Frequently Asked Questions (FAQs) about ISI's Intake / Fish Screens

What are the advantages of a brush cleaned system?

1) Mechanical brushing will remove tough algae and fiberous materials better than any air burst cleaning system can.

2) Brushes can work in backwater areas where other systems fail. Brushing can pulverize small detritus on the screen surface and allow water to flow through the screen.

3) Energy needs are minimal for a brush system. Alternative energy systems, such as solar arrays, have been successfully used when power in not available nearby.

4) Brushes have a very long useful life. While ISI has yet to replace a brush due to excessive wear (with some installations operational since 1995), they can be easily changed if necessary.

5) The reversing action of our brushing systems additionally helps remove debris.

Are there lots of moving parts?

No. The primary moving part is a sealed marine duty submersible hydraulic motor controlled from the surface.

How long do the brushes last?

Brushes have a very long useful life – at least several years under ordinary use. While ISI has yet to replace a brush due to excessive wear (with some installations operational since 1995), they can be easily changed if necessary. ISI recommends that brushes be periodically inspected, at least annually, for wear.

How do ISI screens function in high flow or flood events?

1) Almost all of ISI’s cylindrical screens are designed and installed to be easily retrievable. ISI recommends that screens be retrieved during high flow events or when not in use for long periods of time if possible.

2) Cone screens can be left in place in most applications. By design, they are typically sited on the river bottom and are not subject to the higher currents and floating debris. Its cone shape also helps to deflect debris without damage.

3) ISI screens use durable wedgewire construction and are capable of withstanding severe conditions without damage. We will design a screen system to meet the site needs.

Can ISI screens be used to filter water for irrigation systems?

YES. ISI has operational experience filtering down to 1200 microns using a suction side intake screen only. Filtering on the suction side can eliminate costly maintenance and operations of high pressure filters used on many irrigation systems. Finer filters are possible.

Will ISI screens meet regulatory standards for fish protection?

YES. Each screen is designed to meet tough standards for minimum screen area, cleaning frequency, site application, material selection, and flow distribution of fish screens.

What is an internal flow baffle?

ISI screens distribute intake flows evenly over the entire screen surface by using a an graduated porosity manifold inside each screen. Evenly distributing flows eliminates velocity “hot” spots that can contribute to poor cleaning effectiveness and reduced fish protection.

When should a Cone Intake / Fish Screen be specified?

Cone screens are generally the better choice when intakes are located in very shallow areas, in estuaries, or when a screened intake must be placed out of sight for aesthetic reasons (such as on a golf course lake intake).

When should a Cylinder Intake / Fish Screen be specified?

Cylindrical screens are easily adapted to the intakes of pumping units and many retrofit applications. The diversion rate and water depth will generally be used to determine the cylinder size most appropriate. Cylindrical screens are also easily retrieved using a track system.

YES. ISI has engineering and computer aided design expertise and can help you determine the right application with the proper specifications for your project. We also offer Design/Build services.

Can ISI assist with installation?

YES. ISI has installed a number of screens and necessary support structures. We are licensed to install our systems as required. We also can arrange work with contractors on larger installations that may involve additional facilities.

Will ISI screens reduce diversion capacity?

NO. ISI screens are designed to minimize headloss. When properly sized for the application, our screens will function reliably over a range of conditions. The mechanically cleaned brush system provides better cleaning than other systems available.

How much submergence is required on ISI screens?

Unlike air burst cleaned screens, there is no minimum water depth over the screen required for proper function. In sizing a screen, the minimum wetted screen area should be sufficient to divert the maximum diversion flow.