Pipe at a phosphate mine is currently used to convey a gypsum slurry mixed with sand tailings during upset conditions. The above-ground pipelines have discharge pressures of about 80 psi with slurry temperatures up to 90°F in the summer. The abrasive nature of the gypsum-sand slurry causes material wear in the pipelines. While having experienced varying degrees of success with materials such as lined steel, high-density polyethylene (HDPE), and primarily fiberglass-reinforced pipe (FRP), the mine was on the lookout for an innovative solution to improve the life of their slurry lines.
In laboratory testing conducted by Performance Pipe, Driscoplex® 4800 series medium-density polyethylene (MDPE) pipe proved to have better abrasion resistance than two PE4710 HDPE pipe resins tested, experiencing less material wear than the HDPE pipe samples in both ambient and raised temperature conditions. Test results are explained in PP844-TN Slurry Abrasion Resistance in Polyethylene Pipe. Encouraged by the test results, the mine put in 5,100 ft. of 34-inch DR13.5 and DR17 Driscoplex® 4800 series MDPE pipe to see how it compared in abrasion resistance to their existing HDPE lines.
The Driscoplex® 4800 series MDPE pipe installed in the gypsum slurry lines has experienced less wear over the past year than their existing DR17 and DR13.5 HDPE pipes operating under similar design conditions. These results support the findings of Performance Pipe’s testing detailed in PP844-TN, as well as additional research that has shown that the abrasion resistance of polymers is principally dependent on the effective number of physical cross-links per macromolecular chain of the polymer structure. The Driscoplex® 4800 series MDPE pipe resin has more effective physical cross-links (i.e. has a smaller percentage of shorter chains that do not contribute to the polymer’s structural connectivity) than the HDPE pipe resins. This results in improved abrasion resistance for the Driscoplex® 4800 series MDPE pipe. The positive field results encouraged the mine to order another 5,000 ft. of 32” DR17 Driscoplex® 4800 series MDPE pipe to continue integrating the improved abrasion-resistant pipe throughout their plant.
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