Experience in Operation and Reconditioning of High Pressure Cylinder Heads for Hypercompressors for LDPE

For hyper-compressors safety, operation and maintenance are important characteristics to be accounted during the design for the various components as the process gas reaches pressures up to 350 MPa (50,000 psi). Special cylinder arrangements are used, practically compound pressure vessels, normally excluded by Pressure Vessels design codes, but needing very high attention. A great help is derived by the application of innovative methods of simulation and modelling. Hyper-compressor cylinder heads with axial valves are subjected to very high pressure because of the configuration. To maximize endurance of these components, special considerations regarding materials and technical procedures such as auto-frettage are usually adopted. During operation the pressure pulsations corresponding to discharge and suction influence the mode of operation. Sealing effects generate relative movement between the valve body and the cylinder head which result in the possibility of wear in the area of contact between the seals and the internal bore surface. In addition, assembly and disassembly of the valve requires careful attention to avoid damage to the inner surface.