Multi-layer brushing method for grid filling type non-expansive fireproof coating

Abstract

The invention relates to the technical field of fire prevention, and discloses a grid filling type non-expansive fire retardant coating multi-layer brushing method which comprises the following steps: firstly, spraying a fire retardant coating on a square steel column in a crossed manner to form a grid-shaped spraying inner layer; both volume change and sagging can be absorbed by the pits in the centers of the grids, and the overall thickness of the ridge line position is uniform; after the sprayed inner layer is initially set, the convex points are scraped off, a new fireproof coating is scraped in the grids and is thickened outwards to form the scraped outer layer, the effect similar to reworking is achieved while the total thickness reaches the standard, and defects existing in the sprayed inner layer and local thickness unevenness are covered. Meanwhile, the main body of the blade coating outer layer is separated by the grids, so that the phenomena of thin upper part, thick lower part, edge deformation and sagging caused by paint flowing are avoided; and the inner corner protection net is used for preventing the latticed spraying inner layer from influencing the edge position shaping of the blade coating outer layer, so that the thickness and the appearance of the coating layer can be qualified at a time.

Description

Technical Field

[0001] The invention relates to the technical field of fire protection, in particular to a multi-layer painting method of a grid-filled non-expansion fire-retardant coating. Background Art

[0002] The strength of steel will drop significantly after being burned by fire, so the surface of steel load-bearing components in buildings needs to be coated with fire-retardant coating to use the fire-retardant layer to prevent the steel from direct contact with high-temperature flames.

[0003] Fire retardant coatings used for the construction of fireproof layers usually include intumescent fire retardant coatings and non-intumescent fire retardant coatings. Intumescent fire retardant coatings, as the name implies, will expand and foam after being burned by fire to form a layer of foamed material with good thermal insulation effect. Non-intumescent fire retardant coatings are a kind of refractory material, which will not undergo obvious physical and chemical changes after being burned by fire. It relies on its own thermal insulation properties to prevent the internal steel from contacting the fire. Therefore, the fire resistance time of non-intumescent fire retardant coatings is much longer, and generally does not need to be re-coated after a fire (repair is sufficient), but the required thickness is much larger, and it is a typical thick coating.

[0004] The requirements for flatness and regularity of fire-retardant coatings are significantly higher than those of conventional coatings, because if there are thinner or defective areas on them, these locations will form weak points when a fire occurs. The strength of the weak points will drop significantly after the fire, forming a step-like gap in strength with the surrounding materials, resulting in uncontrollable consequences due to stress concentration at these locations.

[0005] However, for non-expanding fire retardant coatings, which are very typical thick coatings, it is quite difficult to control the uniformity of their thickness. Considering the difficulty of thickness control, the current construction standards are not very strict. GB 51249-2017 stipulates that the thickness of the thinnest part of the non-expanding fire retardant coating shall not be less than 85% of the design thickness; the allowable deviation of the average thickness shall be ±10% of the design thickness. GB / T 50344-2019 stipulates that the evaluation of thick fire retardant coatings shall comply with the following provisions: the thickness that meets the design requirements of the relevant fire resistance limit shall be greater than 80% of the surface area of ​​the component; the thickness at the thinnest part shall not be less than 85% of the design requirement value.

[0006] But even this not-so-strict construction standard is still difficult to achieve. In the prior art, a multi-layer painting method is usually used to control the thickness of thick coatings. Taking the Sanya Cultural Center project involved in the present invention as an example, the thickness of the fireproof layer on the square steel columns is more than 30 mm. According to the practice in the prior art, it needs to be painted in 6 layers, but even so, the actual construction pass rate can only reach 77.9%. Unqualified ones need to be reworked. Due to the large number of square steel columns used in this project, the construction period is unacceptable. In addition, considering the use scenario of the building, the appearance requirements of the square steel columns are higher, so not only the thickness is required, but also the flatness and squareness are also required. At the same time, the coating surface cannot have defects such as dripping that affect the appearance (usually thick fire retardant coatings are mainly used in factory buildings, and there are no requirements for appearance).

[0007] Usually, when applying thick coatings in multiple layers, the same method is used for application, either spraying or scraping. However, the inventors found that spraying has an advantage in overall thickness control, but it is prone to various defects in some parts, and the position of the edges is irregular, while scraping is at a disadvantage in overall thickness control, but has fewer local defects. Summary of the invention

[0008] The invention provides a multi-layer painting method of a grid-filled non-expansion fire-retardant coating.

[0009] The technical problem to be solved is that it is difficult to pass the application of thicker non-expanding fire retardant coatings in one go, and they need to be applied in layers and reworked frequently, and are even more difficult to pass when there are requirements for appearance.

[0010] In order to solve the above technical problems, the present invention adopts the following technical solution: a grid-filled non-expansion fire retardant coating multi-layer brushing method, which is used to construct a non-expansion fire retardant coating layer on the surface of a square steel column inside a building, comprising the following steps: Step 1: Base treatment, remove impurities including dust, floating rust and oil on the surface of the square steel column; Step 2: Cross-spray the fire retardant coating on the surface of the square steel column to form a grid-shaped spray inner layer; Step 3: After the sprayed inner layer is initially solidified, the protrusions on the sprayed inner layer that protrude outside the grid body are scraped off to make the ridge line smooth; and the inner corner protection nets used to assist in shaping and prevent the fire retardant coating layer from cracking at the edges are hung at the four edges of the square steel column, and the inner corner protection nets are wrapped around the edges of the sprayed inner layer and embedded in the sprayed inner layer; Step 4: Scrape the fire retardant coating in the grid of the sprayed inner layer against the ridge line and smooth it, then continue to scrape and thicken it to form a scraped outer layer; Step 5: Check the total thickness and flatness of the fire retardant coating layer; Step 6: Install outer corner guards at the edges of the scraped outer layer to prevent the edges of the scraped outer layer from being damaged before the scraped outer layer solidifies, and then maintain the fire retardant coating layer.

[0011] Furthermore, the maximum allowable deviation of the total thickness of the fire retardant coating layer is recorded as n, and the thickness of the scraped outer layer is thickened by 0.3n~0.5n based on the design value.

[0012] Furthermore, the fireproof layer is arranged in sections along the vertical direction, and thickness detection points are evenly arranged in each section; In step 5, the detection point whose thickness value exceeds the design value and the excess range is greater than the maximum allowable deviation is recorded as a bad point, and the detection point whose thickness value is less than the design value is recorded as a waste point; If there are bad points in a segment, or the proportion of bad points in the detection points of the segment is greater than the allowable threshold, the thickness and flatness of the segment are unqualified.

[0013] Furthermore, the inner corner protection net is a diamond-shaped steel wire mesh, and a diagonal line of the grid of the diamond-shaped steel wire mesh is parallel to the edge of the square steel column; In step three, the diamond-shaped steel wire mesh is annealed and then bent into a long strip with an L-shaped cross section. Fire retardant coating is applied to the edges of the square steel column, and then the inner corner protection mesh is wrapped around the edges of the sprayed inner layer to complete the wet hanging mesh.

[0014] Furthermore, in step 2, the paint spray gun continuously draws an X-shaped spray trajectory line from bottom to top or from top to bottom on each side elevation of the square steel column to form an evenly arranged diamond grid, and the long diagonal line of each diamond grid is set horizontally and the length does not exceed 20 cm.

[0015] Furthermore, the spray-coated inner layer and the scrape-coated outer layer are the same non-expanding fire retardant coating, the surface of the spray-coated inner layer is rough, and the surface of the scrape-coated outer layer is smooth.

[0016] Furthermore, the thickness ratio of the sprayed inner layer to the scraped outer layer is not less than four to one.

[0017] Compared with the prior art, the grid-filled non-expansion fire retardant coating multi-layer brushing method of the present invention has the following beneficial effects: In the present invention, the fire retardant coating is first cross-sprayed on the square steel column to form a grid-shaped spray inner layer. During the solidification process of the spray inner layer as the main body, both volume changes and sagging will be absorbed by the pit in the center of the grid (when the volume changes, the expansion and contraction of the surface is mainly parallel to the direction of the coating layer, which will not affect the thickness at the ridge position, and the sagging will also enter the pit), and the overall thickness at the ridge position is uniform; after the initial solidification of the spray inner layer, the protrusions are scraped off, and new fire retardant coating is scraped in the grid and thickened outward to form a scraped outer layer. While the total thickness meets the standard, it has an effect similar to rework, so that the defects in the spray inner layer and the local uneven thickness are covered. At the same time, because the main body of the scraped outer layer is separated by a grid, it will not flow downward, thereby avoiding the thin top and thick bottom, edge deformation, and sagging caused by the flow of the coating; In the present invention, before constructing the scraped outer layer, the inner corner protection net is first installed at the four edges of the square steel column, which not only has an anti-cracking effect, but also when the edge position of the scraped outer layer is trimmed (that is, regular edges are scraped out), a relatively flat foundation with a certain hardness can be obtained, thereby avoiding the grid-shaped sprayed inner layer from affecting the edge position trimming of the scraped outer layer.

[0018] The combination of the above points ensures that the thickness and appearance are qualified in one construction, avoiding multiple reworks, greatly improving construction efficiency and shortening construction period. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A cross-sectional view of a coating layer using a multi-layer coating method of a grid-filled non-expanding fire-retardant coating according to the present invention; Figure 2 This is a statistical chart of problems found in the sample section constructed using conventional painting technology; the frequency in the figure is the proportion of the frequency of a specific problem type in the total frequency of all problems; Figure 3 To form a spraying trajectory line for spraying the inner layer on a side elevation of a square steel column; Figure 4 The thickness deviation distribution diagram of the fire retardant coating in the D2-D3 section is shown in the figure. The horizontal axis is the number of the thickness detection point, and the vertical axis is the deviation between the thickness measured at the thickness detection point and the design value, in millimeters. A positive value represents a thicker thickness, and a negative value represents a thinner thickness. Figure 5 The thickness deviation distribution diagram of fire retardant coating in the D4-D5 section is shown in the figure. The horizontal axis is the number of the thickness detection point, and the vertical axis is the deviation between the thickness measured at the thickness detection point and the design value, in millimeters. A positive value represents a thicker thickness, and a negative value represents a thinner thickness. In the figure, 1-square steel column, 2-sprayed inner layer, 21-sprayed trajectory line, 3-scrape coated outer layer, 4-inner corner protection net, 5-outer corner protection. DETAILED DESCRIPTION

[0020] Note that the present invention is applied to square steel columns 1, but it can also be used if a steel column with a cross section of a triangle, hexagon or other polygonal shape is encountered. However, in actual construction, these special-shaped steel columns are rare.

[0021] Take the Sanya Cultural Center project as an example. Figure 1 As shown, a grid-filled non-expansive fire-retardant coating multi-layer brushing method is used to construct a non-expansive fire-retardant coating layer on the surface of a square steel column 1 inside a building; In buildings such as exhibition halls and residential buildings, the internal columns are mainly reinforced concrete columns or steel-framed columns, and steel structure columns are generally set in places that are out of reach of people (such as outer frame columns). In buildings such as factory buildings, the internal columns are mainly steel columns to avoid danger caused by collisions between machines and columns (steel columns are relatively tolerant of collisions). Therefore, under normal circumstances, non-expanding fire retardant coatings are usually required to protect square steel columns 1 in places such as factory buildings that have no requirements for appearance. However, square steel columns 1 are also used in the exhibition hall in this project, so their surface also has appearance requirements, which requires the surface to be flat, the four edges to be regular, and no pockmarks or sagging, which significantly increases the difficulty of construction. Figure 2 As shown in the figure, before the actual construction, we used the existing technology to construct a sample section and found many problems. If only the thickness is considered, the existing technology can barely make most of the coating layer thickness meet the standard, but after taking the appearance into account, almost all of them fail to meet the standard. And the thickness problem only accounts for a small part of the total problems, and most of the problems are caused by the appearance not meeting the standard.

[0022] The coating method of the present invention comprises the following steps: Step 1: Base treatment, remove impurities including dust, floating rust and oil stains on the surface of the square steel column 1; Step 2: If Figure 3 As shown, the fire retardant coating is sprayed crosswise on the surface of the square steel column 1 to form a grid-shaped spray inner layer 2; Note that the "cross spraying" here does not mean "spray from one direction first, then spray from another direction, and so on, to ensure uniform coverage in each direction", but a cross grid is drawn, and long strips of protrusions similar to the shape of mountains are formed on the grid lines, and a basin-like pit is formed in the center of the grid. The line connecting the highest points of the long strips of protrusions is also the "ridge line". When actually spraying, the grid lines are not required to be very regular, and there is no requirement to form regular protrusions like long sticks. It can be completely irregular, allowing the sprayed inner layer 2 to still be a continuous layer of paint, but the center of the diamond grid is thinner and even the square steel column 1 is exposed.

[0023] Step 3: After the sprayed inner layer 2 is initially solidified, scrape off the protrusions on the sprayed inner layer 2 that protrude outside the grid body to make the ridge line smooth; The ridge area here is very small, and the spraying method itself makes it easy to make the overall thickness relatively uniform. After scraping, you can get a ridge with uniform thickness, which is used as a reference for subsequent scraping. Of course, the intersection of the grid lines is prone to form convex points, which need to be scraped off to avoid affecting the subsequent scraping. During the spraying stage, you should pass quickly at the intersection to avoid the formation of convex points.

[0024] An inner corner protection net 4 is hung at the four edges of the square steel column 1 to assist shaping and prevent the fire retardant coating layer from cracking at the edges. The inner corner protection net 4 is wrapped around the edges of the sprayed inner layer 2 and embedded in the sprayed inner layer 2. Since the sprayed inner layer 2 is in a grid shape, it is difficult to form regular edges when applying the fire retardant coating on the four edges of the square steel column 1, so it is necessary to partially hang meshes at the four edges to assist. The mesh can also play its own anti-cracking effect (the edges are prone to cracking). The reason why the mesh is partially hung here instead of the whole mesh is that if the mesh is hung as a whole, the mesh will tend to form a cylinder, causing the scraped outer layer 3 to deform, or even push out of the scraped outer layer 3.

[0025] Step 4: scrape and apply fire retardant coating in the grid of the sprayed inner layer 2 along the ridge line and scrape it flat, then continue scraping and thickening to form a scraped outer layer 3; This step of operation will cover up the local defects and local thickness unevenness that may have been formed previously, and its effect is similar to rework without wasting additional time.

[0026] Step 5: Check the total thickness and flatness of the fire retardant coating layer; Step six: Install an outer corner guard 5 at the edge of the scraped outer layer 3 to prevent the edge of the scraped outer layer 3 from being damaged before the scraped outer layer 3 solidifies, and then maintain the fire retardant coating layer.

[0027] The maximum allowable deviation of the total thickness of the fire retardant coating layer is recorded as n, and the thickness of the scraped outer layer 3 is thickened by 0.3n~0.5n based on the design value.

[0028] If the total thickness of the fire retardant coating layer is a little too thick, it is harmless to fire prevention, but if it is too thin, it may cause harm. The construction method of the present invention can eliminate most of the negative deviations (that is, the total thickness of the fire retardant coating layer is too thin), and the amplitude of a small amount of negative deviation is about 0.2n. Therefore, here, the thickness is increased by 0.3~0.5n on the basis of the design value, which can completely eliminate the occurrence of negative deviations.

[0029] The fireproof layer is divided into sections along the vertical direction, and thickness detection points are evenly set in each section; In step 5, the detection point whose thickness value exceeds the design value and the excess range is greater than the maximum allowable deviation is recorded as a bad point, and the detection point whose thickness value is less than the design value is recorded as a waste point; If there are bad points in a segment, or the proportion of bad points in the detection points of the segment is greater than the allowable threshold, the thickness and flatness of the segment are unqualified.

[0030] In this embodiment, n is 5 mm. Since there is an operation of scraping off the convex points and a final step of scraping and coating in this embodiment, visually obvious convexities can be prevented. It is only necessary to ensure that the proportion of bad points in the thickness detection points is lower than the threshold (the threshold is set according to the requirements, generally 80% to 90%) to ensure that the flatness meets the requirements, and there is no need to measure the flatness separately. Of course, waste points are absolutely intolerable. The construction method of the present invention can prevent the generation of waste points, but if waste points appear in the actual measurement, it proves that the section has not been constructed as required.

[0031] like Figure 4-5 After the construction is carried out as required, the method of the present invention eliminates the generation of waste points, and the number of bad points is also very limited, thereby ensuring the fireproof performance and appearance. Note that the standard in the present invention is stricter than the existing national standard, for example, the existing national standard allows the occurrence of waste points.

[0032] The inner corner protection net 4 is a diamond-shaped steel wire mesh, that is, a steel wire mesh with diamond-shaped grids. The diamond-shaped steel wire mesh is bent into long strips with an L-shaped cross-section and then wrapped around the edges of the sprayed inner layer 2, and a diagonal line of the grid of the diamond-shaped steel wire mesh is parallel to the edges of the sprayed inner layer 2.

[0033] In step three, the diamond-shaped steel wire mesh is annealed and then bent into a long strip with an L-shaped cross section, a fire-retardant coating is scraped on the edge of the square steel column 1, and then the inner corner protection mesh 4 is wrapped on the edge of the sprayed inner layer 2 to complete the wet hanging mesh.

[0034] The mesh should not be hung dry here, as the anchors of the mesh will affect the fire protection. The annealing treatment here is to prevent the mesh from rebounding and deforming after bending and breaking the outer coating.

[0035] In step 2, the paint spray gun continuously draws an X-shaped spray trajectory line 21 from bottom to top or from top to bottom on each side elevation of the square steel column 1 to form a uniformly arranged diamond grid, and the long diagonal line of each diamond grid is set horizontally and the length does not exceed 20 cm. This setting is to ensure that the diamond grid effectively supports the subsequent fire retardant coating in the outer layer 3 after initial setting to prevent it from flowing downward. The length of the long diagonal line is limited to control the size of the diamond grid. If the grid is too large, the fire retardant coating in the outer layer 3 in each grid will also have a tendency to flow downward.

[0036] The sprayed inner layer 2 and the scraped outer layer 3 are the same non-expanding fire retardant coating (if they are not the same, the bonding between the two layers may not be strong), the surface of the sprayed inner layer 2 is a rough surface, and the surface of the scraped outer layer 3 is a smooth surface. If the surface of the sprayed inner layer 2 is a rough surface, it can be effectively bonded with the scraped outer layer 3.

[0037] The thickness ratio of the sprayed inner layer 2 and the scraped outer layer 3 is not less than four to one. Because if the scraped outer layer 3 is too thick, it is difficult to control the overall thickness, which will result in the fireproof layer scraped out being worse than that of the simple spraying.

[0038] The embodiments described above are merely descriptions of preferred implementation modes of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A grid-filled non-expansive fire retardant coating multi-layer brushing method for constructing a non-expansive fire retardant coating layer on the surface of a square steel column (1) inside a building, characterized in that: The following steps are involved: Step 1: Base treatment, remove impurities including dust, rust and oil stains on the surface of the square steel column (1); Step 2: spraying fire retardant coating crosswise on the surface of the square steel column (1) to form a grid-shaped spray inner layer (2); Step 3: After the sprayed inner layer (2) is initially solidified, the protruding points on the sprayed inner layer (2) protruding outside the grid body are scraped off to make the ridge line smooth; and the inner corner protection net (4) for assisting shaping and preventing the fire retardant coating layer from cracking at the edge is hung at the four edges of the square steel column (1), and the inner corner protection net (4) is wrapped at the edge of the sprayed inner layer (2) and embedded in the sprayed inner layer (2); Step 4: scrape and apply the fire retardant coating in the grid of the sprayed inner layer (2) along the ridge line and scrape it flat, then continue scraping and thickening it to form a scraped outer layer (3); Step 5: Check the total thickness and flatness of the fire retardant coating layer; Step 6: Install an outer corner guard (5) at the edge of the scraped outer layer (3) to prevent the edge of the scraped outer layer (3) from being damaged before the scraped outer layer (3) solidifies, and then maintain the fire retardant coating layer.

2. A method for applying a multilayer of a grid-filled non-expanding fire-retardant coating according to claim 1, characterized in that: The maximum allowable deviation of the total thickness of the fire retardant coating layer is recorded as n, and the thickness of the scraped outer layer (3) is thickened by 0.3n~0.5n based on the design value.

3. A method for applying a multilayer of a grid-filled non-expanding fire-retardant coating according to claim 2, characterized in that: The fireproof layer is arranged in sections along the vertical direction, and thickness detection points are evenly arranged in each section; In step 5, the detection point whose thickness value exceeds the design value and the excess range is greater than the maximum allowable deviation is recorded as a bad point, and the detection point whose thickness value is less than the design value is recorded as a waste point; If there are bad points in a segment, or the proportion of bad points in the detection points of the segment is greater than the allowable threshold, the thickness and flatness of the segment are unqualified.

4. A method for applying a multilayer of a grid-filled non-expanding fire-retardant coating according to claim 1, characterized in that: The inner corner protection net (4) is a diamond-shaped steel wire mesh, and a diagonal line of the grid of the diamond-shaped steel wire mesh is parallel to the edge of the square steel column (1); In step three, the diamond-shaped steel wire mesh is annealed and then bent into a long strip with an L-shaped cross section, a fire-retardant coating is scraped on the edge of the square steel column (1), and then the inner corner protection mesh (4) is wrapped on the edge of the sprayed inner layer (2) to complete the wet hanging mesh.

5. A method for applying a multilayer of a grid-filled non-expanding fire-retardant coating according to claim 1, characterized in that: In step 2, the paint spray gun continuously draws an X-shaped spraying trajectory line (21) from bottom to top or from top to bottom on each side elevation of the square steel column (1), forming a uniformly arranged diamond grid, wherein the long diagonal line of each diamond grid is horizontally arranged and has a length not exceeding 20 cm.

6. A method for applying a multilayer of a grid-filled non-expanding fire-retardant coating according to claim 1, characterized in that: The spray-coated inner layer (2) and the scraped-coated outer layer (3) are the same non-expanding fire-retardant coating, the surface of the spray-coated inner layer (2) is a rough surface, and the surface of the scraped-coated outer layer (3) is a smooth surface.

7. A method for applying a multilayer of a grid-filled non-expanding fire-retardant coating according to claim 1, characterized in that: The thickness ratio of the spray-coated inner layer (2) to the scraped-coated outer layer (3) is not less than four to one.

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