The invention relates to a method of controlling operation of a rock drilling rig, wherein a rate of flow of a flushing medium of the rock drilling rig is determined and the operation of the rock drilling rig is controlled on the basis of said rate of flow of the flushing medium.
The invention further relates to a rock drilling rig comprising means for feeding a flushing medium into a borehole for removing drill cuttings being produced during drilling out of the borehole, a measurement arrangement for determining a rate of flow of the flushing medium to be fed into the borehole, and at least one control unit for controlling operation of the rock drilling rig on the basis of the rate of flow of the flushing medium to be fed into the borehole.
Rock drilling rigs and rock drills arranged therein are used for rock drilling and excavation e.g. in underground mines, quarries, and earth construction sites. Typically, drilling simultaneously involves the use of four different functions or sectors, i.e. rotating a drill rod in a borehole being drilled, impacting on the rock by impacting on a drill bit by a percussion device via a shank and drill rods extending therefrom, as well as feeding the drill forward in the borehole being drilled, and flushing so as to remove drilling waste, i.e. drill cuttings, out of the borehole being drilled. In so-called rotary applications, in turn, only three sections are used since these applications do not include impacting on the rock by impacting on the shank by a percussion device. Furthermore, so-called DTH (Down-The-Hole) applications are used in which a percussion piston is located in a drill tube at the bottom of a hole and, rather than on the shank, impacts directly on the drill bit. Thus, the breakage of rock mainly takes place due to the influence of the impact while the purpose of rotating is mostly to ensure that buttons of a bit or other working parts of the drill bit located at an outmost end of the drill rods always impact on a new spot in the rock. The feeding enables a sufficient contact to be maintained between a bit and the rock.
Successful flushing, i.e. successful removal of drill cuttings out of the borehole being drilled, is very important as far as efficient drilling is concerned. If, during drilling, problems occur in the flushing, successful drilling quickly becomes endangered. U.S. Pat. No. 6,637,522 discloses a solution for controlling the operation of a rock drilling rig during drilling. In the solution disclosed in U.S. Pat. No. 6,637,522, a flushing flow is measured and a feed rate and/or rotational speed is controlled on the basis of the measured flushing flow. According to an embodiment of the publication, when the flushing flow decreases the feeding and/or rotation is stopped in order to avoid a drilling overload situation. WO 2005/064111, in turn, discloses a solution in which the aim is to control the flush power at least partly on the basis of the depth of a hole being drilled such that no greater power than that necessitated by the depth of the hole being drilled is used for the flushing. The purpose of the solution is thus to control the total power, which includes at least the impact power and/or rotational power and the flushing power, consumed by the drilling.