Common problems and solutions for industrial flow switches

Thread Content

This post was last edited by shrien on 2015-7-8 15:49. What is the difference between a flow switch and a flow sensor? It can be said that a flow switch is a type of flow sensor. A flow sensor is capable of measuring the specific flow rate. A flow switch does not need to measure the exact flow value; rather, a flow sensor sets a certain value, and when the flow exceeds this value, it outputs a digital signal to enable the on/off function. Can a flow switch be used in muddy water? In general, for use in slurry, mechanical flow switches should not be employed; instead, electronic flow switches with a stainless-steel casing (of the thermal conductivity or ultrasonic type) are more suitable. Since it is a slurry pipeline, the fluid flowing within it contains impurities. The principle behind mechanical flow switches is that a flap is displaced by the fluid and then returns to its original position; however, slurry can make the flap less sensitive, resulting in suboptimal performance of the switch. Electronic flow switches do not have this problem, but ultrasonic electronic models are relatively expensive; considering overall cost-performance, electronic thermal-conductivity types are the ones that are chosen in most cases. Does a flow switch require a flow threshold value to be set? Can this value be changed once it has been set? Some flow switches have fixed values that cannot be altered, while those that are adjustable can be adjusted as needed. Is the adjustment screw on a target-type flow switch live electrically? For target-type flow switches, the adjustment screw is not live; just be careful not to touch the wiring terminals on it. Common problems and solutions for industrial flow switches. What is the working principle and characteristics of vane-type flow switches? A vane-type flow switch uses the force of water flow to move the vanes, in order to detect whether there is flow of liquid within the pipe. When no liquid is flowing in the pipeline, the spring presses the magnet downward, causing the vanes to become vertical; at this point, the reed switch does not operate and its contacts remain in the normally open (NO) position. When liquid is flowing through the pipeline and the flow rate is sufficient to lift the vane by about 20°–30°, the eccentric drive plate above the vane pushes the magnet upward; the magnetic attraction then causes the reed switch to activate, resulting in the contacts closing. The blade length also needs to be adjusted according to the pipe diameter.