High-density Polyethylene Liner Research Articles

Study of the Failure Mechanism of a High-Density Polyethylene Liner in a Type IV High-Pressure Storage Tank.

The use of Type IV cylinders for gas storage is becoming more widespread in various sectors, especially in transportation, owing to the lightweight nature of this type of cylinder, which is composed of a polymeric liner that exerts a barrier effect and an outer composite material shell that primarily imparts mechanical strength. In this work, the failure analysis of an HDPE liner in a Type IV cylinder for high-pressure storage was carried out. The breakdown occurred during a cyclic pressure test at room temperature and manifested in the hemispherical head area, as cracks perpendicular to the liner pinch-off line. The failed sample was thoroughly investigated and its characteristics were compared with those of other liners at different stages of production of a Type IV cylinder (blow molding, curing of the composite material). An examination of the liner showed that no significant chemical and morphological changes occurred during the production cycle of a Type IV cylinder that could justify the liner rupture, and that the most likely cause of failure was a design-related fatigue phenomenon.

Quasi-static compression tests of overwrapped composite pressure vessels under low velocity impact

Pressure vessels are being utilised in different applications that are indispensable including automobile, aerospace, underwater vehicles, oil and gas, chemical engineering among other applications. However, there is lack of knowledge on the influence of induced damage and the resulting performance of such vessels under quasi-static loading and axial compression. Specifically, the vessels studied in this study is made up of a high-density polyethylene liner and glass fibre overwraps. Therefore, this research investigated the load bearing capacities and the energy absorbed of the indented vessels in axial and hoop directions to determine the resistance of the vessels after such damaged using experiment, and damage characterisation microscopy, non-destructive testing and analysis.Quasi-static transverse and axial compression testing was performed on composite cylinders made of polyethylene liner and glass fibre overwraps. Both quasi-static and axial compression tests were performed with Universal testing Machines at crosshead speed of 500 mm/min 2.5 mm/min respectively. Microstructural damage characterisation was conducted using microscopy and Dolphicam2 ultrasonic non-destructive testing equipment.This study provides a new understanding on the performance of composite pressure vessel under damaged and undamaged conditions has established the reliability and residual strength capabilities of composites under the scenarios investigated. The results shows that the damage profile and the effect on compressive strength of the composite damaged and non-damaged cylinders was found to be relatively similar. However, when the cylinders are subjected to quasi-static compression, the polyethylene absorbs enough elastic strain energy to recover from the applied compressive load and recover without being plastically deformed. Additionally, the results demonstrate that the quasi-static compression have little or no influence on the axial strength of the cylinders. The damage characterisation on the cylinders revealed fibre break and delamination and local bucking and brooming failure at the bottom of the cylinders. This study has direct impact in composite overwrapped pressure vessels (COPVs) safety design tolerances, manufactururing strategy and operational failure conditions.

Total ammonia nitrogen removal and microbial community dynamics in an outdoor HDPE-lined shrimp pond with no water discharge

This study assessed the characteristics of a zero-discharge outdoor high-density polyethylene (HDPE)-lined demonstration aquaculture pond (400 m2) in terms of water quality variables, total ammonia nitrogen (TAN) removal and oxygen net primary production (NPP) indices, and photosynthetic microbiome over a 76-day crop cycle. The shrimp harvest yield was 4.1 t/ha/crop with an average daily gain (ADG) of 0.15 g/day and a feed conversion ratio (FCR) of 1.49. During shrimp cultivation with a semi-intensive stocking density (40 shrimp/m2), there were low levels of TAN (<1.01 mg-N/L), nitrite (<0.21 mg-N/L), and nitrate (<2.79 mg-N/L). Ammonia removal was mainly mediated by photoautotrophic uptake, as evidenced by the consistent estimated TAN uptake rate of 0.05 ± 0.02 g-N/m3 h, which was calculated based on photosynthesis. The overall TAN removal rate of 0.10 ± 0.08 g-N/m3 h was maintained by suspended microorganisms in water, which exceeded that of microorganisms attached to the HDPE liner surface. A positive oxygen NPP of 0.24–1.16 g-O2/m3 h during light availability indicated prevailing autotrophic conditions. The bacterial community in the water was dominated by Phyla Pseudomonadota (Proteobacteria; 16–32%), Bacteroidota (Bacteroidetes; 15–29%), Cyanobacteria (7–35%), and Actinomycetota (Actinobacteria; 3–39%). The chloroplast amplicon sequence variants (ASVs) indicated abundances of Bacillariophyta (27–97%) and Chlorophyta (0.4–67%). High centric diatom populations (Bacillariophyta) were detected throughout cultivation, while the proportion of green algae (Chlorophyta) was positively correlated with increased TAN availability when feeding was increased. The findings enabled estimations of TAN removal and oxygen NPP rates and provided an understanding of correlations between environmental variables and bacterial and phytoplankton populations in the outdoor lined shrimp pond.

The Influence of Internal Packaging (Liners) on Moisture Dynamics and Physical and Physiological Quality of Pomegranate Fruit during Cold Storage.

Weight loss and decay are common physiological disorders during postharvest handling and storage of pomegranates. The study focused on relating the ability of plastic liners as internal packaging to modify both gaseous and moisture atmosphere around the fruit to moisture dynamics and physical and physiological quality of pomegranate fruit (cv. Wonderful) during storage. Fruit were packed with no-liner, non-perforated ‘Decco’, non-perforated ‘Zoe’, micro-perforated Xtend®, 2 mm macro-perforated high density polyethylene (HDPE), and 4 mm macro-perforated HDPE plastic liners. After 84 days of storage at 5 °C and 90–95% relative humidity (RH), fruit packed with no-liner lost 15.6 ± 0.3% of initial weight. Non-perforated (Decco and Zoe) liners minimised losses to 0.79 and 0.82% compared to Xtend® micro-perforated (4.17%) and 2 mm HDPE (2.44%) and 4 mm macro-perforated HDPE (4.17%) liners, respectively. Clearly, micro- and macro-perforation of liners minimised moisture condensation, fruit decay, and shrivel severity. Micro-perforated Xtend® and macro-perforated 4 mm HDPE were the best treatments in minimising postharvest losses that are often associated with inadequate environment control inside packaging compared to the use of non-perforated liners.

Improving the bonding of polyethylene to E-glass/epoxy composites using ultraviolet irradiation

One of the problems in type-IV pressure vessels (composite pressure vessels with a thermoplastic inner liner) is the quality of bonding between the liner to the outer reinforcement layer. In the present research, the effect of the ultraviolet (UV) irradiation on the surface of the high-density polyethylene (HDPE) for the co-bonding process of E-glass/epoxy composites to HDPE liner was investigated experimentally. To recognize the effect of the UV irradiation on the surface properties, the contact angle measurement, and the atomic force microscopy (AFM) were performed. Asymmetric double cantilever beams (ADCB) tests were conducted to determine the strain energy release rate (SERR) as a factor indicating the crack resistance of the joint. According to the results, it was found that 20 min of UV irradiation exposure time presented the lowest contact angle on the surface of HDPE, and the highest strain energy release rate in ADCB specimens. The result of the tensile test for HDPE under the UV radiation demonstrated less than 8% degradation in the mechanical properties. Therefore, it can be concluded that 20 min of UV irradiation exposure time could be used as a surface treatment of the HDPE liner of type-IV pressure vessels.

Hazardous Waste Disposal in Stromatolitic-Limestone Terrain and Hexavalent Chromium Contamination in Chhattisgarh State, India.

Background.Hexavalent chromium-containing waste from chromite ore processing is a major environmental health hazard due to its high toxicity. There have been instances of improper and unsafe disposal of this waste, leading to environmental health hazards.Objectives.The objective of the present study was to identify the cause of yellow colored water discharge and reported health issues in nearby residents and cattle. In addition, it investigated the improper disposal of chromite ore processing residue (COPR), a hazardous waste, in an abandoned quarry in stromatolitic-limestone terrain in central-east India.Methods.Standard methods of analysis of water and wastewater were used for the analyses of variables, including hexavalent chromium (Cr(VI)), pH, sulfate (SO42−), chlorine (Cl−), total hardness, calcium (Ca(II)), magnesium (Mg(II)), alkalinity and sodium (Na(I)) with proper sampling, quality assurance, and quality control protocols. Onsite Cr(VI) was analyzed using a chromium testing kit, and in the laboratory by atomic absorption spectrophotometry.Results.Large-scale contamination of surface and groundwater was noted due to the migration of hexavalent chromium-contaminated yellow colored leachate. High levels of hexavalent chromium were noted in the samples. The maximum Cr(VI) concentration observed was 1050 mg/L in leachate, 22 mg/L in surface water and 0.26 mg/L in the groundwater sample. Acute health effects were noted in cattle and by residents who consumed the highly contaminated water.Conclusions.A large volume of discharge of hexavalent chromium contamination from the COPR landfill was found, indicating the absence of containment features in the design (double high-density polyethylene liners, clay, leachate collection). Disposal of COPR in an abandoned limestone mine is inadvisable. The highly fractured stromatolitic-limestone environment at the study site was found to offer almost no resistance to the mobilization of Cr(VI) due to the absence of organic or eukaryotic deposition in the stromatolitic environment. It was also noted that the drainage pattern of the area facilitates a possible translocation of contaminated discharge to the nearby river system. Nearby residents were unaware of the adverse impacts of the contaminated leachates and were using the contaminated water for bathing, washing, etc. Applicable Indian governmental regulations regarding the construction of hazardous waste landfills were found to be insufficient with respect to the use of inactive limestone mines as landfill sites.Competing Interests.The authors declare no competing financial interests.

High-Density Polyethylene Liner Safeguards Against Corrosion and Wear

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 199000, “High-Density Polyethylene Liner: Successful Alternative Against Corrosion and Wear Problems in Production Tubing of Mature Fields in Colombia,” by Gloria Isabel Duarte Poveda, Miguel Mateus Barragán, and José Alexander Estévez Lizarazo, Ecopetrol, et al., prepared for the 2019 SPE Latin American and Caribbean Petroleum Engineering Conference, Bogota, Colombia, 5-7 June. The paper has not been peer reviewed. Production tubing in mature fields in the Magdalena Department’s Middle Valley in Colombia has shown a run life between 180 and 300 days, with failures mainly caused by corrosion and abrasive wear or friction mechanisms. Extended use of high-density polyethylene (HDPE) liner in flow and collector lines with corrosion and abrasion problems has resulted in positive results. The complete paper presents the results of evaluation of laboratory and demonstration trials of HDPE liner to mitigate premature failures and prolong the run life of production tubing. Introduction Root-cause analysis determined that failures in production tubing in the mature Casabe and Cantagallo fields could be the result mainly of corrosion by the multiphase fluids transported or as the result of wear mechanisms caused by contact between the internal wall of the tubing and the sucker rod in artificial-lift systems. To solve this problem, HDPE liner was evaluated in the laboratory and implemented in a pilot-scale test. Results proved its ability to absorb abrasion impact from sand particles and resist CO2 corrosion. After 12 months in service, the HDPE liner demonstrated its compatibility with aggressive fluids, remaining thermally stable with no structural variation and absence of swelling, softening, and blistering. After 6 years, the pilot remained failure-free and operationally active. On the basis of these results as well as other research in the literature, HDPE liner was proposed as a downhole alternative to prolong run life of critical wells in the Casabe field. To this end, HDPE lining for carbon steel tubing was developed and manufactured in Colombia through an engineering process that included materials specification, prototype design, mechanical stress analysis, laboratory tests in simulated downhole conditions, redesign of the prototype, and optimization of the production process. To validate the technology, the downhole HDPE liner was installed in three producing wells with progressive-cavity-pump (PCP) artificial-lift systems and a run life of approximately 300 days. After 400 days of service, well intervention was performed not related to tubing; the tubing had not experienced damage and was reinstalled, with a three- to sixfold run-life increase. HDPE Liner Technology HDPE is known for its ability to inhibit corrosion, improve flow fluid because of a lower friction coefficient compared with carbon steel, and resist abrasive wear because of high tenacity properties. The HDPE (PE-100) is used in contact with multiphase fluids (water/crude oil/gas) with maximum service temperature of up to 60°C, depending on the manufacturer. According to laboratory tests, the resistance of HDPE to abrasive wear and corrosion is approximately three times that of carbon steel.

Investigation of structural stability of type IV compressed hydrogen storage tank during refueling of fuel cell vehicle

AbstractThe storage of hydrogen in compressed form has evolved as the primary choice for fuel cell vehicle manufacturers. Currently, composite tanks are a mature and promising option for compressed hydrogen storage for the on‐board application. Type IV tank with carbon fiber/epoxy composite with high density polyethylene liner provides high strength, lightweight, and excellent resistance to fatigue and corrosion. However, high pressure and temperature generated during refueling affect the structural stability of the composite tank. The objective of the work is to investigate the mechanical and thermal response of the tank at different refueling conditions specified in SAEJ2601. For this, finite element analysis was used to examine the stresses, strains, deformation, and failure evolution during refueling. The results show good agreement between simulated and experimental reported burst pressure of the tank with 5.52% difference which might be due to the type of carbon fiber used, fiber winding pattern, number of layers, and loading conditions considered for the analysis. The results presented here show some new insight into behavior of composite tanks under dynamic load conditions of refueling.

Research on Air Pressure Cycle Test of Liquefied Petroleum Gas Cylinder

Air pressure cycle tests were performed on liquefied petroleum gas (LPG) high-density polyethylene liner glass fiber fully wound cylinders. During the repeated filling and discharging of the gas cylinder, the changes of the internal and external surface temperature and internal pressure of the gas cylinder with time were obtained. Through experimental analysis and numerical simulation, the characteristics of the flow field in the cylinder during the pressure cycle test at different pressure cycle rates were studied. The results show that the temperature in the gas cylinder rose steadily during the test. The temperature rise trend of the gas cylinder in Fluent simulation was the same as that in the test. In the air pressure cycle test, the temperature change of the cylinder was larger than that of the cylinder when it was filled with LPG, and the structure and material properties of the cylinder were unchanged. This test can check whether the LPG high-density polyethylene liner glass fiber fully wound cylinders are safe.

Urban heat island mitigation and hydrology performance of innovative permeable pavement: A pilot-scale study

Abstract The permeable pavement is effective green infrastructure that can improve stormwater hydrology and mitigate urban inundation. However, its performance can be sharply weakened when it is used in an area having a high water table and low-permeability soil. This paper proposes an innovative permeable pavement (IPP) wherein capillary columns and an internal water storage zone formed by a high-density polyethylene liner are set up. To investigate the performance of the pavement in terms of its mitigation of the urban heat island effect and hydrological performance in an area with a high water table, four pilot pavements, including an impervious concrete pavement (CP), two permeable interlocking concrete pavements (PICP1 and PICP2), and the IPP, were constructed in a parking lot at our university campus and monitored throughout the year of 2018. Results reveal that the IPP better mitigates the urban heat island effect and had better hydrology performance than the other pavements. PICP1, PICP2, and IPP reduced the overall stormwater volume by 40.2%, 41.9%, and 90.6%, respectively, compared with CP. In 2018, there were only five outflow events for IPP, compared with 32 and 30 for PICP1 and PICP2 respectively. Moreover, the IPP had an obvious effect in mitigating the urban heat island effect throughout the monitoring process. Results revealed that during the hot-summer monitoring period, the maximum surface temperature of the IPP was 15.3, 15.8, and 14.4 °C cooler than those of CP, PICP1, and PICP2, respectively. The cooling effect of the IPP persisted if stormwater remained in the internal water storage zone. Statistical analysis revealed that the IPP significantly mitigated the urban heat island effect and improved the hydrology, compared with CP and PICP1 and PICP2 (p

Evaluation and implementation of High Density Polyethylene liner: Alternative of solution to corrosion-wear problems in flowlines

Failure mechanisms of CO2 corrosion and abrasive wear by production sand have reduced the service life of flowlines and collector lines in Casabe’s mature field located in the middle Magdalena River Valley Basin of Colombia’s Antioquia department, which has required a timely and effective solution. In this work, laboratory tests set to conditions of Casabe’s production fluid were performed to assess abrasive wear and CO2 corrosion resistance on pipeline sections of both HDPE (High Density Polyethylene) and carbon steel API 5L grade X65.&#x0D; The results obtained showed that resistance of HDPE to abrasive wear and CO2 corrosion of HDPE is significant, being three times higher as compared with carbon steel. Additionally, material properties of HDPE remained constant in contrast to performance of carbon steel over time tests. This result is due to the toughness and chemical resistance of HDPE.&#x0D; Based on these results, a field trial was implemented to pilot-scale for evaluating the performance of HDPE liner in a collector line with a service life between 6 to 9 months, which collect fluids of different flowlines from producing wells.&#x0D; After 12 months in service, the field trial of the liner assessed through visual inspection and DSC tests revealed that HDPE liner exposed at multiphasic fluid conditions with production sand remained stable without evidence of swelling, blistering, softening or changes in its geometry associated with liquid hydrocarbon absorption in its physical structure. This was also evidenced in the results of melting temperature and crystallinity obtained from DSC tests before and after exposure to field conditions. Moreover, pilot tests with HDPE lining after six years of service still operate successfully.

Modelling and simulation of high density polyethylene liner installation in engineered landfill for optimum performance

Geomembrane liner is an important part of a landfill system that must be selected and installed properly to avoid high induced stresses and imperfections. Considering a fixed HDPE liner thickness of 2mm and variable masses in this study, the liner was modelled and simulated for 27 scenarios using Solidworks and Artificial Neural Networking approach. Static analysis was further performed on the Solidworks model under a distributed load of 4000kg in properly aligned and improperly aligned conditions to the base and side walls of a landfill system. The minimum stress and width of imperfection obtained from the Solidworks simulation was 77MPa and 34mm while 65MPa and 67mm was obtained from the ANN simulation. The liner failed outrageously in the improperly aligned condition with maximum induced stress of 3,606.521MPa, but no sign of failure was observed for the properly aligned condition which the maximum stress (0.018Mpa) was quite low. This investigation can serve as a guide towards proper installation of geomembrane liners for optimum performance in landfill applications.Keywords: Solid waste, engineered landfill, Geomembrane liner, Installation

A time-saving method for sealing Purdue Improved Crop Storage (PICS) bags

Purdue Improved Crop Storage (PICS) bags were designed to reduce grain storage losses on smallholder farms. The bag consists of three layers: two high-density polyethylene liners fitted inside a woven polypropylene bag. Recently, farmer groups, development relief programs, and government food security agencies have shown interest in PICS bags for large-scale use. PICS bags are conventionally closed by a twist-tie (TT) method, which involves twisting, folding, and tying the lip of each layer individually with a cord. This is not only time and labor intensive, but also may affect the integrity of the liners. We evaluated three new bag closure methods: i) inner liner rolled onto itself and middle liner fold-tied (IR), ii) both liners folded together and tied (FT), and iii) both liners folded and tied separately (FS), along with the conventional twist tie (TT) method. The time to close partially or fully filled 50 kg-capacity PICS bags filled with maize grain was assessed. Results showed that FT was the most time-saving method, reducing bag sealing time by >34% versus the usual TT method. The average internal oxygen levels reached <2% within a week in bags containing grain highly infested with Sitophilus zeamais, while it remained >5% levels for less-infested bags. In both cases, insect population growth was suppressed. Oxygen depletion rates among tying methods remained the same regardless of the closure method used. When large numbers of bags need to be closed, the time-saving FT method is a good alternative PICS sealing method over the conventional twist-tie approach.

Semi Intensive and Semi Biofloc Methods for the Culture of Indian White Prawn, Fenneropenaeus indicus in High-density Polyethylene Liner Ponds

An experiment (triplicated) was conducted to assess the growth and production of Indian white prawn, Fenneropenaeus indicus in semi intensive and semi biofloc culture technique for a period of 120 days in polythene liner ponds (300 m2). Water exchange was done at 10% in semi intensive culture method (control) and zero water exchange was done in semi biofloc method (treatment). Soya hull and molasses were added as carbon sources to induce biofloc formation in treatment ponds. Post larvae (PL20) were stocked at the rate of 100/m2 in each pond and fed with a standard shrimp feed. Shrimp growth, physico-chemical parameters of water, bacteria, phytoplankton and zooplankton population, immune response and physical quality of shrimp were recorded during the period. Significant difference (p < 0.01) in shrimp growth (weight) was observed between control and treatment. Phytoplankton population and total haemocyte count were found to be increased and pathogenic bacteria population decreased in treatment ponds. Strong linear relationship was found between growth and biofloc content in treatment ponds. Shrimp grown in biofloc pond showed better colour and taste compared to control. Semi biofloc technique can be considered as an ideal culture method for bio secure production of white shrimp in semi arid lands.

External pressure induced buckling collapse of high density polyethylene (HDPE) liners: FEM modeling and predictions

Thermoplastic polymers such as HDPE are nowadays widely used as lining materials for oil and gas pipelines. However, during maintenance or unexpected service stoppages, these liners can undergo external pressure induced bucking collapse. The objective of this work is to assess the mechanical response of HDPE liners undergoing buckling collapse by means of Finite element modeling (FEM) simulations on Abaqus 6.10. To accomplish this, an advanced constitutive model, namely the Three Network Model (TNM) was employed. In order to determine the input parameters for the model, a series of tensile and compressive uniaxial tests were conducted. The suitability of the model for this particular application was assessed by contrasting the simulation and the experimental results of a diametral compression test. The complex strain rate and pressure dependent mechanical response of HDPE liners was analyzed by modeling the buckling collapse dynamic event as an increasing volume of fluid entering the gap cavity between liner and host pipe. The model predictions allowed establishing a mathematical relationship between the depressurization velocity of the tubes and the resulting collapse pressure. These relations can be used to improve the current design guidelines for plastic liners.

Assessment of the feasibility of anaerobic composting for treatment of perchlorate - contaminated soils in a war zone

Aims: The objectives of this study were to determine the perchlorate concentrations in surface soils and assess feasibility of anaerobic bioremediation in full-scale for perchlorate-contaminated soils in a war zone. Materials and Methods: Fifteen samples of surface soil were collected using a composite sampling method in the study area. The soil samples, after extraction and preparation, were analyzed by ion chromatography. Anaerobic composting technique (soil excavation, mixing with manure, transfer into treatment cell and cover with a 6-mil high-density polyethylene liner) considered to cleanup perchlorate-contaminated soil in a war zone. Results: The concentration of perchlorate in the soil surface samples ranged from 3 to 107.9 mg/kg, which is more than State advisory levels for residential and protection of domestic groundwater use pathway. This study indicates that technologies, skills, experience, raw materials (manure), lands, and machinery needed for implementation of full-scale composting, are available in the study area. Conclusions: Based on the results, anaerobic composting technique could be considered as a feasible, viable and cost-effective alternative for perchlorate bioremediation in the study area. According to the available of techniques and skills, successful experiences of anaerobic composting in other countries, and potential of study area, The application of anaerobic composting is technically feasible and can be use for perchlorate contaminated soil cleanup in a zone war.

Effects of box liner perforation area on methyl bromide diffusion into table grape packages during fumigation

Plastic liners are used inside boxes of table grapes to retard moisture loss from the grapes and to contain sulfur dioxide gas released inside the packages to control postharvest decay. However, to control organisms of quarantine concern, regulators specify exported packages must be fumigated with methyl bromide (MB), and to enable adequate diffusion of the fumigant into the packages they specify the liners must be perforated. The percentage of the area of the liner that is perforated, formerly stipulated to be not less than 0.3%, was recently increased to not less than 0.9%. Two MB fumigation schedules specified for control of the Chilean mite, Brevipalpus chilensis, were applied to grape packages with a high-density polyethylene liners with perforated areas of 0.9% or with a SO2-releasing liners with perforated areas of 0.3, 0.6, or 0.9%. Package and chamber concentrations were measured repeatedly for up to three hours during MB fumigation at 4.4 or 6.0 °C with a dosage 64 mg L−1 or at 26.7 °C with a dosage 56 mg L−1. Diffusion was similar and rapid into the packages among all perforated areas. MB concentrations inside the packages were not less than 95% of those of the chamber atmosphere within 15 min. After fumigation with an MB dosage 64 mg L−1 at 4.4 °C and subsequent storage at 2.0 °C, mean MB residue content in grapes from most packages 48 h after MB fumigation was below the limit of quantitation of 0.002 mg kg−1. After fumigation with an MB dosage 56 mg L−1 at 26.7 °C and subsequent storage at 2.0 °C, mean MB residue content in grapes from most packages 24 h after MB fumigation was below the limit of quantitation.

Corrosion of galvanised steel cord reinforcement in HDPE composite pipes in petroleum production

In this work, corrosion of galvanised steel cord reinforcement in high density polyethylene (HDPE) composite pipes was studied in electrolytes that developed on the cord surface due to permeation of corrosive species through HDPE liner or damage of the liner in petroleum production. Parametric effects, including solution pH, temperature and concentration of chloride ions, were investigated by electrochemical corrosion measurements. A model was developed to illustrate the mechanism of corrosion of the cord. Corrosion of the galvanised steel cord includes anodic dissolution of Zn coating and the steel substrate. A deposit layer of zinc carbonate and iron carbonate forms on the cord surface to provide protection to further corrosion in the environment. Corrosive ions can diffuse into holes or crevices of the cord assembly to cause corrosion of galvanised steel wires in inner layers. The unique geometry of the cord assembly results in an accelerating localised corrosion at the crevices and holes. Generally, corrosion of the cord is accelerated by increased chloride concentration, reduced solution pH, and elevated temperature.

Changes in pectin methyl esterase activity with different packaging materials and stages of fruit harvesting during cold storage of pear cv. Punjab beauty.

Pear cv. Punjab Beauty has become quite popular in Punjab. Excessive softening during cold storage leading to low shelf life is the major factor limiting its wider adoption. Studies were, therefore, conducted to determine the firmness and pectin methyl esterase (PME) activity at 4 harvest dates (2nd, 3rd and 4th week of July, and 1st week of August). Various packaging materials i.e. corrugated fiber board boxes and crates with high and low density polyethylene liners, corrugated fiber board boxes, crates and wooden boxes were also evaluated for their role in extending the shelf life of fruits. The enzyme activity and fruit firmness was evaluated periodically after 30, 45, 60 and 75days of storage at 0-1°C and 90-95% RH. The firmness of the fruits decreased with the increase in storage intervals but the enzyme activity increased with the storage period up to 60days and declined thereafter. Ripening-related changes in all the harvests were characterized mainly by an increase in the solubilization of pectin with a concomitant decrease in the degree of firmness. There was a continuous increase in enzyme activity with the advancement in harvesting dates and then fell sharply in the advanced ripening stages. Highest pectin methyl esterase activity was in fruits packed in crates followed by wooden boxes and corrugated fiber board boxes while the lowest was recorded in fruits packed in corrugated fiber board boxes with high density polyethylene liners. Therefore, high density polyethylene lined CFB boxes proved to be most effective in preventing the loss in firmness.

Evaluation of the Suitability of a Composite Liner System for Designing a Landfill Bioreactor on Confined Bedrock at Sammanthurai in Sri Lanka

The development of a low cost and environmentally friendly liner system is essential for countries like Sri Lanka because the high-density polyethylene liner is of high cost and much more prone to toxic conditions and failures. This research was carried out at Sammanthurai by using clay-waste polyethylene-clay composite liner and permeability tests were conducted that gave values between 6.3 x 10&lt;sup&gt;-8&lt;/sup&gt; and 2.6 x 10&lt;sup&gt;-8&lt;/sup&gt; cm sec&lt;sup&gt;-1&lt;/sup&gt; under both saturated and unsaturated conditions at the hydraulic head of 86.2 cm. These low permeability values were achieved by laying and compacting one layer after another at the required soil consistency to make a composite liner system. In addition, the use of waste polyethylene based composite liner is more beneficial than the high density polyethylene liner because this waste polyethylene makes an active biofilter which is cheaper and environmentally friendly. The ground penetrating radar survey shows that the confined bedrock is 0.5 to 6.0 m and the water table is 0.4 to 0.5 m from the surface during the rainy season. Therefore, permeate from the liner system will accumulate in the drainage layer above the confined bedrock and that can lead to embankment failure. It is then very important to install a collection and management system to accommodate permeates that were 3.51 x 10&lt;sup&gt;-2&lt;/sup&gt; cm sec&lt;sup&gt;-1&lt;/sup&gt; and 3.86 x 10&lt;sup&gt;-2&lt;/sup&gt; cm&lt;sup&gt;3&lt;/sup&gt; sec&lt;sup&gt;-1&lt;/sup&gt; under saturated and unsaturated conditions, respectively. The &lsquo;water permeates&rsquo; will be reused, thus, overcoming the lack of available water in the dry zone of Sri Lanka for managing wastes as a resource. DOI: http://dx.doi.org/10.4038/tar.v21i3.3300 TAR 2010; 21(3): 266-274