.
5. The butterfly valve design according to claim 1 applies pressure changing areas within the valve that improves flow through the valve.
6. The valve design according to claim 1 and claim 7 increases CV and lowers noise through the valve.
7. The butterfly valve design as a means of attaching the shaft to the disc by either a six sided or eight sided feature, the number of sides would depend on the internal pressure and stresses within the valve.
8. The butterfly valve design according to claim 7 allows any torque generated by the closing action of the valve and/or forces generated by the internal pressure on the internal parts, to be equally distributed along the entire six or eight sided feature and distributed equally between all the faces of that feature, that locks the shaft to the disc, reducing the possibility of stress build-up in any one area thus reducing the risk of stress cracking, that may result in failure.
9. The butterfly valve design according to claim 7, completely covers the shaft and keeps it from being eroded or corrupted by the media being carried by the valve.
10. The butterfly valve design according to 7 reduces hysteresis (Backlash) between the shaft and disc, thus reducing that normally present between moving and mating parts.