Hydraulic Seal Research Articles

Three-dimensional structure of experimentally produced clay smears: Implications for fault seal analysis

The geometries of clay smears produced in a series of direct shear experiments on composite blocks containing a clay-rich seal layer sandwiched between sandstone reservoir layers have been analyzed in detail. The geometries of the evolving shear zones and volume clay distributions are related back to the monitored hydraulic response, the deformation conditions, and the clay content and strength of the seal rock. The laboratory experiments were conducted under 4 to 24 MPa (580–3481 psi) fault normal effective stress, equivalent to burial depths spanning from less than approximately 0.8 to 4.2 km (0.5 to 2.6 mi) in a sedimentary basin. The sheared blocks were imaged using medical-type x-ray computed tomography (CT) imaging validated with optical photography of sawn blocks. The interpretation of CT scans was used to construct digital geomodels of clay smears and surrounding volumes from which quantitative information was obtained. The distribution patterns and thickness variations of the clay smears were found to vary considerably according to the level of stress applied during shear and to the brittleness of the seal layer. The stiffest seal layers with the lowest clay percentage formed the most segmented clay smears. Segmentation does not necessarily indicate that the fault seal was breached because wear products may maintain the seal between the individual smear segments as they form. In experiments with the seal layer formed of softer clays, a more uniform smear thickness is observed, but the average thickness of the clay smear tends to be lower than in stiffer clays. Fault drag and tapering of the seal layer are limited to a region close to the fault cutoffs. Therefore, the comparative decrease of sealing potential away from the cutoff zones differs from predictions of clay smear potential type models. Instead of showing a power-law decrease away from the cutoffs toward the midpoint of the shear zone, the clay smear thickness is either uniform, segmented, or undulating, reflecting the accumulated effects of kinematic processes other than drag. Increased normal stress improved fault sealing in the experiments mainly by increasing fault zone thickness, which led to more clay involvement in the fault zone per unit of source layer thickness. The average clay fraction of the fault zone conforms to the prediction of the shale gouge ratio (SGR) model because clay volume is essentially preserved during the deformation process. However, the hydraulic seal performance does not correlate to the clay fraction or SGR but does increase as the net clay volume in the fault zone increases. We introduce a scaled form of SGR called SSGR to account for increased clay involvement in the fault zone caused by higher stress and variable obliquity of the seal layer to the fault zone. The scaled SGR gives an improved correlation to seal performance in our samples compared to the other algorithms.

Key Aspects in Addressing Friction in Coaxial Hydraulic Sealing Systems

Ensuring energy-efficient operation of a hydraulic cylinder is determined also by minimizing the friction forces caused by mobile sealing systems. The nature of friction in a sealing system on one hand, and the systems sealing ability, on the other, are determined by the thickness of the fluid film built up at the contact between seal and sealed surface. The paper presents an evaluation of the hydrodynamic pressures that causes the occurrence of a fluid-filled gap between the elements of a coaxial sealing system, as well as the influence of various parameters on its size.

Design & Development of Test Rig for Investigation of Contact Mechanics Phenomena in Reciprocating Hydraulic Seals

Investigation of seal performance is of utmost importance for the development of hydraulic seals especially those employed in high pressure applications and subjected to shock loading. Over the years many apparatus and methods have been adopted to experimentally investigate the seal performance in terms of leakage, friction and wear with one or other limitations. This article describes the design and development of a test rig, which can experimentally assess the performance of reciprocating hydraulic seals. This test rig has features to study experimentally the contact mechanics phenomena at sealing interface and verify theoretical results thus can support development of a sealing system for shock loading applications which involves high pressures of the order of 1000bar. The test rig is in line with ISO standard but equipped with added features to cater to high pressure & shock test and test of rotary seals.

No-Contact Hydraulic Dynamic Seal Characteristic Study Base on CFD

Non-contact hydraulic seal (clearance seal) reduce the leakage by the small clearance between the seal. Non-contact hydraulic seal is the simplest form of a seal. The sealing effect depends on the size of the clearance and pressure difference, the length and parts of the sealing surface quality. Among them, the clearance size of the greatest impact on the sealing performance. The hydraulic systems sealing mathematical and CFD model are built in this paper. Studies have shown that eccentricity ratio, seal clearance and pressure are has impact to hydraulic force and leakage. It should be considered in the engineering design.

Recent developments in hydraulic rod seal simulation

Recent developments in hydraulic rod seal simulation

A Numerical Analysis Method of Hydraulic Seals for Downhole Equipments

The aim of this paper is to present a numerical method to predict the work performance of hydraulic seals used in downhole equipments. The impact of key factors, namely, compression rate and the number of seals, on the wearing behavior of seal components is studied. To simulate the wear process of sealing contact surface, a methodology is built with the iterative wear prediction procedure in which the geometry of the contact interfaceprogressively changes according to the wear model. In this method, the structural and the thermal coupled mechanism is investigated and the performance of seal structure containing different number of seals is discussed. By taking a gear pump used in the downhole robots as a case study, both numerical analysis with proposed method and practical experiment are presented. The simulation results of the worn volume of the seals are consistent with the experiment data. This work provides an effective computerized approach to aid seal components design and manufacturing for downhole equipments.

Experimental assessment of wear and plastic deformations of the hydraulic cylinder elastomeric seals

An original technique and results of experimental evaluation of the relationship between «external» and «internal» wears of used seals of hydraulic power cylinders’ movable joints are presented.

Drilling reveals fluid control on architecture and rupture of the Alpine fault, New Zealand

Rock damage during earthquake slip affects fluid migration within the fault core and the surrounding damage zone, and consequently coseismic and postseismic strength evolution. Results from the first two boreholes (Deep Fault Drilling Project DFDP-1) drilled through the Alpine fault, New Zealand, which is late in its 200–400 yr earthquake cycle, reveal a >50-m-thick “alteration zone” formed by fluid-rock interaction and mineralization above background regional levels. The alteration zone comprises cemented low-permeability cataclasite and ultramylonite dissected by clay-filled fractures, and obscures the boundary between the damage zone and fault core. The fault core contains a <0.5-m-thick principal slip zone (PSZ) of low electrical resistivity and high spontaneous potential within a 2-m-thick layer of gouge and ultracataclasite. A 0.53 MPa step in fluid pressure measured across this zone confirms a hydraulic seal, and is consistent with laboratory permeability measurements on the order of 10?20 m2. Slug tests in the upper part of the boreholes yield a permeability within the distal damage zone of ?10?14 m2, implying a six-orders-of-magnitude reduction in permeability within the alteration zone. Low permeability within 20 m of the PSZ is confirmed by a subhydrostatic pressure gradient, pressure relaxation times, and laboratory measurements. The low-permeability rocks suggest that dynamic pressurization likely promotes earthquake slip, and motivates the hypothesis that fault zones may be regional barriers to fluid flow and sites of high fluid pressure gradient. We suggest that hydrogeological processes within the alteration zone modify the permeability, strength, and seismic properties of major faults throughout their earthquake cycles.

Analysis of Vane Hydraulic Damp Dynamic Seal Mechanism and Performance Influencing Factors

In this paper, the force, deformation and other factors of vane hydraulic damp dynamic seal are researched, which is used of theoretical, simulation about the lip seals sealing damping performance factors. In order to improve sealing performance vane hydraulic damp life, dynamic lip seal design, optimization and performance study is to provide the basis for the theory and engineering applications. The factors influencing sealing performance are considered, such as initial compressibility, sealing sping stiffness. The finite element analysis method can be effectively used to solve nonlinear material and sealing failure problem for the seal design, optimization and performance analysis, which provide a new approach and theoretical guidance to the rubber seal research.

Capability of structural–acoustical FSI numerical model to predict natural frequencies of submerged structures with nearby rigid surfaces

Structural–acoustical model is used in industry to determine natural frequencies of runners and impellers in hydraulic turbomachinery in the stage of design. In these calculations the fluid domain is considered with comparable large distances to stationary parts while there are parts of the submerged structure (runner or impeller) that are extremely close (in relation to its thickness) to a rigid surface (hydraulic seals). These seals are not considered in the numerical model because it is assumed that structural–acoustical model is not capable to predict natural frequencies with nearby rigid surfaces. The present work builds a fluid structure interaction numerical model based on structural–acoustic coupling, checks the numerical model’s accuracy, and determines its capability to predict natural frequencies reduction due to nearby rigid surfaces comparing this model against experimental data of submerged cantilever plates. It is found that the structural–acoustical model can accurately predict the natural frequencies for submerged structures with nearby rigid surfaces with averaged absolute errors of 2.5%. This is an interesting result because it suggests that simulation of runners and impellers can be carried out considering the effect of hydraulic seals, therefore, obtaining natural frequencies that are closer to those found under operation.

Effects of multi-scale viscoelasticity of polymers on high-pressure, high-frequency sealing dynamics

Viscoelastic effects on the performance of a hydraulic rod seal are examined using a visco-elastohydrodynamic model. The model consists of coupled macro and micro scale deformation and contact mechanics analyses and micro scale fluid mechanics analysis. Dynamic mechanical analysis and a constrained optimization method are used to extract the spectrum of relaxation time scales and corresponding instantaneous elastic moduli associated with the seal polymer, required by the model. Simulation results show that the seal performance, including leakage prevention and friction force, depends on the relationship between the characteristic time constants of the polymer’s molecular chains and the seal cycle frequency.

Analysis of Vane Hydraulic Damp Static Seal Mechanism and Performance Influencing Factors

Based on the performance of Vane hydraulic damp O-ring seal ,simulation about the O-ring seal was applied by nonlinear finite element analysis method. The factors influencing sealing performance are considered, such as initial compressibility, sealing materials. Applying the method, the seal structure was designed and optimized. At the same time, the sealing performance was improved, and the contract pressure was increased. The finite element analysis method can be effectively used to solve nonlinear material and sealing failure problem for the seal design, optimization and performance analysis, which provide a new approach and theoretical guidance to the rubber seal research. The seal material and compression ratio are both great influence on the sealing performance , which should be based on working conditions to select the appropriate sealing materials.

Numerical modelling of hydraulic seals by inverse lubrication theory

This article describes a methodology used to achieve a numerical analysis of hydraulic seals by the inverse hydrodynamic lubrication method. The main novelties consist of taking into account the influence of the shear stresses in the lubricant film and in the treatment of hydrodynamic effects on the seal inlet. Each step is detailed and discussed in terms of possible error over the predicted seal performances. It has been shown that the pressure field computed directly from the structure model does not give a realistic approximation of the hydrodynamic pressure in the inlet zone, and a hydrodynamic correction is necessary. Furthermore, it has been shown that if the tangential friction due to the shear stress in the lubricant film is not taken into account, error of about 5 per cent can be made, concerning the predictions of leakage and friction force.

The Design of Test System for Comprehensive Performance of Clutch Booster

According to the enterprise standards of "assembly and test norms for ZQ2005 clutch booster", the test projects for comprehensive performance, including pressure seal, hydraulic seal and input -output performance were researched [1]. An integrated test system based on electrical components, such as the data acquisition card, motion control card, supercharger, proportioning valve, solenoid valve was designed. And the data acquisition and data processing modules of detection system based on MFC were developed. Finally, the test procedure and the experimental program were designed. And the TianLong clutch booster 1608ZB7C-010 was tested synthetically efficiency. The results show that the detection system meets the test requirements in contrast to the test data and curves measured by the foreign instrument.

Efficiency-Reinforcement Design Study for Elastomeric Hydraulic Reciprocating Seal Based on Function Analysis

The efficiency-reinforcement design framework for hydraulic reciprocating seal is proposed, and the function attributes analysis model for reciprocating seal system is built. Through analyzing the components, functions and attributes of elastomeric hydraulic reciprocating seal system, the attributes that influence seal efficiency-reinforcement are identified. By eliminating the function attributes that lead to seal leakage and seal failure, and/or by improving the function attributes that are insufficient in seal, the efficiency-reinforcement design concept can be obtained. A new seal efficiency-reinforcement design solution is also present using this method.

Elastohydrodynamic lubrication simulation of O-ring and U-cup hydraulic seals

The recent development of an elastohydrodynamic lubrication rod seal model has made possible the simulation of hydraulic seal performance for design and selection purposes. This model consists of coupled fluid mechanics, contact mechanics, deformation, and thermal analyses. The model yields predictions of such characteristics as leakage and the friction force on the rod, as well as film thickness, fluid pressure, and contact pressure distributions. The model has been used in the selection process for the rod seal in a mini-actuator of a fluid power orthosis (orthopaedic device used to improve the function of movable parts of the body). Two alternative seals have been analysed and compared, an O-ring seal and a U-cup, both of polyurethane.

Rome metro line C: Breakthrough using equipment provided with hydraulic seal

Geomechanics and TunnellingVolume 4, Issue 2 p. 166-169 Site Report Rome metro line C: Breakthrough using equipment provided with hydraulic seal Ing. Gianluca Gulino, Ing. Gianluca Gulino info@metrocspa.com Metro C Spa, via di Torre Spaccata n.172, lotto 3, 00169 Roma, ItalySearch for more papers by this authorIng. Marco Barbanti, Ing. Marco Barbanti info@metrocspa.com Metro C Spa, via di Torre Spaccata n.172, lotto 3, 00169 Roma, ItalySearch for more papers by this authorIng. Tommaso Paolini, Ing. Tommaso Paolini info@metrocspa.com Metro C Spa, via di Torre Spaccata n.172, lotto 3, 00169 Roma, ItalySearch for more papers by this author Ing. Gianluca Gulino, Ing. Gianluca Gulino info@metrocspa.com Metro C Spa, via di Torre Spaccata n.172, lotto 3, 00169 Roma, ItalySearch for more papers by this authorIng. Marco Barbanti, Ing. Marco Barbanti info@metrocspa.com Metro C Spa, via di Torre Spaccata n.172, lotto 3, 00169 Roma, ItalySearch for more papers by this authorIng. Tommaso Paolini, Ing. Tommaso Paolini info@metrocspa.com Metro C Spa, via di Torre Spaccata n.172, lotto 3, 00169 Roma, ItalySearch for more papers by this author First published: 08 April 2011 https://doi.org/10.1002/geot.201190012AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume4, Issue2April 2011Pages 166-169 RelatedInformation

Hydrogeological and Geomechanical Aspects of Underground Coal Gasification and its Direct Coupling to Carbon Capture and Storage

Underground coal gasification (UCG) using boreholes drilled from the surface has been feasible for almost a century, but is only now being implemented in market economies. Good analogues for the hydrogeological effects of UCG are provided by longwall mining. Careful planning of UCG void locations and dimensions can result in minimal disturbance of overlying aquifers as close as 40 m above the burn zone. Moreover, development of a pressure arch above the zone of net strata extension can provide a hydraulic seal to prevent vertical fluid migration. Injection of CO2 into former UCG voids ought to be possible where these are present at depths in excess of ≈ 800 m. Analogies to longwall mining suggest that extensional deformation immediately above the burn zone will render sufficient pore space accessible to accommodate all of the CO2 arising from gasification. In the absence of adequate engineering, the boreholes used in the UCG-CCS processes represent the most likely leakage pathways for injected CO2. Hence high-quality borehole engineering will be required, taking full account of thermal performance of casing and grout, and geophysical testing of borehole integrity. An agenda for management of groundwater issues at all stages in the life-cycle of UCG and UCG-CCS has been developed, as an aide memoire for future developments.

Working chambers for shaping materials with a fluid at ultrahigh pressure

This article discusses problems in the design of the working chambers for the hot and cold shaping of different materials by an ultrahigh-pressure fluid. A description is given of new hydraulic seals that operate at pressures up to 2.0 GPa and are used in modern chambers designed for hydrostatic shaping. An engineering method is presented for designing such chambers on the basis of different optimization criteria.

Repository-Scale Modeling of the Long-Term Hydraulic Perturbation Induced by Gas and Heat Generation in a Geological Repository for High-and Intermediate-Level Radioactive Waste: Methodology and Example of Application

The current design of a deep geological repository for high- and intermediate-level radioactive waste in France consists of a complex system of different underground structures (ANDRA, Dossier 2005 Argile, les recherches de l’Andra sur le stockage geologique des dechets radioactifs a haute activite et a vie longue, collection les Rapports. Châtenay-Malabry, France, 2005). For a comprehensive understanding of the long-term hydraulic evolution of the entire repository, numerical non-isothermal two-phase flow and transport simulation, taking into consideration the generation, accumulation, and release of hydrogen gas and decay heat, are compulsory. However, a detailed numerical model of the entire repository system would require a tremendous computational effort and pose a laborious task with respect to the operation of the model. To handle these difficulties, we have developed an efficient method for the numerical modeling of a complete repository system and its geologic environment. The method consists of the following steps: (i) subdivision of the repository plane into a large number of “sectors” based on the position of hydraulic seals and on other geometrical considerations, (ii) exploitation of existing symmetries (inside or between sectors), (iii) adoption of the “multiplying concept”, and (iv) connection of the individual sectors at the drift interfaces to form the entire repository model. Each sector is modeled as a three-dimensional (3D) block, and the entire model is computed with TOUGH2-MP. The method allows for a massive reduction in overall finite-volume elements and, at the same time, provides an adequate representation of the small-sized structures in the repository. The main characteristics of the method and its application to an entire deep geological repository system in a clay host rock are presented.