Blank Firing

OPERATION

Scoring with the breake

Figure 8. Scoring with the Breaker

Breaker tool binding can cause erratic breaker opera- tion and premature wear on the tool shank. Breaker tool binding is caused by failure to direct the down force in the direction of the tool bit.

Breaker tool bit binding

Figure 9. Breaker Tool Bit Binding

CAUTION

Do not pry with bit and breaker. The tool bit may

break causing injury.

Excessive side force cocks the tool in its bore, prevents proper movement and causes premature tool shank and bushing wear. Since the breaker tool bit must be pushed up into the breaker to operate, a binding tool prevents the breaker from operating correctly. Binding also causes the tool bit and tool bushings to seize and often results in breakage of one or more breaker components.

Always direct the down pressure force in a line toward the point of tool contact with the work.

Moving rocks with the tool bit is another method of bind- ing the tool bit. This practice should be avoided as it may cause tool bit failure.

Rebar reinforced concrete introduces the problem of concrete chunks being held together by the rebar after the concrete has been broken. The best approach to this problem is to use a chisel point tool which permits cut- ting the rebar with the breaker. Another method is to pe- riodically cut the rebar with an oxy-acetylene torch

To understand “Blank Firing”, the operator needs to be aware that the tool bit is able to drop down in the lower body cavity, far enough so that the piston cannot strike it, when the tool bit is not in contact with the work surface. “Blank Firing” occurs whenever the breaker is operating and the piston is not able to strike the tool bit solidly or not strike the tool bit at all. “Blank Firing” accelerates wear and tear on breaker and carrier components and may result in failure of one or more components. Exces- sive “Blank Firing” may be considered equipment abuse and may result in voiding warranties.

Break-through or difficult surface contact results in “Blank Firing” when the material being broken fractures and the tool bit is no longer in “hard contact” with the material but is still pushed high enough in the lower body cavity so that the piston can strike it. In this position, the piston strikes the tool bit and the tool bit, in turn, is driven against the retaining pins because it is not in sufficient contact with the material to be broken. The energy is ab- sorbed by the retaining pins, other breaker components, and the carrier boom components. “Blank Firing” of this type can be experienced in trench work where obtain- ing striking contact with the work surface is difficult or the wrong tool bit is used, or in flat rock work where the operator fails to stop operation of the breaker when slip- page, fracturing or material break-through occurs.

“Blank Firing” as a result of operator error occurs when the tool bit is not in contact with the work surface to be broken and is allowed to drop down in the lower body cavity so that the piston is not able to strike it. Instead, the downward movement of the piston will be stopped by an internal oil cushion located at the bottom of the piston’s stroke and the energy of the piston will be ab- sorbed by breaker components and excavator boom components. “Blank Firing” of this type can be experi- enced when the operator fails to stop operation of the breaker when the material fractures or material break- through occurs, or during re-positioning of the breaker.

MB656 User Manual ◄ 13