Evaluation of the influence of material, manufacturing and testing parameters on the leakage of PTFE and PEEK based sealing materials in reciprocating compressors

Micha Humpel

Research output: ThesisMaster's Thesis

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Abstract

The pressure packing seals the compression chamber of a reciprocating compressor from the environment and is a performance determining component. The pressure packing consists of several containers, also called cups, in which a sealing element is placed. Such a sealing element typically consists of one or more packing rings. The packing rings are designed such, that they can compensate wear geometrically. The sealing element (ring group) is activated by the differential pressure that it seals. The pressure differential over a ring group presses the ring segments against each other and the rings against the piston rod and the cup face. The contact pressure between these surfaces is determined by the pressure differential and the ring geometry. The contact pressure and the gas pressure are in the same order of magnitude. Leakage through a packing ring group can occur in multiple places: • In the dynamic sealing surface between the reciprocating rod and the seal. • In the static sealing surface between a ring and another ring or a ring and the cup. • Due to manufacturing imperfections on the edges between ring segments or between packing rings. The aim of this thesis is to study the impact of various testing, material and manufacturing parameters on the face-to-face sealing elements. The focus lies on the applied gas pressure and the contact pressure and the roughness and flatness. A test rig was designed to test the impact of those parameters on the leakage. The test rig allows a defined application of the contact pressure, which is independent of the application of the gas pressure. Possible leakage is recorded end-of-line. In order to test the influence of flatness and roughness, specimens were produced with different machining methods and parameters. Based on typically used material combinations in a sealing element, a design of experiments was introduced to test different materials and different sealing surfaces. Influencing parameters other than the intended ones were studied and minimized, where possible, before the tests were performed. The developed measurement routine was used for all tested material combinations. The theoretically expected dependencies of the leakage on the contact pressure and the gas pressure were confirmed. Leakage decreases logarithmically with increasing contact pressures. For gas pressures smaller than the contact pressure a linear increase of leakage with increasing gas pressure is detected. As soon as the gas pressure equals the contact pressure its influence on the contact situation cannot be neglected any more and leakage increases more rapidly. For soft materials the roughness plays an important role. Finer surfaces result in less leakage. The flatness is more important for rigid materials as the rings are not as easily deformed. This is especially relevant for low contact pressures.
Translated title of the contributionUntersuchung des Einflusses von Material-, Verarbeitungs- und Testparametern auf die Leckage von Kolbenstangendichtmaterialien
Original languageEnglish
QualificationDipl.-Ing.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Pinter, Gerald Gerhard, Supervisor (internal)
  • Kaufmann, Andreas, Supervisor (external)
Award date20 Dec 2019
Publication statusPublished - 2019

Bibliographical note

embargoed until null

Keywords

  • compression technology
  • reciprocating compressor
  • pressure packing
  • packing rings
  • contact mechanics
  • leakage

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