Ball valve apparatus
A ball valve apparatus with an improved linearity of fluid flow therethrough is provided. The ball valve includes a valve housing including a housing inlet and a housing outlet; a valve ball receivable within the valve housing, the valve ball having a bore therethrough, a ball inlet and ball outlet of the valve ball which are in fluid communication with the bore, a fluid flow path through the ball valve apparatus being defined at least in part by the housing inlet, housing outlet, ball inlet, ball outlet and the bore. There is also provided a valve stem engagable with the valve ball and. To control the fluid flow through the apparatus such that there is a linear or substantially linear relationship between at the angular position of the valve ball and the fluid flow through the apparatus, there may be provided at least one bridging element, positioned on the fluid flow path to alter a fluid flow thereacross and/or ball outlet, and/or at least one of the ball inlet and ball outlet may have a non-circular profile. A ball valve for such an apparatus is also provided, in addition to method of improving the linearity of fluid flow through a ball valve apparatus.
1. A ball valve apparatus having an improved linearity of fluid flow therethrough, the ball valve apparatus comprising:
a valve housing including a housing inlet and a housing outlet;
a valve ball, receivable within the valve housing, the valve ball having a bore therethrough;
a ball inlet and ball outlet of the valve ball which are in fluid communication with the bore, a fluid flow path through the ball valve apparatus being defined at least in part by the housing inlet, housing outlet, ball inlet, ball outlet and the bore;
a valve stein engagable with the valve ball; and
the valve ball being rotatable relative to the valve housing via the valve stem such that as the ball inlet and housing inlet, and ball outlet and housing outlet are brought in and out of alignment and a flow rate along the fluid flow path changing linearly or substantially linearly with a degree of rotation of the valve ball;
wherein at least one bridging element is positioned on the fluid flow path to alter a fluid flow thereacross, the or each bridging element comprises an elongate bridge body and a baffle element which extends laterally of the bridge body within the ball inlet and/or ball outlet.
2. The ball valve apparatus as claimed in claim 1 , wherein the at least one bridging element is associated with the ball inlet and/or ball outlet.
3. The ball valve apparatus as claimed in claim 1 , wherein one said bridging element is provided associated with each of the ball inlet and ball outlets of the valve ball.
4. The ball valve apparatus as claimed in claim 1 , wherein the or each bridging element spans a width of the ball inlet and/or ball outlet so as to segment the ball inlet and/or ball outlet.
5. The ball valve apparatus as claimed in claim 4 , wherein the or each bridging element is aligned in a plane which is perpendicular to an axis of rotation of the valve ball.
6. The ball valve apparatus as claimed in claim 1 , wherein the baffle element is symmetric about the bridge body.
7. The ball valve apparatus as claimed in claim 1 , wherein a plurality of said baffle elements are provided in a spaced apart relationship along the bridge body.
8. The ball valve apparatus as claimed in claim 1 , wherein at least one of the ball inlet and ball outlet has a non-circular profile.
9. The ball valve apparatus as claimed in claim 8 , wherein at least one of the ball inlet and ball outlet has a substantially asymmetric, arched, chevron or D-shaped profile.
10. The ball valve apparatus as claimed in claim 8 , wherein the ball inlet and ball outlet are shaped differently to one another.
11. The ball valve apparatus as claimed in claim 1 , further comprising a valve actuator engagable with the valve ball to effect the rotation of the valve ball.
12. The ball valve apparatus as claimed in claim 1 , wherein the valve ball includes two said ball inlets and one said ball outlets, and the valve housing respectively includes two said housing inlets and one said housing outlets, the flow rate via the one said housing outlets is almost unchanged with the rotation of the valve ball, but the flow rate via one of the two housing inlets increases linearly with a degree of rotation of the valve ball and the flow rate via the other one of the two housing inlets decreases linearly with a degree of rotation of the valve ball.
13. The ball valve apparatus as claimed in claim 1 , wherein the valve ball includes one said ball inlets and two said ball outlets, and the valve housing respectively includes one said housing inlets and two said housing outlets, the flow rate via the one said housing inlets is almost unchanged with the rotation of the valve ball, but the flow rate via one of the two housing outlets increases linearly with a degree of rotation of the valve ball and the flow rate via the other one of the two housing outlets decreases linearly with a degree of rotation of the valve bal.
14. A method of improving the linearity of fluid flow through a ball valve apparatus, the method comprising the steps of: a] providing a ball valve apparatus as claimed in claim 1 ; and b] rotating the valve ball to increase a fluid flow across the fluid flow path, such that the fluid flow is linearly or substantially linearly proportional to the degree of rotation of the valve ball.