Research Papers: Fluid-Structure Interaction

Statististical Performance Evaluation of Soft Seat Pressure Relief Valves

[+] Author and Article Information
Robert E. Gross

Savannah River Nuclear Solutions,
US-DOE Savannah River Site,
704-2H Aiken, SC 29808
e-mail: robert.gross@srs.gov

Stephen P. Harris

Savannah River National Laboratory,
703-41A Aiken, SC 29808
e-mail: stephen.harris@srnl.doe.gov

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received March 26, 2013; final manuscript received December 23, 2013; published online February 19, 2014. Assoc. Editor: Samir Ziada. The United States Government retains, and by accepting the article for publication, the publisher acknowledges that the United States Government retains, a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for United States government purposes.

J. Pressure Vessel Technol 136(3), 031301 (Feb 19, 2014) (6 pages) Paper No: PVT-13-1055; doi: 10.1115/1.4026362 History: Received March 26, 2013; Revised December 23, 2013

Risk-based inspection methods enable estimation of the probability of failure on demand (PFD) for spring-operated pressure relief valves at the United States Department of Energy's Savannah River Site in Aiken, South Carolina. This paper presents a statistical performance evaluation of soft seat elastomer spring operated pressure relief valves. These pressure relief valves are typically smaller and of lower cost than hard seat (metal to metal) pressure relief valves. They can provide substantial cost savings in certain fluid service applications providing that PFD is at least as good as that for hard seat valves. PFD is the probability that a pressure relief valve fails to perform its intended safety function during a potentially dangerous over pressurization. The research in this paper shows that the proportion of soft seat spring operated pressure relief valves failing is the same or less than that of hard seat valves, and that for failed valves, soft seat valves typically have failure ratios of proof test pressure to set pressure much less than that of hard seat valves.

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Fig. 3

Dot plots for ratio (Rp) by valve type and working fluid for used SOPRVs

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Fig. 2

Hard seat SOPRV. The steam valve shown here has a metal nozzle and disc.

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Fig. 1

(a) Soft seat SOPRV (Teflon), (b) view of the metal seat/nozzle

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Fig. 4

Conditional Weibull cumulative probability distribution P(R − 1.30 < 0.2|R ≥ 1.30) = 0.39

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Fig. 5

Conditional Weibull cumulative probability distribution. P(R − 1.17 < 0.13|R ≥ 1.17) = 0.9669, P(R − 1.17 < 0.33|R ≥ 1.17)= 0.999596 (not shown).

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Fig. 6

ANOM plot for proportions failing (Rp ≥ 1.30) air service used SOPRVs

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Fig. 7

ANOM plot for proportions failing (Rp ≥ 1.30) gas service used SOPRVs

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Fig. 8

Clopper-Pearson confidence interval for the percent failing (Rp ≥ 1.30) by fluid service and valve type

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Fig. 9

Set pressure (psi) by seat material and working fluid for used SOPRVs. Dark Plot Points: Failures (Rp ≥ 1.30), average set pressure: 174 psi.

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Fig. 10

Time in service (psi) by seat material and working fluid for used SOPRVs. Dark Plot Points: Failures (Rp > = 1.30) average TIS: 3.99 yr




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