In tanks storing oil for long periods, waxes, gums, asphaltenes, sulfides and mechanical impurities gradually deposit into thick sludge. According to industry data, sludge can reduce effective storage capacity by 15%-30%; a 10,000-ton tank with 10 cm of bottom sediment could lose hundreds of cubic meters of capacity.

The harm goes far beyond capacity loss. Iron sulfide formed by the reaction of sulfides with tank-wall rust can self-ignite in air, a common high-risk accident cause during cleaning; light hydrocarbon volatiles mixing with air can ignite with static or open flame. Sludge and corrosion products together can also increase corrosion rates of the tank floor and walls by 2-3 times.

The industry recommends that reducing sludge at the source is more economical than post-cleaning. Installing spiral mixers or jet anti-sedimentation equipment to circulate and break up sludge layers can effectively extend cleaning cycles, lower cleaning costs and ensure safe, stable tank operation.