Cemented carbide plungers are used in hyper compressors to compress ethylene gas to the reactor pressure between 160 and 350 MPa. Since cemented carbide is a brittle material, the failure load is determined by the nature and distribution of defects. This makes the plunger one of the most critical components in the LDPE production plant. Plunger failure can lead to very high costs because of damage on the compressor and production loss and in the worst case it can cause very high gas leakages that can lead to an explosion and fire.
Typical defects on plungers have been analyzed and related to their origin. Corrosion and thermo-mechanical fatigue cracks are discussed in detail because they are most frequently found. Causes of these defects can be process or component related, but also the influence of reconditioning techniques has been analyzed. Since most of plunger fractures are directly initiated by fatigue cracks, external factors that can lead to these cracks are analyzed.
