Electrically Actuated Plastic Valves

Electrically Actuated Plastic Valves

Electrically actuated valves are an increasing requirement for plastic pipe systems, due to demands for electrical efficiency and 24/7 system operation.

Types of electrically actuated valves

Electrically actuated valves are available in three standard configurations;

·         Open / close

o   Power source is required to open and close the valve e.g. when power is applied to terminal 1 and taken away from terminal 2 the valve will open and the opposite will occur when the power is switched across. Open / close type valves are suitable for automated filling and emptying of tanks, reservoirs. They are also very useful in fully automated processes like backwashing filters and priming pump supply lines prior to an automated pump staring. Open / close type valves are often used at the end of plastic pipe lines, where a line is required to be purged before refilling once a pump starts.

·         Spring Return

o   These are available in either a normally open or normally closed configuration. When normally open the plastic valve will, with the aid of a powerful internal spring, return to the open position when the power is removed. When normally closed, the valve will close when the power is removed. Spring return valves are often used for emergency supply lines, where, in the event of power failure a bypass needs to be opened, a line needs to be drained or a tank needs to be filled or drained.

·         Modulating

o   Modulating valves have the power constantly applied to them and have an additional controlled power source of 0-10volts dc or 4-20mA. The controlled power source is supplied by a controller that is usually responding to input from a sensor, such a s a pressure or flow sensor. The controlled power source partially opens and closes the valve to give a controlled flow. The accuracy of a modulating valve will only ever be as good as that of the sensor and controller.

Modulating valves are excellent at controlling tank levels by using feedback from either a level sensor or a sensitive, submerged pressure sensor. Other applications include controlling the pressure in a supply line, although this is more often done using an inverter (speed controller) if it is a 3 phase pump that is supplying the line.