A level switch seems pretty simple in principle. As liquid rises or falls past a certain point, the switch activates. However despite their simple operation, there are a few ways they can go wrong. Since level switches are often part of safety networks, for example preventing tanks filled with flammable liquids from overflowing, it is important to be able to quickly trace the source of problems.
Frequent On/Off Activation
When the liquid in a tank is near the point of activation for a level switch, operators may find the switch rapidly cycles on and off. If the switch is hooked to a simple indicator such as a warning light on a control panel, this could be nothing more than an annoyance. However if the switch operates a pump, the frequent cycling will put unnecessary wear on the pump and lead to early failure.
This is typically a sign of turbulence inside the tank. If the tank is mounted on a moving base, say on the back of a truck, normal motion will cause waves inside the liquid that will cause the switch to turn on and off. The switch might also have been placed too near the entry port, where incoming fluid causes turbulence.
Putting the level switch behind a slosh shield or inside a tube that opens well below the surface of the liquid will minimize the wave effects. If this doesn't solve the problem, a delay in the control software will ensure any device activated by the switch won't engage until the reading has been steady for long enough to rule out turbulence.
Erratic Operation
Sometimes a level switch doesn't consistently respond to changing liquid level. There might be a delay of several minutes before the switch reacts to a low fluid level, or the switch might not trigger as liquid level passes the activation point. These are often caused by the nature of the liquid being measured.
Sticky or viscous liquids may remain on the switch; either fooling it into thinking there is liquid present or physically obstructing the switch's operation. After the liquid slowly drips off, the switch activates. It may be necessary to look for a switch specially designed to work with these liquids.
In other cases, solids could precipitate out of saturated liquids and clog the level switch. Even simple water can do this if it contains a high concentration of minerals. Regular maintenance to clean deposits off level switches will be necessary to ensure accurate readings.
Although most level switches are designed to be chemically inert, they may still react with certain chemical compounds. Extended exposure can cause parts of the switch to corrode and fail. These switches can either be put on a schedule so they are replaced before failure, or level switches can be found that are made of materials that will better resist the reactive liquids.
Author Resource:-
Author is a freelance writer. For more information on level switch please visit http://www.compac.com/.
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