In order to improve the spraying quality of steel structure fire-retardant coatings and ensure the fire-resistance limit of steel structures, Liaoning Fire-fighting Technology Testing Station formulated the Inspection Rules for Fire-retardant Coatings for Steel Structures in accordance with relevant national regulations and regulations, and purchased equipment and equipment. Since the beginning of the month, the coating quality of fire protection coatings for steel structures has been tested. After statistics on 27 units in Shenyang, the qualification rate only accounts for 70%. This fully illustrates the seriousness of the problem and also proves the application of fireproof coatings on steel structures. The importance and necessity of quality inspection. After publishing these issues in your magazine, we hope to arouse the attention of various parties concerned, effectively increase the spraying quality of steel structure fire protection coating, ensure the fire resistance limit of steel structures, reduce the fire damage, and better protect the country and the people. The safety of life and property.
A spray layer is too thin
The purpose of spraying fireproof coatings on steel structures is to increase the fire resistance of steel structures. The performance index of the fire-resistant limit of the steel structure is closely related to the thickness of the spray. The same kind of fire retardant coating, the thickness of the spray is different, its fire resistance is not the same. If the thickness of the fire-retardant coating of steel structures is not sprayed according to the design requirements, the fire-resistance limit of steel materials cannot meet the requirements of fire protection. According to statistics, the spray layer is too thin, and this type of problem accounts for 25%. For example, on February 26, 2001, when testing fireproof coatings for steel beams and steel columns in a furniture store, the coating was too thin for repainting and sprayed twice in succession on March 13. The third inspection only met the requirements. Another example: on May 29, 2001, when testing the steel structure fire protection coating of the pressure swing adsorption nitrogen plant of Shenyang Chemical Industry Co., Ltd., it was found that the fire resistance rating of the plant was two grades, and the fireproof time of the steel roof truss was 0.5 h. The ultra-thin steel structure intumescent fire-retardant coating produced by a factory has been subjected to a national inspection result. When the coating thickness is 2.55mm, the fire-resistance limit is 91min. After inspection, 15 points are tested and the average coating thickness is 0.34mm. More than 1/7 coating thickness, of which the thickest point of the coating is 0.78mm, which is 1/3 more than the coating thickness, the thinnest point of the coating is only 0.16mm, less than the coating thickness 1/ 16, does not meet the requirements, for this reason to stop the test, let it re-spray, and then test when the thickness of the sprayed coating reaches the requirements.
Second, spraying surface mastoid
In order to ensure that the coating surface is even and smooth, the spray coating thickness must meet the requirements. In Section 3.4.5 of the "Technical Code for the Application of Fire-Resisting Coatings for Steel Structures", the construction of a fire-retardant paint for thick-coated steel structures requires that: after coating, the coating should be removed. Sudden, to ensure uniform formation. However, some construction units disregard this requirement of the specification, and some emphasizing that the painted steel columns are decorated and mastoids are not afraid to wait for themselves to relocate themselves. Such problems account for 10%, such as: July 2001. 2 On a certain day, a construction company asked us to look in advance at the steel beam and steel coating sprayed thick-coated steel structure fireproof coating of a military-industry unit that it was going to inspect. We found that there was a mastoid on the cylinder surface, and the measured mastoid was 10 mm. Gao, we propose that we must eliminate the mastoids and ensure that the cylinders are evenly leveled before they can be tested. Otherwise, they are unqualified.
Third, choose the wrong type
Different types of fire-retardant paints have different spray thicknesses on steel structures, and their fire-resistance limits are also different. Different parts of the steel structure, spray different types of fire retardant coatings, in order to ensure the fire resistance of the steel structure to meet the fire protection requirements. If the wrong type is selected, even if the sprayed layer reaches the thickness, it will not meet the fire protection requirements. For this reason, Article 2.0.4 of the "Technical Code for the Application of Fire-Resisting Coatings for Steel Structures" clearly states: "The exposed steel structure indoors, the light-roof steel structure and the steel structure with decorative requirements shall be fire-resistant at 1.5 hours or less. Thin coating type steel structure fire protection coating should be selected; "Outdoor concealed steel structure, high-rise all-steel structure and multi-storey factory steel structure. When the fire-resistance limit is more than 1.5h, thick-coated steel structure fire protection coating should be used."
On April 26, 2001, when we inspected the fire protection coating for steel structures in the Printing House of a newspaper office, we discovered that the plant was a tall one-story building with a two-story mixture. The fire resistance rating was set to one, and the fire resistance of the plant steel beams was set. The limit is 2.00h and the fire resistance limit of the steel column is 3.00h.
According to the design requirements, the fireproof coatings for steel beams and steel columns of this workshop should be selected as fire-retardant coatings for heavy-duty steel structures. However, they chose the steel structure-expanded fire-retardant coatings produced by certain flame-retardant materials. The national inspection result is: When the coating thickness is 5.6mm, the fire resistance limit is 1.49h. In order to further clarify the coating thickness of its coating, a total of 9 points were examined. The average thickness of fire-retardant coating sprayed on steel beams was 0.41 mm, of which the thickest one was 0.66 mm, and the thinnest coating point was only 0.20 mm. Because of the wrong type of fire protection coating, it is impossible to meet the design fire resistance requirements of steel beams and steel columns. So he chose to adapt to the thick coating steel structure fire protection coating, re-spray.
Fourth, with untruth, Zhang Guan Li Dai
In order to ensure the fireproof performance of fireproof coatings, the state has strict requirements on the quality of fireproof coatings for steel structures. “Technical Specification for Application of Fire-Resistant Steel Coatingsâ€, Article 3.2.1 stipulates: “Fire-retardant coatings used for the protection of steel structures must have the fire-resistance limit test report and physical and chemical performance test report of the national inspection agency, and must have a production license issued by the fire supervision authority. Certificate and production factory product certification." However, we found during the inspection that some of the topcoats were fire retardant coatings and some were crowned and worn. For example, in January 2001, when we examined the construction quality inspection data of a steel structure fireproof coating submitted by a brewery company in January 2001, we found that the building for inspection was a two-story building with a height of 19 meters and an area of ​​4,568 square meters. The "Fire Protection Design Auditing Opinions for Construction Projects" clearly stipulates: "The fire resistance of buildings is extremely secondary." The Design Change Notice of the Planning and Design Institute of the Ministry of Light Industry clearly requires that: “The steel girder of the roof shall be fire-fighting for class E and the fire-resistance grade shall be Grade II. The fire-retardant coating is recommended to use MC-10 fire-retardant steel structure paint. The thickness of the steel beam surface coating is 4mm, if the fireproof coating is changed, the fire-resisting time must reach 1.5 hours."
After reviewing the relevant information of fire-retardant coatings, they discovered that they used a milky white high-polychlorinated polyethylene topcoat produced by a paint factory. The technical performance inspection report was not issued by the National Fireproof Building Materials Quality Supervision and Inspection Center, but China's scientific metal corrosion. With the Institute of Protection and Shenyang Zhongke Corrosion Control Engineering Technology Research Center, it is not a fireproof paint but a finish paint. Therefore, after it is sprayed with a fireproof paint as required, inspections are conducted. For example, in May 2001, when we examined the fire protection coating for a steel structure in a printing shop, we found that the fire protection coating and quality inspection report had some problems. To avoid problems, we repeatedly asked the construction company to purchase fireproof coatings. Invoices, construction units can not provide, the last construction unit admitted that the fire protection coating used and quality inspection report is not a one!? Although this type of problem is rare, it has already illustrated the seriousness of the problem.
Fifth, not a professional team construction
Steel structure fire protection coating is a kind of fire safety material. The construction quality is good or bad, which directly affects the use effect and fire safety performance. According to domestic and foreign experience, in order to ensure the spraying quality, Article 3.1.1 of "Technical Code for Application of Fire Protection Coatings for Steel Structures" clearly states: "Fire protection coating for steel structures shall be constructed by trained professional construction teams." However, some construction units plan to save money or they also want to collect oil from water, and they hire oil painters or organize personnel to brush. Such problems account for about 25%. For example, the steel beams and steel columns of a printing service center in Shenyang, the load-bearing structure in the ceiling of a resin company, and the fireproof coating of a large-scale shopping mall lighting grid bearing rack were all sprayed by non-professional teams because they did not understand this. Spraying technology in the area, the result is thick and thin, thin and thin, like Wangpozi's thrush. Here, one of them, where not, meets normative requirements, is unattractive, and does not meet the requirements.
Six, decoration and welding damage spray coating
The fire-retardant coatings and spray thicknesses of steel structures are sprayed according to the design requirements and technical specifications of fire-retardant coatings. Once the sprayed coating is detached or damaged, the fire-resistance limit of the steel structure will be affected.
According to statistics, about 25% of the sprayed coating is damaged due to renovation and welding. For example, on May 29, 2001, when testing fireproofing steel structures in bottled water workshops and warehouses of a food and beverage company, they found that they installed galvanized plates on both sides of the square columns of the warehouse doors that had been fire-proofed. Because some of the connection points are welded, the fire retardant coating has been baked and carbonized, and some of the four corners of the fire retardant coating have been collided and detached. The steel posts in these places have lost the fire-resistant limit after spraying the fire retardant coating. Another example: when we inspected the spray quality of fireproof paint for steel beams and steel columns in a car manufacturing company and a military factory in June 2001, we found that the construction unit had applied fireproof paint to the steel beam to fix and install machinery and equipment. Some steel angles were welded on the steel column. Due to welding, many fireproof paints at the solder joints were expanded or carbonized and the fireproof performance was lost. In this regard, we require the construction unit to clean up the fire-retardant coatings in places where they are inflated, charred, and peeled off, and then re-spray fire-retardant coatings to ensure that these parts of steel beams and steel columns can meet the design's fire-resistance limits.