Construction instructions of Castable Refractories

Construction instructions of Castable Refractories

1.Construction equipments

1.1 Castables, insulating products, all kinds of anchoring bricks, hanging tiles, metal anchors, metal hanging pieces, filling materia of expansion joints and horizontal sliding joint filling material, anti-sticking template lubricating materials should be classified for usage.

1.2 The template for casting required a smooth surface, sufficient stiffness and strength. Formwork should be strong, dimensions must be accurate. Constructions should be prevent to the displacement and deformation. Seams should be tight with no template leakage of plasma. Plastic film should be pasted on the template or lubricating materials should be coated.

1.3Construction tools are ready, and kept clean. Castable mixing should adopt compulsory mixer. Mixer should be placed near the construction site with water, power supply position. Stirring a small amount of casting material, artificial mixing is also workable. Vibrating tools should adopt the plug-in vibrator (vibrator rod) or flat plate vibrator.

1.4 More than two vibrating tools should be prepared.

2. Mixing

2.1 Dry mixing

Bag packed castables should be put the forced mixer in accordance with the capacity of the feed mixer.

2.2 Mixing with water

2.2.1 The amount of added water: FR-M60: 6.5±0.5%。FR-M65: 6.2±0.5%

2.2.2 First add 80% to 90% of the required amount of water, mix for 2 to 3 minutes uniformly. It can be adjusted for the remaining amount of water according to the construction situation. If you need to continue adding water, please stir 1 to 2 minutes after adding water. Mixing water should be clean water, not waste water, sea water and water containing impurities.

2.3 The determination of the mixing water

   To determine the mixing water is appropriate, can adopt a simple method "hand-pinch ball": Take some mixing materials, and pinch into a tight pellet, throwing the ball high in the air about 30cm, and then catch by hand, if the pellet is deformed without broken, the mixing water is ok; if the pellet is deformed and flow out of the hand, then the water is too much; if the pellet is cracked and scattered, then the water is too little. Mixing water directly affects the quality of casting, and therefore, you need to minimize the amount of water ratio when meeting the construction requirements.

3. Casting Construction

3.1 Remove debris from the mold. Set up and secure the expansion joints and outer insulation material, or put well insulation tiles according to the requirements..

3.2 Stir well to fill the mold for castable vibrated. Thickness of castable should be used according to the type and specifications of the vibrator. When using a vibrating rod, the castable thickness should not exceed 0.9 times the length of the vibrator; When using plate vibrator, the castable thickness should not exceed 20cm. Put the vibrator rod into the casting body. Slowly move the vibrator rod when the castable slurry into a flow state of the surface. Speed with 1 to 2 m / min. Mobile vibrator spacing should not exceed 1.5 times the radius .(generally radius of 20cm or so). Pulled out the vibrator rod slowly, when the rod is close to the surface, it should stay a few seconds to make the surface smooth. It should not be long for vibrator rod at each location, otherwise, it will be easy to make the material segregation.

3.3 Pouring from the furnace wall, the bottom, staggered up the block layer. Each layer should start from the corner. Don’t squeeze the castable template, it will affect the quality of construction.

3.4 Casting furnace wall, it should be covered with a layer of horizontal slip joint filler material (usually with felt paper), then continue pouring. Pouring roof, in accordance with requirements of the thickness, it should be casted for one time with no layered pouring.

3.5 The number, location and the construction of overall casting furnace equipment should be according to the design requirements. When the designer does not provide for expansion joints, the size of linear expansion rate can be leaving adjusted, usually every 2 meters there will a 5mm ~ 8mm seam of expansion joints. Keep it vertical and through. Construction materials of expansion joints should be fixed in order to avoid the material displacement, deformation, or expanding the seam of expansion joints when putting the castable into the body. You’d better use expansion joints board and castable from professional manufacturers. Setting the seam of the expansion joints should pay attention to the anchoring holes and the staggered brick of furnace. The vibrator should be staggered on both sides when working near the expansion joints. Try to keep it vertical.

3.6 Castable should be continuous construction, Otherwise, it requires construction joints,

The seam of expansion joints in the best place to for construction joints. Or construction joints should be made with rough surface.

3.7 Casting with anchor cast, it is best to cast slightly higher the position of the lower surface of the anchoring brick(by about 2cm), then hang anchoring brick. Then it can enable the anchoring close under the surface and the casting material combination, at the same time it can ensure that the levelness of anchoring brick.

3.8 Casting with hanging tiles.  To ensure the verticality and the vibration does not go up, the application of the wedge will be fixed with hanging tiles, non-direct reach with the vibrator on the bricks, and you should cast from both sides and stagger the vibrator appropriately.

3.9 If you are using self-flow castable, the construction can not be vibrated for long, simply use the vibrating rod or stirring with a wooden stick.. In the case of water-cooled tube with a bandage or a vibrator rod is not convenient to be used, you can use the wooden hammer to knock the template slightly.

3.10 If you are self-flow castable for water pipe wrap, insulation fibers should be strapped with plastic sheeting or tape. It can ensure the mobility of construction materials and water won’t be absorbed by the fiber.

3.11 Winter construction should take the necessary insulation measures, the construction environment temperature should not fall below 5 ℃. Mixing water should be heated, water temperature not exceeding 50 ℃. Mixing time should be extended accordingly.

4. Maintainance and Demould

4.1 Maintainance

After construction, it needs maintenance. winter maintenance should be above 5 ℃, the temperature below 5 ℃ It should take precautionary measures when the temperature is below 5 ℃.

The maintainance time for castable in non-winter is 24h-48h and 48h-72h in winter time.

4.2 Demould

4.2.1 Demould can be done after the maintainance. The demould time for overall structure is:non-load-bearing side of the template can be demould when the castable strength reach its surface and edges won’t not be damaged by demould; load-bearing body of the template can be demould when its CCS reach more than 10MPa at room temperature.

4.2.2 If the wood mould is used, be sure to split out all the wood mold, or after the fire, the wood will burn intensely. It will result in casting off the surface material, and even cracks.

5. Dryoff oven

   Dryoff oven is the key step for the effects of castable. Its main function is to rule out free water and pouring the chemical compound with water. To dry off oven properly, it can improve life for furnace and thermal devices. Otherwise, it can result in casting cracks, spalling, and even lead to burst.

5.1 To prevent direct flame burn the casting body and caused peeling off, you can put the aluminium silicate fiber felt at drying location before the fire..

5.2 Heat source for dryoff oven: gas, natural gas, hot air, wood, coal, heavy oil, electric, etc. You must be able to control the heating rate, to avoid local overheating. Gas, natural gas or electric will be preferly used at low-temperature phase. You should not use heavy oil. When the temperature reached 500 ~ 600 ℃, the oven burner can be gradually opened.

5.3 After the start of the dryoff oven, it shall not stop or interrupt. If you have to interrupt, the cooling should be slow. When re-heating oven, you should do it in accordance with dryoff instructions.

5.4 You should strictly follow the temperature curve, and protect the furnace temperature rise and uniform distribution

5.5 After dryoff oven,  a comprehensive inspection of the furnace should be regularly and you should observe the chimney smoke. After the 600 ℃ insulation, if it is still dripping or white smoke is from the chimney joints, you should not heat up immediately. You should continue to heat at this temperature until it did not drip and no white smoke from the chimney. Then you can rise the temperature accordking to the curve.

5.6 Dryoff oven system reference table (This table is only for reference, the specific oven system of technical information will be available with the goods):

System of ordinary castable dryoff oven

Technical Department of Fame Rise corporation