Secondary grouting after equipment installation is complete

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After each piece of equipment is installed and passes strict inspections to meet the installation technical standards, as well as being approved by the relevant authorities, secondary grouting can be carried out. Secondary grouting refers to filling the gaps between the equipment base and the foundation surface, as well as the holes for anchor bolts, with concrete or mortar. One of its functions is to secure the shims (the movable parts of adjustable shims cannot be fixed), and another function is to bear part of the load of the equipment. (1) Key points for secondary grouting: (1) Before grouting, the area to be grouted should be washed thoroughly with water to ensure a strong bond between the newly poured concrete (or mortar) and the existing concrete. (2) Grouting is generally done using fine aggregate concrete (or cement mortar), whose grade should be at least one level higher than that of the original concrete. The particle size of the gravel is approximately 5–15 mm, and cement of grade 400 or 500 is used. (3) During grouting, an outer formwork ring should be placed, with its edge being at least 60 mm away from the edge of the equipment base ； If it is not necessary to grout the entire area under the equipment base, and the grouting layer is required to bear the load of the equipment, internal formwork must also be used to ensure the quality of the grouting layer. The distance from the inner template to the outer edge of the equipment base should be greater than 100 mm, and it must also not be less than the width of the base surface. The height of the grouting layer should be above the bottom surface of the base, on the outside of it. The upper surface of the grouting layer should have a slight slope (slope outward) to prevent oil and water from entering the equipment base. (4) The grouting work must be carried out continuously without interruption, and it should be completed in one go. Concrete or mortar should be tamped in layers. When tamping, do not concentrate the effort in one area; ensure that the anchor bolts remain perpendicular to the installation surface. (5) After grouting, watering for curing is required, with the curing period being no less than one week. The anchor bolts may be tightened only after the concrete has reached a strength of over 70% of its final strength. (II) Grouting: To achieve better contact between the shims and the bottom surface of the equipment base as well as the grouting layer, the grouting method can be employed. The operation method is as follows: (1) First, spot-weld a small round steel bar to the foundation bolt to serve as a bracket for the support shims; the strength of this spot weld should be sufficient to allow it to be removed under pressure during grouting. (2) Thread the anchor bolts with welded round steel bars into the bolt holes of the equipment base. (3) Preliminary alignment of the equipment using temporary shims. (4) Adjust the lifting block of the shimming iron to the lowest position, place the shimming iron on the small round steel bar, and slightly tighten the nuts of the foundation bolts so that the shimming iron makes firm contact with the equipment base, thereby temporarily fixing it in the correct position. (5) During grouting, the anchor bolt holes should generally be filled first; once the concrete has reached 75% of its specified strength, then the grouting layer beneath the shims should be filled. The thickness of this grouting layer is usually 30–50 mm. (6) When the grouting layer has reached the late stage of initial setting (a slight indentation remains when pressed with a finger), adjust the lifting block to expand and dislodge the small round steel, thereby compressing the grouting layer. (7) Once the grouting layer reaches 75% of the specified strength, remove the temporary shims and carry out the final alignment of the equipment. (8) When it is not possible to use anchor bolts to support the shims, screw-adjustable shims or inclined shims can be used to support them. When the grouting layer reaches the later stage of initial setting, loosen the adjustment screw or remove the shims, adjust the lifting block, and compress the grouting layer.