Documented engineering arithmetic
Constant Annual Cash-Flow Calculator
A transparent present-value model for a proposed predictive-maintenance programme or another investment. It calculates only from your documented incremental assumptions; it does not predict or prove savings.
Model results
Model and timing
For years t = 1 … N, the model places the constant annual gross benefit B and recurring incremental cost C at each year-end. Initial investment C₀ occurs at time 0. Residual value R occurs at the end of year N. With d = r/100:
PV(outlays) = C₀ + PV(C)
NPV = PV(B) + PV(R) − PV(outlays)
Discounted return on outlays = NPV / PV(outlays) × 100%
BCR = [PV(B) + PV(R)] / PV(outlays)
Simple payback = C₀/(B−C) years, only when B−C > 0
| Quantity | Meaning and unit |
|---|---|
| C₀ | Incremental investment paid at time 0; currency units |
| B | Constant annual gross incremental benefit; currency units/year |
| C | Constant annual recurring incremental outlay; currency units/year |
| N | Appraisal horizon; whole years |
| r | Annual discount rate entered as percent/year |
| R | Residual value received at end of year N; currency units |
What “ROI” means on this page
“Discounted return on outlays” is deliberately labelled and defined as NPV divided by PV(outlays). ROI has multiple conventions; this result is not IRR, accounting ROI, or a guaranteed PdM return. BCR and NPV are shown separately so the denominator cannot be mistaken.
Source classification
This is general discounted cash-flow arithmetic, not a formula prescribed by ISO. HM Treasury’s Green Book (2026) is an official methodological reference for lifetime costs and benefits, discounting, NPV/BCR, uncertainty and sensitivity analysis. Its public-sector scope and prescribed rates are not imported as commercial PdM defaults. See also the official discounting guidance. Accessed 13 July 2026.
For C₀ = 100, B = 50/year, C = 10/year, N = 5, r = 0% and R = 0: PV(B) = 250, PV(outlays) = 150, NPV = 100, discounted return on outlays = 66.6667%, BCR = 1.6667, annual net cash flow = 40/year, and simple payback = 2.5 years. This is an arithmetic test case, not a typical plant claim.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
