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Intake Screen Selection Tables

Cook Legacy Intake Screens are designed to a maximum through screen velocity of 0.5 feet per second.

To determine the screen requirements for your application you need to know the design flow rate and the desired screen opening size. To determine the required screen index divide the design flow rate (in USGPM) by the fractional open area from the table above. The result is the total Screen Index required for your project. Choose a screen with a screen index equal to or greater than the calculated value. Check to ensure that the minimum water depth is at least twice the screen diameter. For large flow rates or shallow waters multiple screens may be required. Table 1 below is provided to make this process easier. Complete the information on design flow rate, low water level, high water level, and slot size and your are ready to use the sizing tables to select the screen for your project. (Open area can be obtained from Table 2 and screen capacity / screen index is obtained from Table 3.

For assistance in screen sizing and selection please contact your Cook Legacy Coating Company Intake Screens representative or call our office 614-833-4745.

Table 1 Design Information

Screen Information
Design Flow Rate			gpm
Design Low Water			ft	usually water depth at 100 year low flow
Design High Water			ft	usually water depth at 100 year flood
Type of Water Source			River/Stream		Pond/Reservoir/Lake		Open Area
Slot Size		inches	use 0.080" or 0.125" [3/32" in California] or select from Table 2
Other Features: Describe


Calculation of Screen Requirement
Design Flow Rate ________________ / Fractional Open Area (from Table 2) ___________________ = Screen Index
Select Screen Model From Table 3 refer to Tables 4 and 5 for screen dimensions
Verify that there is adequate water depth for the selected screen. Minimum water depth should be at least 2 x the selected screen diameter. Preferred minimum water depth would provide 1 screen diameter clearance above and below the screen assembly
If water depth is not sufficient use multiple screen assemblies.
Number of Screen Assys	Screen Model	Outlet Size	Slot Size	Air Burst Pipesize	Material	Outlet Flange Material	No Of Cones
	S or T
Notes:

Table 2 Slot and Fractional Open Area (FOA)
Slot	1mm 0.040"	*1.5mm* *0.060"*	*2mm* *0.080"*	*3/32"*	*1/10"*	*3mm* *0.118"*	*1/8"*	*5/32"*	*3/16"*	*1/4"*	*3/8"*
*FOA*	0.357	.454	.526	.569	0.585	0.625	0.638	.688	.725	.679	.761

Comments on Screen Model Selection

Lee Cook Intake Screen Co. can provide this information very quickly.

Sometimes the available water depth is marginal for the use of a single screen. In such cases we recommend choosing the tee assembly and providing yourself with the extra clearance margin.

There are some situations where head loss through the screen assembly is a critical design factor. Head loss through a tee assembly is in the range of 1/2 to 3/4 feet of water. Head loss through a single screen is about equal to the entrance losses into the intake pipe. Special design arrangements can be provided on tee assemblies to reduce the head loss , particularly if the screen opening size is less than 1/8". Lee Cook Intake Screen Co. would be happy to work with you if head loss is a special concern for your project.

Note: Standard screen sizes are identified for convenience in establishing and selecting the appropriate screen for your project. All intake screens are made to order. Screen assemblies are not stocked. Tooling controls the diameter of the smaller diameter screens. For larger diameters the screen assemblies are spliced to accomplish the desired diameter. If the screen you need seems to fit in a gap in the table please contact us. Lee Cook Intake Screen Co. would be happy to provide custom sizing information.

Required Screen Index	Single Screen Model Options	Tee Assembly Model Options
500	S-12
600	S-14
700	S-16
800	S-16
900	S-18
1000	S-18	T-12
1200	S-21	T-14
1400	S-21	T-16
1600	S-24	T-16
1800	S-24	T-18
2000	S-27	T-18
2250	S-28	T-21
2500	S-28	T-21
2750	S-30	T-21
3000	S-30	T-21
3500	S-33	T-24
4000	S-36	T-27
5000	S-40	T-28
6000	S-42,S-44	T-30
7000	S-48	T-33
8000	S-54	T-36
9000	S-54	T-36
10000	S-60	T-40
12000	S-60	T-40
14000	S-66	T-48
16000	S-72	T-54
18000	S-78	T-54
20000	S-78,S-84	T-66
25000		T-66
30000		T-72
35000		T-72
40000		T-78
45000		T-84
50000

Screen Model Dimensions

Information on this page is provided to simplify the process of defining the required screen model number. The figures provide general configuration information on the screen assemblies. The tables provide dimension information. The model number format is provided in the middle of the page.

General: The intake screen shall be of all-welded continuous slot construction to provide maximum open area commensurate with the strength requirements identified herein. The slots shall widen inwardly from the screen surface so as to minimize the chance of debris entrapment in the screen openings. The screen includes low headloss flow field control. Screen inflow velocity shall be determined using inviscid flow field modeling. All welding of the screen assembly shall be performed by ASME certified welders. The screen assembly shall be manufactured by Lee Cook Intake Screen Co. or an equal approved prior to bid by the engineer.

It may seem unnecessary to require welding by ASME certified welders. The ability of the welder to pass the certification test should be a given. Your water supply depends on the performance of those welders. Expecting the company to establish the procedures and the welder to be able to produce acceptable welds in accord with those procedures is the minimum one should consider, not an undue restriction. The screen is not an unfired pressure vessel but requiring the welders to have demonstrated the ability to perform to that standard is a reasonable expectation.

1. Screen Index: The screen index shall equal or exceed ___________________.

2. Capacity: The screen capacity shall be _______________ US GPM at a maximum local through slot velocity as a result of water withdrawal not to exceed 0.5 feet per second. At this flow rate the pressure drop through the clean screen surface shall not exceed 0.1 psi. Pressure drop through a single screen assembly shall be in the range of 1/4 foot of water. Pressure drop through a tee assembly shall be in the range of 3/4 feet of water.

Lee Cook Intake Screens can be designed to any maximum through screen velocity that your project requires. 0.5 feet per second maximum through screen velocity is a common design velocity. Some states and some Canadian Provinces require use of a different design velocity. Contact us. We would be happy to work with you in defining the specific screen required for your application.

3. Strength: The screen shall withstand a differential hydrostatic collapse pressure in excess of _____ pounds per square foot (625 pounds per square foot is a common design differential).

4. Construction: The surface wire shall be Lee Cook Intake Screen shape number 69 (or 130 when slot is 1/4 inch or greater) or an equivalent cold rolled shape that will provide the same strength and open area. The surface wire, support beam and stiffener structure are an all welded matrix designed to provide the specified strength while providing minimal interference with the through screen flow pattern. End plates, outlet pipe, and tee body are a minimum of 1/4" thick.

Defining all of the forces to which the screen assembly might be exposed can be a very difficult task. Defining a minimum thickness for the key components of the assembly is good practice.

5. Slot: The screen slot opening shall be __________ inches. The open area for this slot opening is _____ %. Slot size shall be controlled and continuously monitored during manufacture.

6. Materials: The screen assembly shall be manufactured of one corrosion resistant metal, ______ stainless steel except the ______" main outlet flange which shall be a standard AWWA C207, Table 1, Class D flange which is low carbon steel by standard.

Stainless steel flanges can be provided. In general, the mating flange will be a carbon steel flange. The use of a standard AWWA flange would provide significant savings.

7. Submittals: A graph of local through slot velocity indicating maximum, average, and minimum through slot velocity shall be provided along with any other required submittals.