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Research Papers: Materials and Fabrication

Permeability Measurement of Graphite Compression Packings

[+] Author and Article Information
Didier Lasseux1

TREFLE, CNRS UMR8508, University of Bordeaux, Esplanade des Arts et Métiers, 33405 Talence Cedex, Francedidier.lasseux@ensam.eu

Pascal Jolly

TREFLE, CNRS UMR8508, University of Bordeaux, Esplanade des Arts et Métiers, 33405 Talence Cedex, France

Yves Jannot

LEMTA, CNRS UMR7563 2, Avenue de la Forêt de Haye-BP 160, 54504 Vandoeuvre Cedex, France

Emmanuel Sauger Benoit Omnes

 CETIM-74, Route de la Jonelière-BP 82617, 44326 Nantes Cedex 3, France

1

Corresponding author.

J. Pressure Vessel Technol 133(4), 041401 (May 16, 2011) (8 pages) doi:10.1115/1.4002922 History: Received September 10, 2009; Revised October 18, 2010; Published May 16, 2011; Online May 16, 2011

In this work, we address the issue of the sealing performance of ring-shape valve compression packings. Our analysis is focused on the characterization of the permeability of the rings made of die-formed exfoliated graphite. Because of the tight character of the material, significant Klinkenberg effects are expected. In addition, due to the manufacturing process, permeabilities kz and kr as well as Klinkenberg coefficients bz and br in the respective axial and radial directions are markedly different and strongly dependent upon the applied stress. A specific experimental device based on pressure pulse decay of nitrogen through the material was designed for the measurement in each direction under a controlled axial compression. Determination of kz and kr and bz and br is performed on the basis of a nonstationary gas flow model in the radial and axial directions using an inverse procedure applied to the pressure decay signal. Our results confirm the efficiency of the method developed here. They clearly show the anisotropic character of the material (kz is roughly one order of magnitude larger than kr) and the dependence upon axial compression. The present analysis is the key step before further quantification of the leak rate that may result from the permeation through the material as envisaged here as well as through interfaces between the housing, the packings, and the stem.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Experimental device designed for the measurement of the radial permeability

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Figure 2

Experimental device designed for the measurement of the axial permeability

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Figure 3

Annular section of the porous ring

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Figure 4

Experimental pressure signal (open symbols) and p0(t) simulated with the estimated values of the parameters. Radial case. Ring 6, test 2. Compression stress 14.2 MPa and P0=20.4 bars.

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Figure 5

Residuals between the measured and estimated pressure signals. Radial case. Ring 6, test 2. Compression stress 14.2 MPa and P0=20.4 bars.

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Figure 6

Gas temperature in the upstream reservoir. Radial case. Ring 6, test 2. Compression stress 14.2 MPa and P0=20.4 bars.

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Figure 7

Experimental pressure signal (open symbols) and p0(t) simulated with the estimated values of the parameters. Axial case. Ring 7 and compression stress 29.3 MPa and P0=44.4 bars.

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Figure 8

Residuals between the measured and estimated pressure signals. Axial case. Ring 7 and compression stress 29.3 MPa and P0=44.4 bars.

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Figure 9

Gas temperature in the upstream reservoir. Axial case. Ring 7 and compression stress 29.3 MPa and P0=44.4 bars.

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