Chemical Source Switching

Empty Sensing Comparison

The Chemical Source Switching System from Landry Engineering,Inc. employs capacitive empty sensing technology external to a buffer reservoir. The result is a complete siphoning of chemical from the source container and no bubbles in the supply line. The Source Switching System uses more chemical, reducing chemical cost and reducing chemical waste. How does this compare to common empty sensing methods?

Operator Check
Perhaps the least efficient empty detection method is the operator check. This method relies upon the diligence and timeliness of the operator to check the chemical level and make a judgment on when to change the chemical source. Often, the choice is between removing a container with usable chemical or hoping that the container won't empty before the next check. The inevitable result is occasional bubbles in the supply line and a large amount of chemical waste.

Bubble Sensor
A bubble sensor on the supply line is an effective way of detecting empty, but this method has two drawbacks. It allows bubbles to enter the supply line and, because it detects "empty" upon receiving the first bubbles, it leaves usable chemical in the source container, again resulting in a large amount of chemical waste.

Weight Scale
Another common way of detecting empty is by weight. In order to allow reliable detection before bubbles enter the supply line, this method requires the "empty" set point to be set too conservatively. Yet again resulting in a large amount of chemical waste.

Internal Level Probe
Internal level probes are also common in detecting "empty", but like the weight scale, need to be set at too conservative a level, leaving usable chemical in the supply canister. Additionally, internal probes tend to have high initial and recurring costs. Since the level probe needs to be installed on each chemical container, the cost to outfit a fleet of containers is high. These probes are then exposed to harm in transportation to and from the chemical supplier and while cleaning and filling. This results in a large number of probe failures, requiring replacement.