PDA, SPECS, GRLWEAPWhat is the difference between the efficiency of Hydraulic Hammers and that of Diesel Hammers?
The term “efficiency” can have several interpretations. In wave equation analysis (GRLWEAP) it is the ratio of the potential energy to the kinetic energy of the ram just prior to impact. A wave equation efficiency of 80% best matches the normal performance of most diesel hammers, therefore that is the value recommended by GRLWEAP. The wave equation efficiency of hydraulic hammers has variations among the manufacturers; the 95% recommended by GRLWEAP is a good assumption for those with built in energy monitors. In PDA testing, the term “Energy Transfer Ratio” (ETR) is the ratio of the energy transferred into the pile to the maximum rated energy of the hammer. This value depends not only on the hammer but also on the pile type, since typical plywood cushions used with concrete piles absorb some energy. Diesel hammers have a median energy transfer ratio of 37% on steel piles (less on concrete piles), if you compare the energy transferred to the pile to the maximum rated energy of the hamm
