Level switches can be classified in two basic types: stem and cable suspended. Depending on your application, one type may be preferable to use over the other.
The first thing you must consider is the size of the tank. Cable suspended float switches require tanks that are large enough to accommodate the arc of their incline. For example, the smallest tank height our KA float switch can work for is about a foot. This is because the minimum difference between the highest and lowest switch points is 10 inches. Stem floats can have switch points within 2 inches of each other making them ideal for smaller tanks.
In conjunction with size, you must also decide whether or not you have the resources required to transport and mount a stem that could measure over 12 ft. in length. Cable suspended floats, meanwhile, can be moved easily while stored in a small box and can simply be “dropped” into the tank with no mounting required. For tall tanks, a KA float switch with no mount and a long cable would be advantageous to several 12 ft. stems mounted up the side of a tank.
In applications that have tanks with agitators, cable suspended float switches are not a good solution since they would be free to flow with the current of the swirling liquid. Stem float switches, on the other hand, are attached to the tank and are only affected by the rise and fall of the liquid. Make sure, however, that the application does not require the stem length to reach the agitator. In this case, a continuous level device may need to be used.
APG offers the KA cable suspended float switch, which can have up to four switch points, but our FLR stem floats can have up to seven switch points. So, if your application requires multiple on/off switches and high/low alarms, you may be better off with a stem.
If your application requires stainless steel for the wetted material, stem float switches are your solution. Cable suspended floats do not have this as an option. We’ll talk more about chemical compatibility in the near future.
If you have any questions or concerns about deciding between a cable and a stem, feel free to contact our Measurement Experts. They will be happy to assist you.
