The basis of pipeline inventory calculation is the significant difference between Compensated Mass Balance (CMB) and MCMB. Density is calculated as a function of temperature and pressure where available readings from pressure and temperature measurements are utilized. For every segment between two adjacent meters an average density is calculated. A mathematical function approximates a profile between two metered points. The total pipeline inventory is the sum of all segment inventories.
The CMB supports three time frames (balance periods) in order to properly detect small and large leaks and to eliminate random errors. The definition of time frames is always a trade-off between achievable sensitivity and reaction time. Each time frame can be individually configured. The final time frames are usually set during the commissioning stage when the actual instrumentation accuracies and sampling rates are determined. The CMB can be configured for each pipeline section with individual time frames.
A leak alarm is issued when a mass balance falls below a threshold. Warning and alarm thresholds can be set for each time frame.