Corrosion caused by excessive flow rate of pipeline media leading to over-speed operation
Thread Content
Corrosion caused by excessive flow velocity of the fluid in pipelines. Example: A company’s hot water circulation system used copper pipes; after a few months of use, leaks occurred in the pipes. The repair workers attributed the problem to poor installation, while the contractor denied any responsibility for the installation and refused to pay for the repairs. Corrosion experts cut open the hot water pipe to inspect it; the inside of the pipe was severely corroded, with the wall thickness having reduced to zero in many areas. The characteristic wavy pattern on the inner surfaces of the elbows and fittings indicates that the failure was caused by wear corrosion (erosive corrosion). Analysis: It turns out that the contractor wanted to ensure a more adequate hot water supply, so they installed a larger pump. As a result, the flow rate of hot water exceeds 3 to 4 times the allowable value for copper pipes (the normal value is 0.9 to 1.5 m/s; it should be even lower when the water is hot or highly corrosive). Here, we have wear-corrosion damage caused by excessively high flow velocity. This contractor wanted to do things better, but things went wrong; not only was no improvement achieved, but the pipes were also corroded and damaged as a result. The reason is a lack of knowledge about corrosion and protection. It is still unknown how the accident occurred after it happened.
This case shows that flow velocities within the pipe exceeding the safe range for copper pipes led to wear corrosion. As the contractor increased the power of the pump to boost the hot water supply, the flow rate exceeded acceptable levels by a large margin, thereby accelerating the corrosion process inside the copper pipes. This type of corrosion forms under the influence of fluid dynamics, and the wavy pattern on the inner surfaces of elbows and fittings is a typical characteristic of wear corrosion. The contractor caused this problem due to a lack of knowledge regarding pipe corrosion and protection, and failed to identify the cause of the issue in a timely and proper manner. .