Owners of the patent RU 2503747:
Technicia
The invention relates to heat and can be used to protect against scale heating pipes of steam and water boilers, heat exchangers, boiler installations, evaporators, heating mains, heating systems residential houses and industrial facilities in the process of current operation.
BACKGROUND
Operation of steam boilers is associated with simultaneous impact high temperatures, pressure, mechanical stresses and aggressive medium, which is boiler water. Boiler and metal surfaces of the boiler are separate phases of a complex system that is formed during their contact. The result of the interaction of these phases is surface processesarising on the border of their partition. As a result, in the metal surfaces of heating, the phenomena of corrosion and the formation of scale are arising, which leads to a change in the structure and mechanical properties of the metal, and which contributes to the development of various damage. Since the thermal conductivity of the scale is fifty times lower than that of iron of heating pipes, there are a thermal energy loss during heat transfer - with a thickness of 1 mm from 7 to 12%, and at 3 mm - 25%. Strong formation of scale in the system of steam boiler of continuous action often leads to a stop of production for several days a year to remove scale.
The quality of nutritious and, therefore, boiler water is determined by the presence of impurities that can cause different kinds The corrosion of the metal of the inner surfaces of heating, the formation of primary scale on them, as well as the sludge as the source of the formation of secondary scale. In addition, the quality of the boiler water depends on the properties of substances resulting from surface phenomena during the transportation of water, and condensate through pipelines, in water processing processes. Removal of impurities nutrient water It is one of the ways to prevent the formation of scale and corrosion and is carried out by the methods of preliminary (rot) water treatment, which are directed to the maximum removal of impurities in its original water. However, the methods used do not allow to completely eliminate the content of impurities in water, which is associated not only with technical difficulties, but also economic feasibility Application of methods of water treatment methods. In addition, since water treatment is complex technical systemIt is redundant for small and medium performance boilers.
The well-known methods for removing already formed deposits are mainly mechanical and chemical methods Cleaning. The disadvantage of these methods is that they cannot be made during the operation of boilers. In addition, methods of chemical purification often require the use of expensive chemicals.
Also known ways to prevent the formation of scale and corrosion carried out during the work of the boilers.
US 1877389 patent proposed a method for removing scale and preventing its education in water heating and steam boilers. In this method, the surface of the boiler is a cathode, and the anode is placed inside the pipeline. The method is to pass a permanent or alternating current through the system. The authors note that the mechanism of action of the method is that under the action of electric current on the surface of the boiler, gas bubbles are formed, which lead to the detachment of the existing scale and prevent the formation of a new one. The disadvantage of this method is the need to constantly maintain the flow of electrical current in the system.
In Patent US 5667677, a method is proposed for processing fluid, in particular water, in the pipeline in order to slow down the scale of scale. This method is based on the creation of an electromagnetic field in the pipes, which repels the calcium ions dissolved in water, magnesium walls from the walls of pipes and equipment, not allowing them to crystallize in the form of scale, which allows to operate boilers, boilers, heat exchangers, rigid water cooling systems. The disadvantage of this method is the high cost and complexity of the equipment used.
In the application WO 2004016833, a method for reducing the formation of scale on a metal surface is proposed to exposed to an intersted alkaline aqueous solution, which is capable of forming a scale after a period of exposure, which includes the application of the cathode potential to the specified surface.
This method can be used in various technological processesin which the metal is in contact with aqueous solution, in particular, in heat exchangers. The disadvantage of this method is that it does not protect the metal surface from corrosion after removing the cathode potential.
Thus, currently there is a need to develop an improved method for preventing the formation of scale of heating pipes, water-heating and steam boilers, which would be economical and highly efficient and provided anti-corrosion protection of the surface for a long period of time after exposure.
In the present invention, the specified problem is solved using the method according to which there is a current electric potential on a metal surface, sufficient to neutralize the electrostatic component of the adhesion of colloidal particles and ions to a metal surface.
Brief Description of the Invention
The objective of the present invention is to ensure an improved method for preventing the formation of water-heating and steam boilers.
Another objective of the present invention is to ensure the possibility of exclusion or a significant reduction in the need to remove scale during the operation of hot water and steam boilers.
Another object of the present invention is to eliminate the need to use flowable reagents to prevent the formation of scale and corrosion of heating pipes of water-heating and steam boilers.
Another object of the present invention is to ensure the possibility of starting work to prevent the formation of scale and corrosion of heating pipes of hot water and steam boilers on the contaminated pipes of the boiler.
The present invention relates to a method for preventing the formation of scale and corrosion on a metal surface made of iron-containing alloy and in contact with a steam room, which is capable of forming. This method consists in annex to the specified metal surface of the current electric potentialsufficient to neutralize the electrostatic component of the adhesion of colloidal particles and ions to the metal surface.
According to some particular embodiments of the claimed method, the current potential is set within 61-150 V. According to some particular embodiments of the claimed method, the above-mentioned iron-containing alloy is steel. In some embodiments, the metallic surface is the inner surface of the heating pipes of the hot water or steam boiler.
The method disclosed in this specification has the following advantages. One advantage of the method is the reduced formation of scale. Another advantage of the present invention is the ability to use once a purchased operating electrophysical apparatus without the need to use consumables synthetic reagents. Another advantage is the possibility of starting work on the contaminated tubes of the boiler.
The technical result of the present invention, therefore, is to increase the efficiency of water and steam boilers, increased productivity, increase the efficiency of heat transfer, reduced fuel consumption for boiler heating, energy savings, etc.
Other technical results and advantages of the present invention include ensuring the possibility of layer-by-layer destruction and removal of the already formed scale, as well as to prevent its new education.
Brief description of the drawings
Figure 1 shows the nature of the distribution of deposits on the inner surfaces of the boiler as a result of the use of the method according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The method according to the present invention is an annex to a metal surface, subject to the formation of scale, a current electric potential for neutralizing the electrostatic component of the adhesion of colloidal particles and ions forming a scale to a metal surface.
The term "current electric potential" in the sense, in which it is used in this application, means an alternating potential that neutralizing the double electric layer on the metal boundary and a steam room containing salts leading to the formation of scale.
As is known to a person skilled in the art, the electrical charge carriers in the metal, slow compared to the main charge carriers of the electron, are the dislocations of its crystal structure, which carry an electric charge and form dislocation currents. Going to the surface of the heating pipes of the boiler, these currents are part of the double electric layer during the formation of scale. The current, electric, pulsating (i.e., variable), the potential initiates the displacement of the electrical charge of dislocations from the metal surface to the ground. In this respect, it is current dislocation currents. As a result of this current electric potential, the double electric layer is destroyed, and the scale gradually decays and goes into boiler water in the form of a sludge that is removed from the boiler during its periodic purges.
Thus, the term "current potential" is understandable for a person skilled in the art and, in addition, known from the prior art (see, for example, patent RU 2128804 C1).
As a device for creating a current electric potential, for example, a device described in RU 2100492 C1 can be used, which includes a converter with a frequency converter and a pulsating potential regulator, as well as an impulse form controller. Detailed description This device is given in RU 2100492 C1. Any other similar device can also be used, as will be understood by a person skilled in the art.
The current electric potential according to the present invention can be applied to any part of the metal surface removed from the base of the boiler. The place of the application is determined by the convenience and / or efficiency of the application of the claimed method. The specialist in this field of technology, using the information disclosed in the present description, and using standard test techniques, will be able to determine the optimal place of the current electric potential.
In some embodiments of the present invention, the electric potential is variable.
The current electric potential according to the present invention can be applied during various periods of time. The time of the potential application is determined by the nature and degree of pollution of the metallic surface, the composition of the water used, temperature regime and the peculiarities of the heat engineering device and other factors known to those skilled in the art. The person skilled in the art using the information disclosed in the present description and using standard test techniques, will be able to determine optimal time Applications of the current electric potential based on the goals set, the conditions and state of the heat engineering device.
The magnitude of the current potential required to neutralize the electrostatic component of the adhesion force can be determined by a colloidal chemistry specialist on the basis of information known from the prior art, for example, from the book by Dryagin B.V., Churaev N.V., Muller V.M. "Surface forces", Moscow, Science, 1985. According to some embodiments, the value of the current electric potential is in the range of 10 V to 200 V, more preferably from 60 V to 150 V, even more preferably from 61 V to 150 V. The values \u200b\u200bof the current electric potential in the range from 61 V to 150 V lead to the discharge of a double electric layer, which is the basis of the electrostatic component of the adhesion forces in scale and, as a result, the destruction of scale. The values \u200b\u200bof the current potential are lower than 61 V are insufficient for the destruction of the scale, and with the values \u200b\u200bof the current potential above 150 V is likely the beginning of the unwanted electroerosion destruction of the metal of heating tubes.
The metal surface to which the method according to the present invention can be used can be part of the following heat engineering devices: heating pipes of steam and hot water boilers, heat exchangers, boiler plants, evaporators, heating parts, residential houses and industrial objects in the process of current operation. This list is illustrative and does not limit the list of devices to which the method according to the present invention can be applied.
In some embodiments, the iron-containing alloy from which the metal surface is made to which the method according to the present invention can be applied, may be steel or other iron-containing material, such as cast iron, cowar, fahehral, \u200b\u200btransformer steel, Altern, Magnichene, Alnico, Chromium steel, Invar, etc. This list is illustrative and does not limit the list of iron-containing alloys to which the method according to the present invention can be applied. A specialist in the art on the basis of information known from the prior art will be able to such iron-containing alloys that can be used according to the present invention.
An aqueous medium from which scale is capable of forming, according to some embodiments of the present invention, is water water. The aqueous medium can also be water containing dissolved metals compounds. Dissolved metals compounds may be compounds of iron and / or alkaline earth metals. The aqueous medium can also be an aqueous suspension of colloidal particles of iron compounds and / or alkaline earth metals.
The method according to the present invention removes previously formed sediments and serves as an unhappy means of purifying internal surfaces during the operation of the heat engineering device, in the future the non-free mode of its operation. At the same time, the size of the zone, within which the prevention of the formation of scale and corrosion is achieved, significantly exceeds the size of the zone of effective destruction of scale.
The method according to the present invention has the following advantages:
Does not require the use of reagents, i.e. environmentally safe;
Easy to implement, does not require special devices;
Allows you to increase the coefficient of heat transfer and increase the efficiency of the boilers, which significantly affects the economic performance of its work;
It can be used as an addition to the methods used by the methods of water treatment and separately;
Allows you to abandon the processes of softening and deaeration of water, which largely simplifies technological scheme Boiler rooms and makes it possible to significantly reduce costs during construction and operation.
Possible objects of the method can be water-heating boilers, utilization boilers, closed systems Heat supply, installations for thermal destruction of sea water, steam mills, etc.
The absence of corrosion destruction, scale formation on the inner surfaces opens up the ability to develop fundamentally new design and layout solutions of the steam boilers of small and medium power. This will allow, due to the intensification of thermal processes, to achieve a significant reduction in the mass and dimensions of steam boilers. Provide a given temperature level of heating surfaces and, therefore, reduce fuel consumption, volume flue gases and reduce their emissions into the atmosphere.
Example implementation
The method declared in the present invention was tested at the Admiraltey shipyard boiler plants and the Red Chemist. It was shown that the method according to the present invention effectively purifies the inner surfaces of the boilers from deposits. During these works, conventional fuel economy was obtained 3-10%, while the scatter of saving values \u200b\u200bis associated with varying degrees of contamination of the internal surfaces of the boilers. The aim of the work was to evaluate the effectiveness of the claimed method to ensure a non-moneyless, non-free mode of operation of steam bootaggers of average power in the conditions of high-quality water treatment, respect for the water-chemical regime and high professional level operation of equipment.
The test of the method declared in the present invention was carried out on a steam boiler number 3 of DCVR 20/13 of the 4th Krasnoselskaya boiler house of the South-Western branch of the State Unitary Enterprise "TEK St. Petersburg". The operation of the boiler was carried out in strict accordance with the requirements regulatory documents. On the boiler there are all necessary means of controlling the parameters of its operation (pressure and consumption of the produced steam, temperature and feed water, the pressure of blowing air and fuel on the burners, discharge in the basic sections of the gas path of the boiler unit). Steam performance boiler was maintained at 18 t / h, steam pressure in the boiler drum - 8.1 ... 8.3 kg / cm 2. Economizer worked in the heat mode. Water of urban water supply was used as the starting water, which corresponded to the requirements of GOST 2874-82 "Drinking water". It should be noted that the number of iron compounds at the input to the specified boiler room, as a rule, exceeds the regulatory requirements (0.3 mg / l) and is 0.3-0.5 mg / l, which leads to intensive ingrowth of the inner surfaces by ferrous compounds.
Evaluation of the effectiveness of the method was carried out at the state of the internal surfaces of the boiler.
Evaluation of the effect of the method according to the present invention on the state of the internal surfaces of the heating of the boiler unit.
Prior to the start of the test, an internal inspection of the boiler unit was performed and the initial state of the internal surfaces was recorded. The preliminary inspection of the boiler was produced at the beginning of the heating season, a month after its chemical cleaning. As a result of the inspection, it was revealed: on the surface of the drums, solid solid dark brown sediments with paramagnetic properties and consisting, presumably, from iron oxides. The thickness of the deposits was up to 0.4 mm visually. In the visible part of boiling pipes, preferably on the side of the furnace addressed to the furnace, are not solid solid sediments (up to five spots per 100 mm of pipe length with a size of from 2 to 15 mm and a thickness of up to 0.5 mm visually).
The device for creating a current potential described in RU 2100492 C1 was attached at a point (1) to the hatch (2) of the upper drum from the back side of the boiler (see figure 1). The current electric potential was equal to 100 V. The current electric potential was maintained continuously for 1.5 months. At the end of this period, an autopsy of the boiler was made. As a result of the internal examination of the boiler unit, almost complete lack of deposits (not more than 0.1 mm visually) on the surface (3) of the upper and lower drums in the range of 2-2.5 meters (zone (4)) from the drums of the drums (device attachment points To create a current potential (1)). At the removal of 2.5-3.0 m (zone (5)) from deposit luchkov (6), preserved in the form of separate tuberculos (spots) with a thickness of up to 0.3 mm (see figure 1). Further, as it moves to the front, (at a distance of 3.0-3.5 m from the hatches), continuous sediments begin (7) to 0.4 mm visually, i.e. On this distance from the connection point of the device, the effect of a cleaning method according to the present invention practically did not appear. The current electric potential was equal to 100 V. The current electric potential was maintained continuously for 1.5 months. At the end of this period, an autopsy of the boiler was made. As a result of the internal examination of the boiler unit, almost complete lack of deposits (no more than 0.1 mm visually) on the surface of the upper and lower drums within 2-2.5 meters from the drum luchkov (device attachment points to create a current potential) were established. At the removal of 2.5-3.0 m from the hatching of the deposition, in the form of separate tubercles (spots) with a thickness of up to 0.3 mm (see FIG. 1). Next, as we move to the front (at a distance of 3.0-3.5 m from the hatch), continuous deposits begin to 0.4 mm visually, i.e. On this distance from the connection point of the device, the effect of a cleaning method according to the present invention practically did not appear.
In the visible portion of boiling pipes, within 3.5-4.0 m from the drums, there was almost a complete absence of deposits. Next, as it moves to the front, there are not solid solid sediments (up to five spots per 100 pm with a size of from 2 to 15 mm and a thickness of up to 0.5 mm visually).
As a result of this test stage, it was concluded that the method according to the present invention without the use of any reagents makes it possible to effectively destroy previously formed deposits and provides a non-free operation of the boiler.
At the next stage, the test device for creating a current potential was attached at the point "B" and the tests continued for another 30-45 days.
Another opening of the boiler unit was produced after 3.5 months of continuous operation of the device.
An inspection of the boiler unit showed that the remaining sediments were completely destroyed and only in minor quantities were preserved in the lower sections of boiling pipes.
This made it possible to draw the following conclusions:
The size of the zone, within the limits of which the boiler's non-free operation is ensured, significantly exceed the size of the zone of effective destruction of deposits, which allows the subsequent transfer of the point of connection of the current potential to clean the entire inner surface of the boiler unit and further maintain the non-free mode of its operation;
The destruction of previously formed deposits and the prevention of education is provided by various processes in nature.
According to the results of the inspection, it was decided to continue testing until the end of the heating period in order to final purification of drums and boiling pipes and clarify the reliability of providing a non-free operation of the boiler. Another opening of the boiler unit was produced in 210 days.
The results of the internal inspection of the boiler showed that the process of cleaning the internal surfaces of the boiler within the upper and lower drums and boiling pipes ended with almost complete deletion of deposits. On the entire surface of the metal, a thin dense coating was formed, having a black color with blue party, the thickness of which is even in the moistened state (almost immediately after opening the boiler) did not exceed 0.1 mm visually.
At the same time, the reliability of providing a non-free operation of the boiler unit was confirmed when using the method of the present invention.
The protective effect of the magnetite film was preserved up to 2 months after disconnecting the device, which is enough to ensure the conservation of the boiler unit with a dry way when it is transferred to the reserve or for repair.
Although the present invention has been described in relation to various specific examples and embodiments of the invention, it should be understood that this invention is not limited to them and that it can be implemented in practice within the scope of the claim below
1. A method of preventing the formation of scale on a metal surface made of iron-containing alloy and is in contact with a steam room from which a scale is capable of forming an application to the specified metal surface of the current electric potential in the range from 61 V to 150 V to neutralize the electrostatic component of force Adhesion between the specified metal surface and colloid particles and ions forming screens.
The invention relates to thermal power and can be used to protect against scale and corrosion of heating pipes of steam and water boilers, heat exchangers, boiler installations, evaporators, heating parts, residential house heating systems and industrial objects during operation. The method of preventing the formation of scale on a metal surface made of iron-containing alloy and is in contact with a steam room from which scale is capable of forming the application to the specified metal surface of the current electric potential in the range from 61 V to 150 V to neutralize the electrostatic component of the adhesion force between The specified metal surface and colloidal particles and ions that form scale. The technical result is to improve the efficiency and productivity of the operation of hot water and steam boilers, an increase in the efficiency of heat transfer, ensuring layer-by-layer destruction and removal of the resulting scale, as well as the prevention of its new education. 2 Z.P. F-lies, 1 pr., 1 yl.
2.1. Heating surfaces.
The most characteristic damage to the pipes of heating surfaces are: the cracks of the surface of the screen and boiling pipes, corrosion corrosion of the outer and internal surfaces of the pipes, breaks, thinning of the walls of pipes, cracks and destruction of bells.
The reasons for the appearance of cracks, breaks and fistulas: deposits in pipes of salt boilers, products of corrosion, welding graphs, slowing the circulation and causing metal overheating, external mechanical damage, disruption of the water-chemical mode.
Corrosion of the outer surface of the pipes is divided into low-temperature and high-temperature. Low-temperature corrosion occurs in places in the installation of inflows, when the formation of condensate on the heating surfaces was allowed as a result of improper operation. High-temperature corrosion can occur on the second level of the steamper heater when burning sulfur fuel oil.
The most commonly occurs corrosion of the inner surface of the pipes, which occurs in the interaction of corrosionactive gases (oxygen, carbon dioxide) or salts (chlorides and sulfates) contained in boiler water, with metal pipes. Corrosion of the inner surface of the pipes manifests itself in the formation of OSPIN, ulcers, shells and cracks.
The corrosion of the inner surface of the pipes also includes: oxygen parking corrosion, submissive alkaline corrosion of boiling and screen pipes, corrosion fatigue, manifested in the form of cracks in boiling and screen pipes.
Damage to pipes due to creep is characterized by an increase in diameter and the formation of longitudinal cracks. Deformation in places of flexible pipes and welded joints may have different directions.
Progars and the okalnogo formation in the pipes occur due to their overheating to temperatures exceeding the calculated one.
The main types of damage to the welds made by manual arc welding are fistulas that occur due to non-verbal, slag inclusions, gas pores, unlocks on the edges of pipes.
The main defects and damage to the surface of the steamer are: corrosion and scale on the outer and inner surface of the pipes, cracks, risks and bundle of metal pipes, fistulas and pipe breaks, defects of pipe welded compounds, residual deformation as a result of creep.
Damage to the angular seams welding coils and fittings to collectors, causing violation of welding technology, have the form of ring cracks along the fusion line from the serpentine or fittings.
Characteristic malfunctions arising from the operation of the surface pairochholder of the boiler DE-25-24-380GM are: internal and external corrosion of pipes, cracks and fistulas in welded
seams and on the gibs of pipes, sinks that can occur during repairs, risks on the flange mirror, leaks of flange compounds due to the flange skew. When hydraulically testing the boiler you can
determine only the presence of looseness in the steelectricel. For the detection of hidden defects, an individual hydraulic test of the paro detergent should be carried out.
2.2. Boiler drums.
Characteristic damage to the boiler drums are: Crack-holes on the inner and outer surface of the shells and bottoms, crack-holes around the pipe holes on the inner surface of the drums and on the cylindrical surface of the pipe holes, intercrystalline corrosion of the shells and bottoms, corrosion disconnecting of the surfaces of the shells and bottoms, the ovality of the drum Odilines (reversible) on the surfaces of the drums addressed to the furnace caused by the temperature effects of the torch in cases of destruction (or loss) of individual parts of the lining.
2.3. Metal structures and boiler icon.
Depending on the quality of preventive work, as well as from the modes and timing of the boiler operation, its metal structures may have the following defects and damage: breaks and bends of racks and bonds, cracks, corrosion damage to the metal surface.
As a result of the long-term effects of temperatures, there is cracking and disruption of the integrity of the shaped brick, fixed on the pins to the upper drum from the furnace, as well as cracks in brick masonry On the lower drum and the fireballs.
Especially often the destruction of the brick embrasure burners and a violation of geometric sizes due to the melting of bricks.
3. Checking the status of the elements of the boiler.
Checking the state of the elements of the boiler displaced, is made according to the results of a hydraulic test, outdoor and internal inspection, as well as other types of controls conducted in the amount and in accordance with the program of expert examination of the boiler (section "Survey Survey Program").
3.1. Check the heating surfaces.
Inspection of the outer surfaces of the pipe elements, it is especially thoroughly carried out in places of passage of pipes through the stencil, the trim, in the zones of maximum heat voltage - in the area of \u200b\u200bburners, hatches, climbing, as well as in the fields of fiber optic pipes and on the welds.
To prevent the accident associated with the thinning of the pipe walls due to the sulfur and parking corrosion, it is necessary at annual technical surveys conducted by the administration of the enterprise, to monitor pipes for the heating of the boilers operated for more than two years.
The control is performed by an external inspection with the cutting of the pre-peeled outer surfaces of the pipes with a hammer mass of not more than 0.5 kg and measuring the thickness of the pipe walls. At the same time, parts of the pipes undergoing the largest wear and corrosion (horizontal sections, sediments in soot deposits and coke deposits covered).
Measuring the thickness of the pipe walls is carried out by ultrasonic thicknesses. It is possible to cut the pipes of pipes on two or three pipes of the fiber screens and pipes of the convective beam located at the inlet of gases in it and outlet. The remaining thickness of the pipe walls should be equally calculated according to the calculation of the strength (attached to the boiler's passport), taking into account the increase in corrosion for the period of further operation until the next examination and reserve increase of 0.5 mm.
The calculated thickness of the wall of screen and boiling pipes for the operating pressure of 1.3 MPa (13 kgf / cm 2) is 0.8 mm, for 2.3 MPa (23 kgf / cm 2) - 1.1 mm. Corrosion gain is taken by the results of measurements and taking into account the duration of operation between surveys.
In enterprises, where, as a result of long-term operation, there was no intensive wear of the pipes of the heating surfaces, control of the thickness of the pipe walls can be performed when major repairsBut at least 1 time in 4 years.
Internal examination is subject to collector, superheater and rear, screen. Mandatory autopsy and inspection must be subjected to the rear screen rear screen hatch.
The outer diameter of pipes should be measured in the zone of maximum temperatures. For measurements, apply special templates (brackets) or caliper. On the surface of the pipes are removed with smooth transitions of a depth of no more than 4 mm if they do not remove the wall thickness outside the minus deviations.
The permissible difference in pipes is 10%.
The results of the inspection and measurements are recorded in the repair form.
3.2. Check drum.
The day of identification of the areas of the drum damaged by corrosion, it is necessary to examine the surface to the internal purification in order to determine the intensity of corrosion to measure the depth of corrosion of the metal.
Uniform corrosions measure the wall thickness in which it for this purpose to drill a hole with a diameter of 8 mm. After measuring into the hole, set the plug and cut break from both sides or, in the extreme case, only from the inside of the drum. Measurement can also be made by ultrasound thickness gauge.
Main corrosions and yazvins Measure, on prints. For this purpose, the damaged section of the metal surface is cleaned from sediments and slightly lubricate technical vaseline. The most accurate imprint is obtained if the damaged area is located on the horizontal surface and in this case it is possible to pour its molten metal with a low melting point. The hardened metal forms the exact surface of the damaged surface.
To obtain prints, use a supernistant, babbit, tin, if possible, apply gypsum.
Folding of damage located on vertical ceiling surfaces, get using wax and plasticine.
Inspection of pipe holes, drums are carried out in the following order.
After removing the collapsed pipes, check the diameter of the holes using a template. If the template is included in the hole before a hard protrusion, this means that the hole diameter is extended above the norm. The measurement of the exact size of the diameter is carried out by the caliper and is noted in the repair form.
When controlling the welds of the drums, it is necessary to check the main metal adjacent to them on the width of 20-25 mm on both sides of the seam.
The oval of the drum is measured at least every 500 mm along the length of the drum, in doubtful cases and more often.
The measurement of the drum deflection is carried out by stretching the string along the surface of the drum and measuring the gaps along the length of the string.
Monitoring the surface of the drum, pipe holes and welded joints is performed by external inspection, methods, magnetic powder, color and ultrasonic flaw detection.
Allowed (not required) are dewenble and dents outside the seams zone and holes, provided that their height (deflection), as a percentage of the smallest size of their base, will not be more:
to the side atmospheric pressure (doves) - 2%;
in the direction of the pressure of the pair (dents) - 5%.
The allowable reduction in the thickness of the bottom wall is 15%.
The permissible increase in the diameter of the holes for pipes (for welding) is 10%.
