The relationship between the flow and cast iron butterfly valve is basically a linear proportional change. If used to control the flow, its flow characteristics and piping flow resistance is also closely related, if the installation of two pipe valve diameter and form are the same, pipeline loss coefficient is different, the valve flow will be very different.
Electric butterfly valve must be visually inspected before the installation, valve nameplate should be consistent with the national standard "General Valve Logo" GB12220 requirements. For working pressure greater than 1.0MPa, play the role of cutting off, be carried out before the strength and tight performance test before the installation. When we carry out strength test, the test pressure is 1.5 times of the nominal pressure, duration time is not less than 5min, valve shell, packing should be no leakage, which is qualified.