Barrier Envelope Research Articles

Technology Update: Using Schematics for Managing Well Barriers

Technology Update Well integrity and well barriers have been part of the exploitation for oil and gas for nearly a century, with the introduction of the blowout preventer (BOP) in the 1920s. The concept of creating well barrier schematics was inaugurated in Norway in 1992, long before the accidents on the Montara platform in 2009 and the Deepwater Horizon rig in 2010 elevated the global focus on well integrity. A Common Understanding Yet there are large variations in the industry’s perception of well integrity and well barriers, despite the daily use of these terms by drilling and well engineers. Well integrity is defined by the Norsok Standard D-010 (Rev. 4, 2013) as an “application of technical, operational, and organizational solutions to reduce risk of uncontrolled release of formation fluids and well fluids throughout the life cycle of a well.” The definition is so broad that engineers might prefer something that lends itself to a more practical, hands-on description. This is where the well barriers principle comes into play. If you ask someone what a well barrier is, you will get many different answers. However, it is possible to unify them on the concept of an envelope. The well barrier envelope is the physical system that prevents fluids from flowing unintentionally from the formation into another formation or to the external environment. The envelope is designed to contain this pressurized effluent. Barrier Envelope Principle The benefit of using the envelope principle is that we can create two independent envelopes, one outside of the other. We will have primary containment of the pressurized fluid, so that no matter where the pressure might escape through the primary barrier, there will always be a secondary containment behind the primary barrier as a backup (Figs. 1a and 1b). To be consistent and to avoid ambiguity, it is best to define the secondary barrier as the last line of defense rather than barrier No. 2.

Degradation of VIP barrier envelopes exposed to alkaline solution at different temperatures

As covering layers, barrier envelopes of VIPs are always exposed to severe environmental conditions, including high temperatures, alkaline environments and local stress concentration when used as thermal insulation material in concrete structures. This study investigated the time-dependent degradations of three types of commonly used envelopes (aluminium film, metallized film and metallized film coated with alkali-resistant (AR) fibreglass mesh) and VIPs covered by these three envelopes by simulating environmental conditions with four types of alkaline solutions (NaOH solution with pH=7, 11, 13 and saturated Ca(OH)2), two different temperatures (20°C and 60°C) and local stress concentration. The results showed that stress and high temperature accelerated the degradation of envelopes and that such degradation became more serious with increased pH value and temperature. It was also observed that the thermal conductivity of VIPs increases quickly when they are exposed to higher alkalinity combined with high temperatures. After 6-week submerged in saturated Ca(OH)2 solution at 60°C, the thermal conductivity of VIPs increased from 4.413mW/mK to 13.049mW/mK for aluminium foil, from 5.375mW/mK to 10.982mW/mK for metallized film, and from 5.786mW/mK to 8.110mW/mK for AR fibreglass mesh-reinforced film, respectively.

Studies on the barrier performance and adhesion strength of novel barrier films for vacuum insulation panels

Novel cost efficient high barrier envelopes are developed for vacuum insulation panels. In order to fulfil the required maximum oxygen permeability (at 23°C and 50% relative humidity (RH)) of 1×10−14m3(STP)m−2day−1Pa−1 and water vapour transmission rate (at 23°C and 85%→0% RH) of 1×10−6kgm−2day−1, hybrid polymeric (ORMOCER®) and aluminium barrier layers are combined. Using roll-to-roll processes, these materials are deposited from the liquid or gas phase on top of a poly(ethylene terephthalate) substrate film. The low adhesion strength observed between aluminium and ORMOCER® layers is significantly increased by the deposition of an additional aluminium oxide layer between the two materials. The lamination of a polyethylene or polypropylene sealing film does not weaken the adhesion strength. The resulting barrier structure has reached an oxygen permeability of lower than 5×10−14m3(STP)m−2day−1Pa−1 (at 37°C and 30% RH). Electrochemical impedance spectroscopy gives evidence for a possible penetration of the ORMOCER® lacquer into the aluminium oxide layer (synergistic effect), which explains the improved adhesion and barrier performance due to the aluminium oxide layer.

Thermal insulation property and service life of vacuum insulation panels with glass fiber chopped strand as core materials

Thermal insulation performance and service life of vacuum insulation panels (VIPs) dramatically depend on the internal pressure of VIPs. To analyze internal pressure increase of VIPs, VIPs in various geometric sizes are manufactured from threefold metalized polymer laminate barrier envelopes and glass fiber chopped strand core materials. The gas permeation contribution to the internal gas pressure of VIPs through envelope surface area and perimeter are investigated based on theoretical calculation and experiments. The trend of calculated pressure increasing rate is consistent with experimental results. The gas permeation through barrier laminate surface area is measured by a helium leak detector while the thermal conductivity of VIPs is measured by thermal conductivity meter. The accelerated aging experiments are carried out at different temperatures and service life model is proposed based on Arrhenius law. A low cost composite adsorbent is investigated, absorption property of which for water vapor is measured at various relative humidity. As a result, it is recommended to use large square VIPs with thickness of 1.0–2.5cm. Service life of 10–15 years or above 20 years can be achieved by adding different adsorbents for different application fields.

Hints for an additional aging factor regarding the thermal performance of vacuum insulation panels with pyrogenic silica core

Up to now, it was believed, that the deterioration of vacuum insulation panels (VIP) thermal properties is primarily due dry gas and moisture permeation through its barrier envelope. The increase in internal pressure and the absorption of water on the large internal surface of the porous silica core deteriorates the thermal performance by inducing an increase in the thermal conductivity. Based on these findings aging models predicting the evolution of the centre-of-panel thermal conductivity were developed a decade ago. Recent measurements on monitored VIPs installed on a roof for about 8 years have shown a discrepancy to this model by an amount of 1.1–1.4 mW/mK in their centre-of-panel thermal conductivity. The authors presume a redistribution of Si and O atoms around the neck of SiO2 particles, enhancing the structural heat transfer trough the SiO2 skeleton as a third aging factor.

Optimization of glass fiber based core materials for vacuum insulation panels with laminated aluminum foils as envelopes

Two glass fibers with different production process, marble melt process and flame attenuation process (named as chopped strand and flame attenuated glass wool), as core materials of vacuum insulation panels (VIPs) respectively are investigated in this paper. The dependence of thermal conductivity of two glass fibers on gas pressure is determined based on theoretical calculation and experiment. Two VIPs are manufactured with laminated aluminum foils as envelopes and two glass fibers respectively as core materials for performance comparison of thermal conductivity and service life. The increase in thermal conductivity of VIP with time is measured, which depends on temperature and relative humidity. It is found that service life above 15 years can be expected for VIP with chopped strand mat core material and the high gas barrier envelope with four-layer structure of PA(15 μm)/metalized PET(12 μm)/Al(6 μm)/PE(50 μm) only if desiccants or getters are integrated into core materials.

Defective Plastic Infection-Control Barriers and Faulty Technique may Cause PSP Plate Contamination Used in Digital Intraoral Radiography

Infection control in digital intraoral radiography: evaluation of microbiological contamination of photostimulable phosphor plates in barrier envelopes. MacDonald DS, Waterfield JD. J Can Dent Assoc 2011;77:b93. Arthur S. Kuperstein, DDS To determine the infection-control effectiveness of a plastic barrier envelope system for PSP plates. Information not available Cohort study Level 2: Limited-quality, patient-oriented evidence Not applicable

A Novel Rigid Vacuum Insulation Panel: Vacuum Insulation Sandwich

VIP (Vacuum insulation panel), as a high performance insulation component, combine with limited thickness, have recently been introduced to numerous energy conservation applications. VIP consists of a highly insulating core material and a gas tight barrier envelope which is generally composed of plastic film and aluminum film. When the envelope is stainless steel sheet, VIP is called VIS (vacuum insulation sandwich). Because of this hardly permeable rigid barrier, VIS presents more fantastic properties such as resistance against external mechanical loads and penetration of atmospheric gases and water vapor. Consequently, the service life of VIS is significantly longer than that of VIP. Detailed structure and some practical applications of VIS elements are also reviewed in this paper.

Investigation of the resistance welding of multilayers aluminum-coated polymer complexes used as envelopes of vacuum insulation panels

Vacuum Insulation Panels (VIPs) are thermal insulators consisting of a core material enveloped by a high barrier film or envelope required to maintain the vacuum.Multilayered aluminum-coated polymer complex are the common barrier envelopes of VIPs used as high performance thermal insulation in building applications. The multilayer complex is sealed to maintain the vacuum for a long period of time. From a mechanical and barrier properties standpoint, sealed edges represent the weak point of the envelope assembly. This paper investigates the influence of sealing parameters on the properties of the weld. T-peel and tensile tests in combination with Optic Microscopy observations were used to characterize the heat seals. A minimum seal initiation temperature of 115°C was identified for the studied complex. Peel strength increased sharply to reaching a maximum value at (140°C–5s), which considered as optimum temperature–time couple. Above and beyond these values, a gradual decrease was observed and microscopic images indicate the appearance of roll generated by the expelled polymer mass from the center to the edges of the weld which strongly impacts the morphology of the welded area.

Effective thermal conductivity of a staggered double layer of vacuum insulation panels

The use of vacuum insulation panels in buildings has gradually increased in the past few years and developments in their production have occurred in parallel. This has mainly lead to an optimization of different hygro-thermal properties of both the core material as well as the envelope. The issue of thermal bridges caused by the 300nm thin metallic layers of the barrier envelope and by the joints between two adjacent panels remains. The present study investigates the influence of these thermal bridges on the effective thermal conductivity of a staggered double-layer of vacuum insulation panels. For this purpose a series of guarded hot plate measurements on single- and double-layers of vacuum insulation panels was carried out. The variety of the existing thermal bridge situations was accounted for by different panel size compositions. The results hereof were compared to those of a simplified numerical model. The target is to determine the effective thermal conductivity by a minimum number of required tests and the simplest numerical model. This will enable the determination of additional heat loss induced by the mentioned thermal bridges for a specific envelope laminate type without knowing the details of its composition especially the metallic layers.

Vacuum maintenance in vacuum insulation panels exemplified with a staggered beam VIP

Thermal insulation performance of a vacuum insulation panel (VIP) is highly dependent on the inner pressure of the VIP. Long-term vacuum maintenance characteristics are investigated in this study for a VIP with an example of polymer staggered beam structure as the core material. Various gas sources deteriorating the vacuum level in the VIP are investigated based on theoretical models and experiments. Gas permeation occurring through heat-sealed flanges and pinholes in the barrier envelope is the largest gas leakage source. The calculated gas permeation rate is in accordance with the experimental result. To reduce these permeations, a three-side sealing envelope and double enveloping are proposed. Outgassing from the core material and inner surface of the envelope is also critical. It is significantly reduced by a baking pre-treatment in vacuum. When the estimated total gas load exceeds the allowable limit within a few years, a getter material may be applied. Double enveloping structure with a getter is promising as it ensures a lifetime of more than 20 years.

Focused ion beam (FIB) etching to investigate aluminium-coated polymer laminates subjected to heat and moisture loads

Multilayered aluminium-coated polymer laminates are the common barrier envelopes of vacuum insulation panels used as high performance thermal insulation in building applications. These laminates are made of up to ten distinct layers including three aluminium barrier layers applied by vacuum web coating. During their expected lifetime, which is required to last longer than 20 years, they will be subjected to heat and moisture loads induced by internal and external climatic conditions. This paper investigates the deteriorations of the barrier function of two different laminates commonly used for the production of vacuum insulation panels. These were subjected to well defined exterior heat and moisture loads and investigated by means of focused ion beam etching. Delamination of the polyurethane adhesive layers and stress induced relaxation in them are made visible. Oxidised aluminium layers are also detected by this method.

Analytical Model for Predicting Thermal Bridge Effects due to Vacuum Insulation Panel Barrier Envelopes

AbstractBecause of a necessity for sustainability and thus for a reduction of the amount of primary energy generated with fossil fuels, vacuum insulation panels (VIP) have recently caught the attention of practitioners in the building industry. The reduction of layer thickness may be considered among the most promising features for large‐scale application of VIPs in buildings. The high barrier laminate (or casing) with relatively high thermal conductivity envelops the core material, thus introducing a thermal bridge at the panel edges and corners. Especially for barrier laminates containing ‘thick’ metal foils, the thermal bridge effect needs to be considered thoughtfully. In this contribution analytical models are presented which on the one hand allow rapid estimation of the VIP's overall thermal performance and on the other hand show the influence of material and geometric parameters on this performance. The analytical models are validated through numerical simulations.

Analytical Models for Calculating Thermal Bridge Effects Caused by Thin High Barrier Envelopes around Vacuum Insulation Panels

Although vacuum insulation panels (VIPs) are thermal insulators with very low center-of-panel thermal conductivity, their effective thermal conductivity is raised significantly due to large edge heat fluxes caused by a continuously enveloping high barrier laminate, especially if metal based foils are applied. This study therefore presents and validates two analytical approximating models for calculating this thermal edge effect for thin high barrier laminates around VIPs. A comparison of these models with numerical simulations shows that they can be applied with an inaccuracy of <5% for idealized barrier laminates, considering the limitations specified. These models also demonstrate that the linear thermal transmittance, representing this edge effect, amongst others depends on envelope thickness and thermal conductivity, panel thickness, and center-of-panel thermal conductivity. Moreover, this study shows that these models are able to estimate the linear thermal transmittance resulting from more realistic VIPs with seams near their edges, as well. For these realistic panels, deviations between numerical data and prediction model maximally amount to about 9%. Using the presented models then, enables VIP designers, architects, and building engineers to estimate the overall thermal performance of a VIP.

Investigation of multilayered aluminium-coated polymer laminates by focused ion beam (FIB) etching

Multilayered aluminium-coated polymer laminates are the common barrier envelopes of vacuum insulation panels used as thermal insulations in building applications. These laminates are made of up to ten distinct layers including three barrier layers made by vacuum web coating. The thickness of each aluminium layer (30–100 nm) influences the overall thermal performance of the panels as well as the temperature at joints between adjacent panels. Two commercially available barrier envelopes have been investigated by means of focused ion beam etching for an adequate determination of the effective thickness of the aluminium layers. Additional information has been gained on interfacial failure between aluminium and its neighbouring polymeric film or adhesive layer as well as disruptions in the aluminium layer itself. These provide hints related to air and moisture permeation, the key properties of barrier envelopes in building applications where a lifetime of 20 to 50 years is required.

Effective thermal conductivity of vacuum insulation panels

Vacuum insulation panels (VIPs) with evacuated fumed silica as the core material and different barrier envelopes were subjected to a series of tests in a guarded hot plate apparatus. The process was conducted to determine thermal conductivity at the centre-of-panel and the edge effect, i.e. the linear thermal transmittance due to the thermal conductivity of the barrier envelope, which is many orders of magnitude higher than that of the evacuated fumed silica. Numerical simulations using a two-dimensional model were carried out in parallel and compared with measured results. In a further step, the influences of different parameters such as panel size, metal layers in the barrier envelope and the shape of the joint between two adjacent VIPs were quantified. Based on these findings, an effective thermal conductivity can be attributed to a system of VIPs. Investigations were performed within the framework of an international research programme of the IEA, Annex 39 ‘High Performance Thermal Insulation in Buildings and Building Systems’, Subtask B.

Advanced insulations for refrigerator/freezers: the potential for new shell designs incorporating polymer barrier construction

The impending phase-out of chlorofluorocarbons (CFCs) used to expand foam insulation, combined with requirements for increased energy efficiency, make the use of non-CFC-based high performance insulation technologies increasingly attractive. The majority of current efforts are directed at using advanced insulations in the form of thin, flat low-conductivity gas-filled or evacuated orthogonal panels, which we refer to as Advanced Insulation Panels (AIPs). AIPs can be used in composite with blown polymer foams to improve insulation performance in refrigerator/freezers (R/Fs) of conventional design and manufacture. This AIP/foam composite approach is appealing because it appears to be a feasible, near-term method for incorporating advanced insulations into R/Fs without substantial redesign or retooling. However, the requirements for adequate flow of foam during the foam-in-place operation impose limitations on the allowable thickness and coverage area of AIPs. This report examines design alternatives which may offer a greater increase in overall thermal resistance than is possible with the use of AIP/foam composites in current R/F design. These design alternatives generally involve a basic redesign of the R/F taking into account the unique requirements of advanced insulations and the importance of minimizing thermal bridging with high thermal resistance insulations. The focus here is on R/F doors becausemore » they are relatively simple and independent R/F components and are therefore good candidates for development of alterative designs. R/F doors have significant thermal bridging problems due to the steel outer shell construction. A three dimensional finite difference computer modeling exercise of a R/F door geometry was used to compare the overall levels of thermal resistance (R-value) for various design configurations.« less

Barrier Envelopes for X‐ray Films

Barrier Envelopes for X‐ray Films