Cleaning oil storage tanks: instructions

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

The need to clean equipment that has contained oil products may be due to the need to perform repairs or preventive maintenance. The frequency of such events is determined by the scope of use of the oil product, its type and characteristics. For example, tank cleaning of fuel materials and aviation oils is usually done once a year, and maintenance of equipment in which oil or fuel oil was stored twice a year.

Which surfaces are cleaned?

During the work activities, the maintenance personnel cleans the surfaces of the walls and the bottom, and also degasses the atmosphere of the tank. For walls, after cleaning, there may be rust and a slight layer of product, but no detergent particles should remain.

The most problematic part of the tank is the bottom. Mechanical impurities, sediment and rust remain on it. Together, these elements can remain at the bottom after cleaning, if their volume is not more than 0.1% of the total. As required by the instructions for cleaning tanks from petroleum products, the residue from detergent inin this case, it may persist if it is within the allowable concentration established for a particular formulation.

During the degassing process, the personnel also eliminates the remaining vapors that were released by the oil product during the containment process. At the end of stripping, the concentration of characteristic vapors must also be within the allowable value.

Preparing for stripping

Preparatory activities can be divided into two stages. The first is more formal and organizational in nature. At this stage, stripping methods, cleaning products, equipment and consumables are agreed, and working documentation is prepared. At the second stage, technological preparatory operations are performed. First of all, the site is fenced off, where the tanks will be cleaned and oil products serviced. Further, if necessary, bypass roads are provided, a technical utility room is equipped and fire safety systems are installed. The main work at this stage is devoted to the organization of pipeline channels for pumping out the existing oil product and lines for supplying detergent. In the event of the presence of large volumes of oil products, technological zones of sedimentation tanks are also equipped for temporary storage of material before disposal.

Removal of residual petroleum products

Usable products in the form of petroleum, fuel oil, oil and other fuelsfuel materials must be selected from the tank even before preparation for stripping. If by this time the products have not been selected, then their residues are pumped out through organized pipelines and disposed of. However, this procedure has its own difficulties. The fact is that the pumping of petroleum products should be provided by liquefaction. As a rule, three liquefaction methods are used in tank cleaning operations from oil residues:

• With water and steam. Water with a temperature of about 80-90°C is evenly spread on the surface of the remaining product. Also, the so-called hot steam can be sent as a supplement.
• Liquification with a hydromonitor. In this case, water is also used, but the main action is provided by a hydraulic monitor that controls the force of the washing jet under high pressure. In parallel, the blurry material is pumped out.
• Dilution with the same oil product. A multi-stage circulation wash is carried out inside the remaining product. A similar oil product is used as a washing material, but in a heated form.

Gas-air cleaning of tanks

The task of this stage is to create a gas-air environment that is safe for a person to stay in the tank. The most accessible technically and financially the way to update the air in the tank is the organization of natural ventilation. But it will provide the proper effect only with a wind speed of about 1 m / s. In other cases, forced ventilation is usually used. For example, these can be steam ejectors or fans. But it is important to keep in mind that the cleaning of tanks for the storage of petroleum products in contact with the gas-air environment can only be carried out by spark- and explosion-proof equipment. As an alternative option for air renewal, the steaming method is also used at a temperature of 90 ° C.

Reservoir washing

This is the main stage of cleaning, before which the tank must be freed from the remnants of the old oil product and polluted air. That is, the conditions in the tank should allow washing operations to be carried out directly by people. For washing, special devices are used that supply hot water with a jet. In this way, formation corrosion and wall residues of the product are removed. Moreover, the work begins from the upper belt to the lower one, therefore, during the washing process, the lower pumping of the cleaned mixture can be carried out several times.

As indicated by the instructions for cleaning the tanks, at the bottom, the removal of the residue must be carried out by a pneumatic conveyor. At the final stage of cleaning, a wash with a solvent is carried out and the final treatment of the surfaces with a clean rag.

Waste disposal

The oil product collected during the cleaning process is first sent to settling tanks and temporary storage facilities, and then, according to an agreed project, it is transported to special landfills and disposal stations as waste. It is important to note that sometimes the cleaning of tanks leaves a valuable product for use. But for himapplication, special processing must be carried out - as a rule, the percentage of useful material does not exceed 40-50%. Transportation of products is carried out using vacuum machines, vacuum pumps and tankers.

Conclusion

After stripping, quality control is carried out using flaw detectors to determine the parameters of the remaining material and the level of gas contamination. At the same time, the quality of such events is characterized not only by the result of the work done.

Since the cleaning of tanks from oil products throughout all stages is accompanied by risks of explosion and fire, the most important condition for the quality of such work will be precisely the observance of fire and environmental safety measures. To do this, the instructions prescribe separate sections with instructions on the operation of fire extinguishing agents. Also, working equipment with cleaning devices and transport must meet the requirements for efficiency, productivity and functionality - all these qualities together will determine a decent cleaning result.