› Stainless steel 316 construction ensures
reliable trouble free operation
› The maximum storage level setting may be
easily modified after installation of the device
› Hydraulically ideal shape of the weir flap
ensures blockage free discharge
› Integrated counterweight design eliminates need
for separate counterweight chamber
› Easy retrofitting of existing basin overflows
possible (additional storage volume gain)
› The Overflow Bending Weir Type U is available
with seals on all four sides, so that it can act as a
backflow prevention device for flood protection
› Lower storage tank construction costs owing to smaller tank volumes (the Overflow Bending Weir
Type U allows for 100 % utilization of storage tank volume as opposed to only 70 to 80% for
› Increased water pollution protection since discharge from the storage tank to receiving stream
commences only after complete filling of the available storage volume or after reaching maximum
Once a combined sewer overflow (CSO) tank (or sewer) or a stormwater overflow tank (or sewer) is full, any additional influent water must be able to reach the receiving stream. In the past this was usually accomplished with the use of fixed weirs. However fixed weirs have inherent disadvantages including: increased water pollution, lower usable tank and sewer storage volumes and no backflow protection. To avoid the disadvantages of fixed weirs increasing use is made of overflow bending weirs such as the unique Overflow Bending Weir Type U.
The Overflow Bending Weir Type U is designed to ensure that a constant maximum storage level is maintained upstream of the weir so that full utilization is made of all the available upstream storage volume. The Overflow Bending Weir Type U is designed to open just enough to allow the additional influent water to overflow the weir while maintaining the upstream water level. This ensures that the frequency of overflow events is reduced which results in reducing the discharge of highly polluted water to the receiving stream.
The entire overflow weir length can be utilized for overflow level control. The compact design makes the system particularly suitable for structures with limited space and for installation in existing structures. The special weir construction makes virtually constant maximum storage levels possible, even under backflow conditions.
The Overflow Bending Weir Type U is installed on the existing fixed overflow weir, with its pivot points attached to the structure’s ceiling, sidewall or crossbeam. The pivot balances the forces produced by the hydrodynamic loading on the overflow weir flap with those of the counterweight. This ensures equilibrium in any weir position, resulting in a highly sensitive response to the slightest change in the upstream water level. The Overflow Bending Weir Type U remains in the rest position (closed) until the maximum design storage level is reached. Upon reaching this level, the Overflow Bending Weir Type U immediately responds and swings away from the sill, allowing the excess water to overflow while maintaining a constant upstream water level.
The special shape of the weir body and the arrangement of the hinged flap and counterweights are the result of extensive calculations and hydraulic testing. The relationship between static and dynamic hydraulic forces, as well as the passive forces of the counterweights (and weir), have been optimized. This results in a high discharge coefficient for the Overflow Bending Weir Type U which ensures that a constant upstream water level is maintained without negatively impacting the upstream hydraulic grade line.
If required, the maximum storage level setting may be adjusted on site by removing or adding counterweights.
According to the Poleni formula, the hydraulic capacity of the Overflow Bending Weir Type U is at least equal to that of a standard overflow weir. This means that the upstream water level is not adversely affected by the presence of the Overflow Bending Weir Type U overflow bending weir type U.