In this study, several failure mechanisms of o-ring type seals are investigated with analyses and subscale tests. The mechanisms of o-ring seal establishment and seal failure are characterized under a variety of conditions including temperature, pressure, lubricant, o-ring position, extrusion gap, seal damage, and seal contamination. The results include analytical prediction of seal establishment, cut seals may either fail or heal because of the orientation of the damage relative to the direction of applied pressure, o-ring extrusion is of potential problem primarily after repetitive' excursions into the gap, contaminations on seal surfaces have characteristic behavior, and several methods of leak detection of gaseous leaks are feasible. Both a pressure decay and a mass flowmeter leak detection system were designed' and built for the study. The results are reflected in recommendations of seal testing procedures for several types of' oilfield equipment applications.
O-Ring seals are frequently the sealing mechanism for a variety of offshore pressure containment systems and hence the characterization of sealing performance can be critical. o-ring seals usually : are applied to face or annular concentric applications; performance characteristics of an o-ring seal are affected, by the application type. Of interesting is also the parameters which effect sealing in critical applications. This investigation examines both analytical and experimental parameters affecting sealing performance.
Many rules of thumb regarding o-ring seal performance are used in the oil patch which are based on a qualitative rather than quantitative basis. 1) However, in some applications, traditional approaches are insufficient, especially when applications are extremely leak sensitive.
O-ring seals are capable of high seal integrity, approaching the permeability of the seal material. However, to achieve the high integrity seal requires the thorough understanding of seal performance as affected by pressure direction, temperature, seal position, lubricant, seal damage and sealing surface damage.
This investigation quantifies several aspects of seal performance and compares experimental results to analytical results. Molari 2) reports stresses in o-ring seals; however, the mechanisms of makeup and pressurization remain complex. Included in the investigation are effects of pressure magnitude, pressure direction, lubrication, temperature, seal damage, and seal surface damage. Highly accurate measurement of gas pressure containment requires appropriately sensitive equipment. A flowmeter based leak check system is demonstrated to be light weight, portable, low cost, highly accurate, and provides fast real time measurement of systems.
Because of the nature of the issues of seal performance, a highly empirical approach with analytical support is used. The experimental approach included the use of a flat plate fixture which simulates a large face seal application, and would allow examination of the differences between face seal and barrel seal applications. A doubly nonlinear finite element model is developed of an o-ring in a seal gland and results are compared to experimental observation.
