Our
fish diversion screens are used in dam and river systems throughout North
America to protect fish from hydroelectric turbines and pumps. Our fish
screens comply with NMFS standards and they are specified by the U.S.
Department of Fish and Wildlife, Corp of Engineers and many
State Departments of Fish and Wildlife for the protection of fish. Our
fish screens are environmentally friendly to fish and other aquatic
life.
Profile
Bar for Fish Screen Applications
Hendrick Screen has a long history of success in the
production of screens used in fish protection/diversion projects and
continues to be a leader in this market.
When the strength and flatness of the fish screen is
critical or a screen cleaner is used, the Hendrick Screen Profile
Bar Screen construction should be specified. It is the strongest,
flattest, most durable screen construction offered.
Past history has shown that some screen manufacturers
will, as a substitute construction, quote "welded wedge",
"resistance welded", "vee-wire" or "wire
wrapped" screen "as equal" in place of the Hendrick Screen
B69 Profile Bar screen. These other types of screens are usually less
expensive than B69 Profile Bar screens and when represented as "an
equal" screen offers a tempting cost saving alternative. You should
be aware of the differences in these screens and why the B69 is purposely
specified over the other less expensive welded designs.
A critical part of a mechanically cleaned screen
installation is the screen itself. Construction of these welded types of
screens are vastly different than the Profile Bar screens and are not an
"equivalent", simply a less expensive "alternative".
Differences in the screens include the following points and issues.
1.
Construction:
Profile Bars screen wires (bars) are over twice the
height and weight of other screen wires. The taller Profile Bar makes the
individual wires substantially stronger and stiffer than the v-wire found
on other screens. The cheaper welded screens require a thicker wire to
achieve reasonable wire strength. Wider wires substantially limit the open
area of a screen, especially a screen with a 0.069" slot, as required
on most fish projects. Profile Bar screens provide a large open area and
narrow wire width with superior wire strength and stiffness.
2. Assembly:
Profile Bars are assembled into "U" shaped
clips with retaining pins staking the bars into place. The precision slots
in the "U" clip are .250" deep holding the bars firmly in
place, making the bars very resistant to bending or tilting out of place.
Other screen wires are held in place by resistance (spot) welds or TIG
welds.
Profile Bar screens are less subject to damage in
instances where a heavy object such as a tree trunk, truck tire or animal
carcass is forced against the screen by the cleaner scrappers. Profile Bar
also has the greatest impact strength of the commonly used screens. Other
wires can be subject to bending or weld breakage under heavy loads or
impacts.
3. Supports:
The stronger bars on Profile Bar screens allow the
spacing between the support rods to be greater. The greater distance
between support rods decreases the accumulation of stringy debris impinged
on the screen.
4. Flatness:
Profile Bar screens are an assembly, not a weldment. The
height of the bars and the absence of welds provide a very flat and stable
screen face that is ideal for use with a screen cleaner. Welded screens
have thousands of weld stress points that cause them to have a
"wavy" surface and an overall "out of flat" perimeter.
Profile bar screens are flat to .060" per sq ft of screen.
5. Open Area:
The new B69 profile bar wire with a .069 face width will
provide a 50% open area for fish screen applications while providing much
greater strength than the .069 V-wire welded constructions.
6.
Service life/economy of use:
The superior damage resistance of Profile Bar screens
when used with a mechanical screen cleaner will provide an improved
economy and less maintenance than the initially less expensive welded
screens.
We ask that you consider the Hendrick Screen B69 profile
bar construction and evaluate the initial price of the screen to the long
term cost and maintenance of the welded screen construction when designing
you next fish or diversion screen.
If your application does not require the flatness and
strength of profile wire construction, Hendrick Screen produces a wide
variety of resistance welded v-wire screens for your diversion
requirements.
If
you have any questions or comments, please call the Hendrick Screen
Engineering Dept. at 270-685-5138. Samples of various screen types are
available upon request.
See the Engineering
Section for Sample Engineering Specifications & Documents