Flow hits the plate, is disrupted, and then rolls around the sides of the plated and then is smoothed and directed out of the manhole by the cheek walls. In an Energy Absorbing Manhole, the energy absorber is a flat plate set perpendicular to the flow stream. In-flume energy absorbers are somewhat different than those used in Energy Absorbing Manholes. When more than one tranquilizing rack is used, the Parshall flume inlet end adapter usually has to be lengthened to accommodate the installation of the racks. Tranquilizing racks are fabricated from 304 or 316 stainless steel and are secured to the flume or upstream channel through the use of bolts or screws through the top mounting plate. Like the perforated baffle plates above, tranquilizer racks are typically used in groups of two or more, with the first rack disrupting the flow and the second rack straightening it out before it enters the converging section of the Parshall flume. Tranquilizer racks are vertical racks that are slid down into the channel or end adapter upstream of the flume. As a result, Openchannelflow offers tranquilizing racks to condition flow in larger Parshall flumes. For these sizes, the perforated plates used above tend to flex under the force of the incoming flow and reinstallation under flow conditions can be difficult. Larger Parshall flumes – 6-inches and above – require more robust flow conditioning. Baffle plates are not normally retrofitted into existing applications as the recesses for the baffle plates are molded into the sidewalls / floor of the inlet end adapter – although surface mounted baffle plates are possible. Constructed of 1/4-inch PVC sheet, the plates rest in side / bottom cavities and can be easily removed should they ever become clogged or if the flume needs more flow capacity. The baffle plates are perforated in a staggered pattern and, used in groups of two or more, help to break up poor inlet velocity profiles. Smaller Parshall flumes – typically 1-3-inches in size – can have perforated baffle plates installed in the inlet end adapter. In-Flumeįor in-flume conditioning, the inlet end adapter can be lengthened to allow for the installation of baffle plates, f low tranquilizing racks, and energy absorbers. For industrial customers where space constraints limit upstream straight runs, or where higher than desired slopes are exist, Energy Absorbing Manholes can create the conditions necessary for accurate pretreatment flow measurement. After fully disrupted / dissipated the flow, it is guided out of the Energy Absorbing Manhole and into the downstream pipe so that when it enters the flume manhole / vault, it is smooth and subcritical – two key elements for accurate flow measurement.Įnergy Absorbing Manholes work well on sanitary, industrial, and mixed flow streams. Upstreamįor applications where the flume is installed below grade either in a fiberglass Packaged Metering Manhole (PMM) or a concrete manhole / vault, Openchannelflow offers Energy Absorbing Manholes (EAM).Īn Energy Absorbing Manhole is placed immediately upstream of the flume manhole and serves to disrupt the flow stream and dissipate excess energy. Some of the conditioners are in-flume accessories, while others are installed upstream of the flume itself. Openchannelflow offers a number of different flow conditioners to help to normalize the flow before it enters a Parshall flume.
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