Johnson Intake Screen - Zebra Mussels

[ch81pc]

Hi

We are looking to install a Johnson intake screen on our river intake. Does anyone have any experience (good or bad) with regards fouling due to zebra mussels? I know that Johson's can supply the screen in either 316 stainless or "mussel repellant Z-alloy." Does Z-alloy actually make a difference to mussel fouling?

Many thanks

 

[cub3bead]

The Z alloy contains copper that the mussels are not fond of.

 

[bimr]

Sure, the z-alloy works. It is recommended that you visit an installation near to you on the same river so that you can see for yourself.

 

[ch81pc]

Unfortunately there are no other sites that use Johnson screens on the effected section of the Thames. I may be being over cautious, but can I assume that the mussels will colonise the screens, as they seem to colonise everything else?

I dont think we will be able to get approval to use the z-alloy as its not on the approved list, so we will be stuck with the 316.

 

[bimr]

As cub3bead suggested, the mussel are not fond of the metal and will not colonize the screen like they would do with other materials.

http://www.filterite.com/ContentManager/Display.asp?Location=/The+Group/What+New/New2.html

http://www.weatherford.com/weatherf...hnologies/js_flatpanelfishdiversion.hcsp?js=1

Here is a sample of permit text:

Screen Material – The wedge wire screens will be fabricated by Johnson Screens, Inc., of “Z-Alloy”, a material selected to prevent the colonization of zebra mussels on the screens. The nature of this material is such that it will leach a certain amount of copper into the water around and drawn through the screens. It has been calculated that the leaching of copper from the screens will cause an increase in copper in the freshwater outfall by 0.015 ug/L. By comparison, the chronic criterion for copper is about 17 ug/L and the background concentration is about 0.44 ug/L. The leaching of copper from the wedge wire screens is, therefore, not significant and will have no impact on aquatic life.

Not sure what regulation that you must meet to use the screen material, but would suggest that you push back and try to get the screen material approved. I do not understand why they would not approve it. It is likely that the screen material was invented after the regulation was written.

 

[ch81pc]

Thanks for your information bimr. I have been told that the z-alloy doesn't appear on the DWI (UK) approved list. We can retrospectively apply to get it put on but its a long hard struggle and if they refuse to approve it we would be forced to take it back out again.

 

[cub3bead]

ch81pc,

Did some checking with Johnson about their Z alloy. It is 90/10 CuNi, UNS 70600. The DIN equivalent is 2.0872; the EN equivalent is CW352H.

Hope this helps you out. Good luck in solving the zebra mussle problem.

I would be curious to know if the 90/10 is on your approved list.

 

[ch81pc]

Thanks for all your help. Its been very useful. I'll let you know if the 90/10 is approved.

 

[JimCasey]

CuNi alloys are very popular for direct exposure to water. I can't quote alloy designations, but I recall CuNi tubing in heat exchangers....used for its high heat transfer characteristics and also for its resistance to fouling. If you find that your specific 90-10 is not specifically approved, I suggest you brief the inspecting authorities on approved similar alloys. Unless your inspector is an absolutely mindless Vogon bureaucrat he will see that there is no technical reason for rejection.

 

[jaymcc]

Check out the Wearlon Product as a coating for intake screens regarding zebra mussels. The website is

http://www.wearloncorp.com.