Consultation on piston machine cylinder seizure issue
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Piston compressor, two-stage compression, outlet pressure of 9 kg. The cylinders are arranged horizontally in opposition to each other, with two high-pressure and two low-pressure cylinders; forced lubrication is provided by a gear pump. The technology adopted by the company has been in use abroad for nearly 50 years; production is carried out according to detailed specifications. There were no issues during the first 7 years, but later, as the manufacturers that produced pistons, connecting rods, and piston cylinders shut down, new manufacturers were chosen. Recently, five cases of cylinder seizure have occurred, all of which took place shortly after the air compressors left the factory, with a total operating time of less than 200 hours. The lubricating oil remained clear and did not darken. In all cases, the right-side high-pressure piston was stuck to the cylinder block (with the exhaust port located near the left side of the cylinder block). Separation using wire cutting revealed severe damage to the piston skirt; the piston rings were not stuck to the piston, and no obvious wear marks were visible on the piston rings. An inspection of the oil lubrication system revealed no abnormalities. By checking the original records, it was found that the gap between the cylinder block and the piston is small; the inner diameter of the cylinder is at the lower limit, while the outer diameter of the piston skirt is at the upper limit. Both the cylinder and the piston are made of HT200 material; the piston is cylindrical in shape with a smaller diameter at the top and a larger diameter at the skirt. All these values fall within the specified dimensional tolerances (the tolerance range is 0.03–0.09 on both sides). The piston ring grooves are too wide, exceeding the upper limit by 0.05–0.07, and their roughness does not meet the required standards. Other geometric tolerances were checked and all were within acceptable limits. The dimensions of other components such as the connecting rod, crankcase, and piston pins are also satisfactory, with no abnormalities detected. What could be the possible causes of this failure?
The clearance between the faulty cylinder and the piston is approximately 0.03 (on both sides)
The piston rings are not seized to the piston, and there are no obvious signs of wear on the piston rings. I’m not quite sure where the seizure occurs; could the original poster upload a picture to show it?
By disassembling it, can we find the part that caused the damage? It doesn’t belong to the category of \"hugging the tank\", right? It’s best to have a device image. The most critical issue when replacing original manufacturer spare parts is ensuring accurate inspection and measurement of those parts. The principles of mechanics need to be clear. It’s better to send a video for a look.
Is it possible that stress concentration is the cause?
The gap is 0.03 mm – isn’t that too small? Won’t thermal expansion cause them to stick together?
If the piston rings are not worn, then how can the piston and the cylinder block get stuck together? Further explanation is needed
If the gap between the piston and the piston cylinder is too small, it can be set at the upper limit. Furthermore, is the gap a radial value? Is it considered to use different materials for the piston and cylinder?
If the gap between the piston and the cylinder liner is too small, thermal expansion will occur during operation, leading to seizure
It’s best to check the clearance between the piston and the cylinder liner to see if the alignment between them is poor and the clearance is too small, which could lead to seizure during thermal expansion.