The need for cleaning equipment that contained petroleum products may be due to the need to carry out 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, cleaning of tanks from 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.
What surfaces are cleaned?
In the process of working activities, the maintenance staff cleans the surfaces of the walls and the bottom, and also performs degassing of the atmosphere of the tank. As for the walls, after the cleaning is completed, rust deposits and a small layer of the product may remain, but no particles of detergent should remain.
The most problematic part of the tank is the bottom. On it remain mechanical impurities, sediment and rust. Together, these elements can remain at the bottom after cleaning, if their volume is not more than 0.1% of the total. As the instructions for cleaning the tanks from oil products require, the sediment from the detergent in this case can be preserved if it is within the acceptable concentration established for a specific composition.
In the process of degassing, personnel also removes residual vapors that were released by the oil product during the containment process. Upon completion of stripping, the concentration of characteristic vapors should also be within the acceptable value.
Stripping preparation
Preparatory activities can be divided into two stages. The first is more formal-organizational in nature. At this stage, cleaning methods, cleaning products, equipment and consumables are agreed upon, and working documentation is prepared. At the second stage, technological preparatory operations are performed. First of all, the site where the tanks will be cleaned and oil products serviced will be enclosed. Further, if necessary, bypass routes 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 existing oil product and detergent supply lines. In the case of the presence of large volumes of oil product, technological zones of settlers are also arranged for temporary storage of material before disposal.
Removal of oil residue
Suitable products in the form of oil, fuel oil, oil and other fuel and fuel materials must be selected from the tank before preparation for stripping. If at this point 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 must be provided by dilution. As a rule, in the measures for cleaning tanks from oil product residues, three dilution methods are used:
- Using water and steam. Water with a temperature of about 80-90 ° C is evenly spilled on the surface of the remaining product. Also, as a supplement, so-called hot steam can be sent.
- Fluid monitor dilution. 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 pumping out of blurred material.
- Liquefaction with the same oil product. A multi-stage circulation wash is performed inside the remaining product. As a washing material, a similar oil product is used, but in a heated form.
Gas-air tank cleaning
The objective of this stage is to create a gas-air environment safe for a person to stay in the tank. The most technically and financially affordable way to renew air in a tank is to organize natural ventilation. But it will provide the proper effect only with wind at a speed of the order of 1 m / s. In other cases, usually used means of forced ventilation. For example, it can be steam ejectors or fans. But it is important to keep in mind that the cleaning of tanks for storing oil products in contact with a gas-air environment can only be carried out with spark and explosion-proof equipment. As an alternative air renewal method, a steaming method is also used at a temperature of 90 ° C.
Tank washing
This is the main stage of cleaning, before the onset of which the tank should be freed from the remnants of the old oil and gas polluted air. That is, the conditions in the tank should allow washing directly to people. For washing, special devices are used that supply hot water with a jet. Thus, formation corrosion and wall product residues are removed. Moreover, the work starts from the upper belt to the lower one, therefore, in the process of washing several times the lower pumping of the cleaned mixture can also be carried out.
As indicated by the instructions for cleaning tanks, at the bottom, the removal of the residue should be carried out by a pneumatic conveyor. At the final stage of cleaning, a solvent wash and final surface treatment with a clean cloth are carried out.
Waste management
The oil product collected during the cleaning process is first sent to sedimentation tanks and temporary storage facilities, and then, according to the agreed project, it is transported to special landfills and utilizing stations as waste. It is important to note that sometimes tank cleaning leaves a product valuable for use. But for its application, special processing must be carried out - as a rule, the percentage of useful material does not exceed 40-50%. Products are transported using vacuum machines, suction pumps and tankers.
Conclusion
After stripping, quality control is performed using flaw detectors to determine the parameters of the remaining material and the level of gas contamination. Moreover, the quality of such events is characterized not only by the result of the work done.
Since the cleaning of reservoirs from oil products during all stages is accompanied by the risks of explosion and fire, the most important condition for the quality of such work will be the observance of fire and environmental safety measures. To do this, the instructions prescribe separate sections with instructions on the operation of fire extinguishing means. Also, working equipment with cleaning devices and vehicles must meet the requirements for efficiency, productivity and functionality - all of these qualities in the aggregate will determine a worthy cleaning result.