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Research Papers: Other (Seals, Manufacturing)

Short Term Relaxation Modeling of Valve Stem Packings

[+] Author and Article Information
Mohammed Diany

 Ecole de Technologie Superieure, 1100 Notre-Dame Ouest, Montreal QC H3C 1K3, Canadamdiany@yahoo.com

Abdel-Hakim Bouzid

 Ecole de Technologie Superieure, 1100 Notre-Dame Ouest, Montreal QC H3C 1K3, Canadahakim.bouzid@etsmtl.ca

J. Tribol 131(3), 032201 (May 26, 2009) (6 pages) doi:10.1115/1.3118787 History: Received September 27, 2008; Revised March 04, 2009; Published May 26, 2009

The long term tightness performance of stuffing-box packings, used in valves, is conditioned by the capacity of its sealing material to maintain a contact pressure to a predetermined minimal threshold value. Due to the creep, this contact pressure decreases with time depending on the creep properties and the stiffness of the housing. Assessing relaxation is a key parameter in determining the tightness performance of a valve stem packing over time. An analytical model based on the packing viscoelastic behavior is developed to assess the contact pressures between the packing material and the stem and the housing and their variation with time. In parallel, an axisymmetric 2D finite element model was build to validate and support the analytical model. The valve stem packing relaxation performance is an important design parameter to consider when selecting compression packings.

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Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Packed stuffing-box

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Figure 2

Packing model under load

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Figure 3

A generalized Maxwell model

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Figure 4

FE model of stuffing-box packing

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Figure 5

Finite element ID, MD, and OD axial stress relaxation

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Figure 6

Finite element radial contact stress relaxation

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Figure 7

Comparison of axial stress variation with time

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Figure 8

Comparison of radial contact pressure variation with time

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Figure 9

Relaxation of the gland compression stress from 50 MPa

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Figure 10

Relaxation of axial stress at three different axial positions

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Figure 11

Relaxation of radial contact stress qi at three different positions

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Figure 12

Comparison of lateral pressure coefficients

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Figure 13

Comparison of lateral pressure coefficients ratio

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Figure 14

Radial displacement at the packing ID and OD

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