In the application process of unshaped refractory materials, there are many factors that affect their performance, such as material selection, construction, maintenance and other aspects. Among them, the importance of construction is crucial.
Regulations to be followed during construction
(1) If the packaging of refractory castables is damaged, the materials are obviously leaking, contaminated or damp and deteriorated, the packaging should not be used.
(2) The surface of steel structures and equipment in contact with amorphous refractory materials should be cleaned of floating rust first. (3) The mix ratio of amorphous refractory materials shall not be changed arbitrarily during construction. Water or other materials should not be added to the mixed amorphous refractory materials at will.
(4) The surface of the refractory prefabricated components transported to the construction site should have: ① the production unit mark; ② the quality inspection pass mark; ③ the part number consistent with the construction drawing on three different faces; ④ the hanging point mark; ⑤ the production date.
(5) When placing refractory prefabricated components, the position and method of support should be consistent with the stress conditions of the components and should not cause overstress and damage to the prefabricated components. They should be pre-moistened before pouring and spraying.
(6) Metal tamping tools such as vibrating rods and tamping hammers shall not act directly on the anchor. If necessary, wooden boards should be used as pads.
(7) The allowable dimensional error of the amorphous refractory material lining can be determined by referring to the requirements for the refractory brick lining.
(8) Clean water should be used for mixing refractory castables. In coastal areas, the mixing water should be tested and its chloride ion (C1-) concentration should not be greater than 300 mg/L.
(9) The formwork used for pouring should have sufficient rigidity and strength, the formwork size should be accurate, and deformation should be prevented during construction. The formwork joints should be tight and leak-proof. Anti-sticking measures should be taken for the formwork. Waterproof measures should be taken for the surface of the insulating masonry in contact with the castable.
(10) The castable should be mixed with a forced mixer. The mixing time and the amount of liquid added should be strictly in accordance with the construction instructions. When changing the material brand, the mixer, the upper hopper, the weighing container, etc. should be cleaned.
(11) The stirred refractory castable should be poured within 30 minutes, or poured within the specified time according to the requirements of the construction instructions. The castable that has been initially set shall not be used.
(12) The steel bars or metal embedded parts in the castable should be placed on the non-heated surface. The contact part between the steel bars or metal embedded parts and the refractory castable should be provided with an expansion buffer layer according to the design requirements. Note: The operating temperature of ordinary steel bars should not exceed 350℃.
(13) The setting of the expansion joint of the integrally cast refractory lining should be specified by the design. For clay or high-alumina refractory castables, when the design does not specify the expansion joint value, the average value of the expansion joint per meter of the lining can be the following data: ① Clay refractory castable is 4-6mm ② High-alumina cement refractory castable is 6-8mm; ③ Phosphate refractory castable is 6-8mm ④ Water glass refractory castable is 4-6mm ⑤ Portland cement refractory castable is 5-8mm.
(14) The castable should be vibrated and compacted. The vibrating machine should be an inserted vibrator or a flat plate vibrator. In special cases, an attached vibrator or manual compaction can be used. When using an inserted vibrator, the thickness of the casting layer should not exceed 1.25 times the length of the working part of the vibrator; when using a flat plate vibrator, its thickness should not exceed 200mm. Self-flowing castables should be implemented according to the construction instructions. Insulating refractory castables should be compacted manually. When mechanical vibration is used, segregation and increased volume density should be prevented.
(15) The pouring of castables should be carried out continuously. The second layer of castables should be poured before the previous layer of castables solidifies. If the interval exceeds the solidification time, it should be treated according to the construction joint requirements. The construction joint should be left on the center line of the same row of anchor bricks.
(16) After construction, refractories castables should be cured according to the method specified in the design. If there are no special regulations, it can be carried out according to the provisions of the table. During the curing period of castables, they must not be subjected to external forces and vibrations. The heating rate of steam curing should be 10-15℃/h, and the cooling rate should not exceed 40℃/h.
(17) Non-load-bearing formwork should be removed only when the strength of the castable can ensure that its surface and edges will not be damaged or deformed due to demolding; load-bearing formwork should be removed only after the castable reaches 70% of the design strength. Thermosetting castables should be baked to the specified temperature before demolding.
(18) For the on-site pouring quality of castables, for each brand or mix ratio, 20m3 of test blocks shall be retained as a batch for inspection. If the number is less than this, a batch inspection shall be conducted. When the same brand or mix ratio is used for multiple constructions, test blocks shall be retained for inspection each time. The inspection items and technical requirements may refer to the provisions of the current industry standard "Clay and High Alumina Dense Refractory Castables" YB/T5083.
(19) There shall be no defects such as peeling, cracks, holes, etc. on the surface of the cast lining. Slight mesh cracks are allowed. (20) When lifting castable prefabricated parts, the strength of the prefabricated parts shall meet the strength required by the design for lifting. Prefabricated parts shall be lifted and placed gently during lifting, and the lifting requirements shall be strictly followed. The width of the masonry gap of the prefabricated parts and the treatment of the gap shall comply with the design requirements.
(21) Prefabricated parts shall be equipped with lifting rings, and the lifting rings shall be lifted when lifting prefabricated parts. For furnace roof prefabricated parts that use hanging bricks as the force transmission system, during the lifting and installation process, it is necessary to ensure that each hanging brick is evenly stressed and the hanging bricks must not be damaged by collisions. Furnace roof prefabricated parts should not be stacked, and when stacking, the prefabricated parts must not be directly stacked on the hanging bricks of the furnace roof prefabricated parts.
