Weekly Topic: How should cracks in the coal mill pinion be addressed?
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What should be done if cracks appear on the pinion gear of the coal grinder?
Use a manual grinder or a machine tool to create a bevel at the crack site, and then carry out repair welding using stainless steel electrodes with a low welding current. Then, the worn or repaired areas are ground and welded manually or on a machine; after use, care should be taken to keep the load on the gears low, as stainless steel has low strength.
Grind after patch welding; RT is preferred
For safety reasons, I think it’s better to replace it; the welding isn’t good, and this doesn’t guarantee a proper weld, nor does it ensure that there will be no issues with gear meshing after welding.
1. Spare parts are available; replace it immediately； 2. Prepare spare parts as soon as possible ； 3. Temporary treatment: ㈠ Thoroughly clean the pinion, and use a developing agent to reveal the number of cracks as well as the exact location of the crack ends ； (ii) Drill small holes at the end of the crack (to prevent further propagation of the crack) ； (iii) Remove material along the crack line to form a rectangular groove centered on the crack; an appropriate amount of material can be removed from various points ； (IV) Gear materials are mostly medium-carbon steel or low-alloy steel; repair welding is carried out using 507 or 506, and units with the necessary facilities can perform localized weld stress annealing ； (v) Coarse filing, followed by fine grinding to restore shape and the required precision ； Who knows how long it will last!
It is recommended to replace it with a new one. If welding is to be done, crack arrest holes must be drilled first before surfacing is carried out.