Abstract: A method for controlling an arc welding equipment (21) used in a welding operation and adjustable by varying at least one welding parameter value, comprising the steps of determining said at least one welding parameter while using a theoretical model (24) of the welding process associated with the welding operation, and controlling the operation of the welding equipment and the welding process associated therewith by using said at least one welding parameter for adjusting the welding equipment and a device comprising an arc welding equipment (21) used in a welding operation and adjustable by varying at least one welding parameter and an arrangement (22) for controlling the operation of the arc welding equipment, said control arrangement including a means (23) adapted to determine the value of said at least one welding parameter while using a theoretical model (24) of the welding process, and a member (25) adapted to control the operation of the welding equipment and the welding process associated therewith by

Abstract: Measures of a torque and rotational speed of a pump or fan are obtained, from which a mechanical input power can be calculated. By further using predetermined relations between mechanical input power and flow rate through the pump or fan, a measure of the flow rate can be derived without use of in-line flow or pressure sensors. In preferred embodiments the torque and/or rotational speed is obtained by measuring the input current and voltage of a motor driving the pump or fan and using predetermined relations between on the one hand current and voltage and on the other hand torque and rotational speed. Furthermore, also other flow properties, such as pump head, pump efficiency and total efficiency can be determined in this manner.

Abstract: Measures of a torque and rotational speed of a pump or fan are obtained, from which a mechanical input power can be calculated. By further using predetermined relations between mechanical input power and flow rate through the pump or fan, a measure of the flow rate can be derived without use of in-line flow or pressure sensors. In preferred embodiments the torque and/or rotational speed is obtained by measuring the input current and voltage of a motor driving the pump or fan and using predetermined relations between on the one hand current and voltage and on the other hand torque and rotational speed. Furthermore, also other flow properties, such as pump head, pump efficiency and total efficiency can be determined in this manner.