This article describes the basic requirements, norms and rules for the technical operation of tanks intended for the storage of oil and oil products. In addition, the basic provisions on the use of various methods of non-destructive monitoring of the condition of tanks, the protection of special steel structures from corrosion and the harmful effects of the environment, the reduction of oil losses during technological operations, and the prevention of oil spills are given. Attention is paid to the procedure for repair work at facilities such as oil and oil product storage tanks.
Normative legal acts and documents
Detailed repair instructions and tank operating rules were approved by the Goskomnefteprodukt of the Soviet Union back in 1986. Already, such a country does not exist, and this document has not lost its significance. When developing their own documentation, many oil producing and oil refining companies take these rules for the technical operation of reservoirs as a basis. The status of this document is invalid. But he has not lost its relevance. Many experts recommend that all interested parties familiarize themselves with the rules for operating Rosneft reservoirs.
Fundamentals of safe operation of reservoirs for storing oil and oil products
In accordance with the rules for the technical operation of tanks for the storage of combustible materials, all engineers and technical personnel of the enterprise are required to know the design and features of the systems for pumping and storing petroleum products. This requirement is fully justified and understandable. Indeed, a person who does not know through his actions can provoke a large-scale technological disaster.
Observance and implementation of the rules for the technical operation of tanks can guarantee safety only if no mistakes were made at the stage of system design (all the initial data were correctly selected and accepted), if the technological discipline is observed (the operation mode is not violated), if the assembly was carried out without violation of regulations.
General requirements for the design and reliability of steel tanks
Tanks for storing oil and oil products are made, as a rule, from special building grades of steel. However, there is no universal standard for form. Tanks can be made both in vertical execution, and in vertical. In addition, for certain purposes and under certain circumstances, spheroidal steel containers can be manufactured. In some cases, enterprises give orders for the manufacture of special containers. Such equipment is much more expensive. But some major players in the energy market can afford it (for example, Rosneft). The rules for the technical operation of tanks in this regard may vary. But in general, the set of rules that ensure safe operation is applicable to any enterprise that is engaged in the storage and processing of oil and oil products.
Features of vertical tanks
Tanks in vertical design can have a variety of usable volumes - from 100 to 50,000 cubic meters. They can be built both above the ground, on and below it. In addition, such tanks can be used both for storage of liquid without pressure and under it. Reservoirs capable of maintaining operability at pressures up to 2,000 Pascals inclusive are referred to overpressure tanks. For certain purposes, containers that can operate under high pressure (up to 70,000 Pascals inclusive) may be required. The main customer of such products is Rosneft. Rules for the technical operation of tanks can vary significantly. After all, vessels that work under pressure need a more thorough examination and increased attention from both engineering and working personnel. This defines the rules for operating vertical tanks.
The roof of such vessels can be both stationary and floating. And this also affects the procedure and rules for the technical operation of oil storage tanks. The stationary roof can be made in the form of a sphere, cone, etc.
It is far from always that welded joints can be used for the manufacture of tanks. It has its drawbacks, which can become critical (for example, in certain weather conditions). An alternative to welds is riveting. The complexity of the production of such tanks is an order of magnitude higher, but on the other hand, reliability is many times greater than cheaper welding. When welding, the sheet material can be joined in the butt, lap (or partially overlap). Rivets can join sheets overlap or butt. In the second case, special pads will be needed.
Features of horizontal tanks
The capacity of horizontal steel tanks is an order of magnitude less than vertical (from three to two hundred cubic meters). They can also be mounted both on the ground and under it. By default, such tanks are designed to withstand pressures of 4,000 pascals. The bottom of such tanks may be flat, conical, or spherical.
Each tank can be operated only with all the necessary auxiliary equipment. Storage of oil and oil products in a dismantled tank is prohibited. All containers in which gasoline is stored must be coated from the inside with a special protective layer aimed at ensuring static spark safety.
In the manufacture of the tank, its dimensions cannot exceed the permissible deviations. These indicators are strictly regulated and spelled out in the design documentation.
Tanks of small capacity (up to eight cubic meters inclusive) should have a flat bottom. Flat bottoms are also allowed for larger tanks. But these conditions must be agreed with the customer.
The procedure for receiving oil and oil products into tanks
The feed rate of liquid cargo (oil and oil products) into an empty tank should not exceed one meter per hour. This restriction is maintained until the reception-distribution pipe is filled. Then it is allowed to increase the speed to three and a half meters per hour.
It is very important to organize the supply of a new batch of oil products to the tank so that it is carried out below the level of the liquid already in the tank.
To avoid the formation of air bags, the tanks must be filled and emptied completely.
Spray, spraying or rough and rough mixing of oil products is not allowed. In other words, pouring using a freely falling liquid stream is not allowed. The distance from the end of the loading pipe to the bottom of the tank should not be less than 0.2 meters. In this case, the jet should be directed along the wall. These and similar requirements can be found in the rules for the technical operation of tanks and Rosneft, and other oil companies. This rule is also contained in the old requirements developed and approved back in Soviet times. However, it should be said that the status of the rules for the technical operation of the 1986 tanks is not valid. Currently, all large companies have in their staff the necessary personnel who are involved in monitoring the situation, developing and updating their own regulatory and technical base.
In accordance with the rules for the operation of reservoirs of main oil pipelines, pumping of oil products into a tank can only begin if there is a written order from the responsible director for transport operations.
To tear off valves and special valves of tanks is necessary without sudden movements, without resorting to the use of auxiliary means. If the valves are equipped with an electric drive, then an alarm must be installed without fail, clearly indicating the state of the valve (closed or open). Any transfer is strictly required to be entered by the senior operator in the service journal.
Rules and procedure for stripping tanks for storing oil and oil products
In accordance with the rules for the technical operation of metal tanks, work on cleaning containers should be carried out in compliance with the requirements and rules of fire safety in production.
The frequency of these works is carried out by GOST 1510. When storing fuel for jet engines, aviation kerosene, and also oils for use in aviation, stripping is carried out at least once every six months. When using a filter of forty micrometers in the pump injection system, it is allowed to carry out treatment works with a frequency of once a year. In the case of storage of other oils, gasoline for automotive vehicles, diesel fuel, cleaning should also be carried out once a year. The frequency of these types of work for tanks with fuel oil and motor fuel. The tank must be cleaned before changing the product, before conducting non-destructive testing by a flaw detector specialist.
In accordance with the rules of operation of oil product tanks, cleaning is preceded by preparatory work: installation of technological and auxiliary pipelines (water, steam), preparation and adjustment of equipment for surface cleaning. The sequence of work cannot be violated. She is indicated in the admission order. This document is signed by the responsible official.
Only competent and experienced engineer who has been trained in relevant courses and advanced training in the relevant department can manage such work. He must arrange for all workers to undergo safety training and emergency assistance before starting work.
The rules of technical operation and repair of tanks strictly regulate the procedure for cleaning the inner surface of the tank. First of all, the tank must be completely freed from any residual oil products. For this, a special pumping hose is used. For a more thorough and thorough cleaning, the tank is filled with water. The density of oil and its derivatives is much lower than the density of water. Oil and fuel float to the surface, after which they are eliminated.
Safety precautions for cleaning operations inside tanks
The rules for the technical operation of oil product tanks are prohibited from use when cleaning general equipment. All devices and apparatus must be explosion-proof class. Special should be wiring.
In order to avoid accidents, the pumping speed of a mixture of oil products with water should not exceed certain limits, taking into account recommendations for protection against the occurrence of static electricity.
In the event that the remnants of the flammable products are pumped out, the lower one must be ensured that the lower hatches are hermetically closed. This category includes substances whose flash point lies below 61 degrees Celsius.
After the complete removal of all residues, all pipelines are disconnected from the tank and special plugs are installed. Installation of stubs is fixed in a special log. This is necessary in order to avoid confusion when commissioning the tank after cleaning operations, as well as for safety reasons.
It is forbidden to carry out work on filling and emptying tanks located at a distance closer than forty meters from the tank being cleaned.
When conducting work on cleaning the inner surface of the tank, it is necessary to exclude the admission of unauthorized persons to the area of work. Workers involved in the work must be provided with all necessary protective equipment (glasses, respirators, gloves, etc.) and degassing equipment.
The internal surface of the container is degreased by spraying and applying the active substance (potassium permanganate solution in water) using a nozzle.
When a critical mass of oil product waste accumulates in water (1,500 milliliters per liter of liquid), its further use is excluded. Such a liquid needs filtration and purification from oil products.
Protection of the inner surface of tanks against corrosion
In accordance with the rules for the technical operation of steel tanks, the inner surface of oil storage tanks for the purpose of corrosion protection can be coated with paints or combined metallization and paints. The application of any coating is preceded by thorough surface preparation (cleaning) and other preparatory work.
The choice of a particular protection method depends on many factors. First of all, from the aggressiveness of the impact of petroleum products and the environment on metal structures.
It is recommended to start processing with anti-corrosion coatings from above. The paintwork is last applied on the bottom. However, when painting the inner walls of tanks with a floating roof, a different order is allowed: initially, a layer of paint is applied to the bottom and roof. Then water is poured into the tank. She raises the roof, and work on painting the inner walls is carried out afloat. Similarly, when painting the walls of tanks equipped with pontoons. This procedure is established by the rules for the technical operation of reservoirs of oil trunk pipelines.
Painting of internal surfaces is carried out in accordance with a specially designed project. This document indicates the degree of surface cleaning before applying the paint, acceptable and recommended methods of cleaning, the number of coating layers and other information. The service life of this coating is three years. After expiration, its paintwork must be completely changed. If this requirement is neglected, then the surface will begin to actively corrode whether it will quickly become worthless. The occurrence of a leak of oil products and environmental pollution is not ruled out.
Features of tread protection
The rules for the technical operation of tanks (Nedra, Moscow 1988) confirm the particularities of the organization and design of the tread protection of tanks. When designing it, you must take into account the alkalinity, mineral composition and chemical composition of groundwater.
Materials such as zinc, magnesium and alloys based on them and aluminum are used as a tread for corrosion protection of carbon steels. The installation of tread plates on the inner surface of the tank is preceded by their thorough preparation. It consists in applying an insulating layer to one of the surfaces of the plate.
Protectors can be mounted both on the bottom of the tank and on its walls. The area on which the protector will be mounted must be cleaned from dirt and rust. Epoxy is ideal for fastening. This substance reliably glues the tread to the surface and serves as a good insulating material. Contact of the tread with the bottom is carried out by welding a small section of rolled steel.