Consumption

A ledger, not a tank figureA tank figure entered by hand at noon and again at midnight is two independent guesses, and the difference between them is reported as consumption. A ledger of receipts, transfers and consumption, with a stated opening stock, produces a balance that can be reconciled against a sounding rather than replaced by one.

Fuel is the largest number on a supply vessel’s operating statement and the one most often recorded in a way that cannot be audited. A daily report that carries only a tank figure records the result of a measurement and loses the events that produced it.

This module keeps a ledger. There is an opening stock at a stated boundary, then receipts, transfers between tanks and consumption, and the balance follows from them. A sounding is entered as a reconciliation — with the difference visible — rather than as the truth that overwrites what the ledger said.

• An opening stock at a stated boundary. Every ledger needs a beginning. The boundary stock is explicit, dated and attributable, so a figure a year later can be traced back to where the counting started.
• Receipts, transfers and consumption as separate events. A bunkering is not a consumption correction. Keeping them apart is what makes a month’s figures explainable.
• The balance is derived. Nobody types a balance. It is computed from the ledger, which means it cannot silently disagree with the events behind it.
• Soundings as reconciliations. Enter what the tank actually measured and the difference from the ledger is shown. Over a voyage that difference is a measurement of how good the figures are.
• Per grade, per tank. MGO and lube oils are different ledgers, and a transfer between tanks of the same grade moves stock without consuming it.
• Feeds the daily report. The consumption figures on the daily report are the ledger’s, so the report to the charterer and the record on board cannot disagree.

• Consumption — the ledger, the balance and the reconciliation
• The figures as they appear on the daily report

When a charterer queries a month’s fuel, the conversation is either about events — this bunkering, that transfer, these sea days — or about whose tank gauge is right. The first conversation ends. The second does not.

That is the whole reason this module exists as a ledger rather than as two more fields on the daily report.