Tank Calibration

What is Tank Calibration?

Tank Calibration is the process of accurately determining the capacity or partial capacities of a tank and expressing this capacity as a volume for a given linear increment or height of liquid. In other words tank calibration also means measuring storage tanks, horizontal bullets, spherical tanks, vats, casks, barges, ship tanks and liquid bulk containers. These measurements provide the necessary dimensions for calculation of calibration charts.

At its simplest, a calibration of any vessel requires knowledge of the nominal dimensions of the vessel from which the volume may be calculated. For a water tank this may be enough and you probably will not need to call in a specialist tank calibrator. 

At the other end of the scale, if you are selling a product on the basis of tank levels, a tank can be measured precisely and calculations can be made to take into account factors such as hydrostatic expansion of the tank during filling and thermal expansion of the tank shell in service.

For most situations in India or anywhere in the world where you are selling from a tank or where duties are levied on tank contents you will need to have a tank calibrated by a suitably certified tank calibrator.

For the purposes of this exercise we shall assume that you have decided that you do require a precise calibration of your tank.


Benefits of accurate tank calibration

If you need to know what has gone in, or what has gone out of a tank, if spillage or overfilling is of concern or if you require any indication of quantity of product inside a tank then you probably need tank calibration of some sort.

In a world where cost of petroleum, LNG, chemicals, spirits is increasing every day, accurate tank calibration is essential. During storing, blending or processing, strict consistency in volumetric measures is imperative.  Accurate calibration of storage tanks and process vessels ensures not only helps in maintaining a very high standard of your products but also less trouble with customers, government departments and internal stock taking and accountability. Furthermore, storage tank calibration and storage vat calibration has been made mandatory by various departments in India and all over the world.


Re-Calibration of Storage Tanks. Why should a tank be re-calibrated at regular intervals?

Imperceptible to the human eye a tank may change its calibration whenever the operating conditions are changed. This could be for a variety of reasons. For example:

·        Expansion or contraction of tank shells due to hydrostatic liquid head pressure or changes in operating temperature.

·        Any modifications to the tank or the dip plate - i.e., new pipe inverts, floor repairs, floating roof modifications, changes in deadwood, etc.

·        Changes in tank plate thickness.

·        Re-location of the tank.

·        Tilt and settlement of the tank with resultant changes in the tank geometry.

·        Change of product density - this will affect the expansion characteristics of the tank, hence the volume.

It is generally recommended that a tank should be recalibrated at not more than 5 year intervals, especially considering tank settlement. In areas where tank settlement or ground subsidence is known to be a problem, an external settlement survey can be performed which we also specialize.


Storage Tank Calibration in India and abroad is mandatory

Tank calibration, tank inspection and certification of storage tanks has been made mandatory in India at least once every 5 years by the Directorate of Legal Metrology and worldwide as per rule by the respective governmental or special agencies of the particular country.