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duckbill valves

Case Study
PROCO Check Valves Provide Better
Diffusion Value on Sea Floor
he Water Authority of Istanbul, which owns a biological wastewater
treatment plant, serves a population of about 15 million people in the city
of Istanbul, Turkey. To meet stricter environmental regulations, the Water
Authority approached Marine Consultants Group (MCG) in the spring of 2017
to find a suitable product to provide adequate diffusion for their marine waste
water outfall.
Marine Consultant Group worked with PROCO to design and engineer duckbill diffusers to accommodate outfall sewage from the treatment plant through an
87-inch-diameter steel pipe. The pipe extends 1.35 miles (2230 meters) along
the bottom of the ocean and discharges at about 154 feet below sea level.
There were several challenges PROCO needed to keep in mind for this
project. One concern was that diffusers and duckbill check valves might be
damaged by passing marine vessels. To address this concern, PROCO needed
to determine the appropriate diffuser length, which in this project was about
741.5 feet at the farthest end of the 1.5 mile run on out fall pipe.
Previously, engineers and contractors were often required to blind flange
some of the ports so that they would be functional with less flow rates and
opened to allow for future maximum flow rates. Maximum flow was calculated
to handle requirements with a 20-year future outfall rate. However, the present
Project: Marine Wastewater Outfall
Location: Istanbul, Turkey
Owner: Water Authority of Istanbul
Designer: Marine Consultants Group
Case Study
flow rate will not be functioning at maximum output, as a result, PROCO and
MCG needed to design appropriately sized check valves to alleviate this
The Marine Consultant Group recommended that the Water Authority use the
PROCO ProFlex Style 710 duckbill check valves for this project, and each
port discharge was equipped with two, 10-inch diameter (250 mm) duckbill
check valves.
Duckbill valves are frequently used to prevent back flow in deep marine
outfall/diffuser projects. The PROCO ProFlex 710 duckbill check valves provided several advantages for this marine outfall. First, there was no need to blind
cap some of the ports during the first years of operations. Secondly, the use of
PROCO ProFlex 710 duckbill check valves eliminates the need to blind flange
ports since the lines can operate with full efficiency from the initial startup,
which decrease maintenance and reduce diver time to add additional valves in
the future.
Another benefit of using duckbill check valves for this project was to
prevent saline intrusion into the line when there is no inlet pressure. Different
head pressures between sea water and discharge water cause sea water to
enter the line when there is low head pressure or when there is no inlet flow.
If this back flow is not prevented, the ports may be blocked or plugged, and
marine life can enter the lines. As a result, the calculated and engineered
dilution ratios will then not be achieved.
Finally, duckbill check valves increase the jet velocity and provide a better
dilution value than traditional flap gates, even with low flow rates.
In addition to these benefits, the PROCO ProFlex Style 710 duckbill check
valves’ highly engineered elastomer maintains its memory after a long period
of staying open or staying in a closed position. One of the biggest advantages of the elastomeric check valves is that they are 100 percent barnacle- and
Algae-resistant, which is an important feature for a salt water project.
PROCO’s engineering team also provided full assistance with supplying
the head loss calculations.
Following the installation of the PROCO ProFlex Style 710 duckbill check
valves, the finished assembly was charged with air to allow buoyancy and
was then dragged into a determined position and allowed to drop to the sea
floor. This allowed the PROCO 710 valves to become operational and allow
the appropriate outfall diffusion through each of the 46 valves.
The system has been a fully functional success for the region, and Proco
continues to offer assistance and engineering expertise on systems comparable to this on a globally active basis.
An example of a sized diffuser flow rates
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