Arrangement and method for feeding flushing fluid

Abstract

The present disclosure relates to a flushing system and a method of controlling the feeding of flushing fluid. The flushing system includes a pump unit for feeding pressurized flushing fluid to a feed duct connected to a rock drilling machine. The flow rate of the flushing fluid to be fed is controlled by controlling the pumping of the flushing fluid. The flow rate is determined by one or more sensing devices.

1 . A flushing system of a drilling unit, wherein the drilling unit comprises a drilling machine and a tool connectable to the drilling machine, the flushing system comprising:
 a pump unit for feeding pressurized flushing fluid, wherein the pump unit includes a pump and a power device for driving the pump;   at least one feed duct for feeding the pressurized flushing fluid from the pump to the drilling machine;   at least one valve disposed in the feed duct for controlling flow of the flushing fluid conveyed to the drilling machine;   at least one sensing device arranged to measure at least one property of the fed flushing fluid;   at least one control unit for controlling the feed of the flushing fluid in response to a sensing data received from the at least one sensing device; and wherein the pump unit is a variable flow rate pump unit provided with adjusting means allowing flow rate of the flushing fluid to be varied, the control unit being configured to determine flow rate of the flushing fluid on the basis of the received sensing data, and the control unit being further configured to control the flow rate of the fed flushing fluid by adjusting the pressure supplied by the pump; and   at least a first feed duct and a second feed duct, which are operationally parallel relative to each other; the first feed duct being provided with a first valve and a first throttle; and the second feed duct is being provided with a second valve and a second throttle, the first throttle and the second throttle each having orifices, which differ in size, the first valve and the second valve being independently controllable, wherein the control unit is configured to control opening and closing of the first valve and the second valve according to the operation of the drilling unit.   
     
     
         2 . The flushing system as claimed in  claim 1 , wherein the valve is an on/off-type without adjusting means. 
     
     
         3 . The flushing system as claimed in  claim 1 , wherein first and second throttle is an integrated element of a respective valve. 
     
     
         4 . The flushing system as claimed in  claim 1 , wherein the throttle is a separate element relative to the valve. 
     
     
         5 . The flushing system as claimed in  claim 1 , wherein at least one throttle is arranged in the at least one feed duct, wherein the at least one throttle causes a pressure drop. 
     
     
         6 . The flushing system as claimed in  claim 1 , wherein the at least one feed duct is provided with at least one flow meter for determining the flow rate of the flushing fluid. 
     
     
         7 . The flushing system as claimed in  claim 1 , wherein the pump is driven by an electrical motor, the operating speed of the pump being adjusted in order to adjust the produced flow of the flushing fluid, wherein the rotational speed of the electric motor is adjusted by an adjusting device. 
     
     
         8 . The flushing system as claimed in  claim 7 , wherein the pump is a fixed displacement pump and the supplied pressure of the pump is adjusted by adjusting the rotational speed of the pump. 
     
     
         9 . The flushing system as claimed in  claim 7 , wherein the adjusting device is a frequency converter. 
     
     
         10 . The flushing system as claimed in  claim 9 , wherein at least one pressure sensing device is arranged to detect pressure of the flushing fluid acting in the drilling machine, the pressure of the flushing fluid being adjusted by adjusting the pump, a maximum pressure rate tolerated by the drilling machine being set to the control unit, and wherein the control unit is arranged to control the pump unit to supply a pressure close to the predefined maximum pressure. 
     
     
         11 . The flushing system as claimed in  claim 1 , further comprising an air-mist flushing system and at least one compressor for supplying compressed air for the flushing and the pump is a water pump arranged to supply pressurized water for the flushing, wherein the supplied pressurized flushing water and the pressurized flushing air are mixed in the feed duct, whereby air-mist is produced, the control unit being arranged to control the operation of the compressor. 
     
     
         12 . The flushing system as claimed in  claim 11 , wherein the compressor is driven by a second electrical motor; and an operational speed of the second electrical motor is controlled by a frequency converter in order to adjust the flow rate of the compressed air. 
     
     
         13 . A method of controlling feeding of flushing fluid of a flushing system of a rock drilling unit, according to  claim 1 , the rock drilling unit including a drilling machine and a tool connectable to the drilling machine, the method comprising the steps of:
 pressurizing flushing fluid by at least one pump unit and conveying the pressurized flushing fluid to the drilling machine through at least one feed duct;   controlling the feeding of the flushing fluid by at least one valve arranged in the feed duct;   monitoring the fed flushing fluid with at least one sensing device; and   controlling the flow rate of the flushing fluid by adjusting the pressure supplied by the pump unit;   directing the flushing fluid through at least two valves being operationally parallel and having flow paths which are different in size; and   selecting selectively opening and closing of the at least two valves in response to magnitude of the supplied volume flow of the pump unit.   
     
     
         14 . The flushing system of  claim 5 , further comprising at least one first pressure sensing device for detecting pressure of the flushing fluid acting before the at least one throttle and at least one second pressure sensing device for detecting pressure of the flushing fluid acting after the at least one throttle, the sensed pressure data being transmitted to the control unit, wherein the control unit is configured to determine a pressure difference caused by the throttle and determine the flow rate of the flushing fluid on the basis of the detected pressure difference.