2121 Brooks Avenue
Neenah, WI 54957
Tel: (920) 725-7000
Toll-Free: (800) 558-5075
Fax: (920) 729-3661
Web site: www.nfco.com
Webster defines potential as "existing in possibility; capable of development in actuality (benefits)." When evaluating existing, or proposed storm water systems, the potential amount of water captured is the design and performance criteria most commonly used in evaluating performances. Potential can also be evaluated when comparing the performance of different styles of inlets used in storm water systems, with the installation having the capability of removing the most water at the highest efficiency being the most desirable.
A grate exists which is hydraulically superior to the conventional style in that it utilizes a vaned shape crossbar to capture the water. The curved shape on the leading edge of the vane supplies a surface for the water to adhere to, with the flat face of the second vane redirecting the flow downwards. Efficiency of the vaned grate is 100% for typical design flows, thus one of the first steps which can be utilized to achieve the desired potential would be to incorporate a vaned configuration for inlet design.
Neenah Foundry has developed the Slotted Vane Drain which offers the superior performance of the vaned configuration as well as the strength, durability, and economy of gray iron. When the Slotted Vane Drain is installed perpendicular to the flow, the unique vaned shape provides a capacity of 0.5 cfs per lineal foot of drain for longitudinal slopes from 0% to 6%. The ideal installation would utilize a vaned grate to capture the flow in the gutter and the Slotted Vane Drain to collect the flow extending into the road way. The Slotted Vane Drain can also be utilized in the conventional manner by installing it in the gutter parallel to the curb, utilizing the transverse slope of the street to force the water to the openings. The length of the installation required is then a function of the surface slopes and the anticipated amount of flow. One can see the savings which can be realized if the installation is as described earlier, using one Slotted Vane Drain perpendicular to the flow and a vaned grate in the gutter.
Installation is relatively simple, using materials which are commonly found at construction sites. A slot, the width of a standard two-by-four, cut in the top of the PVC pipe allows the Slotted Vane Drain to be positioned atop the pipe and wired securely in place. PVC pipe is utilized as a form only for the concrete encasement, which should completely surround the assembly and extend to the pavement surface. The assembly is adjusted to grade using blocks and lath, then the concrete placed in two lifts to the surface to prevent floatation.
The advantages of utilizing the Slotted Vane Drain are numerous: I) Cast gray iron as a material offers durability, economy and strength resulting in a dimensionally consistent product capable of withstanding heavy duty loading applications. Shear tabs and the overhang of the vane effectively transmit the live load to the concrete with more severe loadings being accommodated by extending rebar from the Slotted Vane Drain into the surrounding concrete. As with all gray iron, the corrosion properties are such that painting is not required, thus the quality of the material can be inspected and determined at the job site without a cosmetic covering to hide potential defects. II) The geometry of the cross section was designed with the narrowest part occurring at the top, thus objects too large to pass through the openings would be noticeable, and would not get lodged below grade to accumulate debris. III) From a designers standpoint, given the high potential capacity of the Slotted Vane Drain and vaned grate combination, the spacing between inlets can be increased and overall construction costs reduced. The combination offers an additional safety factor in northern climates where snow could be covering the gutter inlets during thaws or spring rains. Snow plows readily expose the Slotted Vane Drain providing a method of capturing the runoff and reducing the possibility of flooding or ponding. The installation can be used at low points to provide additional free open area for inlets to handle area runoff, with the likelihood of plugging reduced since the openings are not concentrated in one area, but rather stretched out over the length of the Slotted Vane Drain.
The combination of the vaned grates and the Slotted Vane Drain provides a method of achieving potentials not realized before when designing storm water systems, thus accomplishing the main objective in storm water management; getting the water off the street as quickly and efficiently as possible. Video tapes depicting the efficiencies of the vaned grates and the Slotted Vane Drain as well as design aids are available. For more information, contact our Product Engineering Department.