Underground stainless steel sewage tanks

A properly functioning sewer system is essential for wastewater processing. Tank fabricator Gpi helped a client to renovate their existing vacuum sewer system. Due to corrosion of the old steel collection tanks, new underground sewage tanks were required.

Text & images by Gpi

Underground stainless steel sewage tanks

The client explained that the vacuum sewerage tanks have reached the end of their lifespan, prompting Gpi to replace them gradually. The client explains: “Holes had formed in the old steel tanks, and the connections and pipes were heavily affected by corrosion. For better protection against corrosion in future, we have now chosen stainless steel because this material has better resistance. This led us to Gpi because they are experts in the field of stainless steel tanks. They also offered a good price-quality ratio, which was the decisive factor for awarding the contract.”

About the assignment

The first new sewer tank was delivered at the beginning of 2023, with two additional tanks being delivered recently. The tanks are used as the first storage location for wastewater before it is pumped to the wastewater treatment plant. The sewage tanks are made of 316L and are placed horizontally underground.
Underground tanks are subject to very strong corrosion due to minerals in the ground. The new tanks have, therefore, been treated with a very wear-resistant and corrosion-resistant coating. The diameter is 1.8 meters, and they are over 3.7 meters long. What is striking about the tanks is the position of a manhole placed high on top of the tanks that remains accessible after installation. Furthermore, the tanks are equipped with connections for the incoming and outgoing sewer pipes and access for pumps, sensors, the power supply, and controls.

Detailed schematics of the tanks showing the incoming and outgoing sewer pipes and access for pumps, sensors, the power supply, and controls.
Detailed schematics of the tanks showing the incoming and outgoing sewer pipes and access for pumps, sensors, the power supply, and controls.

The execution

The client is enthusiastic about the execution of the assignment: “Gpi clearly described what it would deliver, with which specifications, and at what time. A clear schedule for engineering and production was also included. They neatly worked out our sketch with dimensions and specifications into 3D models, which we received for verification. After this phase, the tanks went into production. At the end of the production process, we were invited for the factory acceptance to view and check the tanks. It was impressive to be able to see the production process of these and other tanks up close.”

Collaboration

“We are satisfied with the quality and cooperation. It has been a streamlined process where quality was monitored and recorded throughout the production process. After production, we received complete documentation for each tank: the drawing, material list, certificate, user instructions, and quality reports. Gpi is a fine company with skilled employees who go for quality and know how important cooperation and good communication are.’

Due to the corrosive conditions underground, the 316L tanks have been treated with a highly wear-resistant and corrosion-resistant coating.
Due to the corrosive conditions underground, the 316L tanks have been treated with a highly wear-resistant and corrosion-resistant coating.

The result

The client discusses the result and the plan for the future: “We plan to systematically replace our collection tanks in the coming years. In addition, we have already initiated a follow-up order for two more tanks. Each new tank entails its own project, wherein we meticulously inspect the pumps, power supply, and control systems. Once installed, the tanks are completely underground, except for the access hatch. While they may no longer be visible after installation, being situated underground, the tanks remain a vital component of our sewer system. They are an indispensable part of a properly functioning sewer system. With the addition of the new stainless steel tanks, our vacuum sewer system will be reliable and sustainable.’

About this Tech Article

This tech article appeared in Stainless Steel World, March 2024 magazine. To read many more articles like these on an (almost) monthly basis, subscribe to our magazine (available in print and digital format) – SUBSCRIPTIONS TO OUR DIGITAL VERSION ARE NOW FREE.

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