In tunneling and mining operations, rock‑drilling rigs often operate in winter conditions or at high altitudes where temperatures are extremely low. The adverse effects of such cold environments on equipment are multifaceted: the viscosity of engine and hydraulic oils increases markedly, battery capacity declines substantially, diesel fuel’s flowability deteriorates—sometimes leading to wax precipitation that clogs pipelines—and condensation in pneumatic systems can freeze. Improper cold‑start procedures may result in difficulty starting or sluggish actuation; in severe cases, they can cause cylinder scoring, bearing seizure, or damage to the hydraulic pump. Consequently, mastering standardized cold‑start and operational procedures is a fundamental prerequisite for ensuring continuous construction and prolonging equipment life.
I. The Comprehensive Impact of Ambient Temperature on Equipment
Increased oil viscosity is the direct cause of cold‑start difficulties. In diesel engines, the engine oil’s viscosity rises at low temperatures, creating additional friction between moving parts during crankshaft rotation and making it difficult to reach the minimum required starting speed of approximately 150 rpm. Similarly, elevated hydraulic‑oil viscosity impairs suction at the pump, resulting in insufficient flow; consequently, hydraulic cylinders are prone to delayed initial movement or exhibit “sticking” and “creeping” during startup. This not only degrades operational smoothness but may also compromise drilling‑positioning accuracy.
Battery performance deteriorates significantly at low temperatures. As ambient temperature decreases, the electrolyte density increases, its permeability declines, and internal resistance rises, leading to a corresponding reduction in both capacity and terminal voltage. In extremely cold conditions, a battery’s output may drop to approximately 40% of its rated capacity, while the starter’s torque and speed fail to meet the requirements for diesel engine starting, resulting in difficult cranking.
Insufficient compression temperature within the cylinder. In winter, the air entering the cylinder, as well as the cylinder walls and pistons, are at low temperatures. As a result, much of the heat generated by the piston’s compression of the combustible mixture is absorbed by the surrounding components, leaving the mixture’s temperature at the end of compression below the autoignition point of diesel fuel, which directly leads to starting difficulties.
The air‑line system of the air compressor is prone to icing and blockage. After shutdown, a sudden drop in ambient temperature causes the compressed air to cool, resulting in substantial condensate formation within the compressor’s air‑line piping. If this condensate remains in the lines and is not drained, it may freeze and obstruct the pipes, impairing the chip‑removal function during drilling.
II. Low-Temperature Starting Measures for the Engine
Start the engine using a staged preheating method. Before starting, thoroughly preheat the engine either by using hot‑water preheating or a flame‑preheating device. For the hot‑water method, inject 90–95°C hot water into the cooling system, adding more as you drain; once the water discharged from the drain valve reaches 30–40°C, close the drain valve. Typically, after injecting hot water for 10–15 minutes, the engine can be started. For the YZP131 rock‑drilling rig manufactured by China Railway Construction Heavy Industry, the start-up procedure is as follows: turn the key to the “ON” position—all indicator lights on the instrument panel should illuminate—then press the preheating button and wait for preheating to complete (usually 10–15 seconds, depending on ambient temperature). Finally, turn the key to the “START” position to start the machine.
Use low‑temperature‑grade fuel and engine oil. Select a light diesel grade appropriate for the local minimum temperature; it is recommended to choose a grade that is 5–8°C lower than the local minimum temperature (the cloud point of the diesel). For engine oil, switch to a winter‑specific, low‑viscosity grade to reduce crankshaft rotational resistance during cold starts. Install metal heat shields on the intake and exhaust manifolds to harness exhaust‑manifold heat for preheating the air‑fuel mixture, which helps improve fuel atomization.
Battery insulation and maintenance. Before the onset of winter, check the specific gravity of the battery electrolyte and adjust it if necessary. Use wooden or insulated double‑walled enclosures to keep the batteries warm; where feasible, store them indoors. For equipment that will remain idle for an extended period, disconnect the batteries or remove them and store them indoors. If the equipment is only temporarily out of service, start the engine and recharge the batteries periodically to maintain adequate charge. When using a generator, increase the charging voltage by adjusting the regulator so that the voltage on the charging circuit is 0.6 V higher than in summer, thereby compensating for the reduced capacity of the battery at low temperatures.
Key points for preheating: Turn the ignition key to the preheat position to warm the cylinders; typically, preheat for 30–40 seconds. The maximum duration of a single preheating cycle is generally 30–40 seconds. During startup, maintain an engine speed of approximately 150 rpm. If the first attempt fails, wait 2 minutes before trying again to prevent repeated starts from draining the battery.
III. Low-Temperature Operation Assurance for the Hydraulic System
Use low‑temperature hydraulic oil and install a preheating device. Conventional hydraulic oils experience a significant increase in viscosity below –30°C; therefore, switch to low‑temperature hydraulic oils—such as L‑HV32 wide‑range hydraulic oil or L‑HS32 ultra‑low‑temperature hydraulic oil—whose pour points can reach below –45°C, ensuring excellent fluidity even in extremely cold conditions. The CYTJ76A remote‑controlled hydraulic tunneling rig, operating at Arctic‑circle mining sites where winter temperatures can plunge to –50°C, has successfully addressed the challenge of hydraulic system freezing and blockage by employing dedicated low‑temperature hydraulic oil and an advanced intelligent temperature‑control system with heating and antifreeze features.
Methods for preheating hydraulic oil. Electric heaters, circulating heating, or tank-mounted heaters may be used to gradually raise the oil temperature to an appropriate range; abrupt heating should be avoided, as it can accelerate oil oxidation. For safe system startup, it is recommended to wait until the oil temperature reaches 10–15°C. During the preheating process, the hydraulic system should be run at low pressure and under no-load conditions for a period of time (approximately 5 to 10 minutes) to allow the oil to warm naturally through internal friction while simultaneously venting any trapped air from the lines.
Gradual loading after temperature rise. Hydraulic oil may be subjected to loading only once its temperature has reached at least 5°C; however, operations must be conducted with a steady, gentle control rhythm to avoid sudden high‑flow impacts. As the oil temperature continues to increase and exceeds 30°C, and once the hydraulic fluid has fully attained its optimal working viscosity—ensuring smooth cylinder operation without creep or vibration—the equipment may then be put into full‑load continuous service. Under extremely cold conditions, this process may take considerably longer, so operators should remain patient. During breaks in operation, the equipment should be started every 3 to 5 hours to prevent the hydraulic oil from cooling too much, which could make subsequent startups difficult.
IV. Low-Temperature Protection for Electrical Systems
In low-temperature environments, the electrical system faces challenges no less severe than those of the hydraulic system. Components such as the rock‑drilling rig’s control cabinet, sensors, and wiring harnesses may exhibit frequent electronic‑component alarms and occasional control‑system delays under extreme cold conditions. At high altitudes, where the air is thin, electrical insulation strength diminishes, increasing the risk of leakage currents or short circuits.
Electrical protection configuration of the entire machine. High-altitude rock‑drilling rigs, such as the CRRC Equipment DJ3G three‑arm high‑altitude rock‑drilling rig, are equipped with specialized electrical components for high‑altitude operation, including high‑altitude cable reels and high‑altitude batteries. The overall control system, particularly the core rock‑drilling subsystem, employs proven control technologies; the electrical control system incorporates impact‑resistant, interference‑immune motion controllers and utilizes a fieldbus for signal transmission.
Cabin microenvironment control: A fully enclosed cab is equipped with heating and cooling air conditioning to maintain an optimal temperature, ensuring operators can comfortably execute all operational commands. Cabin noise is kept below 75 decibels, and the cab features an FOPS‑compliant protective canopy, a reinforced steel mesh, and an onboard oxygen generator, thereby guaranteeing the safety and comfort of personnel working in extreme high‑altitude conditions.
V. Antifreeze Protection for the Cooling System and Water Lines
In low-temperature environments, the cooling system and water supply lines are prone to freezing, which can result in inadequate engine cooling, damage to the water pump, and blockage of the sludge‑discharge passages.
Antifreeze protection for the cooling system. The appropriate grade of antifreeze should be added according to the expected minimum ambient temperature, with a recommended freezing point at least 10°C below the local lowest air temperature. Equipment not using antifreeze must have its water drained and be tagged “Drained” as a warning when shut down overnight. When operating a heating furnace, ensure that the ball valves are in the correct open or closed position to establish an effective circulation loop, and verify before startup that the furnace is completely filled with antifreeze and all air has been purged.
Water supply and pipeline draining. After construction is completed, drain all fluids from the pump head, water tank, centrifugal pump, and other components to prevent low‑temperature freezing from damaging parts or affecting subsequent operations. Open the quick‑connect plug on the rear drain line to promptly discharge any residual liquid from the mixing tank; open the union fitting on the suction/discharge manifold and the drain ball valve at the bottom of the centrifugal pump housing; and open the clamp‑type plug or ball valve at the bottom of the fluid‑addition pump housing, keeping the suction inlet open until the system is completely drained to avoid freezing in the cavities and pipelines.
VI. Heating and Break-In Procedures After Startup
After starting the engine, allow it to idle for approximately 5 minutes to warm up. Once the oil pressure has stabilized and the oil temperature has risen, gradually increase the speed to 1,800–1,900 rpm before commencing operation. If the equipment stops unexpectedly during operation, immediately remove the load and restart it to prevent damage to the turbocharger.
During the initial phase of operation, maintain close monitoring of the hydraulic system and operate all actuators—such as outrigger extension/retraction, boom swing, and rock‑drilling machine feed/retract—slowly to ensure thorough circulation of the hydraulic fluid and gradual attainment of normal operating temperature. The low‑temperature embrittlement of structural components must also be taken into account; at extremely low temperatures, avoid performing large‑amplitude impact maneuvers or sharp turns before the equipment has been adequately preheated, to prevent the development of brittle cracks in the structure.
VII. Incident Handling for Low-Temperature Operation Abnormalities
In low-temperature environments, rock‑drilling rigs may experience abnormal operation due to excessively high hydraulic oil viscosity, blocked oil lines, or hardened seals. Note that in extremely cold conditions, starting the machine immediately after a hot shutdown can cause seal failure owing to the thermal shock between hot and cold components; likewise, rapidly switching the directional control valve group may exacerbate sticking and creeping. In such situations, reduce the operating frequency or increase the number of no‑load cycles, and avoid forcing the equipment to operate while faulty.
When the air lines freeze, resulting in insufficient pressure and an inability to release the braking system, use hot air or low-pressure steam to thaw the lines. Never use an open flame to directly heat air‑line components, as this could scorch rubber seals and cause pipe rupture. If the hydraulic pump emits unusual noises due to cavitation or its temperature rises abnormally, shut down the machine immediately, check the hydraulic oil level and preheating conditions, and restart only after confirming that the fault has been resolved.
VIII. Targeted Configuration for High-Altitude Equipment
To meet the demanding operating conditions of high-altitude, low-temperature environments, China Railway Equipment has developed the DJ3G plateau‑type three‑arm rock‑drilling rig. Its structural components are fabricated from low‑temperature‑resistant, impact‑tough steel; the engine is equipped with a turbocharger and an intake‑air preheating system to ensure adequate power; the undercarriage employs four‑wheel‑drive transmission technology; the electrical control system incorporates plateau‑specific electrical components such as a plateau cable reel and a plateau‑rated battery; the hydraulic oil tank is fitted with an auxiliary cooling unit; and the water‑and‑air system is outfitted with a high‑power water pump and an air compressor. This suite of specialized configurations provides comprehensive technical support for the stable operation of the drilling rig in extreme cold at high altitudes.
When operating rock‑drilling rigs in extremely cold regions, it is essential to strictly adhere to the operational guidelines of “change oil with the season, preheat before startup, warm up under no‑load conditions, and apply load gradually.” Enhanced modifications to improve low‑temperature performance and routine maintenance of hydraulic fluid, batteries, the cooling system, and the pneumatic circuit are also critical. By implementing standardized low‑temperature start-up procedures and operational management, the adverse effects of extreme cold on equipment performance can be effectively mitigated, ensuring continuous operations for tunneling and mining projects during winter and at high altitudes.