Humanity has in its arsenal many inventions that allow people to produce a huge amount of goods used in life and to create comfort. Many technologies pose a potential danger to the manufacturer, and sometimes the consumer. Improper handling of pressure vessels is a risk factor. Using such equipment, you need to be fully equipped.
What it is
Pressure vessels are found even in everyday life. These are cylinders for gas stoves, which are still found in dachas and in the countryside, and cylinders for diving, and widespread heating boilers. If such reservoirs are removed from industry, then we will immediately come close to the standard of living of primitive man. So, a pressure vessel is a hermetically sealed tank that is used in the course of chemical reactions and for the conservation and movement of gases, liquids, and powdered masses. Fittings are welded onto its holes, through which other elements of the system are connected.
The laboratories use autoclaves, compressors, vacuum chambers, LPG cylinders. Pressure-resistant containers work in the food industry and in the energy sector. They regularly serve in mining, in submarines in the form of nuclear reactors, in astronautics. The pressure vessels experience extreme loads in the oil refining industry. This mode gives the highest efficiency yield of high-quality fuel.
What is the danger
Each vessel is designed for specific load standards, exceeding which can lead to disastrous consequences. The pressure drop between the inner and outer part of the vessel, regardless of whether it has arisen as a result of a chemical reaction, heating, cooling or vacuum, is fraught with potential danger. Accidents of such equipment bring many victims. After all, it works under tremendous pressure, and rupture of the vessel can cause the release of poisonous gas, fire or explosion. The conditions for the development, production, testing and certification are set forth in the Federal Norms and Rules (FNP) for pressure vessels.
Is it easy to protect yourself?
Scientific research and the experience of successful industrial use of such equipment indicate that it is difficult, but possible, to maintain safety. A fair amount of responsibility is required. In order to prevent accidents, industrial injuries, and to create a safe environment during operation, low-pressure filters have been prepared for vessels operating under pressure> 0.07 MPa. Filler are:
- water at t> 115 0 C;
- other liquids at t> boiling points;
- steam, gas.
The form
The design of vessels is an important characteristic that affects the durability and reliability of operation during the warranty period. The Department of Rostekhnadzor requires that it takes into account the possibility of external and internal inspections, repairs, cleaning, washing, metal and joint inspections, and complete release. Most often, a spherical, cylindrical or conical shape is used for the production of vessels, although any others are found. A cylinder with round or oval-shaped plugs is the cheapest to execute and simpler than others to analyze the processes inside. A sphere can withstand twice the load than a cylinder, but it is difficult to manufacture.
Special attention days
The Department of Rostekhnadzor has developed a procedure for handling pressure vessels. Capacities need inspection:
• after assembly, before joining the production cycle;
• regularly during use;
• out of turn for emergency reasons;
• at the time of the end of the factory warranty.
The survey periods for the most heavily used reservoirs are presented in the table below.
| Name | Speed | Internal and external inspections, years | Hydraulic test, years |
| Not included in Rostekhnadzor |
| Vessels filled with a medium that destroys and physically chemically converts metal at a speed | ≤ 0.1 mm / year | 2 | 8 |
| > 0.1 mm / year | 12 months | 8 |
| Registered |
| Vessels (petrochemicals) containing a medium that destroys and physically chemically transforms metal at a speed | ≤ 0.1 mm / year | 4 (6) | 8 (12) |
| > 0.1 mm / year | 4 | 8 |
| Sulfite-acid boilers and acid-proof hydrolysis apparatus | | 5 | 10 |
The operating instructions list the methods for performing the examinations. The day of the technical examination of the pressure vessel shall be appointed by the administration before the date indicated in the passport. The specialist responsible for the satisfactory condition of such equipment examines. With a certain periodicity, inspections by Rostekhnadzor are undertaken. If the container contained extremely and highly hazardous substances, it is treated in accordance with the instructions for working with such material.
The care that the necessary procedures have been carried out before anyone begins to carry out internal work falls on the shoulders of the appropriate engineer. The findings of any technical inspection of a pressure vessel are included in its passport. Repair is possible when the repaired vessel is disconnected from the pressure. It is unacceptable to bring lamps with a power supply above 12 V into the tank. At the slightest possibility of an explosion, only special, safe light sources are used. It may be necessary to analyze air for the concentration of hazardous components in it.
Official information
The Federal Industrial Safety Rules of Rostekhnadzor require ten days after issuing an order to connect a pressure vessel to production operations to register it with the transfer of information necessary for safety control. The local authority must have the following data:
- information about the owner provided in the application for registration;
- the location of the apparatus on the production area or the conditions for the operation of the containers, the estimated terms of their presence in the indicated place;
- location of the site for repair and inspection;
- copies of the certificate of readiness of the equipment for work and the order on the start of operation;
- vessel passport data: designation, manufacturer, production date, serial number, operating and limit indicators, permitted contents, warranty period, testing date, periods of required inspections.
Who can be trusted
The staff must:
• undergo a medical examination, safety training;
• pass the test based on the results of assimilation of the theory and internship;
• obtain a document for the right to service vessels with specific operating parameters.
Re-examination of knowledge is carried out every calendar year.
Invulnerability Conditions
Work with hazardous equipment requires the fastest possible action in critical situations. The rules for the operation of vessels operating under pressure include the installation of tracking devices, marking, and prompting. Facilitate the coordination of processes:
• taps, valves, dampers;
• manometers and thermometers;
• circuit breakers;
• level gauges.
Shut-off and control valves seal the system and set the desired characteristics. Its flywheel shows the direction of rotation when closing or opening. The fuses do not allow the pressure vessel to be turned on when the cover is not sealed and prevent leakage when pressure is present in it. Valves equalize pressure at the moments of its jumps. The number of valves is calculated based on the task so that the pressure in the tank does not exceed a predetermined percentage in excess of the working one. Surveillance devices are mounted no higher than 3 m from the surface of the observation deck. They equip each vessel.
Tanks with wall temperature differences (for example, boilers, pipelines) are equipped with benchmarks to control the thermal movements of structural sections. Verification of the readings of the benchmarks with the data of the calculated displacements determined by the designing organization allows us to evaluate the correct expansion of the vessel. Devices with delimited environments are provided with level indicators with alarms and fuses. Tanks that can turn over during emptying, repair or inspection are fixed securely, eliminating the slightest possibility of self-tipping. Despite these precautions, the technical examination of vessels operating under pressure is carried out within the time specified in the passport by the manufacturer.
Search
Inspection inside and out covers:
• research, assessment of metal thickness;
• stress analysis;
• looking around the pressure relief valves in the tank;
• physical examination;
• audit of insulation and any structural joints;
• study of welds.
Less often, but also with a certain periodicity, a hydrostatic pressure test is carried out. Vessel metal and welds are examined using non-destructive testing methods. GOST R 56542-2015 indicates their types. The specialist conducting the inspection chooses at least two ways to diagnose the connection: one for external quality control, and the second for internal. Especially carefully checked are the intersections of the welds. For this purpose, the following methods are applied:
• visual and measuring;
• capillary;
• magnetic particle;
• ultrasound;
• eddy current;
• radiographic.
Zones of areas with obvious deformations are cleaned, the thickness of the metal is measured. In case of damage that violates the safe operation of pressure vessels, the container is either removed from the production process or the load decreases after recalculation of its performance. The date of the next inspection is being revised. This fits into the passport of the vessel by the persons who carried out the re-examination. Such a procedure is possible for a tank with an expired warranty period from the manufacturer. Cracks, dents, other signs of wear are analyzed in detail for reasons of occurrence in order to identify improper conditions of use or defects in factory technology.
Welds - Risk Area
It is possible to evaluate the quality of welded joints without destruction not only upon completion of welding, but also during it. To do this, use:
• thermal expansion of the metal with its thickness> 1 mm;
• temperature of the weld area;
• the intensity of penetration of ultrasonic vibrations through the welding region.
The volume of control work is determined by specialists on the basis of previous examinations. The main goal is to achieve complete clarity about the state of the vessel. During the technical examination of vessels operating under pressure, due to their effectiveness, ultrasound is widely used. They determine the thickness of the metal, identify areas of corrosion. The photo below shows an engineer conducting ultrasound diagnostics of a weld.
Acoustic emission control
AEC diagnoses the entire vessel, identifying defects of dangerous size. Therefore, it is combined with other verification methods. AEC is carried out at the beginning or at the end of the examination procedure. In the second case, the degree of danger of the defects found is determined. AEC is indispensable when there are doubts about the correctness of indicators obtained in other ways.
Water treatments
According to the schedule of technical inspections of containers subject to physical and chemical effects, after diagnostic tests, a hydraulic test of vessels working under pressure, test pressure (≈1.25 calculated) is performed. It is designed to test the strength and density of the vessel. Usually injected water. But if there is permission from the design organization, other non-toxic and non-explosive environments can be used. In case of contraindications to the hydraulic test, it is replaced by a pneumatic test, be sure to use the AEC method to be sure that the container will not collapse. All work on the care of hermetic containers and their inspection can be undertaken by specialized organizations licensed by Rostekhnadzor. Personnel training is also possible at external educational institutions.
State control
In addition to registering vessels operating under pressure, scheduled and extraordinary inspections of Rostekhnadzor help to keep people responsible for the safety of production in good shape. After all, traditionally, humanity is more afraid of revision than an atomic explosion. Therefore, this "terrible" organization also deserves a bit of gratitude along with employees of hazardous industries, from ordinary to management. If not for their risky work, the lives of other citizens would be less secure.