Fuel-consumption figures must match the specific operating conditions
Fuel consumption varies with the drilling method, engine and emissions version, rock or soil, hole diameter, depth, bit condition, compressor load, hydraulic demand, operator behavior, idle time, altitude and ambient temperature. A seller can report real figures from one job and still give you a misleading prediction for another.
The useful question is not just how many liters per hour. It is fuel per unit of acceptable output under recorded conditions: liters per drilled meter, per completed hole or per pile. Fuel per hour is still useful for budgeting, but it must be paired with output and idle time.
Choosing a Denominator That Matches the Job
For open-air blasthole drills, record liters per drilled meter and per acceptance hole, including hole opening and rod changes. For rotary piling rigs, record liters per completed hole or per working hour, and note the diameter, depth, geological conditions, casing, and delays in spoil removal. For air compressors, record loaded and unloaded time separately.
Also record fuel consumption outside of drilling. Warm-up, travel, positioning, idling while waiting for support equipment, and cleaning all add to the daily cost. A machine that is efficient while drilling can still waste fuel through long idling periods or poor cycle coordination.
Conduct a controlled pre-purchase fuel test
Have qualified personnel measure fuel according to the machine manual and site safety requirements. Define the measurement boundary around the tank and connected supply and return system, identify the engine, and check whether the supply is shared. Record starting and ending fuel stocks, all external inputs, the measurement method and its limits, test duration, engine hours and work completed. Starting stock plus external inputs minus ending stock estimates total system outflow; do not count internal return flow again as an input or consumption. To estimate the engine's consumption, deduct all reliably measured non-engine outflows, such as leaks, withdrawals and fuel used by other equipment, account for other external flows and stock changes, including fuel in the lines, and state measurement uncertainty. If these cannot be quantified reliably, a single-machine estimate is not reliable. Where safe, record the measurement continuously, showing the instrument or container; do not rely solely on an unverifiable onboard average.
- Start from a known fuel quantity and record the measurement method
- Record warm-up, idling, travel, positioning, drilling and auxiliary operations separately
- Record the hole diameter, depth, geological conditions, bit or tool, drill rods, and working pressure
- When the equipment and site conditions permit, run to normal operating temperature and cover multiple work cycles; stop and record the limitations if conditions become unsafe or abnormal
- Record the operator, weather, altitude and any waiting time
- Calculate L/h and the production metrics relevant to the project
Compare test results against operating conditions
A site test without drilling can reveal leaks, excessive idling and basic system behavior, but it cannot predict jobsite productivity. A drilling test in convenient material is stronger evidence, but it still only represents those conditions. Keep the original measurement data, and state its limitations when using the results for a purchasing decision.
If two machines were tested differently, don't rank them by the liters per hour shown. Standardize the operating conditions or retest. Fuel-consumption comparisons are only reliable when load, duration and output are comparable.
Investigate the causes of high fuel consumption
Unexpected fuel consumption may come from worn drill bits, clogged filters, compressor leaks, excessive system pressure, poor hydraulic efficiency, cooling problems, injector or turbo issues, prolonged idling, incorrect drilling parameters, or a mismatch between the machine and the hole. Investigate the cause before concluding that the entire model is inefficient.
During inspection, check the exhaust, engine load, temperature, fault codes, repair records and filter condition. On a DTH drilling rig, record the compressor pressure under load and check for air leaks. On a rotary drilling rig, observe the hydraulic temperature and whether high-power mode is used for work that does not require it.
Turning fuel data into a business comparison
To estimate annual fuel use, multiply the applicable consumption rate for each operating mode, such as production, travel and idling, by its expected hours, then add the results. Do not apply one rate to every mode or multiply it by total calendar hours. Divide the estimated fuel cost by expected accepted output for the same period, and separately account for consumables, planned maintenance and possible downtime. Where rates or hours lack measured evidence, state the assumptions and uncertainty. The lowest fuel consumption rate does not automatically mean the lowest operating cost if production is slower or reliability is poorer.
Calculate low, expected and high scenarios, stating assumptions for fuel price, utilization, ground conditions and output. Compare how sensitive the results are to those assumptions.
What information to provide in an inquiry when fuel consumption is a concern
Please provide the project, drilling method, diameter, depth, geological conditions, production targets, local fuel price and planned working hours. Ask about the engine and compressor or hydraulic configuration, the maintenance records available, and a repeatable operational test. State which metric governs in the contract — hours, meters, holes or piles.
GLOBMACH can include a fuel-test plan in an inspection request and compare machines under the same assumptions. Record the test conditions and the data supplied by the seller, and use traceable estimates to support equipment selection and budgeting.
