Temporary Air Fuel Logistics Calculator

The calculator separates machine fuel burn from storage capacity, reserve policy and delivery logistics so that a temporary compressor is not treated as operationally ready simply because its airflow and pressure are adequate.

1. Purpose and Engineering Decision

Temporary compressed air can fail for reasons that have nothing to do with compressor capacity. A diesel compressor may be correctly sized for flow and pressure yet still stop because its onboard tank is too small for the shift pattern, a night refuelling window was missed, a fuel truck cannot reach the workfront, or the fuel plan assumes full-tank volume is fully usable.

It is a logistics calculator, not a combustion or engine-performance model.

2. Fuel-Burn Input Must Match Operating State

Fuel consumption should come from a verified machine curve, measured site data or a supplier/OEM operating estimate at a defined load.

Fuel per Period = Sum(Fuel Rate_i x Time_i)

3. Shift / Daily Fuel Demand

Shift Fuel = Sum(Fuel Rate_i x Hours_i) + Fixed Shift Allowance

Daily Fuel = Sum(Shift Fuel_j)

Fixed allowance may represent warm-up, repositioning, short unlogged idle periods or a user-defined contingency. It must remain visible as an input rather than being hidden inside the fuel rate.

4. Tank Usable Volume

A nominal tank capacity should not automatically be treated as fully usable. The calculator should allow a maximum fill fraction and a minimum retained/reserve fraction.

Usable Tank Volume = Nominal Tank x (Maximum Fill Fraction - Minimum Retained Fraction)

If the machine has a verified manufacturer-defined usable capacity, that value may be entered directly and should take priority over a generic fraction method.

5. Autonomy and Refuelling Interval

Autonomy (h) = Usable Fuel Volume / Average Fuel Burn (L/h)

Refuelling Interval (h) = Autonomy x Operating Availability Factor

The availability factor can be used when the site deliberately refuels before the theoretical tank-empty point. For example, a planner may use only 80% of calculated autonomy to protect against burn-rate variation and late delivery.

6. Reserve Fuel Policy

Reserve Fuel = Planned Consumption over Reserve Window

Reserve should be expressed as an operating window - for example one shift, six hours or one delivery interval - rather than a universal percentage. This makes the result operationally meaningful.

7. Delivery Quantity and Frequency

Delivery Quantity = Consumption until Next Delivery + Required Reserve - Fuel on Hand

Deliveries per Project = Ceiling(Total Project Fuel / Usable Delivery Quantity)

A delivery plan must also consider tanker capacity, site tank free space, access windows, working-hour restrictions and whether fuel can be transferred while the compressor remains in operation.

8. Input Model

9. Reference Test Case A - One 12-Hour Shift

A temporary compressor operates 8 hours loaded at 32 L/h, 3 hours unloaded at 14 L/h and 1 hour stopped. Add a 10 L fixed shift allowance.

Shift Fuel = (8 x 32) + (3 x 14) + 10 = 308 L

10. Reference Test Case B - Tank Autonomy

The compressor has a 500 L nominal tank. Maximum planned fill is 95% and minimum retained fuel is 15%. Use the average 25.7 L/h from Test Case A.

Usable Fuel = 500 x (0.95 - 0.15) = 400 L

Theoretical Autonomy = 400 / 25.7 = 15.6 h

With an 80% operating-availability factor, planned refuelling interval becomes approximately 12.5 hours. That interval is shorter than theoretical autonomy by design.

11. Reference Test Case C - Four-Compressor Shutdown Fleet

Four compressors have expected daily fuel demands of 620 L, 540 L, 410 L and 350 L. The shutdown lasts 10 days.

The fleet total should then be checked against site tankage, tanker capacity and the permitted delivery window.

12. Reference Test Case D - Delivery Plan with Reserve

Fleet daily consumption is 1,920 L/day. The site wants two days of operating reserve and receives fuel every three days. Fuel on hand immediately after the previous delivery is 5,000 L.

Required stock for next 3-day interval + 2-day reserve = 5 x 1,920 = 9,600 L

Next Delivery Quantity = 9,600 - 5,000 = 4,600 L

If tanker capacity is lower than the calculated quantity, the logistics engine should split the quantity into multiple deliveries while preserving the required reserve floor.

13. Fuel Cost

Fuel Cost = Total Fuel Volume x Fuel Price per Litre

Total Logistics Cost = Fuel Cost + Delivery Charges + Handling / Pumping Allowance

14. Refuelling Trips and Tanker Capacity

Required Trips = Ceiling(Required Delivery Volume / Tanker Deliverable Volume per Trip)

Deliverable volume per trip may be lower than tanker nameplate capacity because of route limits, compartmenting, site tank free space or a company operating limit. The calculator should use the user-entered deliverable quantity.

15. Multi-Site / Multi-Workfront Planning

16. Fuel Burn Uncertainty

Actual burn varies with load, ambient condition, engine condition, compressor pressure setting, idling, operator behavior and measurement accuracy. The calculator should therefore allow low/base/high fuel-rate multipliers.

Scenario Fuel = Base Fuel x Burn Multiplier x Runtime Multiplier

17. Schedule Risk and Delivery Delay

The calculator may model a delivery-delay window by adding the fuel required to survive the delay to the reserve stock.

Delay Reserve = Average Burn x Maximum Planned Delivery Delay

This is especially useful where access depends on security windows, weather, road condition or shutdown permits.

18. Electric Temporary Air Boundary

19. Confidence Model

20. Validation and Guardrails

21. Output Specification