CME Automatic Hammer Operations Bulletin

This report is a summary of experience with the Central Mine Equipment (CME) automatic hammer operation during performance in the Standard Penetration Test (SPT). The CME automatic hammer is run by a hydraulic chain-cam lifting system, and the drop height of the hammer depends on the speed of the chain cam. This report addresses energy transmission characteristics of the hammer system. Historical energy transmission data are reviewed. Manufacturer’s operating instructions are reviewed. In a field study, the rate of the hammer was changed, and the drop height and energy measurements were taken. The data show that when the hammer is run at a slow rate of 30 blows per minute, energy loss was almost 15 percent. The data show that it is important to observe the hammer rate while testing and to operate the hammer at the design speed of 50 blows per minute.