Boiler insulation

Insulation paint for boiler furnace walls, thermal equipment, and pipelines 9.1 General provisions 9.1.1 This chapter applies to the construction and acceptance of boiler furnace wall construction as well as the insulation painting of thermal equipment and pipelines. 9.1.2 The refractory and insulating materials as well as the products used for furnace walls and insulation must have raw materials and finished products of quality that complies with the relevant current **standards or industry standards; the current standards for commonly used refractory and insulating materials and products are listed in Appendix R. 9.1.3 The mix ratios for refractory concrete, thermal insulation concrete, and plastering mortar prepared on-site shall be in accordance with the provisions in the equipment’s technical documents; in the absence of such provisions, they may be selected in line with the requirements specified in \"Technical Conditions and Inspection Methods for Thermal Insulation Materials of Thermal Equipment and Pipelines in Thermal Power Plants\" (SDJ 68—85) and \"Technical Conditions and Inspection Methods for Refractory Materials in Thermal Power Plants\" (SDJ 66—82). 9.1.4 When mixing different types of fire-resistant concrete, thermal insulation concrete, and mortar, it is necessary to clean the machinery and tools used. The water used for mixing must be clean; it is strictly prohibited to use seawater, alkaline water, or water containing organic suspended particles that could affect the quality of the concrete. 9.1.5 It is strictly prohibited to lift or move fire-resistant concrete furnace walls until they reach 70% of their designed strength ； During lifting and transportation, the furnace walls, as well as the insulated pipes and equipment, should be protected from excessive vibration and impact. 9.1.6 Measures to protect against rain and freezing should be taken during the construction of insulation for the boiler furnace walls, as well as for equipment and pipelines. 9.1.7 The following conditions must be met prior to the construction of the boiler furnace wall: 9.1.7.1 The assembly or installation of the steel structure, heating surfaces, furnace wall components, and other devices in the area to be constructed (including inspections and tests for the integrity of the welds) must have been completed and approved ； 9.1.7.2 All temporary facilities at the furnace wall construction site must be removed and inspected to ensure they are in good condition. 9.1.8 The expansion joints in framed concrete furnace walls and brick-built lightweight furnace walls shall meet the following requirements: 9.1.8.1 Expansion joints shall be provided in the furnace walls in accordance with the specifications outlined in the equipment’s technical documents; the width deviation of these joints shall be ±3 mm, and the edges of the expansion joints shall be smooth ； 9.1.8.2 The expansion joints must be kept clean, free from mortar, broken bricks, and other debris ； The filling inside the seam should consist of fire-resistant ropes whose diameter is slightly larger than that of the gap, and which are suitable for the operating temperature; the outermost fire-resistant rope on the side facing the fire should be aligned with the surface of the fire-resistant brick wall, without extending outward or sinking inward ； 9.1.8.3 Reliable sealing measures shall be adopted for the furnace wall outside the expansion joint. 9.1.9 During the construction of the furnace wall, attention should be paid to the gaps between various components, especially those with the heated surfaces. The allowable deviation for the main gaps in the furnace wall shall not exceed the values specified in Table 9.1.9. Table 9.1.9 Allowable Deviations for Major Gaps in the Furnace Wall Sequence Number Location Allowable Deviation (mm) 1 Distance between the center of the water wall tubes and the furnace wall surface① -10 +20 2 Distance between the center of the tubes in the superheater, reheater, and economizer and the furnace wall surface① -5 +20 3 Gap between the steam drum and the furnace wall surrounding it -5 +10 4 Gap between the smoke extraction wall and the side wall surface +5 5 Gap between the heat-exchanging tubes at the areas where the brick furnace wall passes through and the furnace wall +10 6 Distance between the lower water wall header and the furnace wall of the ash chamber +10 Note: ① If, due to cumulative deviations in the installation of the steel structure and heat-exchanging elements, the allowable deviation limits cannot be met, it is permissible to reduce the net distance between the furnace wall and the outer wall of the tubes, as long as expansion is not affected; however, this distance must not be less than 5 mm. 9.1.10 For sealed furnace roofs with large enclosures, the construction of insulation for the furnace roof and its walls must meet the following requirements: 9.1.10.1 The primary sealing iron plates for the furnace roof must be installed before the overall pressure test of the boiler, and inspection and acceptance must be carried out, along with the completion of relevant documentation for concealed work ； 9.1.10.2 Expansion gaps provided in the design or gaps where welding is not permitted according to the design shall be filled with aluminum silicate refractory fibers, after which refractory concrete or refractory plastic (casting material) shall be applied as specified in the design ； 9.1.10.3 The welding of the secondary sealing cover must be thoroughly inspected to ensure there are no missed welds; the insulation inside the sealing cover shall be installed in accordance with the design, and then sealed after inspection ； 9.1.10.4 The welds of the large enclosure must pass an oil penetration test before insulation is applied to it; the thickness of the insulation layer shall be in accordance with the design requirements, and it must be tight, even, and of the correct thickness. 9.2 Furnace Walls and Insulation Materials 9.2.1 Before the construction of furnace walls and insulation, for each batch of raw materials and finished products that arrive at the site, it is necessary to first check the product certificates, conduct an visual inspection, and then carry out sampling tests on each batch. Only those that pass the tests may be used; the use of substandard products is strictly prohibited ； The inspection items shall comply with the provisions of clauses 9.2.2 to 9.2.8 ； The inspection methods are in accordance with the \"Technical Requirements and Inspection Methods for Insulation Materials of Thermal Equipment and Pipelines in Thermal Power Plants\" and the \"Technical Requirements and Inspection Methods for Refractory Materials in Thermal Power Plants\". 9.2.2 The inspection items for refractory bricks used in boilers are shown in Table 9.2.2. 9.2.3 The inspection items for thermal insulation products are listed in Table 9.2.3. Table 9.2.2 Inspection Items for Refractory Bricks Item Refractory Clay Bricks Light Refractory Bricks Ordinary High-Alumina Bricks Bulk Density △ Aluminum Oxide (Al2O3) Content △ △ Refractoriness △ △ △ Compressive Strength at Room Temperature △ △ △ Thermal Shock Stability △ Dimensional Deviations and Appearance Requirements △ △ △ Note: △ indicates “to be inspected”; the same applies below. Table 9.2.3 Inspection items for thermal insulation products. Items: Expanded perlite, diatomite, vermiculite, calcium silicate products; slag wool, glass wool products; asbestos rope. Density: △ △; Compressive strength: △; Thermal conductivity: △ △; Loss on ignition: △; Moisture content: △; Operating temperature: △ △ △; Dimensional tolerances and appearance requirements: △ △. 9.2.4 The inspection items for loose thermal insulation materials are listed in Table 9.2.4. 9.2.5 The inspection items for fire-resistant mortar are listed in Table 9.2.5. Table 9.2.4 Inspection Items for Insulating Loose Materials Item Expanded perlite, diatomite, vermiculite, etc. Slag wool, glass wool, etc. ① Diatomite powder, etc. Bulk density △ △ △ Thermal conductivity △ △ △ Particle size △ △ (fiber diameter) Operating temperature △ △ △ Note ① The content of slag balls also needs to be checked. 9.2.6 The binders for various types of refractory concrete shall meet the following requirements: 9.2.6.1 Portland cement and ordinary Portland cement shall comply with the provisions of \"Portland Cement and Ordinary Portland Cement\" (GB 175—92), while slag Portland cement shall comply with the provisions of \"Slag Portland Cement, Pozzolanic Portland Cement, and Fly Ash Portland Cement\" (GB1344—92) ； 9.2.6.2 High-alumina cement shall comply with the relevant provisions of \"High-Alumina Cement\" (GB 201—81) ； Table 9.2.5 Inspection items for fire-resistant mortar Item Clay-based fire-resistant mortar High-alumina fire-resistant mortar Aluminum oxide (Al2O3) content △ Fire resistance △ △ Fineness △ △ 9.2.6.3 Phosphoric acid shall comply with the specifications in “Industrial Phosphoric Acid” (GB2091—92); it is 85% phosphoric acid, which is diluted with water to the desired concentration before use ； 9.2.6.4 Water glass (i.e., sodium silicate) shall meet the requirements of the four categories specified in \"Sodium Silicate\" (GB4209—84); its modulus shall be not less than 2.2, and its specific gravity Be (at 20°C) shall be not less than 39. 9.2.7 For the aggregates in fire-resistant concrete, clay-based fire-resistant brick fragments, fired clay clinker, or fired bauxite clinker are generally used; however, for special sections of the furnace walls (such as the bottom wall of liquid slag discharge furnaces and the lining of cyclone furnaces), the requirements specified in the equipment’s technical documents must be followed ； The inspection items for various aggregates are listed in Table 9.2.7. Table 9.2.7 Inspection items for aggregates in fire-resistant concrete Item Fire-resistant clay brick particles Fired clay aggregates Fired bauxite aggregates Bulk density △ △ △ Fire resistance △ △ △ Particle size △ △ △ Aluminum oxide (Al2O3) content △ △ △ 9.2.8 Admixtures shall be added to silicate cement fire-resistant concrete, slag silicate cement fire-resistant concrete, and water glass fire-resistant concrete; the proportion of materials with a fineness of less than 0.088 mm shall be greater than 70% ； The other technical requirements and inspection items for various admixtures are the same as those for aggregates. Note: For refractory concrete made from slag silicate cement with a maximum service temperature of 700°C, no admixtures are required if the slag content is greater than 50%. 9.3 Construction of Fire-Resistant Concrete 9.3.1 Before constructing fire-resistant concrete, test blocks shall be prepared according to the mix ratio specified in the design. Only after they have been inspected by a qualified testing agency and meet the requirements in Table 9.3.1 is construction permitted. Table 9.3.1 Inspection Items for Fire-Resistant Concrete Test Blocks
Ultimate Service Temperature | Inspection Items | Technical Requirements
≤700℃ | Bulk density | Compressive strength at room temperature | After being heated to the ultimate service temperature and then cooled | ≤Design bulk density | ≥Design compressive strength grade at room temperature | ≥45% of the compressive strength grade at room temperature
900℃ | Bulk density | Compressive strength grade at room temperature | Residual compressive strength grade | (1) Fire-resistant concrete with cement binder | (2) Fire-resistant concrete with water glass binder | Thermal shock stability | ≤Design bulk density | ≥Design compressive strength grade at room temperature | ≥30% of the compressive strength at room temperature; no cracks allowed | ≥70% of the compressive strength at room temperature; no cracks allowed | ≥Number specified in the design
1200℃, 1300℃ | Bulk density | Compressive strength grade at room temperature | Residual compressive strength grade | (1) Fire-resistant concrete with cement binder | (2) Fire-resistant concrete with water glass binder | Thermal shock stability | ≤Design bulk density | ≥Design compressive strength grade at room temperature | ≥30% of the compressive strength at room temperature; no cracks allowed | ≥70% of the compressive strength at room temperature; no cracks allowed | ≥Number specified in the design
Note: Minor hair-like cracks in test blocks for compressive strength at room temperature can be ignored. 9.3.2 During construction, fire-resistant concrete shall be sampled on-site to conduct tests for its compressive strength at normal temperature and residual compressive strength, in order to assess the construction quality. 9.3.3 The allowable deviations in the mix proportions of fire-resistant concrete shall meet the following requirements: 9.3.3.1 Cement and admixtures: ±2% ； 9.3.3.2 Coarse and fine aggregates ±5%. 9.3.4 The material and specifications of the rebar used in fire-resistant concrete shall strictly comply with the provisions of the equipment’s technical documents; the rebar and iron components embedded in the fire-resistant concrete must have any oil or dirt removed from them and coated with asphalt. 9.3.5 The formwork for fire-resistant concrete shall meet the following requirements: 9.3.5.1 The bottom formwork shall be sturdy, free from any sagging or deformation; its flatness deviation shall not exceed 2.5 mm/m, and the total deflection over its entire length shall not exceed 10 mm ； 9.3.5.2 The surface of the template should be smooth, and the joints should be tight ； 9.3.5.3 There should be a separation measure between the formwork and the fire-resistant concrete, and the formwork shall be wetted before pouring the concrete. 9.3.6 The mixing of fire-resistant concrete shall meet the following requirements: 9.3.6.1 Aggregates larger than 8 mm should generally be soaked in water for 4 hours prior to use (except for alumina clinker, which does not require soaking) ； 9.3.6.2 The water-cement ratio of fire-resistant concrete must be strictly controlled; when mechanical vibration is used, the slump of the concrete should not exceed 30–40 mm ； When compacting by hand, it should be no more than 50–60 mm ； The water-cement ratio can be adjusted appropriately in special areas such as the locations where pipes are densely installed through walls ； 9.3.6.3 The storage time for the prepared bauxite cement refractory concrete is generally not more than 0.5 hours, while the storage time for silicate cement refractory concrete is generally not more than 1 hour. 9.3.7 The pouring of fire-resistant concrete shall meet the following requirements: 9.3.7.1 Debris at the construction site shall be removed completely ； 9.3.7.2 Compaction shall be even and dense ； 9.3.7.3 Fire-resistant concrete should generally be poured continuously; if construction must be interrupted, the interval between interruptions shall not exceed the initial setting time of the concrete in the previously poured layer ； When continuing with the pouring, the surface of the already poured concrete should be roughened and cleaned, then wetted with water ； 9.3.7.4 When pouring refractory concrete on insulated concrete, it shall be carried out after the curing period of the insulated concrete has elapsed ； 9.3.7.5 During installation, when the joint in the fire-resistant concrete is greater than 20 mm, additional concrete should be poured. Before pouring this additional concrete, the rebar within the existing concrete must be removed so that it is exposed; the surface of the concrete should be cleaned and wetted with water. The newly poured concrete should be compacted carefully and cured as required. 9.3.8 The curing of fire-resistant concrete shall meet the following requirements: 9.3.8.1 The curing regime for fire-resistant concrete is specified in Table 9.3.8.1 ； Table 9.3.8.1 Table of Curing Regimes for Fire-Resistant Concrete. Type, Curing Environment, Curing Temperature (°C), Number of Curing Days, Time from Pouring to Start of Curing (hours). Silicate cement fire-resistant concrete: Moist curing, 15–25, >7, 12; Slag silicate cement fire-resistant concrete: Moist curing, 15–25, >14, 12; Alumina cement fire-resistant concrete: Moist curing, 15–25, >3, 12; Water glass fire-resistant concrete: Natural curing, 15–30, 7–14; Phosphate fire-resistant concrete: Natural curing, >20, 3–7. 9.3.8.2 When fire-resistant concrete made with cement binders is constructed at temperatures higher than those specified in Table 9.3.8.1, it needs to be watered for curing within 3–4 hours after pouring; cooling measures should be taken for alumina cement fire-resistant concrete ； 9.3.8.3 After the phosphoric acid refractory concrete is molded, it can be baked and subjected to high-temperature treatment in accordance with the relevant provisions of the \"Technical Specifications for the Production and Construction of Clay-based and High-alumina Refractory Concretes\" (Ministry of Metallurgical Industry) ； 9.3.8.4 Phosphoric acid and water glass refractory concrete must not be exposed to moisture or rain during construction and before baking heat treatment. 9.3.9 Under normal curing conditions, the allowable time for removing formwork from fire-resistant concrete is: not less than 1 day and 1 night for alumina cement fire-resistant concrete ； For silicate cement refractory concrete and slag silicate cement refractory concrete, it shall be not less than 3 days and nights ； If minor defects are found after demolding, they should be repaired promptly. 9.3.10 When constructing phosphoric acid refractory concrete, in addition to complying with the relevant regulations mentioned above, the following requirements must also be met: 9.3.10.1 When normal-temperature strength is not required for phosphoric acid refractory concrete, accelerators should be used as little as possible or not at all ； When using bauxite cement accelerator, its dosage shall not exceed 3% ； 9.3.10.2 The mixing of materials generally consists of three steps: mixing, holding the mixture, and secondary mixing. About half of the required phosphoric acid is added during the first step; the mixture should be held for at least 16 hours. After adding the setting accelerator to the mixed material, it should be used up within 20–30 minutes. 9.3.11 In addition to complying with the relevant regulations mentioned above, the construction of water glass refractory concrete shall also meet the following requirements: 9.3.11.1 Sodium fluosilicate should be preferred as the accelerating agent, with a dosage of 8% to 15% of the amount of water glass used ； When silicate cement is used as a setting accelerator, its dosage is 8% to 12% of the dosage of water glass ； 9.3.11.2 The mixture to which a setting accelerator has been added must be used up within 30 minutes. 9.3.12 When using fire-resistant plastic compounds, the following requirements must be met: 9.3.12.1 The storage of fire-resistant plastic compounds shall be carried out in strict accordance with the storage guidelines provided by the manufacturer; the packaging bags must not be damaged. Fire-resistant plastic compounds that have exceeded their storage period need to be retested and analyzed to ensure that their properties meet the required standards before they can be used ； 9.3.12.2 Before the application of fire-resistant plastic materials, sampling inspections must be carried out to verify the various technical specifications of these materials; each type of fire-resistant plastic material should only be used in areas where its operating temperature is suitable ； 9.3.12.3 When constructing fire-resistant plastic materials, thorough tamping is required; if there are special design requirements (such as the inclusion of vent holes), those requirements must be followed ； 9.3.12.4 The ramming construction of fire-resistant plastic materials should be carried out continuously. If work is interrupted, the rammed surface should be covered with plastic sheeting to prevent dehydration and hardening. If the interruption lasts for a long time, the hardened layer on the rammed surface must be removed before work can resume; hardened material must not be used ； 9.3.12.5 Non-through expansion joints shall be provided in refractory plastic with a large ramming area. 9.4 Construction of insulated concrete 9.4.1 Regardless of the formulation used, the bulk density should be determined and tests for compressive strength at room temperature should be carried out prior to construction ； When insulating concrete is prepared using new materials, tests on thermal conductivity, operating temperature, dry shrinkage rate, etc., must be conducted; it may only be used after passing the inspection by a qualified testing agency. 9.4.2 During the construction of insulated concrete, test blocks should be prepared to conduct tests on its compressive strength at normal temperatures and its bulk density, in order to assess the construction quality of the insulated concrete. 9.4.3 The areas where insulated concrete is applied should be kept clean and dry to ensure good adhesion ； Insulated concrete should be poured immediately after mixing, and the holding time should generally not exceed 1 hour. 9.4.4 Insulated concrete shall be compacted evenly, with a smooth surface and no cracks. 9.4.5 When insulating concrete is poured on fire-resistant concrete, this can only be done after the fire-resistant concrete has been cured for more than 24 hours ； When pouring insulating concrete on the insulation layer, a waterproof layer should be used as a separator to prevent excessive water loss after the concrete is poured, which could reduce its strength. 9.4.6 Insulated concrete generally does not have expansion joints; when pouring additional insulated concrete, the loose concrete on the surface of existing joints should be cleaned thoroughly and wetted with water. 9.4.7 The curing regime for insulated concrete shall be carried out in accordance with Table 9.3.8.1 for refractory concrete, depending on the type of cement used. 9.5 Framed refractory concrete furnace walls 9.5.1 In addition to complying with the requirements of sections 9.3 and 9.4 of these specifications, the construction of framed refractory concrete furnace walls shall also meet the following requirements: 9.5.1.1 The position of the rebar must be accurate, and there must be a protective layer of sufficient thickness between the rebar and the fire-facing side of the concrete; this thickness should generally be no less than 25 mm ； 9.5.1.2 When pouring and vibrating concrete, it is necessary to ensure that the hooks and supports are in the correct positions and can expand freely ； The expansion joints in the refractory concrete layer should ensure that the concrete is completely separated from one another, with no misalignment allowed ； 9.5.1.3 The fire-resistant concrete at the brackets and pull hooks shall be thickened ； 9.5.1.4 During concrete construction, it is advisable to draw tie wires from the rebar network in order to connect them to the outer wire mesh. 9.5.2 After the construction of the frame furnace wall, the visual inspection shall meet the following requirements: 9.5.2.1 The surface of the fire-resistant concrete shall be free of cracks (except for hairline cracks) ； 9.5.2.2 The surface of fire-resistant concrete shall be flat and smooth, without defects such as honeycombing or pitting ； 9.5.2.3 The dimensional tolerances for fire-resistant concrete components are generally +3, -5 mm in the length and width directions, with the difference between the two diagonals not exceeding 8 mm. 9.5.3 The allowable deviations for the flatness of the frame furnace wall, its thickness, as well as its levelness and perpendicularity after installation alignment, shall meet the requirements specified in Table 9.5.3. Table 9.5.3 Permissible deviations for frame furnace walls (mm)
Flatness: Not more than 3 per meter
Levelness: Not more than 5 over the entire length, not more than 10 every two meters
Verticality: Not more than 3 per meter; not more than 15 for the entire wall height
Thickness: For the fire-resistant concrete layer, ±5 for the entire wall, ±10

9.6 Furnace wall with pipes
9.6.1 In addition to complying with the requirements of sections 9.3 and 9.4 of this specification, the construction of the concrete for furnace walls with pipes must also meet the following requirements:
9.6.1.1 The installation of fixing elements (such as hooks, bolts, etc.) for furnace walls with pipes must comply with the specifications outlined in the equipment’s technical documents; fixing elements are not allowed to be installed at the bends of the pipes ； 9.6.1.2 The wire mesh covering the furnace wall shall be firmly connected to the combustion apparatus, openings, doors, etc., and the wire meshes shall be connected together as a single unit ； 9.6.1.3 When a shaped insulation material (other than mineral fiber products) is used for the furnace wall lining, mortar must be applied or fibers must be used for sealing; the mortar should also be even and fully filled in ； When the furnace wall is constructed using cast methods, it is essential to strictly control the amount of water added and the ramming compression ratio ； 9.6.1.4 The wire mesh surrounding the combined pipe-laying furnace wall should have sufficient connection allowance ； 9.6.1.5 The gland or nuts used to secure the furnace wall fixtures should be tightened properly, and these fixtures must not rise more than 15 mm above the main insulation layer. 9.6.2 The supplementary pouring after the pipe-laying furnace wall is in place shall meet the following requirements: 9.6.2.1 Adjacent wire meshes shall be firmly connected (the inner wire mesh is preferably welded together) ； 9.6.2.2 Clean the surface of the area where concrete is to be poured additionally, and moisten it with water. The concrete poured in this area must be compacted carefully, and cured as required ； 9.6.2.3 When it is difficult to pour the supplementary concrete, the water-cement ratio can be appropriately increased, the slump can be set at 70–80 mm, and the particle size of the aggregates can be reduced. 9.6.3 The bottom wall of the liquid slag discharge furnace shall meet the following requirements: 9.6.3.1 It is necessary to ensure that the area where the furnace bottom is constructed is free of rust and debris, and measures shall be taken to prevent corrosion of the pipes ； 9.6.3.2 The expansion joints in the bottom wall of liquid slag discharge furnaces shall be provided as specified in the equipment’s technical documents, and the expansion joints in the refractory concrete between different layers must be offset from each other ； 9.6.3.3 The surface slope of fire-resistant concrete must be ensured. 9.6.4 The construction of the furnace wall in the combustion zone shall meet the following requirements: 9.6.4.1 The diameter, length, and layout density of the gripping nails shall be in accordance with the provisions specified in the equipment’s technical documents ； 9.6.4.2 The pipe surface at the flame arrestor zone must be free of rust, and fire-resistant materials (such as aluminum silicate fibers) should be used for insulation between pipes with non-membrane walls; it is strictly prohibited to integrate the flame arrestor zone with the exterior wall. 9.6.5 The allowable deviations for the flatness and thickness of the furnace wall where tubes are laid are specified in Table 9.6.5. Table 9.6.5 Permissible deviations for furnace wall linings (mm): Planarity after plastering – not more than 5 per meter; Thickness – single layer: entire wall ±5, +15, -10. 9.7 Brick-built lightweight furnace walls: 9.7.1 The mortar used for constructing the furnace wall must meet the following requirements: 9.7.1.1 The mortar can be selected from those listed in Table 9.7.1.1, depending on the type of masonry used ； Table 9.7.1.1 Furnace Wall Mortar: Sequence Number, Type of Brick, Type of Mortar 1 Clay refractory bricks – Clay fireclay mortar 2 High-alumina bricks – High-alumina fireclay mortar 3 Light refractory bricks – Clay fireclay mortar 4 Diatomite, perlite, vermiculite bricks – Diatomite raw material mortar, diatomite raw material–clay raw material mortar, diatomite raw material–diatomite cooked material mortar, asbestos-diatomite mortar 9.7.1.2 The maximum particle size of the mortar should be less than 50% of the gap between the bricks ； 9.7.1.3 Refractory mortar mixed by hand should be soaked in water for one day and one night first ； 9.7.1.4 The consistency and viscosity of the mortar should be selected according to the brick joints ； 9.7.1.5 The mortar shall be kept clean and free from impurities and flammable materials. 9.7.2 General requirements for bricklaying of boilers are as follows: 9.7.2.1 The allowable tolerances for the brick joints in brick walls are shown in Table 9.7.2.1 ； Table 9.7.2.1 Allowable deviations for brick joints: Name of masonry structure, specified brick joint width (mm), maximum allowable brick joint width (mm), maximum number of brick joints per square meter. For refractory brick walls in combustion chambers and superheaters: 2, 3, 5; for refractory brick walls in economizers: 3, 4, 8; for walls with insulation layers: 5, 7, 10. 9.7.2.2 In furnace walls, bricks with a length that is 1/3 or less of the normal brick length shall not be used, and the number of bricks with a length greater than 1/3 of the normal length in each layer should generally not exceed three ； 9.7.2.3 Special tools or machinery should be used to break bricks; it is not allowed to use a hammer directly for this purpose. The surface after breaking the bricks should be smoothed out, and broken bricks or those with missing edges or corners must not be used on the side exposed to flames ； 9.7.2.4 When laying bricks, the joints should generally be in a stepped shape; vertical or toothed joints are not allowed ； Toothed joints with a size of 1/4 to 1/2 brick length are allowed only when brickwork is laid in combination ； 9.7.2.5 When laying refractory bricks on beams, brackets, or fire-resistant concrete, a small amount of refractory plasticizing compound may be used for leveling; soft materials shall not be used as a base layer ； 9.7.2.6 When laying bricks, the mortar joints must be offset from each other and compacted; there should be no vertical joints between upper and lower layers, and no joints that run from the inside to the outside in multi-layer bricklaying ； The mortar in the brick joints must be full and even ； 9.7.2.7 When constructing brick walls, the mortar that oozes onto the surface of the wall should be removed at all times; firebrick walls must not have any dust accumulation or other debris that could cause the wall to get stuck to the pipes ； 9.7.2.8 For interior walls made of fire-resistant bricks and exterior walls made of insulating bricks, bonding in the masonry is generally not allowed, unless specified in the equipment technical documents ； 9.7.2.9 When laying insulation bricks, any missing corners or cracks should be filled tightly using mortar and small pieces of insulation material; the surface flatness deviation of the insulation brick wall shall not exceed 5 mm/m. 9.7.3 The bricks used for constructing tie bricks shall meet the following requirements: 9.7.3.1 The two opposite tie bricks shall be aligned with each other, and their fire-facing sides shall be in the same plane as the wall they are part of ； 9.7.3.2 The end of the brick-pulling hook that faces the fire side should be slightly lower; -10mm is generally appropriate ； 9.7.3.3 The gap between the hook brick and the gas pipe should be filled with insulating filler. 9.7.4 When laying refractory bricks on the brick backing plates, the following requirements shall be met: 9.7.4.1 The refractory brick walls above and below the brick backing plates shall be in the same plane ； For composite brick furnace walls, the misalignment between the upper and lower surfaces of the brick support plates should not exceed 10 mm ； 9.7.4.2 The space between the lower special-shaped bricks and the brick support plates, as well as behind the special-shaped bricks, should be filled with wet thermal insulation filler. 9.7.5 When constructing the pull hooks for the water wall and the furnace wall at those locations, the following requirements shall be met: 9.7.5.1 The brick wall shall not catch on the ear plates of the water wall nor affect the expansion of the water wall ； 9.7.5.2 The areas adjacent to the pull hooks and hooks should be carefully filled with thermal insulation material. 9.7.6 The arch bricks used for constructing the combustion device shall meet the following requirements: 9.7.6.1 A trial mixing of the arch bricks shall be carried out prior to construction ； 9.7.6.2 Allowable deviation for the inner diameter and elevation of the circular crown: ±5mm ； 9.7.6.3 The extension lines of the joints in circular arch bricks shall all pass through the center of the circle ； 9.7.6.4 When constructing the lower half of the arch, the bricks adjacent to the circular arch must be laid simultaneously. 9.7.7 The construction of arch ribs shall meet the following requirements: 9.7.7.1 Construction shall proceed from both ends toward the center ； 9.7.7.2 The extension lines of the brick joints in the arch rib shall all pass through the center of the circle ； 9.7.7.3 The number of bricks in the arch rib should be odd ； 9.7.7.4 After the brick arch is constructed, the arch ribs with a span of more than 600 mm should wait for at least 2–3 hours before the arch supports can be removed ； 9.7.7.5 The height deviation of the arch rib is ±5mm. 9.7.8 When continuing to lay bricks on the arch, vertical bricks should be laid first; the lower end of these vertical bricks should fit snugly into the arc of the arch. The height of the vertical bricks should be more than 1/3 of the length of a brick, and they should align with the horizontal joints of the bricks in the corresponding layer. 9.7.9 The masonry of suspended bricks shall meet the following requirements: 9.7.9.1 The flatness deviation of the suspended bricks shall not exceed 4 mm ； 9.7.9.2 When cutting special-shaped bricks, the strength of the main load-bearing areas must not be reduced, and when trimming the suspension holes of such bricks, the clearance between them must not exceed 5 mm. 9.7.10 The construction of inclined shield walls shall meet the following requirements: 9.7.10.1 The furnace wall shall not be leveled by filling it with mortar ； 9.7.10.2 The flatness deviation of the inclined guard plate wall surface shall not exceed 4 mm/m. 9.7.11 The brick walls of the ash chamber shall meet the following requirements: Table 9.7.13 Permissible deviations for brick-built furnace walls (mm) Planarity: Not more than 3 per meter; Levelness: Not more than 10 over every two meters, with a maximum of 5 over the entire length. Verticality: Not more than 3 per meter, with a maximum of 15 for the entire wall height. Thickness: ±10 for the entire wall. 9.7.11.1 The refractory bricks at the upper part of the water spraying device in the ash chamber shall extend beyond the wall surface ； 9.7.11.2 Bricks in the sloped section of the ash chamber should not be laid in the direction of the slope. 9.7.12 The expansion joints in the brick furnace wall and the gaps between various parts of the furnace wall shall comply with the provisions of 9.1.7 and 9.1.8. 9.7.13 The allowable deviations for the flatness, levelness, perpendicularity, and thickness of brick furnace walls shall meet the requirements specified in Table 9.7.13. 9.8 Construction of Furnace Wall Protection Layers 9.8.1 This section applies to the construction and acceptance of plastering, sealing coatings, and the application of glass fiber cloth on boiler furnace walls. 9.8.2 The wire mesh used for the furnace wall shall meet the requirements specified in the equipment’s technical documents. If no such requirements are given in the technical documents, galvanized wire mesh with a diameter of 1.6 mm and a mesh size of 20 mm×20 mm is generally to be used, as this facilitates the thermal expansion of the furnace wall. The installation of the wire mesh shall comply with the provisions of 9.9.7. 9.8.3 The requirements for the plastering of furnace walls, in addition to those specified in 9.9.8, shall also meet the following requirements: 9.8.3.1 After plastering is completed, the fixing hardware on furnace walls with pipes installed shall not be exposed, and the plastering layer on furnace walls made of brick frames shall not prevent the installation of protective panels ； 9.8.3.2 When a plaster coating is used as the protective layer for the furnace wall, expansion joints in the form of grids or I-shaped patterns about 1.5 m in size should be carved out after the plaster layer has partially dried. 9.8.4 The glass fiber cloth to be applied to the furnace wall shall meet the following requirements: 9.8.4.1 The surface of the furnace wall shall be dry and clean ； 9.8.4.2 The storage temperature for vinyl acetate polymer emulsion should be between 10 and 40°C; before use, it should be diluted with water at a temperature above 10°C, in an amount corresponding to 20% to 40% of the volume of the emulsion ； It must not be used when the emulsion temperature is below 10°C; it needs to be heated to 30–40°C before use ； 9.8.4.3 Gluing the glass fiber cloth should be carried out at an emulsion temperature of 30–40°C, and air should be removed promptly; the glass fiber cloth after application should be flat with no wrinkles ； 9.8.4.4 A layer of polyvinyl acetate emulsion should be applied to both the plastering layer and the glass fiber cloth, ensuring even coverage in each case ； 9.8.4.5 Polyvinyl acetate emulsions must not be exposed to freezing during transportation and storage; emulsions that have frozen are prohibited from use ； 9.8.4.6 Waxed glass fiber cloth should be soaked in warm water to remove the wax before use. 9.9 Insulation of Thermal Equipment and Piping 9.9.1 The insulation work on equipment and piping shall be carried out under the following conditions: 9.9.1.1 The equipment and piping that require insulation must have been installed, and must have passed welding inspections as well as integrity tests ； 9.9.1.2 Equipment and pipelines with pre-insulation have measures such as reserved welds or oil penetration tests on the welds taken ； 9.9.1.3 Dust, grease, rust, and other contaminants on the surfaces of equipment and pipelines must be removed completely. If the use of an anti-corrosive coating is specified in the design, work may proceed only after the anti-corrosive coating has fully dried. 9.9.2 The construction of fasteners and supports used for insulating equipment and pipelines shall meet the following requirements: 9.9.2.1 For the hooks and pins used in the insulation layer, if there are no specific design specifications, galvanized iron wire or low-sulfur round steel with a diameter of 3–6 mm can be used; these elements should be welded directly to carbon steel equipment or pipelines. The spacing between them shall not exceed 350 mm. Generally, there should be no less than 6 hooks or pins per m2 on the vertical surfaces, and no less than 8 per m2 on the horizontal surfaces ； 9.9.2.2 For the thermal insulation supports of vertical pipes and equipment, if not specified in the design, sectional support brackets should be installed every approximately 3 meters; their width may be slightly less than the thickness of the main insulation layer. These support brackets must not be installed at welds or attachments. The mounting of the brackets should be horizontal, with a deviation of no more than 10 mm. When direct welding to the equipment or pipes is not allowed, clamp-type support brackets should be used, and insulating materials such as insulation boards should be used to separate the clamps from the equipment or pipes, ensuring a secure fit. 9.9.3 The construction of the main insulation layer using shaped insulation materials shall meet the following requirements: 9.9.3.1 When the thickness of the main insulation layer is greater than 100 mm, it shall be constructed in layers ； The insulation layer should be fitted together tightly; the seams of adjacent layers should overlap, while those of layers on top of each other should be pressed together. For square-shaped equipment, the insulation at the four corners should be arranged in an overlapping manner, and the gaps should be filled with soft, high-temperature resistant insulation material. The binding should be secure ； 9.9.3.2 A expansion joint of 20–30 mm should be provided in the main insulation layer at the bends of high-temperature pipelines, and it should be filled with an insulating material with good elasticity ； 9.9.3.3 Insulation at expansion joints and pipe sliding supports shall provide sufficient clearance in the direction of expansion ； 9.9.3.4 Insulation at the flange shall provide sufficient space for bolt removal ； 9.9.3.5 Where expansion may be obstructed (such as where pipes pass through platforms), gaps should be provided in the direction of expansion ； 9.9.3.6 Appropriate gaps must be left between the insulation layers of pipes with different expansion directions or at different medium temperatures ； 9.9.3.7 The weld locations of the main feed pipes, main steam pipes, and reheat steam pipes shall be clearly marked outside the protective coating ； 9.9.3.8 The weight of the insulation layers on pipes and equipment shall comply with the design specifications, in order to avoid excessive loading on the supports; the weight deviation shall not exceed 10% of the originally designed value. 9.9.4 When using mineral fiber rigid boards, semi-rigid boards, or sewn pads as the primary insulation layer, the following requirements must be met: 9.9.4.1 For single-layer insulation, the seams should be offset; for double-layer insulation, the seams should be overlapped. The seams must be smooth and tight ； 9.9.4.2 Regardless of the fixing method used, the main insulation layer must be secured firmly. 9.9.5 When loose materials are used directly as insulation, the following requirements shall be met: 9.9.5.1 The insulation material shall be filled evenly, and its bulk density shall comply with the design specifications ； 9.9.5.2 The wire mesh (or tin sheet) device used to wrap the insulation material must be properly installed in order to ensure the proper thickness of the insulation material (the tin sheet should be fitted tightly) ； 9.9.5.3 Reliable technical measures shall be taken to prevent the insulation material from sinking. 9.9.6 The insulation of the turbine cylinder shall be carried out in strict accordance with the equipment’s technical documents and the requirements of the \"Technical Specifications for Turbine Insulation\" (GB7520—87). The structure, materials, and thickness of the insulation shall not be altered arbitrarily; the insulation at the bolt connections between the upper and lower cylinders must be tight and easy to remove ； When fixing insulation hooks on cylinders or valves, as well as insulating turbine equipment and pipelines, the procedures shall comply with the provisions of 8.2.4 and 8.2.5 of the \"Technical Specifications for Construction and Acceptance of Power Generation Facilities (Turbine Units Section)\". 9.9.7 The wrapping of the main insulation layer with galvanized wire mesh shall meet the following requirements: 9.9.7.1 The two sheets of wire mesh shall be joined together ； 9.9.7.2 The wire mesh and spikes must be securely fastened, ensuring they are firmly attached to the insulation layer ； 9.9.7.3 After construction is completed, there should be no exposed wire ends on the surface of the wire mesh, nor any bulges or voids. 9.9.8 The application of the finishing coat shall meet the following requirements: 9.9.8.1 The finishing coat shall be applied in two stages, with the second application being carried out after the first one has dried slightly ； For the first time, it is required to be smooth and tightly compressed; for the second time, it is required to be polished and smoothed ； 9.9.8.2 When resurfacing, working at joints, or carrying out layer 2 work after a long period since the previous work was done, the existing surface layer should be roughened up and lightly moistened with water before proceeding with the work ； 9.9.8.3 Expansion joints shall be provided in the plaster layer at the supports and hangers of the off-temperature pipelines ； When applying plaster to large-scale high-temperature equipment, grid-shaped or circular expansion joints should be left in the plaster layer depending on the degree of expansion ； The expansion joint should be 5 to 10 mm in size ； 9.9.8.4 The surface of the finish coat shall be flat and smooth, with well-defined edges; its flatness shall not exceed 3 mm/m. In the cold state, the surface shall be free from cracks (except for minor hairline cracks). 9.9.9 When a metal enclosure (such as galvanized thin iron sheet or aluminum alloy thin sheet) is used as the insulation protective layer, the following requirements shall be met: 9.9.9.1 The enclosure shall be firmly attached to the main insulation layer, with secure overlap required ； 9.9.9.2 The circumferential lap joints should face downward, and the direction of adjacent lap joints shall be consistent with the slope direction of the pipeline (or equipment) ； The length of both the circumferential lap and the adjacent lap shall not be less than 25 mm. 9.9.10 For areas that require frequent maintenance or monitoring, such as creep monitoring sections, creep measurement points, flow measurement devices, flanges, valves, expansion joints, etc., a detachable insulation structure should be used. 9.10 Painting Work 9.10.1 The painting of equipment, pipelines, and their insulated surfaces shall be carried out in accordance with the provisions of this section, as well as the relevant regulations and standards issued by **. 9.10.2 Painting of equipment, pipelines, and metal structures shall be carried out after the installation of those components is completed, while painting on the surface of insulation layers shall be done only after the insulation material has dried. 9.10.3 The color of the paint on equipment, pipelines, and metal structures shall be determined in accordance with the design specifications and relevant regulations. In the absence of specific provisions in the design, Appendix I of the \"Technical Specifications for Construction and Acceptance of Power Generation Facilities (Turbo-generator Sets)\" may be referred to. 9.10.4 Before applying paint, an oil-color sample should be prepared; only after the color and quality of the oil meet the requirements can large quantities of the oil be prepared for use in the painting process. 9.10.5 The painting of metal surfaces shall meet the following requirements: 9.10.5.1 Oil, dust, and rust on the metal surface must be completely removed ； 9.10.5.2 A layer of anti-rust paint should be applied to the metal surface first ； 9.10.5.3 During multi-layer coating, attention must be paid to the required drying time for each layer; the adhesion between layers should be strong, with no delamination occurring ； 9.10.5.4 The color of the surface after painting should be uniform; there shall be no defects such as visible underlying colors, peeling, wrinkles, flow marks, loose film, paint particles, or obvious brush marks. 9.10.6 The painting applied to the surface of the insulation layer shall meet the following requirements: 9.10.6.1 Dust and debris accumulated on the surface of the insulation layer must be removed, and any cracks must be filled in and smoothed out ； 9.10.6.2 After painting, the surface shall meet the requirements of 9.10.5.4. 9.10.7 Painting work must be carried out under relatively dry climatic conditions, and the painted surface should be protected from drastic temperature changes and exposure to hot air until it dries. 9.10.8 When applying the final coat of paint, it is generally not advisable to add a drying agent to the paint. 9.11 Construction in Winter 9.11.1 Construction is considered to take place in winter when the average outdoor temperature day and night is below 5°C and the lowest temperature is below -3°C. However, for cementitious binders and refractory concrete, construction is also regarded as taking place in winter when the temperature is below 7°C; for phosphoric acid refractory concrete and water glass refractory concrete, it is considered winter construction when the temperature is below 10°C. 9.11.2 Fire-resistant products, as well as the powders and aggregates used in the preparation of fire-resistant concrete, should be preheated to above 0°C. The temperature of fire-resistant mortar and insulation mortar should be kept at least at 5°C, and care should be taken to prevent the materials from deteriorating when they are heated. 9.11.3 During winter construction, cold protection measures shall be taken to ensure that the average temperature at the construction site and its surroundings reaches 5°C before work can commence. 9.11.4 When constructing fire-resistant concrete, insulating concrete, plastering mortars, and masonry mortars in winter, the following requirements must be met: 9.11.4.1 For cement-based fire-resistant concrete and insulating concrete, the heat retention method or heating methods (such as electric heating or steam heating) can be used. During heating, the temperature for ordinary cement and slag cement-based fire-resistant concrete and insulating concrete should not exceed 60°C; when using steam curing, this temperature should not exceed 85–90°C℃ ； Alumina cement refractory concrete and insulation concrete: not more than 30℃ ； 9.11.4.2 Water glass or phosphoric acid refractory concrete may only be heated using the dry heat method; the temperature during heating of water glass concrete shall not exceed 60℃ ； 9.11.4.3 Chemical accelerators shall not be used in cementitious refractory concrete, thermal insulation concrete, plastering mortars, and masonry mortars. 9.11.5 Fire-resistant concrete and insulated concrete must not be exposed to freezing until after the curing process is complete and the finishing work is done, and before it has dried out. 9.12 Project Acceptance 9.12.1 Test reports, construction records, and approval documents related to the application of insulation paint on boiler walls, thermal equipment, and pipelines: 9.12.1.1 Formulas and test reports for refractory concrete, insulating concrete, and wall coating materials prior to and during construction ； 9.12.1.2 Records of expansion joints and expansion gaps in key areas of the furnace wall ； 9.12.1.3 Inspection and approval for concealed works ； 9.12.1.4 Mix ratios and test reports for the insulation plastering mortar for pipes and equipment. 9.12.2 Hot-state acceptance of furnace walls and insulation works: During the full-load trial operation of boiler units with a capacity of 670t/h or higher, hot-state inspections shall be carried out on the surfaces of the insulation layers or metal enclosures surrounding all four sides of the boiler, as well as its roof, main steam pipes, reheat steam outlet pipes, hot air ducts, and flue ducts. The inspection standards are specified in the \"Regulations on Technical Management in the Power Industry\": at an ambient temperature of 25°C, the temperature of the furnace walls and insulation surfaces shall not exceed 50°C.

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