surface drilling
axis and break the foot valve, causing the hammer to stop drilling. The hammer’s chuck or drive sub needs to be opened and the drill bit must be changed, or the broken piece removed and a new foot valve installed. Heat issues can also change the properties of the thermoplastic material that the foot valves are made from and cause the valve to gradually come out of the drill bit.
Problem solved To eliminate the foot valve from the drill bit while maintaining high productivity or increasing performance has usually meant changing to proprietary shanks. This leaves unused products in stock and can increase lead times to ramp up stocks of the new product. The new Mincon MQ range of DTH hammers has now eliminated the need for the foot valve while maintaining the use of industry-accepted drill bits. In developing this range of hammers, a number of design features were incorporated to increase performance over Mincon’s standard models that use these shanks with the foot valve. During extensive testing in Australia and the US, increases in penetration rates in some instances of 10% or more were experienced. The drilling performance increases even further when downtime caused by broken foot valves is eliminated. Another benefit that comes from removing the foot valve from the drill
bit is more efficient exhausting of the operating air from the hammer. When using a drill bit with a foot valve, the air does not exhaust from the bottom air chamber until the piston clears the foot valve and the air can escape down through the centre of the drill bit. Removing the foot valve allows the hammer to exhaust from the moment the piston strikes the drill bit. This aids in removing the cuttings from the drill-bit face quicker and thus increases the penetration rate. This more efficient exhausting of the hammers’ operating
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air also helps greatly when drilling in wet holes where ground water is encountered. The drill-bit shanks that are used with the Mincon MQ range are accepted industry standards with their foot valves removed. The MQ40 hammer uses the TD40 shank, the MQ55 uses the QL50 shank and the MQ60 and MQ65 uses the QL60 shank. The Mincon MQ68 is a large-bore production hammer for drilling 6¼in (159mm) to 7½in (190mm) holes and uses the QL60 shank with no foot valve.
PROVEN PERFORMANCE IN THE MOST EXTREME CONDITIONS. At MINCON, we understand that high quality products increase productivity. The New Mncon MQ Range of premium performance DTH hammers raises the bar once again for productivity, reliability and longevity in blast hole applications. Utilizing industry standard shanks without need for a foot valve the Mincon MQ Range delivers high performance and greatly reduces downtime. Visit mincon.com to find out how our superior products deliver savings, improve performance and reduce downtime.
A bit with a broken foot valve
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Mincon.com
June 2014 16/05/2014 11:17