types of positive barrier screens

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Types of Positive Barrier Screens Rotary Drum Fixed Vertical Plate Vertical Traveling – belt and panel Non-Vertical Fixed Plate Horizontal Fixed Plate Eicher Screen Modular Inclined Screens End-Of-Pipe (Pump) Intake Screens

Acceptance of Existing Screens  If constructed prior to 1989, approval of

existing screen considered based on:must function as designed and in

good working condition.upon replacement, mesh must be

replaced with current criterion.provides safe timely and effective

passage.no emergent fry at siteaccess allowed for NMFS inspection.

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Rotating Drum Screens

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Rotating Drum Screens

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Rotating Drum Screens

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Rotating Drum Screen

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Seals

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Seals

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Rotating Drum Screens - Advantages

Proven fish protection Self-cleaning by rotation Passes debris downstream

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Rotating Drum Screens - Disadvantages

Susceptible to direct hits from large debris Large civil works are required. Seals require much maintenance. Susceptible to abrasions by sand - mesh requires

periodic replacement. Need control to maintain submergence between 65%

and 85% - easy step usually.

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Vertical Fixed Plate Screens

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Vertical Fixed Plate Screens

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Vertical Fixed PlateScreens

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Vertical Fixed Plate Screens

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Vertical Fixed Plate Screens

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Vertical Fixed Plate Screens - Advantages

Easy to seal Mechanically simple Can be installed on river’s edge - small screens

No bypass requiredCan use profile wire (very strong)

Mechanical/brush cleaning usually effective Air burst cleaning system is on back side of

screen. Cleaning is started by timer or head loss.

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Vertical Fixed Plate Screens - Disadvantages

Must be cleaned mechanically Large bypass flows required Brush arms can be damaged by large debris. Circular air burst cleaners do not clean

entire screen.

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Vertical Traveling Screens

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Vertical Traveling Screens - panels

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Traveling Screens - Belt

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Traveling Screens - Belt

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Traveling Screens - Advantages

Small screens can be installed on riverbank. Compact civil works Self cleaned by rotation Jet sprays provide additional cleaning.

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Traveling Screens - Disadvantages

Mechanically complex Seals can be a problem. Make sure meets all NMFS criteria

(old styles may not)

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Non-Vertical Fixed Plate Screen - Coanda

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Non Vertical Fixed Plate Screen – Coanda

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Non-Vertical Fixed Plate Screen

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Non-Vertical Flat Plate Screens

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Non-Vertical Fixed Plate Screens - Advantages No moving parts No bypass required if built in-river

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Non-Vertical Fixed Plate Screens - Disadvantages

Self-cleaning may not be reliable Risk of injury/mortality on screen during low flow Must raise and control water surface Tricky, unreliable flow rate control Adult upstream passage concerns Potential issues with hydraulic gradients

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Eicher Screens and Modular Inclined Screens

Eicher Screens

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End-Of-Pipe Screens

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Fixed Cylinder Screens

Source: Johnson Screens, Inc..

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Fixed Cylindrical Screens - Advantages

Good option for deep intakes Air burst cleaning system can be made to be

effective Some off-the-shelf models with water

backwash systems meet NMFS criteria for active screens.

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Fixed Cylindrical Screens - Disadvantages Out of sight, out of mind Need sweep velocity to transport debris from

screen site. Air burst systems on large installations don’t

always clean entire screen - especially the bottom.

Long, stringy vegetation is a problem on small pump screens.

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Pump Screens

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Pump Screens

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Pump Screens

Passive Screens (not self-cleaned)Selection Criteria : Only considered for use when site is not

suitable for an active screen. Uniform approach velocity must be apparent

from the conceptual screen design. Approach velocity not to exceed 0.2 ft/s. The combined rate of flow at the diversion site

must be less than 3 cfs.

Passive Screens (not self-cleaned)Maintenance and debris management: A maintenance program must be approved by NMFS and

implemented by the water user.

The screen must be frequently inspected with debris accumulations removed, as site conditions dictate.

Sufficient stream depth must exist at the screen site to provide for a water column of at least one screen radius around the screen face.

The screen must be designed to allow easy removal for maintenance, and to protect from flooding.

Passive Screens (not self-cleaned)

Maintenance and debris management: The debris load must be low.

Sufficient ambient river velocity must exist to carry debris away from the screen face.

Passive Screens

A maintenance program must be approved by NMFS and implemented by the water user.

The screen must be frequently inspected with debris accumulations removed, as site conditions dictate.

Sufficient stream depth must exist at the screen site to provide for a water column of at least one screen radius around the screen face.

The screen must be designed to allow easy removal for maintenance, and to protect from flooding.

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Passive Screens

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Passive Screens

Flow Distribution - Passive Pump Screens

Passive Pump Screens - Installation

Passive Pump Screens – Anchor Blocks