Application and Development of New Technologies in Hydraulic Rock Breakers

1.6 Application and Development of New Technologies in Hydraulic Rock Breakers

With the continuous development of hydraulic rock breaker products, various related new technologies have also been widely applied in hydraulic rock breakers, thereby forming the technical development direction of hydraulic rock breaker products.

(1) Dust suppression technology

During demolition work or when excavating tunnels, dust is very large, which damages the health of operators and reduces field visibility. The Rammer City Jet hydraulic rock breaker has a water pipe and nozzle installed on the machine frame; when the hydraulic rock breaker is working, water sprays out from the two nozzles at the front end of the machine frame. The pump flow can be adjusted, with a maximum flow of 40 L/min, and water pressure of 20 MPa. The sprayed water mist particles are small and velocity is high, effectively cleaning dust.

(2) Noise reduction technology

With the strengthening of people's environmental awareness, restrictions on hydraulic rock breaker noise are becoming increasingly strict. Currently, the main noise reduction measure for hydraulic rock breakers is to use an enclosed box-type machine frame, hanging the rock breaker body between elastic damping elements made of special plastic with pre-stress. The elastic damping elements and high-standard wear-resistant plastic plates increase the sound absorption effect. These measures can greatly reduce noise; at a distance of about 15 metres, noise can be reduced to 85 dB. Noise reduction technology is not only beneficial for environmental protection, but also reduces vibration of the hydraulic rock breaker, eases the reaction force on the hydraulic rock breaker, and has a protective effect on both the hydraulic rock breaker itself and the excavator.

(3) Diversification of working media

Most hydraulic rock breakers use hydraulic oil, but for environmental protection purposes, Krupp hydraulic rock breakers can also use water-glycol hydraulic oil, synthetic ester hydraulic oil, and vegetable oil-based hydraulic oil. Of course, before using environmentally friendly hydraulic oil, it is necessary to consult and obtain consent from the excavator manufacturer and the hydraulic rock breaker manufacturer. For underground work, to reduce danger, Krupp hydraulic rock breakers can use fire-resistant hydraulic oil.

(4) Underwater operation technology

An ordinary hydraulic rock breaker cannot work underwater without modification; if water enters the chisel seat, a water pressure wave is generated at each impact. This water pressure wave can damage the sealing parts of the hydraulic system, and may also cause water to infiltrate the hydraulic system, causing the piston to rust and be damaged. To avoid damage to the hydraulic rock breaker, Krupp company developed a special connecting device for underwater operation, equipped with various necessary waterproof components, using compressed air to prevent water from entering the hydraulic rock breaker. Rammer and Furukawa also have hydraulic rock breakers capable of underwater operation.

(5) Dust prevention technology

Krupp Marathon-type hydraulic rock breakers have a chisel dust prevention device installed, which includes guide rings, floating rings, dust blockers, and dust scrapers. The steel floating ring can prevent coarse particle impurities from entering, while the dust scraper made of elastic material can prevent fine dust from entering; this dust prevention system is significantly effective. Krupp also uses compressed air for dust prevention — using compressed air to flush the interior of the chisel seat and the chisel. When the chisel strikes downward, it can prevent the intrusion of water and rock powder, and can simultaneously lubricate the chisel.

(6) Lubrication issues

Krupp hydraulic rock breakers have an automatic continuous lubrication device installed on the hydraulic rock breaker frame; it can automatically and continuously lubricate the chisel.

Krupp's automatic lubrication device is actually an integrated grease pump. This pump is installed near the maintenance hole of the box frame, connected to the hydraulic rock breaker body through two oil pipes; one oil pipe connects the hydraulic rock breaker oil inlet to the pump input, and the other connects the pump output and rock breaker body's lubrication grease input. Each time the hydraulic rock breaker starts, the hydraulic rock breaker system pressure acts on the supply piston of the grease pump, and delivers grease through the supply pipe and internal passages of the hydraulic rock breaker to the chisel sleeve portion at the lower end of the hydraulic rock breaker. When the hydraulic rock breaker stops, the pressure drops, and the supply piston returns under spring force; simultaneously under atmospheric pressure it draws grease into the pump. The supply volume of grease depends on the frequency programme of rock breaker start and stop and the pump flow adjustment knob.

The automatic lubrication device is an optional device for hydraulic rock breakers; if not selected or if it fails, manual lubrication can still be used. Generally oil must be added every 2 hours of work. Furukawa F series hydraulic rock breakers can be remotely automatically dosed with lubricating grease by the driver in the cab, and can also be automatically dosed by a timer. Currently, domestic hydraulic rock breakers such as Jingye company's GT series rock breakers also have this configuration.

(7) Blank-firing prevention technology

A blank fire is when, during the reciprocating motion of the hydraulic rock breaker piston, the bottom end of the piston has no contact with the top end of the chisel — that is, it does not strike the chisel. Blank firing can be further divided into complete blank firing and incomplete blank firing.

① Complete blank firing: the piston and chisel have no contact at all; at this time the hydraulic rock breaker has no energy output and converts to heat energy.

② Incomplete blank firing: the piston has hit the chisel, but because the excavator has not pressed the hydraulic rock breaker tightly, the impact reaction force lifts the hydraulic rock breaker body, the chisel advances at a considerable speed along with the piston, until the chisel hits the chisel pin before stopping. This causes serious damage to the chisel, chisel pin, chisel seat, and long bolts, and is more severe than complete blank firing.

Under the following two situations, a hydraulic rock breaker can have complete blank firing or incomplete blank firing:

① The chisel has not contacted rock, or the hydraulic rock breaker is started without pressing the rock.

② The rock has broken and the hydraulic rock breaker has not stopped in time.

If a hydraulic rock breaker can block starting or auto-stop under the above two situations, it is said to have the blank-firing prevention function; currently most brand hydraulic rock breakers have added this function in their structural design.