Product Spotlight - March 2022

Product Spotlight - March 2022

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Determining the appropriate conduit wall thickness can be a time-consuming and sometimes arduous task in preparing for a horizontal directional drilling job. Fortunately, the Plastics Pipe Institute has released a free software tool that aids in determining the best wall thickness of high-density polyethylene conduit being installed: the Conduit Design Calculator.

Published on the company’s website at or at, the calculator simplifies complicated calculations into an easy-to-use online application. 

The calculator automates the Mini-HDD calculations pioneered by Dr. Larry Slavin and described in PPI TR-46. It uses inputs such as directional changes in the underground bore path, drill rod diameter, bore depth and length to determine the calculated tensile load on the selected HDPE conduit, as compared to its allowable safe pull strength. The calculator gives users the options of HDPE conduit manufactured from a standard strength HDPE resin or higher strength HDPE resin. Benefits of HDPE conduit, according to PPI, include availability in long lengths without joints, high strength, flexibility, proven reliability and installation toughness. It is widely used in trenching and HDD installation methods.

“As long as the job site conditions are known, the calculation for a given installation can be completed in two to three minutes, for most projects,” says Plastics Pipe Institute engineer Lance MacNevin, one of the project leaders. 

Users can select the conduit diameter and wall thickness type from a menu with three pre-loaded sizing systems. All conduit dimensions and properties are in accordance with industry standards such as ASTM F2160, NEMA TC 7 and UL 651A. After the inputs are entered, the calculator shows the safety factor for the selected wall type, along with potential alternatives. A safety factor greater than 1.0 indicates that the displayed wall thickness types will have sufficient tensile strength to meet the calculated tensile forces for the given installation. In some situations, more than one wall type will have sufficient tensile strength, and the user can select the wall type based on those results, and other factors.

“Output can be emailed directly from the calculator, saved as a PDF file, or printed as a paper file to simplify sharing and record-keeping,” says Patrick Vibien, director of engineering for the company’s power and communications division. “We are very pleased to be able to bring another helpful tool to the industry.” 469-499-1044;


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