Overflow Pipe Protection
Screens and flapgates have historically been installed on overflow pipes, but those have become inferior technology for protecting tanks from birds, animals, airborne pathogens, and most recently - risk of terrorist attack. Flapgates can hang open and can corrode or rust in the open or closed position.
Screens can rust, become dislodged, collect materials like leaves in the overflow pipe, encourage icing on the screen when the surfaces are wet (screen gets blown out on next overflow), do not prevent insects from entering the tank, and do not prevent cold drafts from entering the tank through the overflow pipe which can promote icing.
After 9/11, water utilities had to conduct vulnerability assessments and one area identified for potential terrorist attack was water storage tanks. For example, an overflow pipe with a 2-foot air gap between ground level and the end of the overflow pipe was considered by many to be an easy access to the potable water in the tank. Screens or flapgates installed on the end of the overflow could not stop the injection of a liquid or gas into the water volume.
Tideflex Engineers developed the Overflow Security Valve (OSV), to address this concern. The OSV is an assembly that incorporates a Tideflex Series 37. The OSV is either welded or flanged into the overflow pipe with tamper-proof bolts. The OSV is installed above the end of the overflow. The Tideflex Series 37 within the OSV cannot be seen and is be extremely difficult to access, manipulate or damage.
The OSV is customized for every tank based on the tank height, overflow pipe size and material, and peak overflow rate.
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US Patent No. 7,104,279
Canada Patent No. 2,409,009