The Design and Installation of Underground Storage Tanks

 
Underground storage tanks are vital for liquid storage. Their design and installation not only affect safety and operational stability but also involve environmental protection and maintenance efficiency. Therefore, several factors must be considered during the design process to ensure the underground storage tank is efficient, safe, and economical. This article will explore key aspects such as opening design, manhole installation, pressure balance, leak monitoring, waterproofing measures, anchoring methods, and pump installation.

Opening Design

The design of openings is crucial for underground storage tanks. Minimizing the number of openings can reduce the risk of leaks and simplify future maintenance. Concentrating connections helps lower the number of welds, thereby decreasing corrosion and failure risks. The choice of materials for these openings should be based on the chemical properties of the stored liquids, ensuring long-term stability. For corrosive substances, materials like stainless steel or other corrosion-resistant options are recommended. Additionally, the design around the openings must ensure a good seal to prevent leaks from external environmental factors.

Manhole Installation

Manholes are essential for the installation, cleaning, and maintenance of tanks. The number and placement of manholes should depend on the tank size and usage frequency. It is often advised to install a DN1100 manhole with a ladder above it to facilitate access for maintenance personnel. A rain canopy is necessary to prevent water or other liquids from entering the manhole. Some companies may require two separate manholes for liquid entry and maintenance operations, enhancing safety and efficiency.
For sealing manholes, using high-performance sealing materials is vital to prevent leaks under various operating conditions. Additional lighting and ventilation can be integrated into the design to improve safety and comfort for those using the manholes.

Pressure Balance

Pressure balance is crucial when liquids enter or exit the tank, directly affecting its stability. Underground storage tanks should be equipped with high-performance breathing valves to ensure smooth gas flow, maintaining internal and external pressure balance. The selection of these valves should consider the tank's volume, liquid characteristics, and surrounding environment. The installation of flame arrestors can prevent flames from entering the tank, reducing safety hazards due to pressure fluctuations.

Leak Monitoring and Waterproofing

To ensure tank safety, a leak monitoring system is essential. By incorporating sumps and detection pipes, liquid leakage can be monitored in real-time, allowing for prompt action to prevent environmental contamination. The sump design should facilitate drainage and cleaning, ensuring that leaks do not cause further damage.
To protect the tank from groundwater erosion, the tank pit should be coated with waterproof and corrosion-resistant material and designed with a slope to direct water to a safe drainage area. Implementing a drainage system around the tank pit can further mitigate groundwater threats. Using advanced waterproof materials and techniques can effectively extend the tank's lifespan and enhance overall system stability.

Anchoring Methods

There are primarily two methods for anchoring underground tanks, with the choice depending on the tank's size, weight, and environment. The first method involves placing the tank directly on a concrete saddle foundation, with welded liners and locating plates at the bottom to prevent rotation. After positioning the tank, the locating plates can be welded or bolted to embedded steel plates on the foundation.
The second method uses a saddle with bolt holes to secure the tank to the foundation plate. The design must ensure that at least one support is fixed while the others are sliding supports, allowing for thermal expansion or material impact without adding excessive stress.
Additionally, soil characteristics must be considered in the design to ensure the foundation can bear the tank's weight and prevent settlement or movement, ensuring long-term stability.

Pump Installation and Cavitation Issues

The liquid inlet of the tank is located below ground level, and the height difference between the inlet and the centrifugal pump, along with pipeline resistance, must be controlled to avoid cavitation issues. The pump should be positioned close to the inlet, with an installation height within an acceptable range. Calculating the pump's maximum installation height is necessary to ensure the actual height is less than this value, preventing cavitation caused by poor pipeline design. Attention should also be given to how altitude affects pressure, ensuring the pump operates effectively under various conditions.

Conclusion

In summary, the design and installation of underground storage tanks involve several critical factors, including opening design, manhole installation, pressure balance, leak monitoring, waterproofing, anchoring methods, and pump installation. Through scientific design and comprehensive protective measures, the safety and reliability of underground storage tanks can be significantly improved, ensuring their long-term stable operation. Regular maintenance and inspections are also essential; proactive measures and thorough checks are necessary to guarantee safe operation, protecting both the environment and public safety. These comprehensive considerations will lay a solid foundation for the efficient and environmentally friendly operation of modern storage systems.