A
Mass Balance is a means of accounting for the
operations/activities of a refinery over a period of time in units
of mass. It provides assurance that a balance exists between stock
levels, receipts and deliveries. At its highest level the balance
is reported for the whole of a refinery but it is prepared from
balances obtained at process and storage item level. The Mass
Balance is not concerned with duty liabilities or duty accounting.
Data concerning processes, storage plant and the connections
between processes and plants is defined.
The balance is produced by a computer system which models a
refinery’s plant and production processes. Each item of
refinery plant which stores, receives and delivers product is
defined. The system is provided with details of every movement in
the specified period and by reference to the definitions a balance
for each process and storage location can be established.
No refinery will produce a mass balance which has no losses
or gains. The principal discrepancies will arise through the
tolerances in measurement devices. With the measurement tolerances
of each storage tank and meter defined the system, having
identified a discrepancy, will attempt to remove the discrepancy by
attributing the loss to measurement tolerances and correct the
amounts moved.
