Maintenance Due Forecast Worksheet
Forecast when a documented hour-meter threshold will be reached. Tie every meter reading to its date,retain the meter value from the last completed service,and optionally apply a calendar due date from the same maintenance plan.
Document one maintenance task
Use the exact task and interval from the asset-specific OEM manual,approved maintenance programme or work order. Do not infer the last-service meter from a rounded interval multiple.
Effective planning due date
Target meter
Hours remaining
Hour-based forecast date
Hour-based days remaining
Hours since last service
Equations and time points
| Quantity | Equation | Required interpretation |
|---|---|---|
| Hour-meter target | Htarget=Hlast service+I | Both meter readings refer to the same non-reset counter and I is the documented interval for this task. |
| Hours remaining | R=Htarget−Has-of | R=0 means due now;R<0 means the hour threshold has passed. |
| Hour-based calendar estimate | d=R/u; Dhour=Das-of+d | u is planned average operating hours per calendar day. This is a forecast,not a reconstruction of actual use. |
| Earlier-of rule | Deffective=min(Dhour,Dcalendar) | Applied only when an explicit calendar due date from the same task source is entered. |
Date arithmetic uses date-only UTC values to avoid local daylight-saving shifts. Fractional forecast days are retained for the numerical result;the displayed ISO date is the calendar date containing the estimated threshold.
What was corrected
The former calculator derived hours remaining from the current meter but added those days to the last-service date. Those quantities belong to different time points. For example,if the current reading is recorded long after the last service,the reported date is shifted backwards by that elapsed calendar time. The replacement adds forecast days to the meter reading’s as-of date.
The former code also rounded the current meter up to an interval multiple. That silently assumed service occurred at a zero-based multiple and discarded the recorded meter at the last completed task. The target is now the recorded last-service meter plus the documented task interval. Empty fields,negative readings,numeric prefixes,calendar reversals and more than24 average operating hours/day are rejected;pre-filled examples and generic interval presets were removed.
Primary-source boundary
Cummins Operation Manual 0981-0149,Issue12 (2024),Maintenance Schedule instructs the user to perform each procedure at the stated time period or operating hours,whichever comes first,and notes that severe conditions can require more frequent maintenance. This supports the optional earlier-of calendar limit;it does not supply a universal interval.
Perkins scheduled-maintenance guidance states that no two schedules are exactly the same and directs users to the Operation and Maintenance Manual for the particular engine. Caterpillar’s 926M example reports that84h on the meter leaves416h to a500h service threshold;that published arithmetic is included in the independent tests.
The equations on this page are transparent planning arithmetic,not a formula established by ISO. The task interval,scope,environmental modifiers and authority must come from the applicable equipment documentation or approved maintenance programme.
Do not use this worksheet without adjustment when
- the hour meter was reset,replaced,rolled over or does not measure the same operating state as the maintenance rule;
- the task is governed by starts,cycles,distance,energy,condition monitoring or a combination other than hours/calendar;
- future operation varies materially from the entered average or shutdown periods are scheduled;
- the manual defines initial-service,seasonal,severe-duty or serial-number-specific rules;
- an approved CMMS/EAM work order or regulatory requirement gives a different due rule.
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.
