Hazard of water accumulation in double-layer underground oil tanks

1. Harmful effect of water on oil
① water can accelerate the corrosion of metal oil tank equipment. Although the metal oil storage tank is coated with anti-corrosion paint during installation, if the management is not good, there will be moisture and impurities at the bottom of the double-layer oil tank for a long time, which is easy to accelerate the failure of the anti-corrosion coating, causing chemical or electrochemical corrosion of water and metal, greatly shortening the service life of the double-layer oil tank, leading to leakage at the bottom of the tank and causing economic losses.

② if the gas station does not operate according to the regulations, it is easy to send the oil products containing moisture and impurities to the customers, resulting in oil quality accidents, affecting the corporate image, and causing huge economic compensation losses.

③ when there is water in light oil, it will accelerate the oxidation of raw rubber, make the quality of oil worse, and affect the service performance of oil.

2. Analysis of the source of water in the double layer underground oil tank
In the process of processing, transportation, storage and application of oil products, some water will be brought into the oil tank for various reasons. Generally, water exists in oil products in three states: dissolved state, suspended state and free state. There are three main sources of water in the double-layer underground oil tank of gas station ① free water produced by "small breathing" during oil storage. If the volume of oil changes with the change of temperature, the moisture in the air enters the double-layer oil tank through the exhaust pipe, which is called at the bottom of the tank. When the oil is not stored in full tank, there is a certain space from the liquid level to the top of the tank, so the chance and quantity of free water travel are relatively increased.

② water brought by oil depot: Generally speaking, the oil depot can inject "bottom water" of appropriate height at the bottom of the tank storing light fuel oil. If the management is poor or the work is negligent, the moisture may be brought to the gas station along with the raw materials.

③ water leakage: water seeps into the oil tank from the water well through the gasket of the manhole cover valve disc of the double-layer oil tank. In case of rain and snow or the rise of groundwater level, the stagnant water in the well is caused due to poor drainage. If the manhole cover of the oil tank is short of maintenance for a long time, or the rubber gasket is aged, the fixing screw is rusted and loose, and the opportunity of water accumulation is encountered, the water level at the bottom of the oil tank will increase.