Ball Valves .:
Ball valves, like pinch trigger valves and pull valves, are devices for controlling water flow through a water blaster with the use of a trigger mechanism. Akin to pinch trigger valves, ball valves can allow water (or air) to pass through the valve in either direction unhindered; the purpose of this valve is not to control flow direction; it is simply for controlling whether flow should occur or not, allowing the water (or air) to move in the direction from highest to lower pressure. However, unlike pull valves which are technically more related to spring-based check valves in how they operate, ball valves are not as affected by the amount of internal pressure and operate somewhat differently.
Parts of the Valve:
A ball valve is comprised of several (six or more) parts:
- trigger - where the user's finger contacts the system
- wire/trigger rod - transferring the force of the pull from the trigger to the valve
- lever - amplifies the force from the finger-pulled trigger towards pulling the valve open
- ball (with hole) - this rotatable part serves as the gating device for the valve
- spring(s) - the primary spring is used to push/pull the lever back to the closed position; there are also often another secondary spring that helps to push the trigger back to its at-rest position
- housing - holds the other pieces in place and creates the water tight seal about the ball, preventing flow until the ball is rotated into the right position
Water Blasters that Use This Valve:
Some blasters that use ball valves include*:
* Note: water blasters that use Max-D valves (a more complicated version of the basic ball valve) are not included in the above listing
Functional Steps:
Closed:
When there is no significant pressure on the trigger (either from internal or external force), the spring pushes (or pulls) the trigger forward. This, in turn, rotates the ball such that the open passage through the ball is not in line with the entry and exit ports of the valve. Since rotating the ball valve to the open position requires a rotary force, no amount of increased internal pressure will cause the valve to open (unlike pinch trigger valves). As such, some sort of pressure relief valve at another point in the internal tubing assembly is highly recommended for, without one, it would become possible for too much pressure to be pushed into the water blaster, resulting in structural failure at some point of the assemble (typically at tubing connection joints)
Partially Open:
Applying pressure using one's finger on the trigger will pull on the lever, causing the ball to rotate and begin to align the opening with the direct path from entry to the exit point of the valve. As can be seen from the diagram, when the ball vale is only partially open, the full cross-section of the hole through the ball is not accessible to the incoming water, thus meaning reduced maximum flow. Additionally, since the path through the ball is not completely straight with the path into and our of the valve's housing, turbulence is also introduced, further limiting the flow rate in this state. Of course, as the trigger is pulled further, the ball becomes further rotated, increasing the available cross-sectional area of the opening and linearity of flow through the valve.
Fully Open:
On a properly designed water blaster, depressing the trigger completely should make the ball in the ball valve line up perfectly with the entry and exit ports of the valve. If the trigger system is not designed well, the ball may not rotate enough and fail to achieve linear flow or rotate too much and pass the optimal orientation.
When fully open, unlike pull valves, ball valves offer straight flow through the system. In most cases, however, the diameter of the hole through the ball is smaller than the inner diameter of the entry and exit ports, thus reducing maximum possible flow rates.
Flow Analysis:
As can be seen illustrated in the diagram above, there is a direct path through the ball valve when it is fully open. In the partial open state, the amount of turbulence added to the system depends on how far from linear the ball's opening is rotated. Also, as noted above, the hole through the ball is often smaller than that of the entry and exit ports, reducing possible flow rate had the valve not been present. If the inner diameter of the hole through the ball portion is less than the connective tubing, that, too, will introduce some turbulence into the flow path.
Even in the case when the hole through the ball is more-or-less identical to the entry and exit ports, since this also means part of the outer sphere is missing, there are some resulting gaps/indents between the housing and the ball that will add in some turbulence to the flow (albeit only minor amounts). Compared to pinch trigger valves and pull valves, however, ball valves can offer superior laminar flow when done properly.
Strengths and Limitations:
The ball valve is another fairly common valve type found in modern water blasters. It does offer some advantages over other valve types. Unlike the pull valve, the ball valve does not get harder to operate as the internal pressure within a water blaster increases. Like the pull valve, since it will not open with increased internal pressure, a pressure relief valve is needed to prevent over-pressurization and possible structural failure of a pressurized water blaster system.
As can be seen by the diagrams, the amount of contact area between the ball and the housing in the ball-valve is fairly substantial. While this can help prevent undesired leakage of pressurized water and air around the ball, it also means that if the ball is damaged or not properly lubricated, it can end up becoming very difficult to operate or even lock up altogether. A good waterproof, non-petroleum-based lubricant is highly recommended to be applied to ball valves in order to keep them moving smoothly through repeated use.
The main advantage to ball valves are their ability to permit very good laminar flow through them when fully open. Unlike pull valves, water can flow linearly from entry to exit ports of the valve. However, due to the geometry involved, as one attempts to increase the inner diameter of the hole through the ball, a significantly larger overall ball is required in order to maintain the seal when the valve is intended to be in its off position. After a point, it actually becomes more costly from a materials standpoint to create a large-opening ball valve versus a pull valve with similar maximum flow rate. While the flow lamination from the pull valve will not be as good as that of the ball valve, lamination can be corrected after the valve through use of a flow lamination device (to be discussed in another article). Thus, the cost effectiveness of ball valves lies within a limited range of optimal flow rates and amount of material needed to build all the parts of the valve.
Beyond cost of materials, as a ball gets larger if more direct flow is desired, this also increases the amount of surface area around the ball that must be kept water tight. As the amount of contact surface area of the ball with the housing increases, more force becomes necessary to rotate the ball into its open and closed positions. This, too, becomes a limiting factor since water blasters typically rely on manual, finger-pull triggers to operate. A high amount of needed force would make larger ball valves too difficult to manually operate for the typical user. This can be offset, in part, by having a longer lever attached to the ball. However, a longer lever would both have to be strong enough to withstand the forces applied as well as require a longer distance for the trigger to move in order to rotate the ball far enough to open and close properly.
Overall, ball valves offer the smoothest laminar flow when fully open, but have a practical size limitation when one needs to factor in cost and strength required to operate.
