山南Maintenance problems of thin oil dry seal gas holder

As an important facility for storing gas, the thin oil sealed dry gas holder was widely used in oil refining enterprises in the 1990s. Its working principle is to maintain the oil level of the gas holder piston and seal the gas in the tank by relying on the intermittent start and stop of the circulating oil pump. Because of its simple operation, flexibility, stable pressure (adjustable 3.00~10.00 KPa), it has played a huge role in the gas balance process of Sinopec refining and chemical enterprises. In recent years, due to the increase of the sulfur content in the gas, the corrosion problem of the equipment has become increasingly prominent. Some problems have generally occurred in the gas tank put into use in the above period, such as corrosion and perforation of the oil groove at the bottom of the tank, the bottom plate of the oil-water separator, the perforation of the diaphragm, and the failure of the piston sealing slider, which seriously threaten the safe production of the gas tank.
What are the main problems encountered in gas tank maintenance? Let's follow the installation of dry gas holder.
1.1 Oil accumulation on piston top
During the operation of the gas tank piston, due to the splashing phenomenon of the sealing oil at the top oil overflow port during the falling process, the splashing oil is scattered between the piston roof counterweight blocks, which is very difficult to repair and clean.
1.2 Oil and gas treatment at the bottom of gas tank
After the gas tank is shut down, the piston falls off the bed, and the bottom space is narrow, so the cleaning personnel cannot enter for cleaning. See Figure 1. It is particularly pointed out that there is a large amount of oil sludge in the oil ditch at the bottom of the tank, which contains condensed oil and other hydrocarbon components and dissolves H2S at the same time, and has a foul smell; A large amount of oil sludge and light hydrocarbon components are also stored at the bottom of the tank (the oil sludge is mainly composed of a mixture of coking carbon powder and polypropylene powder). The treatment risk of the above substances is high.
1.3 How to support the piston to the maintenance height after the maintenance of the gas tank
In order to achieve the maintenance of the bottom of the tank, the piston must be supported to the maintenance height, but the piston weight of the 20000 m3 gas tank is about 240 tons, which cannot be solved by the existing construction equipment, and a new mode must be adopted. We have solved the above problems by using the method of inflating and floating and installing legs during the maintenance.