What is a Motorized Ball Valve?
Motorized valves, commonly called actuated valves, are used in applications requiring automated valve control. Unlike manual valves which involve manually turning a handle or gearbox, motor-operated ball valves open or close the valves automatically by energizing an electric motor after receiving a control signal. The combination of a ball valve with an electric actuator is called an electrically actuated valve.
In order to be motorized the valve and actuator must be able to bolt together. Valve manufacturers typically accomplish this by including the mount as part of the valve body casting allowing the valve (and integrally cast mounting pad) to be directly mounted to the actuator. Automatic ball valves with an integrally cast mounting pad are referred to as direct mount valves.
Valve and actuator manufacturers ensure their respective products bolt together by using to a standard mounting pattern. The most common mounting standard is ISO 5211. This standard calls out bolt hole patterns and sizes for different sized mounting pads.
Electric actuators are available in a variety of voltages and torques. Valworx offers electric actuators in voltages ranging from 12V- 240V AC or DC, with torque ranges from 17Nm for our compact electric actuator to 600Nm (5310 in lbs) for our most powerful electric actuator. Most actuators are designed for a set voltage like 24VDC or 120VAC. Multi-voltage actuators, as the name implies, auto sense the input voltage and regulate the internal voltage accordingly.
Actuator valves often require different actuator functionality depending on the type of valve. For example, ball valves and butterfly valves open and close by rotating a ball or disc. Actuators for these types of valves only need to rotate 90° to be fully open or closed. These actuators are called quarter turn actuators. Valves that operate with linear motion- like gate, globe or diaphragm valves require a different type of actuator. Achieving linear motion directly can be costly or imprecise, so linear motion is commonly achieved by an electric motor rotating a jack screw. Depending upon the pitch of the jack screw and the linear stroke, several complete revolutions may be required to open or close the valve. Actuators for these types of valves are called multi-turn actuators.
For purposes of this discussion, we'll discuss quarter turn actuators in greater detail.
On/Off Ball Valves
On/Off electric actuated valves switch from completely open to completely closed without stopping anywhere in between. Once the valve is completely cycled fully open or closed the motor is switched off by internal cams striking limit switches. For example, when a "close" signal is received, the motor is energized and begins rotating. As the motor closes the valve an integral cam turns on an internal shaft. Limit switches ride on this cam until the cam lobe causes the limit switch to break the circuit and shut off the motor. The reverse is true for opening the actuator valve.
Positioning Valves
Some applications require an actuator valve to open partially or react to varying flow conditions. For electrically actuated valves, this is accomplished by a digital position sensor. An external control signal (such as 4-20mA or 0-10V) is generated based on flow requirements. A microprocessor in the actuator continuously compares the analog input signals to the physical position via an output feedback system, moving the actuator as required to balance the signals and find the desired position. In most cases the low end of the signal range (4mA or 0V) is used to close the valve. This is called "normally closed" operation. Some applications might require the valve to be normally open in which case either the signal limits or the valve mounting would be reversed.
Conclusion
Electric motorized valves are used in nearly every application that involves remotely stopping or starting the flow of a fluid. The above discussion is just a brief outline of the many types of electrically actuated valves; the variations are as numerous as the applications. When purchasing from Valworx, you benefit from our wide selection of high-quality equipment, as well as our free shipping on orders of more than $99.
For more information, please visit our technical support page, or give us a call at 1-800-511-0100.
