Flow Control Units Brochure

Sustainable Drainage Systems Ltd – Vortex Flow Control Unit Purpose Built Flow Controls Developed specifically for use in drainage systems, the individually designed vortex flow controls offer an effective solution to storm water management problems. Each unit is configured to suit the site and to fit easily into the drainage infrastructure. The SDS vortex flow control units are currently in use throughout the U.K, Ireland and Europe. Vortex flow control units do not rely on external power supplies or moving parts. An internal vortex, generated by the incoming water controls the through flow. The unique flow characteristic of the vortex flow control ensures optimum use of upstream storage while the large cross sectional areas greatly reduce the risk of blockage. The Vortex flow control units have no moving parts to wear or fail. Made from stainless steel plate they will resist scour, degradation and chemical attack. A Vortex flow control unit should easily outlast the system in which it is installed. Performance Characteristics The discharge curve of a flow control unit has a bistable characteristic. At low heads the discharge coefficient is relatively large allowing water to flow comparatively freely. At a predetermined head the vortex begins to form within the Vortex Chamber causing a reduction in the discharge coefficient. There is a short transitional phase where the coefficient is reduced as the vortex becomes fully formed. This is represented by the classic “kickback” in the curve. Once formed the vortex establishes a reduced but stable discharge coefficient. The significant points to note on the curve are: 1) The flush point - The point at which the initial flow peaks. For optimum performance this should be as close as practical to the design flow without exceeding it. 2) The initiation point - The point at which the vortex becomes fully formed and the discharge coefficient is stabilized. 3) The design head - The head at which the design flow is to be archived. This should always be above the initiation point. 4) The design flow - The maximum discharge rate required for the system. This should always be in the stable region above the initiation point. The construction of the vortex flow control unit is varied to alter the head at which the flush point and initiation point occur. This gives rise to a number of different types and many variations within each type. For example reducing the cone angle of a conical unit or reducing the casing diameter of a radial type will lower the head required for initiation Types of Vortex Flow Control Unit Flow Control units fall into Three Main Categories: Within each Category the Vortex Chamber and the inlet and Outlet Dimensions are varied to give a vide variety of flow control units with differing characteristics. Example Emergency Drain down A flow control unit is a choke point in the network and there is potential for a blockage. Consideration should be given to dealing with a blockage. In the event it is likely that the chamber will be full of water and the flow control will probably be inaccessible. An alternate means of draining the chamber is highly recommended. The emergency drain down, MUST BE CAPABLE OF BYPASSING THE ENTIRE FLOW CONTROL UNIT. A blockage can occur at the inlet but it may equally well be inside the vortex chamber or obstructing the outlet. The drain down should be independent of the flow control unit. SDS have always advocated the use of an entirely separate drain down pipe in the control chamber controlled by a penstock or disc valve. Where there is only a single outlet pipe from a chamber there should be a branch off this pipe inside the chamber to allow for independent drain down. We offer a preformed stainless steel assembly which enables the contractor to install this branch pipe and drain valve quickly and simply before bolting on a vortex flow control unit or other flow control device. We do not advocate siting the drain down valve on the upstream face of the flow control unit. This arrangement bypasses only the inlet and may be ineffective if there is an internal blockage (such as a plastic bin bag) in the vortex chamber. DESIGN Individual Design. All of our Vortex Flow Control's are individually designed to meet our client’s optimum performance criteria. Will our Vortex Flow Control's Block? The relatively large cross sectional areas and high internal velocities greatly reduce the risk of blockage. How Long Will They Last? Vortex Flow Control's have no moving parts to wear or fail. Made from stainless steel plate they will resist scour, degradation and chemical attack. A Vortex Flow Control should easily outlast the sewer in which it is installed. MANUFACTUREAll of our Vortex Flow Control's are manufactured as follows. Material Used. 304 Grade Stainless Steel as standard. Other material optional. Plate Thickness. Generally 3mm thickness, thicker where required. Welding. Coded welders approved to BS4872 - All welded seams continuous for maximum strength. Rodding Access. Removable access plate on each unit, most units easily removed for access to the downstream pipe. QUALITY ASSURANCE We operate an externally regulated ISO 9000 Quality Assurance System. INSTALLATION All of our Vortex Flow Controls are purpose built to suit the specific site and to fit easily into the drainage infrastructure. For example, units can be made with curved faces to fit directly into circular chambers and can be supplied in sections to ease assembly within confined spaces. MAINTENANCE Vortex Flow Control units themselves require no routine maintenance. Inspection chambers require inspection & maintenance in line with current practice. WHAT DESIGN INFORMATION DO WE NEED?We require the following basic information to specify a Vortex Flow Control for you. 1) The design Flow - Maximum Discharge 2) The design Head - Invert to Top Water Level 3) Type of drainage - Surface or Foul From this information we will size and design the Vortex Flow Control to meet the design criteria and to suit the proposed infrastructure. Sustainable Drainage Systems Ltd Clearwater House Castlemills Biddisham Somerset BS26 2RH Tel: 01934 751303 Fax: 01934 751304 Email: info@sdslimited.comWeb: www.sdslimited.com