Compressor major repair

Most of the questions asked before were about this: ring-shaped marks on the piston, striations on the piston rod, frequent leaks, and so on. It was overhauled a few years ago; there wasn’t enough time, so the units were installed in a hurry. The main shaft bearing has poor contact; a knocking sound is heard after operation for some time. Several minor disassemblies revealed that the piston and piston rod are loose. No abnormal noises after tightening. After running directly for a year, the second stage frequently experienced problems such as leaks and high exhaust temperatures. A month ago, new support rings and piston rings were installed; yet after just 10 days of operation, the piston rings had already worn down by 1.5 mm. There was also black carbonized engine oil beneath the bearing seats of the three shafts. This is my first time performing major maintenance on a compressor, and I would appreciate it if fellow forum members could offer me some advice on the things to keep in mind

What were the clearances before disassembly? What are the diameters of the three-stage secondary main shafts, and what is their ellipticity? What is the oil pressure supplied to the main shaft bearings? What is the normal temperature of these bearings? What are the top clearance and side clearance of the bearings, as well as the tightening force on the back of the bearings? What are the clearances of the larger and smaller bearings? What is the ellipticity of the crosshead pin? What is the clearance between the crosshead slider and the guide rails? What are the clearances of the three-stage secondary packing? What are the clearances at the upper and lower dead centers of the piston? What is the exhaust pressure during operation? What is the compression ratio? What is the ellipticity of the cylinder, and is the cylinder worn?

The main shaft was removed, and grooves formed at the bearing seats in the two and three rows; I don’t have the installation data from the last time. Replace all the tiles today. The inner diameter of the small-end bearings was measured with an inside dial gauge yesterday; the vertical dimension of their inner diameter was generally 100.04, while the horizontal dimension was between 100.06 and 100.07. The crosshead pins had a diameter of around 99.91 to 99.93, with those in the second row being slightly smaller, at 99.89 to 99.91. However, when trying to insert the pin into the connecting rod, a feeler gauge with a 0.15 gap cannot be inserted; only those with two rows can be fitted in. The maximum gap specified in the manual is 0.136, and the value for these two columns is well above that limit. The remaining values all show a deviation due to the gap between the maximum and minimum values, but 0.15 is not sufficient to cover that gap – does this mean they all need to be replaced?

1. To view the image, it is necessary to replace the thin tile roof and adjust the grinding and pressing force. 2. Is the temperature increase caused by piston leakage? The compressor uses a piston design with oil-free lubrication; is there any leakage of lubricant? Into the cylinder body along the piston rod? Is there a large amount of carbon buildup inside the cylinder? 3. Has the cylinder diameter been measured? Wait

There is no definite conclusion regarding the high pressure and temperature; the piston is equipped with an oil injection system, there is carbon buildup inside the cylinder, and the wear in the vertical direction at the center of the cylinder bore is 3-4 times greater than that on the sides.

Today, I measured the clearance between the big end bearings of the connecting rod and the crankshaft; I also used red lead to check the contact area and whether the force is distributed evenly across the four bearings. The contact of the bearing shells in the first and second rows is a bit off, but since it’s already past the halfway point, there should be no problem. The main shaft has several depressions as well as protrusions, which were treated with an emery stone. Tomorrow, I plan to apply lead wire pressure to the main bearing shells. When measuring the clearance between the big end bearings of the connecting rods and the crankshaft, the value obtained by applying pressure to just one side is smaller than the sum of the values obtained by applying pressure to both sides. However, I’ve seen experienced workers use only one side for this process; the maximum allowable clearance when using pressure on one side is 25 units, while if pressure is applied to both sides, the value reaches 30 units, which exceeds the acceptable limit. Should I get that data? We use gasoline for cleaning, and then blow it with nitrogen. Will it have any impact on the parts?

In the morning, the clearance at the top of the large lead wire support was quite good, around 22. In the afternoon, I planned to carry out alignment work; however, I have never done alignment for bearings with the components mounted externally like this. The positioning pins are tilted, which means that adjusting the shims will not allow for proper alignment. Is there anyone experienced who can help think of a solution?

Based on our factory’s maintenance experience, the main checks include the roundness/cylindricity of the spindle. In addition, it is necessary to adjust the crankcase tie rods (with regard to the spindle bearing grooves), check the dimensions of the spindle bearings, ensure that the lubrication channels of the spindle bearings are unobstructed, and verify that the lubricant in the oil supply system is clean!