Bore hardness of reciprocating compressor crankshaft
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Our company has 4M32 compressors, and during a major maintenance inspection it was found that the journal surfaces of the crankshaft were severely worn. The hardness of these journal surfaces was measured to be between HB152 and HB156, while the material used for the thin-walled bearings is 11-6 tin-based babbitt alloy. In my opinion, the hardness of the crankshaft journals is insufficient; no relevant crankshaft design specifications were found. According to the appendix of GB/T 18326-2001 \"Sliding bearings – Multilayer metal materials for thin-walled sliding bearings\", the hardness of the crankshaft when used in conjunction with SnSb8Cu4 babbitt alloy, which is similar to 11-6 tin-based babbitt alloy, should be no less than HB220. Apart from the reasons related to the lubricating oil, can low crankshaft hardness cause wear on the crankshaft? The operating time is only 16,000 hours, at which point a major overhaul is required per regulations. If it is relevant, are there any related standards?
The material used for crankshafts is usually 45# steel, and the journal and crank arm areas are subjected to surface hardening treatment after processing. Once the surface wears out, the rate of further wear becomes very fast. Therefore, to ensure a long service life, the ground surface also needs to be hardened.
Check the oil pressure and bearing temperature
Insufficient oil pressure leads to poor local lubrication, resulting in wear of the shaft journals