Measurement of a ball valve as a control valve

There are more possibilities how to control flow rate in a pipeline system. When the flow is provided by pump, it is very economic to use frequency converter to change the pump speed which leads to flow rate change. Another possibility is to change number of running pumps, when pump station contains more than one unit. Control valve is used in systems without pump regulation especially, when the initial costs has to be low. The paper is focused on measurement of control ability of a ball valve. Generally, ball valves are not suitable to fulfil flow control function, but in an emergency case, when the control valve is damaged and the system has to be operated, there is no other possibility, but to use the ball valve.