In many industrial production processes, centrifugal fans are required to supply or exhaust air. However, due to the presence of large dust and even corrosive gases in the workshop, the impeller blades of the centrifugal fan will be worn every time, causing serious When the blades need to be replaced, how to replace the centrifugal fan blades?
1)Disassembly of centrifugal fan impeller
1. First remove the conical guard plate from the impeller, then remove the coupling on the rotor and the impeller from the main shaft by heating, and clean the main shaft assembly surface and bearings. Thoroughly inspect and document the spindle. Form a comprehensive test report.
2. Sandblast the impeller to remove the dust and rust on the surface of the impeller, but pay attention to protect the mating surface of the hub plate and the main shaft.
3. The workshop shall apply anti-rust oil on the mating surface of the hub plate and the main shaft for anti-rust treatment.
2) the centrifugal fan blade replacement method
1. Part of the blade replacement method
If the blade is only worn at the outlet, and other parts are not worn or the wear is relatively light, only some of the blades and wear-resistant plates need to be replaced.
(1) When disassembling, support a φ20 round steel between every two blades at the blade outlet. The height of the round steel is equal to the width of the impeller outlet to control the deformation of the wheel cover when cutting the blade and the deformation of the wheel cover when welding the blade.
(2) Draw a parallel line on the outlet edge at a distance of 7~10mm from the blade wear, as the blade cutting position line, manual gas cutting the blade, the cutting area is from the outlet side to the blade cutting position line, up to the root of the blade and wheel cover weld bead, down to the root of the blade and wear plate weld bead. Use an angle grinder to remove the remaining part of the blade and the hardened layer left by the butt joint of the gas-cut blade.
(3) The blade is cut according to the drawing, and an appropriate amount of process allowance is left along the profile line in height. The actual length (from the outlet side) is determined according to the scribed line, and the material is cut and blanked according to the line, and the corresponding standard is applied for blanking, and then the welding groove of the butting part of the blade and the original blade and the contact part of the blade and the original wear-resistant plate are planed. The groove type is a single V-shaped groove, the groove angle is 45°, the blunt edge is 1~2mm, and the groove direction is the same side.
(4) In addition to the reserved area for surfacing, the blade is surfacing with D K65 wear-resistant alloy powder blocks (δ=3mm) on the working surface, and surfacing is 30mm every 15mm. After surfacing welding, use a hydraulic press to trim the blades according to the drawing. The reserved area for surfacing welding is temporarily not used for surfacing welding, and the surfacing welding is performed after the impeller is formed.
(5) After the actual position of the blade is aligned, grind the blade according to the wheel cover profile, and fix the blade between the wheel cover and the wear-resistant plate after grinding. According to the imported standard welding, the welding sequence is to weld the butt seam first and then the fillet seam, first to weld the inner arc and then to the outer arc, and the size of the welding leg should meet the strength requirements.
2. Integral blade replacement method
If the entire blade and wear-resistant plate are seriously worn, they must be completely replaced. The steps are as follows:
(1) Disassemble the blade, fix the non-working surface of the wheel cover to prevent the deformation of the process vertical ring (the number of the process vertical ring is determined according to the size of the wheel cover), cut off the blade, and remove the wheel cover (for the double suction type, in order to prevent deformation, The other side waits for this side to be reassembled). Use carbon arc gouging or electric welding to remove the wear plates and residual blades on the wheel cover and the wear plates and residual blades on the wheel disc, and smooth the weld bead.
(2) Reproduce the blade set and wear-resistant plate according to the corresponding size of the drawing. When the blade is made, there is an appropriate amount of process allowance along the profile line in height, and no allowance in the length direction. The liner is made according to the drawing to leave a process hole, so that the process hole can be welded flat after connecting with the blade. The wear-resistant plate is cut according to the net size of the drawing.
(3) When the platform is repaired, the size of the rear wheel cover should meet the requirements of the drawing.
(4) Impeller assembly. Draw the blade position line on the wheel disc, and use the craft round steel to support the wheel cover to ensure that the width of the impeller outlet is as required by the drawing. Align the coaxiality of the inlet ring according to the inner hole of the wheel disc, and ensure that the position of the new blade is between the original two blades. After aligning the actual position of the blade, grind the blade with the wheel cover profile. After grinding, fix the blade on the wheel cover and the resistant blade. Between grinding plates, the length of the spot welding bead should not be less than 50mm to prevent cracking of the bead and deformation of the wheel cover.
(5) Replace the blade on the other side after spot welding.
(6) After the blades on both sides are all replaced, symmetrically weld the blades to prevent welding deformation. After welding, deposit D65 electrode on the blade liner and wear-resistant plate 200mm away from the outlet (except the wear-resistant plate on the wheel cover).
3. Inspection and assembly of centrifugal fan impeller
1. After the impeller is formed, perform non-destructive testing on all welds.
2. Use D65 electrode to surfacing the blade reserved area and blade head, use D212 electrode to surfacing the transition area, and use D65 electrode to surfacing a triangular wear-resistant block at the seriously worn part of the working face of the wheel cover, and the surfacing height is 3mm.
3. After repairing, the weld bead is checked for coloring.
4. The impeller is subjected to vibration aging treatment to eliminate the stress of its welding.
5. Prepare and assemble the parts according to the drawings. Balance according to the standard, remove the original balance block before balancing. After painting and packaging.