Third-Party Rating Curve Development and Debris Testing for Thirsty Duck® TDP Series Floating Outlet and Skimmer

Abstract

The University of Minnesota, St. Anthony Falls Laboratory (SAFL) was contracted by Thirsty Duck, LP to conduct a testing program on a series of floating outlets and skimmers. The purpose of the study was to develop rating curves, conduct a freezing test, and analyze performance under extreme debris loading conditions for their TDP series product. The models tested include the TDP-248 and TDP-184. An additional hydrostatic pressure test was conducted on the 8-inch bellows component of the TDP-248. Performance under debris load was evaluated using a mixture of grass (hay), cans, plastic bottles, plastic bags, and rope. The discharge rate was monitored during the debris performance tests to determine if the debris impaired the function of the product. A freeze test was also performed on a TDP-248 with an 8-inch bellows. The results of the rating curve experiments were used by Thirsty Duck, LP to calibrate their analytic model for predicting flow rates.

The TDP products are designed to connect to the outlet pipe with a standard 150# ANSI flange connection. Figure 1 contains a concept diagram of the TDP system. Major components include an orifice to control discharge, a float to suspend the orifice at a fixed distance below the water surface, a skimmer to prevent fouling, and an expanding conduit ("bellows") to convey water from the orifice to the outlet pipe. The orifice is cut from a conical plenum that connects the float to the bellows. This allows the orifice to be custom sized by the installer. Both floating outlet and skimmers were tested for multiple orifice sizes. Testing specifications are provided in Table 1.