Questions regarding gas tanks

Wet-type gas cylinders require less steel, have fewer mechanically processed components compared to dry-type gas cylinders, and are easier to construct. However, due to the presence of a water seal device, the cabinet is prone to rusting, resulting in high maintenance costs. A dry gas holder maintains and regulates the output pressure by means of the upward and downward movement of a large-area piston inside it. It requires high precision in installation and component manufacturing, and its construction is complex; however, it occupies less space, can handle high storage pressures, offers good stability, has a long service life, saves steel, and causes less environmental pollution. By the 1990s, the largest wet gas holders built in our country had reached 200,000 M3, while the largest dry gas holders had reached 150,000 M3. A wet gas holder is mainly composed of a vertical cylindrical water tank, one or several cylindrical tower sections, a bell cover, and guiding devices. A bell jar is a cylindrical structure with a dome and an open bottom. Between the sink and the bell jar is a cylindrical, movable tower section. The gas pipeline passes through the bottom plate of the tank and the water in the tank to enter the bell jar, thereby enabling the intake or exhaust of gas. The interconnected tower sections are sealed by water-filled hanging rings: when gas is pumped into the gas holder, the bell-shaped cover rises, and the hanging ring at its lower part draws water from the water tank ； When the bell jar rises to a certain height, the hanging ring at the bottom of the bell jar connects with the hanging ring on the second tower section; the vertical plate of the hanging ring on the second tower section is inserted into the water seal of the hanging ring at the bottom of the bell jar, and thus the second tower section is lifted, and each tower section is lifted in this manner. When discharging gas, the movement processes of the bell jar and the tower section are opposite. The bell cover and tower sections rely on guide rails and idler wheels to ensure smooth lifting. Based on the type of guide rail, they are divided into vertical type and helical guide rail type. Dry gas cabinets typically adopt the traditional Wiggin’s dry gas cabinet design and consist of main components such as the bottom plate, columns, side walls, roof frame, piston system, sealing devices, and balancing mechanisms. In addition, there are walkway platforms, ladders, and various auxiliary devices for inspection and operation, including internal lifting cages and rescue equipment, external elevators, and venting and purging systems. The dry gas holder has the shape of a regular polyhedron. Large I-beams are erected at the top corners of the cylinder, serving as connectors for the side wall panels as well as as lifting tracks for the large lifting piston. The cylinder’s side walls are constructed by stacking and welding stamped wall panels. The ceiling frame adopts a steel truss structure, while the ceiling panel is made by welding steel plates or stamped panels; ventilation devices are installed on the ceiling. Inside the gas holder, there is a regular polygonal piston that matches its shape; concrete precast blocks are placed on this piston to regulate the pressure of the gas being output. Flexible sealing devices are installed around the piston, and these sealing devices can be further divided into thin oil seals and rubber sheet seals depending on the type of sealing. Depending on the type of sealing used, the structure of the piston varies as well. In gas tanks with thin-oil sealing, the piston’s framework is made of steel trusses, and a steel plate is welded to the bottom of this framework to ensure airtightness. The piston that seals the gas tank with a rubber sheet curtain is composed of a piston plate welded from steel plates, concrete supports, brackets, piston struts, and other components.