Things to know 
Plunger, Packing, Lubricant – a complex tribological system in LDPE hyper compressors
 
1. Introduction

TRIBO Hartstoff GmbH is manufacturer of cemented carbides on basis of tungsten carbide and cobalt. Due to their outstanding properties with regard to compressive and wear resistance these cemented carbides are used as components in so called hyper compressors where they are of enormous significance for a stable high-pressure generation. In this area of high pressure products TRIBO is cussion we will refer to plungers with carbide coating layer, solid cemented carbide plungers and carbide-tipped high-pressure bushes are to be mentioned.

Today hyper compressors using plungers are critical machines used for the production of LDPE. In these compressors plungers are operated together with high pressure packings made of special bronze which guarantee the sealing of discharge pressures up to 350 MPa. In order to ensure this sealing system will work efficiently and safely over a long period of time mineral or synthetic lubricants are used. The outcome is a tribological system consisting of 4 components - ethylene, high pressure packings, plunger and lubricant.

In many years of analysing the issues in the tribological system we have gained considerable knowledge, and in particular concerning the cemented carbides, its influence and the system components involved. This knowledge is based upon real failures in the field and subsequent investigation carried out in rectification. Conclusions from these investigations have proved of crucial importance to plant managers in providing the basis for future process improvement.



Picture 1: The 4 components of the tribological system
Differences between Hot Isostatical Pressing (HIP) and Sinter HIP Procedure
Differences between Hot Isostatical and Sinter HIP
1. Hot Isostatical Pressure
2. Sinter HIP Procedure Pressure

Plunger, Packing, Lubricant – a complex tribological system in LDPE hyper compressors
1. Introduction Pressure
2. Elementary structure of a plant for high-pressure polymerization of ethylene
3. The tribological system
4. Wear process in the tribological system
5. Practical knowledge from a carbide metal producer’s point of view
6. Other partners of the tribological system
7. Outlook
8. Summary
9. Reference
2. Elementary structure of a plant for high-pressure polymerization of ethylene