Electric Actuators

In this instance we are referring to quarter turn electric actuators that give rotational force through a 90 degree turn. There are other styles such as multi turn and linear.They utilise a motor and gearbox combined in one assembly to open or close an object (in most cases it is a valve of some description). They can have features such as a manual override, position indicator and switches to give feedback to external control units. Actuators can also give intermediate control (modulating) to partially open or close a valve. Rotation is usually 90 degree or part thereof. Most commonly electric actuators are used on ball, butterfly, globe and plug valves for water treatment, mining, food, petrochemical and general industry. Thermal motor overloads are standard and optional torque limiters can be factory fitted to prevent overtorque. All standard voltages are available, 12v DC 24v AC/DC, 110v 50/650Hz, 230v 50Hz, 415v 50Hz.Three phase motors are available. Electrical environmental protection is usually IP67 or Exd (ICEX) depending upon the application.

Quarter turn electric actuators utlilise an electric motor mounted on a gearbox to create a rotational force. Rotational output speeds vary depending upon the internal gearing but as a rule of thumb the bigger the actuator (torque output) the slower the rotation. Cams on the shaft will cut power to the actuator once it has reached the end of its stroke. For modulating actuators a 4 to 20 mA input and output signal are utilised to turn the actuator to any position within its 90 degree turn allowing for proportional flow control.

The actuator sizing is based on the torque requirement for the valve to be actuated. From the valve data sheet obtain the Working Torque Nm (torque required to turn the valve at the required pressure, temperature and media viscosity) and add a minimum 30% safety factor. Always check breakaway- torque for the valve. Especially on butterfly valves this can be higher than the working torque because of the unseating of the valve disc off the seats. Using this find the corresponding actuator with this figure (or greater) and select. Also check the actuator mounting pad configuration against the valve hole pattern. It may be necessary to step up an actuator size to accommodate ease of mounting.

Like any valve this depends upon the usage case of your actuator, its environment, media and how many times it is cycled. The actuator's life will depend mainly upon the environment and the cycle frequency. Alway use an IP67 rated gland connection for the cable entry. Water getting inside the actuator through incorrectly rated cable glands causes the most problems. We have had these actuators operating for decades without any maintenance.

The Electric Actuator can be installed either by direct mounting or via an adaptor to any ball, butterfly or plug valve that requires a 90 degree rotation. The actuator can be mounted in any position from horizontal to vertical and tolerate most environments. Do not mount upside down as grease can migrate out of the gearbox. Preferably in the vertical position with the position indicator to the top.  If the valve does not have the ISO 5211 mounting pad an adaptor can be customized to fit. Drive adaptors can also be supplied to accommodate various stems. Alway use an IP67 rated gland connection for the cable entry (or IECEx rated for the EXD actuator). Check with your electrician or instrument engineer if required. Internal zero voltage microswitches are supplied as standard to give Open/Close feedback to PLC or other controllers. The stricker cams are adjustable and extra microswitches can be fitted. If a torque limiter is required for the application it must be factored fitted and cannot be retrofitted in the field. As the actuator is an enclosed unit the duty cycle of that particular model must be adhered to as to allow for heat dissipation.

Applying rotational control through 90 degrees the electric actuator can operate ball, butterfly and plug valves in many sizes. There are many uses outside actuating a valve and can be applied wherever rotational control is required. The IP67 rating gives protection against extreme weather and immersion for a set period of time at a rated depth. With the Exd actuator the IECEx certification allows the site engineer to use the actuator in petrochemical and hazardous atmospheres according to the standard ratings etc.

This depends upon where you are based and the freight method chosen. If the express freight option is selected it is usually next day delivery to metropolitan areas in Australia for under 5kg. If free freight has been selected it will go by road freight which can be anywhere from 1 to 10 days depending upon your location. It usually averages 3 days.

All of our products come standard with a 12 month warranty. The good news is we have very strict quality controls and all actuators leave our warehouse tested (full material and testing certificates to API598 are available) and inspected so there are rarely any issues. Also once your valve is in and operating it will most likely continue to do so for a very long time barring any debris getting caught in the valve or power spikes causing the coil to fail..