Brackett Green Travelling Band Screens Fine Screening for Water Intakes

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1 Brackett Green Travelling Band Screens Fine Screening for Water Intakes A COMPANY

2 Brackett Green Travelling Band Screens Brackett Green Travelling Band Screens are designed for installation on raw water intakes where a continuous and efficient means of removing floating and suspended solids is required in order to protect pumps, heat exchangers and other critical equipment. Fitted with mesh aperture sizes from 2mm to 10mm, these screens can be installed as a single system or as part of a two or three stage system. Economical screen Where the difference between high and low water and the location of deck level dictate a comparatively deep chamber, the Brackett Green Travelling Band Screen is often the most economical screen. Endless band The Travelling Band Screen has an endless band of screening panels through which the water passes. Debris collected on the mesh panels is raised to deck level and removed by backwashing. Main chains, supported by two sprockets above deck, carry the screening band and the drive is provided by an electric motor through a shaft-mounted reduction gear unit. Underwater, the mainchains run in guide sections fitted with wearing strips located in a self-supporting fabricated frame. Applications include: Screening fresh and sea water Intake for nuclear, thermal and CCGT power stations First stage treatment and pump protection at water treatment and desalination plants Refineries Petro-chemical plants Common cooling water intakes Aluminium plants Steel works 2

3 Screen Operation Purpose designed Brackett Green Travelling Band Screens are purpose designed for each individual application and can incorporate specific features to suit the operating and site conditions. Through-flow: Again EWT recognises that in some situations using a through flow pattern may be preferable and EWT can design and supply screens to this pattern. 3D Cad model of the Dual Flow Band Screen Flow Patterns Dual-flow: Eimco Water Technologies (EWT) experience designing Band Screens for water intakes shows that the dual flow or out to in flow pattern is the most suitable flow pattern for the majority of water intakes. With this pattern, after flowing through the mesh panels to the inside of the screen, the water exits through the back opening normally formed by the civil work (see top diagram). With this flow pattern debris cannot be carried over to the clean water area, which is a problem experienced with the through-flow pattern of Band Screen. This flow pattern produces a converging flow, which is preferable when the pump is close coupled to the screen. Central-flow: EWT recognises that in some situations it may be preferable to utilise a central flow or in to out flow pattern. With this flow pattern the water passes into the centre of the screen frame and then out through the mesh panels to the clean side of the screen. This flow pattern also prevents debris carry-over to the clean side of the screen. Band Screen Flow Patterns 3

4 Screen Construction Frame construction The main chain guides and head frame assembly, complete with drive gear, are carried in a fabricated steel frame which is built up in sections and free-standing in the screen chamber. This design solution reduces civil work and eliminates the need for accurate alignment of chain guides as builtin components. Ancillary Equipment EWT can supply all plant required for a complete screening station, including: Coarse bar screens Automatic raking machines Isolating stopgates Local or centralised control systems Washwater pumps and pipework Manual or automatic fine strainers Debris disposal systems Cathodic protection Additionally, this style of frame construction allows the complete screen to be removed for periodic maintenance in sections which reduces headroom space requirements. Fresh and seawater applications EWT developed the DF100 Band Screen featuring injection molded, a segmented plastic mesh panel suitable for use with fresh and seawater applications. Travelling Band Screens with up to 8 metre deep sumps, effective widths of 1.5 metres and flows up to 2m 3 /sec can be supplied with this arrangement. For flows above this level a traditional mesh panel and support is utilised. 4 Contact Seal When using the fine mesh, or where particular types of debris may bypass the screen, a contact seal can be incorporated. This consists of a flexible neoprene seal attached to the main structure and running in contact with the main chain sealing fins. Top: The robust design of Brackett Green s Travelling Band Screen is highlighted by the headshaft arrangement of these Screens awaiting despatch. Above: A typical intake incorporating Brackett Green stopgates and Brackett Bosker Monorail for the Bar Screen Raking machine. Left: Typical section of contact seal arrangement for finer mesh apertures.

5 Screen Selection for Dual Flow Pattern How to use the graphs The graphs provide a general indication of the size and layout of the installation. Graph 1. Based on a 10 mm mesh with 0.75m/sec. velocity through the clean screen. Multiply flow by 0.68 for a 5 mm mesh. 1 Determine the maximum quantity of water required to be handled by one band screen. 2 Refer to Graph 1 and relate this quantity (in cubic metres per second) to the vertical immersion applicable (vertical immersion is the distance between the minimum water level at the screen, and the sump base). 3 Plotting these levels and quantities on Graph 1 will determine the effective width of the screen required. 4 Refer to Graph 2 to discover the back opening dimension needed. The screen size is then indicated. 5 Minimum sump dimensions can be determined by reference to the site dimension drawing. Graph 2. Charts and diagrams below illustrate the comparative widths, measurements and information required for Brackett Green s Travelling Band Screens. EWT will provide additional data for your intake including the provision of mechanically raked bar screens for primary screening, isolating gates for maintenance and recommendations on material selection. Details of ancillary equipment such as controls, cathodic protection and wash-water pumps can also be provided. 5

6 Engineering Services Design and analysis EWT uses state-of-the-art computer aided design programmes at its manufacturing facilities with ProEngineer used as the basis for design and draughting activities. With advanced 3D graphics and modelling, products are designed and tested in different operating conditions and requirements for its customers. This system, in conjunction with our finite analysis package, always ensures sound engineering is always applied to each project. Install, commission, maintain EWT s service engineers will install, commission and maintain all machines supplied by the EWT Group. Our team of international engineers will visit sites around the world to advise on all aspects of our products. EWT is able to provide long-term agreements covering spares and maintenance,relieving you of costly overheads by providing trained personnel where and when you need them particularly during planned shut downs. Spare parts EWT retain comprehensive records of all the machines they have built. The records can be accessed quickly on our computerised spare parts database held in Colchester, UK, and Houston, USA. The spares supplied are genuine, guaranteed and backed by our detailed knowledge of all the subsequent modifications, or upgrades, that may have occurred since the machines were supplied. Our spares managers are available for advice at any time. We can recommend suitable spare parts both for holding on site as strategic spares, and for your long term needs for planned maintenance shut downs. Spares are ex-works, delivered to site for installation. Training As a supplier of engineered capital equipment, it is natural for us to offer our end users on-site or in-house training courses. We have skilled instructors available and can train your staff in all aspects of equipment use, including detailed instructions for replacement of parts, adjustment and monitoring. 6 The training courses are for individuals on a oneto-one basis or for groups of up to eight, either on-site or in our UK or American HQ s. Contact our spares and service managers for details of the courses available.

7 Brackett Green Travelling Band Screen Traditional design band screen with framed metallic mesh panel arrangement. DF100 under manufacture featuring non-metallic injection moulded mesh panels. 7

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