The most important parameters of control include power supply voltage, control voltage, minimal pressure of control air or oil and of course control function – as we can say, what the control should be able to do and how it should be equipped.

Because the control is used to close and open the valve, the characteristic of the valve is prerequisite for the right choice of the size of the control. Exact parameters of the valves, such as control torque, size of the connection between the control and the valve and another, are always determined by designer according to the operating parameters, for example due to the temperature, pressure of the medium in the pipeline, speed of the flow etc. If the exact parameters will not be specified, it may happen that the control will not suit its purpose. In practice, that means, that the control might be too small and not able to control the valve, or it can be too big and that might damage the valve. The price of the control is related to its size and type.

Types of controls

Basic types of valves control:

• manual (gearbox)
• electric actuator
• pneumatic actuator
• hydraulic actuator
• electric-hydraulic actuator
• “DIRECT GAS” actuator

The most used are electric actuators, which can be used for all types of valves – quarter turn, multi turn, with rod and lever. The standard controls need permanent supply of electricity and during power cut they stay in position, in which they currently are. There are also electric actuators with spring to ensure emergency function, but these are limited with a small moment and longer adjustment time.

Pneumatic and hydraulic actuators are single-act or double-act and are used where they can be connected to air source or hydraulic. The advantage is smaller electricity consumption. They also have emergency functions FO or FC and fast closing or opening (within about 0,5 seconds). The control pressures are up to 10bar of air at pneumatic actuators and up to 230bar of oil in hydraulic actuators. 

Electric-hydraulic actuators have the own closed hydraulic circle, powered by an electric engine and a hydraulic pump. 

“DIRECT GAS” actuators are powered by gas, directly from the pipeline, on which they are built. 

Equipment of the control

All controls can be equipped by various equipment, which they use depends for example on the temperature of the surrounding (up to -60 °C) and work environment. Next to the standard environment, we also have environment with the risk of explosion, called Ex etc. The control can be control from the place or from long distance. Then are the control equipped for example with control units with display, binary remote controls, analog etc.

The type of the control is always specified by the customer, including the control equipment. The correct choice also depends on how the valve will perform its function as part of the technological unit.

For more information: Patrik Novák, Manager of valve controls, ARMATURY Group a.s.