Pit & Quarry, August 2013

ing 7 days per week and traveling by air from Reserve La to St Louis One truck housed their tools Field services costs including lodging and local transportation totaled 154884 Also calculated in the conversion cost were shipping costs of 15050 and crane costs of 17326 As part of the calculation for payback conditions Johnson considered that increased production with an electric dredge would improve profit margins for production results achieved at a lower cost Since the additional tons per hour is achieved without adding extra manpower or machinery it would suggest that the additional productivity would be completed at a higher profit percent than initial productivity Johnson says If we estimate that the average productivity is at a 25 percent profit margin and the additional productivity to be half as expensive as initial productivity this means we should achieve a 625 percent profit margin on the additional productivity DSCs project revealed that a dredge operated with an electric motor used 4857 percent less energy per year 4962 percent less energy per hour and 5257 percent less energy cost per ton Based on adjusted increased profitability 135543 tons of production would equal 1084344 of added revenue at 8 per ton and 677715 of additional profit With operational savings of 129729 per year the annual payback would equal 807444 With our conversion costs we calculated that our payback would take 153 months Johnson says After the conversion cost was recovered the company would add 806748 to its bottom line each year Clean energy Some of the less obvious benefits of converting to an electric motor include elimination of engine oil and fuel filter changes oil disposal requirements and no frequent or risky dredge fueling Electric motors can have a 20 to 30 TABLE 2 Dredge Energy Consumption Diesel Electric Avg HP Demand 80218 Avg HP Demand 85424 Gallons Hour 3842 kW Hour 63701 Cost Hour 339 Gal 13024 Cost Hour 103 6561 Use of an electric motor in the 20 to 30 year lifespan of a dredge could result in substantial cost savings year service life with low maintenance and high reliability due to reduced moving parts Johnson adds Electric power is cleaner which could lead to additional financial implications since many projects for public and private entities now call for inclusion of sustainability goals Firms positively affecting the environment are often given preference in the bidding process In fresh water conditions the average life of a dredge is 30 years In salt water 20 years is a typical lifespan Use of an electric motor in that time would provide an overwhelming financial impact Johnson estimates that between 50 and 60 percent of dredges in the market were manufactured with diesel engines He notes that dredge owners considering a conversion might also review their options for upgrading dredge controls at the same time Touch screen controls that replace manual gauges could add automation to increase efficiency Johnson says That kind of feature allows dredge owners to access data about dredge operations and essentially analyze how the dredge is used every minute of the day The information makes dredge management much easier This information is especially important if youre evaluating a worn out dredge Johnson says You have to consider whether or not youre going to put the same kind of machine back in operation or look at other alternatives With an electric motor youre going to have more uptime fewer breakdowns and less maintenance You can spend more time dredging P Q Loretta Sorensen is a freelance writer in Yankton S D who produces material about a variety of topics serves as a ghostwriter and has authored her own books DREDGING 22 PIT QUARRY August 2013 www pitandquarry com