Control System Instrumentation

Trigonometry in Calculation Vessel Volume

This is one of my case studies to calculate the volume vessel of a Diesel Tank.

The purpose of the scope of work was to improve diesel fuel management as part of a fuel management improvement campaign.

The objective is to convert measurement height liquid in Diesel Tank to volume basis (in liter). The level transmitter type was DP(Differential Pressure) transmitter using hydrostatic pressure to measure the level.

According to process calculation of vessel diesel tank.

(Partial liquid volume of the tank with ellipsoidal head).


It was Putting this equation direct to DCS (TDC3000) one function of arccos was not available

Option I :

Using the trigonometry function found on the list of Built-in Arithmetic

This approach is manipulating the original equation using the available function on the controller PCS, unfortunately, it becomes more complicated, but the advantage it has no error

Option II:

Using the Regression Linear approach.

Option III: Totalizer

Totalizer is one feature that is available in flow computers. This totalizer has a function to accumulate the volume.

Error in option I and option II originated from % error measurement and % error calculation due to error measurement. That is the reason why it doesn’t match the sounding table

On the other hand, totalizers don’t respect the shape of the vessel. Therefore it could minimize the error resulting from measurement, However, the outlet of the vessel should be equipped with a totalizer the outlet

Thus the remaining volume vessel is Qremain=Qin-Qout.

This should be written in the PLC to retrieve the value in the control room along with the push button start and stop.

Oleh Lizwan Arief Lubis

Tertarik dengan teknologi dan programming

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