At a recent technical seminar on the advantages of using deep sumps to minimize floor space within plant walls, engineers from Vanton Pump Co. described the installation of a 12-foot-tall thermoplastic pump in an area where the available headroom above the top flange of an in-ground storage tank was slightly more than seven feet.
When the problem of servicing the in-ground tank was presented, the solution originally offered involved using a self-priming, horizontal thermoplastic centrifugal pump located next to the tank on the plant floor. While feasible, installing such a pump would require 8 to 12 square feet of additional floor space.
The alternative was to specify a vertical sump pump. This would save floor space and avoid some maintenance issues. But the low headroom made installing a single-piece shaft difficult. To solve that problem, a pump with a segmented shaft design was specified.
Design and construction of the pump involved two five-foot subassemblies bolted together with thermoplastic hardware. This made it simple to install the individual sections. All wetted components of the immersed sections were specified in chemically inert thermoplastic materials. The metal shaft was sleeved in the same material and the columns were ribbed for rigidity.
Using section shaft construction required isolating the metal shaft connector and the components joining the two sections from the corrosive fluid. This was accomplished with Vanton's proprietary "Giraffe" design. The Giraffe system incorporates a movable, sliding thermoplastic coupling sleeve and associated elastomeric O-rings to assure complete sealing where the unit mates with the thick-sectioned thermoplastic shaft sleeve.
