*We have a horizontal cylindrical type tank which has a diameter of 2 meter and a length of 7 meters. This tank is used for storage of chemicals. I want to measure the volume of chemical stored in the tank, please suggest the kind of sensor and how it could be used to monitor the chemical contents of the tank.*

A hydrostatic pressure sensor mounted close to the bottom of the tank will provide a hydrostatic pressure reading signal that is proportional to the height of liquid regardless of the shape of the tank. To determine the total liquid contents you will need to convert the pressure reading to liquid height and then enter the result with the radius of the cylinder into the following formula to determine the volume of liquid in a horizontal cylindrical storage tank:

**V = L * ((****R² * arccos{(R – h)/R}) – ((R -h) * √(2Rh – h²)))**

###### Symbols

- R = Radius of cylinder
- h = height of liquid in tank
- arccos = Inverse cosine, (using radians)
- A = Cross sectional area of liquid contents
- L = Horizontal length of cylinder
- V = Volume of liquid contents

Many types of programmable process instrumentation such as PLC controllers include the ability to input mathematical formula to convert pressure readings into other types of measurement, and some will include this formula.

To measure the hydrostatic pressure of the chemical contents we would suggest the LMK351 which is a hydrostatic tank level sensor for use with chemicals with options for a plastic housing, ceramic diaphragm in 96% or 99% purity Alumina Al2O3) and a choice of FKM (Viton), EPDM or FFKM (Kalrez) media exposed seals. The corrosive effects of chemicals will vary with type, concentration and temperature the combination of materials required will depend on the corrosive properties of the chemical being measured.

**Tank level measurement products**