Part One of this two-part series discussed progressive cavity pump selection, mechanical seal maintenance and how spiral stator technology can improve the performance of these pumps. Part Two explains why peristaltic pumps are a good option for handling solids. Peristaltic pumps cannot reach the high flow rates that progressive cavity pumps experience, but they are a good choice for handling high solids. A peristaltic pump can efficiently move solid contents in the range of 60 to 80 percent solids. They will likely have a more simplified and less costly maintenance-to-cost ratio. Peristaltic pump maintenance usually requires changing the hose and replacing glycerin. In most applications, this can be accomplished in less than an hour by unskilled labor. However, before purchasing peristaltic pumps, the end user should examine some design differences and advantages. Like progressive cavity pumps, significant maintenance and spare cost savings can be realized by selecting the appropriate design for an application.
These pumps require regular attention, so end users should carefully consider the design options.
06/16/2014
Roller design
Peristaltic pump flow capabilities have been expanding, and new designs can produce up to 440 gallons per minute (gpm) continuously. This high continuous flow rate has never been accomplished by peristaltic pumps. Their use is gaining popularity in many industries, especially for pumping highly concentrated slurries. The advantage of a peristaltic pump is that only the hose contacts the corrosive and highly abrasive slurries. The hose is typically the only wearing part of the pump. The hose pump is easier to repair, and peristaltic pumps typically cost less than centrifugal pumps. In the past, the disadvantage of certain peristaltic pumps has been the relatively short hose life.
Table 1. The economics of a 2.5-inch pump versus a 4-inch pump. The 2.5-inch pump has 69 percent less operating costs, and the savings are enough to buy another 2.5-inch pump in one year. The data are courtesy of the City of Hamilton, Ohio, power plant.
A 2.5-inch cam offset shaft pump operates at 21 rpm compared to 6 rpm for the 4-inch shoe pump. The hose lifetime of the cam offset shaft pump is more than four times longer than the shoe-design pump. Ultimately, the one-year operating costs of the cam offset shaft pump are $20,148 less than the shoe-design pump.
Peristaltic pumps and progressive cavity pumps have advantages and disadvantages when compared with each other and competing technologies. A peristaltic pump is often an excellent choice for pumping high-solid-content slurries (with 60 to 80 percent solids) and corrosive media because the hose is the only component that touches the pumped fluid. In some cases, the use of exotic alloys can be completely eliminated. With any pump, paying close attention to the pump design features and maintenance requirements may be beneficial for years, with thousands to even hundreds of thousands in potential savings.