One of the most overlooked factors when doing a total cost analysis on pumping systems is energy consumption.
In the case of AOD pumps, most do not consider the high cost of compressed air.
This was evidenced recently by a Roper salesman when visiting a sealcoat manufacturing plant that was pumping an asphalt emulsion sealcoat product. They were using a 2” AOD pump to transfer 60 GPM at 50 PSI of the 1000 SSU, slightly abrasive liquid. The plant ran the pump roughly 8 hrs./day, 50 weeks per year (2,000 hours/year).
The plant manager had some initial misgivings about the high acquisition cost of the 3600 EVO versus a diaphragm pump. However, when shown the energy consumption comparison, the 3600 EVO was a relative bargain after only one year of operation.
To do the calculation we used some (generous) assumptions about the air system. Using 125 PSI plant air with no leaks or losses, and a screw compressor at 92% loading. The equivalent electrical brake horsepower for the AOD pump was 17.5 bhp. Conversely, a 3611EGHBFRV EVO pump running at 545 RPM had a bhp of 3.5. Assuming an industrial electricity rate of 5¢ per kWh, the operator would save over $1,000 per year! And this speaks nothing of the other costs associated with diaphragm pumps such as running air lines, pulsation dampener, air regulator, air dryer, etc.
An even larger cost benefit that a user could capture by running an EVO pump versus an air operated diaphragm pump is derived from greatly reduced downtime and fewer spare parts requirements. In this particular example, the abrasive nature of the liquid resulted in required replacement of the AOD pump wetted parts roughly quarterly. Including downtime, this resulted in a net loss of approximately $1,000 per repair. In this application, the 3600 EVO with its extreme wear resistant bushings and shafts is expected not to require any maintenance within the year. Based on these anticipated cost savings, the plant has now replaced several AOD pumps with the Roper 3600 EVO.