Reasons for the breakage of reciprocating compressor piston rods

This post was last edited by mmliuqing on 2019-6-26 at 18:42. If the breakage wasn’t caused by the cylinder block seizing due to a lack of oil, check whether the crack is an old one or a new one. How long has this device been in use? If it’s new, it might be a quality issue; if it’s old, then the cylinder block may have been seizing on a regular basis. It may be caused by the mismatch in expansion coefficients between the heating cylinder and the piston materials.

It seems to be a material quality issue with the film; did anything like cylinder collision occur with the additional components? Otherwise, it’s difficult for such accidents to occur. Check whether there are any signs of impact on the side of the piston where the shaft broke.

One is that there is a problem with the material. One is the machining issue; the tooth grooves have sharp angles.

First, determine whether the machine is operating at 50% load or if one of the air valves is damaged. The reverse angle is related to the combined forces acting on the crosshead pin; damage to the air valve or its incorrect installation affects the gas force, which in turn affects the combined forces and consequently the reverse angle. When the valve fails, compression cannot occur in one of the cylinders, resulting in only one cylinder operating. As a result, the piston is subjected to force in only one direction, and consequently the crosshead also experiences force in only one direction. If the air valve in the cylinder on the cover side is damaged, the piston can only withstand tensile force. When moving back, there is normally a tensile force; when moving towards the cylinder side, since there is no gas available for compression on that side, there should be a thrust force. However, the pressure from the cylinder on the engine block side results in a tensile force instead.

From a technical perspective, it is necessary to calculate whether the force on the piston exceeds the allowable limit; attention must also be paid to the material used for manufacturing and heat treating the piston rod, as well as to the stress concentrations at the threaded areas.

A broken piston rod is a serious accident, and there are various causes for it, all of which need to be identified and ruled out one by one. 1. The most direct process parameter is the change in inlet and exhaust pressures, which affects the overall piston force exerted by the piston rod; manufacturers need to determine whether this force exceeds the allowable value. 2. Installation or maintenance records: After maintenance, many compressors fail to meet the requirements regarding alignment or the axial and radial clearances of the piston rod; as a result, stress fatigue can lead to fractures after they are operated for some time. Many maintenance personnel handle these tasks in a careless and hasty manner. 3. Compressor operation records: whether the gas contained liquid before failure, and if there were any other abnormalities with the compressor. 4. Quality issues: whether there are defects in the piston rod design and whether the quality of the forgings meets the standards. 5. As for the reverse angle, it only causes cooling of the crosshead pin. Damage to the intake and exhaust valves, as well as wear on the rings, do not cause this directly; it is ultimately changes in intake and exhaust pressure that lead to changes in the overall piston force.

It might be a quality issue with the material......

Our company has also experienced an accident of this kind; after ruling out issues related to the manufacturing process and installation quality, it was determined that there were defects in the piston rod. Moreover, this location is precisely a point where stress concentrations occur, leading to fatigue damage.

Was it the locking nut that broke? Did it loosen, causing the piston to move and break it?