Measuring level for liquids, especially for corrosive and acidic applications, is not always cut and dry. Due to the caustic tendencies of the fluids, certain materials such as PTFE, CPVC, PVDF, etc. need to be used.
Going the traditional route of using a float level transmitter or a capacitive level transmitter coated in PTFE or another chemical resistant material is certainly a good option. However, these tend to be very expensive and often don’t come with local indication if that’s desired by the end user.
Another good option is to use a non-contact type level transmitter that uses ultrasonic technology. These instruments can be very accurate, have no moving parts, and can give the desired level readings. However, if the media gives off vapor or fumes, which acids can often do, the ultrasonic sound waves won’t reflect back to the transmitter properly causing a false reading.
As a lesser expensive option, pictured in this blog is a level gauge Kodiak recently custom designed for a customer of ours who was trying to measure level of hydrochloric acid (HCL) in a 12 foot tank. Due to the height of the tank, we could utilize the atmospheric pressure by measuring the level using a 0-5 psi pressure gauge. However, because of the corrosive properties of HCL, we used a CPVC/PTFE diaphragm seal to isolate it from the gauge. Then per the customer’s specifications we assembled the gauge to a 2″ CPVC isolation ball valve with a 90° elbow. Then on the other end of the valve, assembled a 2″ socket by 2″ NPT connection to be screwed into the bottom the tank.
By using this custom level gauge, the customer can now accurately measure the level of the tank locally and relatively inexpensively compared to the other options. If a 4/20mA output is needed, a low pressure transducer can be used instead of the pressure gauge for future applications.