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Gunnar Wijk

Modified by Andreas Nordbrandt / 2003-08-13

Lubrication systemLubrication system

Bench drilling - Tunnel driving - Roof bolting - Reaming - Production drillingBench drilling - Tunnel driving - Roof bolting - Reaming - Production drilling

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The surfaces between moving parts must be lubricated if the components areto have a good service life. The percussion mechanism and rotation motor in ahydraulic rock drill are obviously lubricated by hydraulic oil, but in the case ofpneumatic rock drills, lubricating oil must be added to the compressed air thatdrives the machine.

This applies to both the percussion mechanism and the rotation motor. Thereis always a certain overpressure in all the inner spaces in a pneumatic rockdrill, relative to the atmosphere, which means that air continuously blows outthrough the various slots and holes. This movement of air effectively preventsdust and other impurities from entering the machine. Sometimes, however, therotation motor is switched off while the drill hole is blown clean. During suchoperations, it is possible that drill cuttings can enter the rotation motor, withdevastating effect.

To prevent dirt and water from entering hydraulic rock drills, all spaces in the

machine that are not filled with oil must be given a certain overpressure relativeto the surrounding atmosphere. This is achieved by supplying the machine witha flow of compressed air, which is mixed with a suitable quantity of oil. Inunderground drilling applications, it is important thatALL external matingsurfaces are supplied with pressurized lubricating air, since it is technically

impossible to create effective sealing surfaces without the use of gaskets.

2.7 The lubrication circuit

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Gaskets do have the desired effect, but suffer from short service life, which is why internalpressurization of the machine is a much better alternative. In surface drilling applications, theingress of impurities is almost negligible, and "sweating" around mating surfaces that areinternally pressurized by lubricating air can have negative consequences.

On surface machines therefore, it must be made possible to easily switch off pressurization ofthe mating surfaces. Lubricating oil is needed primarily at two places in a hydraulic rock drill,namely between the splines of the driver and shank adapter, and between the nose bushingand neck of the shank adapter. Traditionally we have a generous amount of air blowing outaround the nose bushing, in order to prevent the ingress of dirt in both surface and underground

drilling applications.

In surface drilling, the hole diameters are usually larger, which means that higher torque have tobe transmitted via the shank adapter. For this reason, it is especially important that the dosageof lubricating oil is correct, in terms of both. quantity and quality.

Lately, it has become an issue in surface drilling to reduce this amount to zero.

Almost all our surface rock drills are prepared to collect the lubrication oil and lead it back to therig if desired.

2.7 The lubrication circuit

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Under no circumstances should the lubricating oil be too thin, otherwise the flow of lubricatingair will simply blow it off the surfaces to which it is supposed to stick.

The dirt is especially important to keep away in upward-directed drilling, when flushing waterand drill cuttings from the hole shower down continuously over the machine. Different types ofdrill collars are available to lead the cuttings and water away from the rock drill front.

In underground drilling applications using water flushing, the shank adapter splines are well-cooled by the flushing water streaming into the adapter, even though the heat has to travelforward somewhat through the adapter steel in order to reach the water-cooled surfaces. Insurface drilling applications, the cooling properties of

air flushing are much less efficient.

We normally call the lubricationcircuit the ECL-system Electrically Controlled Lubrication. Inour system, a fixed displacementpiston pump delivers an amount of oil in proportion to howmanyelectrical pulses the coil of the pump is set to.

In DTH or CR applications, the amountof oil that pump delivers is not sufficient. Therfore thereis the HECL pump (Heavy ECL) which is electrically-hydraulically operated and delivers 6-9times as much lubricationoil as the ECL pump

2.7 The lubrication circuit

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