Conventional Lining Research Articles

Performance evaluation of a novel adaptive temperature-controlled lining technology based on thermo-hydro-mechanical coupling analysis

To mitigate the hazards of high geotemperatures in hydraulic tunnels, the performance of a novel adaptive temperature-controlled lining was investigated across various working phases of high geothermal tunnels using the thermo-hydro-mechanical coupling analysis with the finite element software COMSOL. The results indicated an error margin of only 2% to 6% compared to the field measurements, proving the feasibility of the method. Compared with the conventional concrete lining, the adaptive temperature-controlled lining reduced the average inner wall temperature by approximately 55% during construction, decreased the maximum thermal deformation by approximately 37%, transferred the localized energy elevation from the inner wall to the outer lining, and lowered the maximum elastic strain energy density by approximately 62%. During the water-filled operational phase, the radius of temperature influence in the low-temperature zone of the adaptive temperature-controlled lining expanded by approximately 20%, whereas the maximum thermal stress decreased by approximately 76%, the thermal deformation by 50%, and the elastic strain energy density by 88%. Throughout both the construction and operational phases, the adaptive temperature-controlled lining significantly enhanced the temperature control, improved the stress distribution, and reduced the risk of concrete cracking. These findings could offer the innovative engineering insights into the design, construction, and operation of high-geothermal tunnels.

Steel Fibre-Reinforced Shotcrete as an alternative to conventional concrete tunnel lining: a case study of Gulpur Hydropower Project

ABSTRACT For the first time in Pakistan, Steel Fibre-Reinforced Shotcrete (SFRS) is used as the final lining for the Diversion Tunnels of Gulpur Hydropower Project. The project’s diversion tunnels were opened for operation since 2016 and along with the normal operating inflow of the river, over the course of 3 years, have experienced two major floods as well. Due to schedule constraints, conventional-reinforced concrete lining was only used in the invert portion and the side walls up to a height of 1.6 m in both tunnels and for the remaining portion of the tunnels, SFRS was used. The major advantage of SFRS over conventional lining is the reduced construction time compared to when conventional lining is used. Quantity and cost comparisons of both lining methods show that SFRS is almost 25% more costly per meter length of tunnel while more than 40% faster to construct compared to conventional lining. As-built sections show very little reduction in the area of lining which exemplifies SFRS as not only stable but flood resistant as well.

Analysis of Energy Loss through Conventional Refractory Lining in Refinery Heater and its Conservation Measures

The work of this project is to analyze theinsulation materials currently used in the furnace of CPCL refinery which is a crude distillation unit heater to minimize the heat loss through the radiant wall section by substituting them with advanced insulating materials.There are some advanced materials whose properties are well suited for the insulation purpose in the furnace wall which could apparently reduce the heat loss through the walls. The general properties which include weight, thickness, thermal conductivity, are calculated to prove that these materials can be used as a replacement to those of the regular insulation materials.The materials which have been taken for analysis can reduce heat loss and improve thermal efficiency it will not require much maintenance activities compared to the old insulation and installing the new insulation is much easier than old as it can be handled easily.This paper will prove that replaced materials will act as an effective insulation than old type.

Support performance of functionally graded concrete lining

By inverse analysis, the concept of functionally gradient is introduced into thick-walled lining to improve its supporting performance. Analysis shows that an ideal functionally graded lining has a higher elastic limit than a conventional single-layered lining. The ideal functionally graded lining model requires that the Young’s modulus of the material should monotonically increase with the increase radius, which cannot be achieved in a single-layered lining. A composite lining composing of multi layers that have different Young’s modulus can approximately function as an ideal functionally graded lining. Such a two-layered lining was studied and was compared with a single-layered lining. The study involved elasto-plastic analysis and model testing. The elasto-plastic analysis shows that the elastic load bearing capacities of the ideal functionally graded lining and the two-layered functionally graded lining are higher than the traditional single-layered lining. The model test results confirmed the analytical conclusion.

Physics of failure analysis of power section assembly for positive displacement motor

Power section assembly is the core part of positive displacement motor (PDM), and its mechanical behavior and service life determine the drilling efficiency and cycle. In this paper, fault tree of power section assembly was established, failure reasons were analyzed and improvement measures were put forward. Finite element models of conventional lining and uniform wall thickness lining of 5/6 PDM were established, and the mechanical behaviors were investigated. Working parameters such as drilling fluid pressure, rubber hardness, downhole temperature and pressure difference were discussed. The results show that wear and rust are the main failure modes of the rotor. Failure modes of rubber lining are wear, tear, rupture, peeling off, thermal failure and fatigue failure. Under the action of drilling fluid pressure, the maximum effective stress of rubber lining appears in the bottom of arc, and the minimum stress appears at the top of arc. But deformation distribution is opposite to the effective stress. Deformation of uniform wall thickness lining is more uniform. Effective stress of the lining increases with the increasing of drilling fluid pressure and rubber hardness, but it decreases with the downhole temperature increases. Deformation of the lining increases with the drilling fluid pressure increases, but it decreases with the increasing of rubber hardness and downhole temperature. Effective stress and deformation distribution of rubber lining are more uneven with the pressure difference increases. High stress area lies between the two smallest chambers.

Three-year clinical evaluation of class II posterior composite restorations placed with different techniques and flowable composite linings in endodontically treated teeth.

The objective of this study is to evaluate the clinical performance of direct resin composite restorations placed with different techniques (incremental or bulk) and different flowable linings (conventional or bulk-fill) in endodontically treated teeth. Forty-seven pair class II (mesio-occlusal or disto-occlusal) composite restorations were placed in 37 patients. In all cavities, Adper Single Bond 2 was used. In one of the cavities of each pair, a conventional flowable composite, Aelite Flo, was applied in approximately 2mm thick, and the remaining cavity was restored incrementally with GrandioSO. In the second cavity, a bulk-fill flowable composite, x-tra base, was applied in approximately 4mm thick in bulk increments and the remaining 2-mm occlusal part of the cavity was restored with GrandioSO. All cavities were restored with open-sandwich technique by the same operator. At baseline and after 6-month, 1-, 2-, and 3-year follow-up visits, restorations were evaluated by modified USPHS criteria. At 3-year recall, 33 restorations with Aelite Flo lining and 33 with x-tra base lining were available. Two restorations from each group (6.0%) were scored as Bravo in terms of surface texture. One restoration's color match from x-tra base group scored as Bravo (3.0%). All other evaluated criteria were scored as Alfa (100%) for all restorations. No statistically significant difference between the two groups was found in all evaluated criteria during 3-year period (p>0.05). Bulk-filling technique showed clinically acceptable performance comparable to the incremental technique. Restorations placed with bulk-filling technique with x-tra base lining and incremental technique with a conventional flowable lining showed highly clinical performance over 3-year period.

REDUCING BUG-HOLES ON TUNNEL LINING CONCRETE BY USING COVERING SHEETS

This study focused on bug-holes on sidewalls of tunnel lining concrete. The bug-holes of lining concrete may negatively affect aesthetics and durability of NATM (New Austrian Tunneling Method) tunnels. Most bug-holes appeared on concrete surface are generated from entrapped air during consolidating concrete. In particular, the sidewall of tunnel lining is constructed with negative angles, so bug-holes are often observed on the sidewall. Seven concrete specimens were prepared to simulate conventional tunnel lining. In the experimental investigation, breathable-waterproof material sheets and permeable sheets were used. The primary experimental parameters are (a) covering-sheet materials and (b) form surfaces such as ceramic-coated steel with grooves. The study examined bug-hole distributions in the concrete specimens using the various sheets. The bug-hole distributions were quantified by using an image analysis developed in this study. The test results show that quantity of bug-holes of concrete using the sheets is lower than the quantity of concrete without sheets. It was noteworthy that the bug-holes were hardly observed in the test using the form covered with the permeable sheets.

Performance Calculation and Test Analysis of PDM Lining with Super-Elastic Constitutive Model

Based on performance comparison of PDM equidistant and conventional elastomer lining, the impacts on the PDM performance were presented with different equidistant lining thickness. According to the Mooney-Rivlin two-parameter model and the Poisson radio equaling to 0.5, the elastomer is incompressible during the calculation and its relational material parameters such as elastic modulus and shear modulus were determined. The PDM stator and rotor curve equations were established according to hypocycloid theory. The lobe configuration is 3:4, the performance comparisons were investigated including deformation and Mises stress between conventional and equidistant elastomer lining of PDM with contact model. The test data pointed out torque, rotation speed, volumetric and overall efficiency variation results with the motor pressure difference changing from 1.93MPa to 5.90MPa. The presented results could be used for PDM design optimization and performance improvement.

NEW GENERATION ENERGY EFFICIENT REFRACTORY APPLICATION IN SOAKING PITS OF BHILAI STEEL PLANT, SAIL

In Bhilai Steel Plant (BSP), soaking pits are used for heating ingots for successive rolling into blooms. Pits are operated at a temperature of around 1350°C. Mixed gas (Mixture of Blast Furnace gas & Coke Oven gas) of calorific value around 2040 kcal/Nm3 is used as fuel. The walls of soaking pits were lined with traditional 38% Al 2 O 3 firebricks and top 500mm was cast with 70% Al 2 O 3 low cement castable (LCC). This type of lining results in frequent damages due to hitting by ingots while being lifted from pit by overhead cranes thus affecting the availability of pit. Life of pits was 2 to 2.5 years in BSP with 3-4 cold repairs and 3-4 hot repairs. Energy loss through the wall is also quite high in this type of lining. To triumph over the limitations of the conventional lining, a lining design was developed for the walls which consist of special 70% Al 2 O 3 LCC having high hot strength (HMOR) in combination with specially design flexible SS-304 anchors. Ceramic fiber blanket and insulation bricks were provided between castable and the metallic shell of the pit to minimize the heat loss. A heating schedule was developed and introduced based on available infrastructure at BSP for proper curing of modified LCC based lining. After introduction of modified lining, pit no. 14/2 is running for more than 2.5 years without any repair. To capitalize the success, two more pits i.e. 12/1 and 9/2 were converted to modified lining. These pits are also running satisfactorily for more than 1.5 years. The modification has resulted in higher availability with substantial increase in production. Shell temperature of the modified pits reduced to 90° – 140°C from 120° – 200°C of conventional pits. This shows reduction in heat loss through walls, resulting less fuel consumption and energy saving of about 18%.

Fluid-Solid Coupling Analysis of External Water Pressure Distribution Patterns on Drainage Segment Lining

Drainage segment lining is a new structure type formed by setting up drainage holes on the conventional segment lining. Based on continuum fluid-solid coupling analysis model of fractured rock mass, the distribution patterns of water pressure behind the lining walls and in surrounding rock are studied under three kinds of water pressure, while the segment lining with double drainage holes at each side of one ring has been applied. The results show that the water pressure behind segment lining wall could be effectively reduced by setting up drainage holes, and the pressure distribution patterns are in horseshoe shape approximately. The reduction effect of water pressure is more and more obvious from the tunnel crown to the elevation where the drainage holes are provided. But the drainage hole leads to uneven distribution of water pressure, causing the increase of local moment. So, more attention should be paid to the drainage segment lining during design.

Freeze-Lining Formation of a Synthetic Lead Slag: Part II. Thermal History

Recently, freeze linings have been selected more frequently to protect pyrometallurgical reactor walls, due to a number of advantages over conventional refractory lining such as a self-regenerating capability and the possibility of operating under high-intensity process conditions. A freeze lining is formed on a cooled reactor wall in a time-dependent temperature gradient. To model freeze-lining behavior, input data on several assumptions, such as the phase formation and the temperature at the bath–freeze-lining interface during freeze-lining formation, are needed. In order to provide experimental data, the freeze-lining formation of a synthetic lead slag system (PbO-FeO-Fe2O3-ZnO-CaO-SiO2) is investigated. A lab-scale freeze lining was produced by submerging an air-cooled probe into a liquid slag bath for 120 minutes. The temperature evolution during freeze-lining formation was estimated using the experimentally determined position and composition of the phases, the phase-temperature relations predicted with the thermodynamic computer package FactSage, and the results of reference experiments. For the studied slag system, it is concluded that heat transfer is much faster than mass transfer and crystallization. As a result, the liquid in front of the freeze lining undercools. The degree of undercooling depends on the solidification rate. It is concluded that the temperature at the bath–freeze-lining interface varies between the glass transition and liquidus temperatures of the slag bath during freeze-lining formation.

Optimierung der Vakuumtherapie bei ausgedehnten Wundtaschen

Extensively undermined wound cavities represent a common surgical problem. By a modified vacuum therapy the healing of such wounds can be accelerated. Based on our experience in selected cases with wound healing disorders or extremely undermined wounds following degloving injuries or abscess formations the application of topical negative pressure therapy to fix wound margins to the wound ground while at the same time allowing exudates emission with additional drainages is described. In 5 patients we were able to demonstrate the efficacy of vacuum dressing system described here with successful and lasting adaptation of the wound margins to the defect. All wounds were brought to permanent healing. Extensive tissue degloving and wound healing disorders after excessive tissue mobilization during plastic surgical defect coverage can be treated successfully with topical negative pressure therapy (TNP). Whereas longterm complete conventional polyurethane foam lining of wound cavities is an effective method and may be necessary in special situations, the application of TNP can lead to a firm adhesion of wound margins in extensive subcutaneous or epi-fascial wounds to the undersurface. To avoid exudate formation in the adjoining tissue TNP can be effectively optimized by the placement of drainage tubes into the surrounding tissue.

Endodontic complications after plastic restorations in general practice

To test the hypothesis that dentine and pulp protection by conditioning-and-sealing is no less effective than using a conventional calcium hydroxide lining. A cohort of healthy adults requiring a new or replacement restoration in a posterior tooth was recruited in six general practices. All procedures received local Ethics Committee approval. Exclusion criteria included signs and symptoms of pulp necrosis or inflammation, and patients unable to commit to a long-term trial. Cavity preparations were randomized to receive a calcium hydroxide lining or conditioning-and-sealing with a smear-removing bonding system. Choice of bulk restorative material (composite resin or amalgam) was at the discretion of the dentist. The key outcome measure was evidence of pulpal breakdown identified at unscheduled (emergency) or scheduled recall examinations. Postoperative sensitivity was recorded on 100 mm VAS at 24 h, 4 days and 7 days. Pulp status was assessed at 6, 12, 24 and 36 month recall, and at any emergency recall appointment. The relationship between pre-treatment and treatment variables and pulp breakdown was assessed by logistic regression (P = 0.05). A total of 602 teeth were recruited, with comparable numbers of cavities lined (288, 47.8%) or conditioned and sealed (314, 52.2%). The majority (492, 81.7%) were replacement restorations, and amalgam was the most common bulk restorative material (377, 62.6%). A total of 390 (64.8%) restored teeth were reviewed at 6 months, 307 (51%) at 12 months, 363 (60.3%) at 24 months, and 279 (46.3%) at 36 months post-restoration. Sixteen cases of pulp breakdown were identified within 36 months of restoration placement, 11 presenting as emergencies and five detected at routine recall examination. Logistic regression showed that preoperative pain, cavity treatment by lining or conditioning-and-sealing and the use of rubber dam isolation had no association with pulp breakdown. Pulp breakdown was associated with deep or pulpally exposed cavities (P < 0.001, odds ratio 7.8) and with composite rather than amalgam restorations (P = 0.001, odds ratio 2.13). Re-coding to identify teeth with pulp exposures revealed that pulpal exposure was the key determinant of adverse pulp outcomes (P < 0.0001, odds ratio 28.4) and that composite resin restorations were again more likely to be associated with pulp breakdown than amalgam (P = 0.017, odds ratio 3.92). Considered within the context of routine primary dental care: Dentists can be confident that pulps will be equally well protected from post-restorative breakdown up to 36 months by calcium hydroxide lining and conditioning-and-sealing with adhesive resins. Residual dentine thickness appears to be a key determinant of pulp responses after restorative dental treatment. In deep and pulpally exposed cavities in posterior teeth, composites were associated with more pulpal breakdown than amalgams.

The use of permeable refractory linings for enhancement of the thermal performance of a high-temperature furnace

A mathematical model is developed to simulate the replacement of part of the conventional refractory lining in a continuously-operated gas-fired furnace by a permeable ceramic section. This involved a sub-model of the flow and heat transfer through the porous section of the lining linked together with another sub-model of heat transfer in the furnace chamber. The overall model was applied to predict the thermal performance of the furnace when heating steel billets to a nominal discharge temperature of 1250°C. The effects of varying the emissivity, size, orientation and location of the permeable section were studied and, in addition, simulations were undertaken for a range of furnace thermal inputs and billet throughputs. The model predicts that the rate of radiative heat transfer to the steel billets can be substantially increased with consequent improvements in both furnace throughput and efficiency. Therefore, it appears that installing permeable sections in a conventional refractory lining may provide significantly improved furnace performance.

Hybrid Method for Analysis of Segmented Shotcrete Tunnel Linings

When driving tunnels according to the New Austrian Tunneling Method. (NATM), shotcrete is applied onto the newly excavated areas of the tunnel surface. Large deformations occurring when driving tunnels under squeezing rock conditions lead to the destruction of a conventional shotcrete lining. As a remedy, segmented shotcrete linings characterized by an increased compliance have successfully been installed. In this paper a hybrid method for the analysis of such segmented tunnel linings is presented. It combines in situ displacement measurements with a thermochemomechanical material law for shotcrete. The application of this method to the Semmering pilot tunnel provides new insights into the load-carrying behavior of segmented tunnel linings.

The effects of skirt lining properties on comfort and movement

AbstractThis study was conducted to clarify the influences of the lining properties of skirts upon comfort and movement. The comfort of lining fabrics and real skirts with and without lining was rated by sensory tests on the basis of sensorial comfort on the skin and body movement. Actual body movements were investigated by motion analysis while the skirts were being worn. The results are described: (1) Comfort on the skin, movement and overall preference for the lining fabrics were evaluated by sensory testing, comparing skirts made with five kinds of lining fabrics. Conventional non‐stretch cupro lining was ranked first on the basis of smoothness and good feel to the skin. Two‐way stretch lining was also ranked highly in terms of ease of movement. We discuss how sensorial comfort on the skin and ease of movement related to overall preference for lining fabrics. (2) Sensory test of the actual skirts with and without lining clearly confirmed that lining played a role in improving comfort. (3) For a non‐stretch fabric skirt, conventional lining was ranked highly for good feel to the skin, and two‐way stretch lining was considered useful for ease of movement. There was no significant difference between the two lining fabrics in overall preference. (4) For a stretch fabric skirt, stretch lining is the most useful because it maintains easy extension of the outer fabric, thus allowing ease of body movement. (5) Motion analysis showed that a combination of knitted stretch skirts with stretch lining was the best for ease of movement. Comparing the sidelines and the hemline of the stretch fabric skirts demonstrated a better shape using lining.

A theoretical study of passive control of duct noise using panels of varying compliance

It is theoretically demonstrated that, in a duct, a substantial amount of sound energy can be transferred to flexural waves on a finite wall panel when the upstream portion of the panel is made to couple strongly with sound. The flexural wave then loses its energy either through radiating reflection sound waves or by internal friction. The effectiveness of the energy transfer and damping is greatly enhanced if the panel has a gradually decreasing in vacuo wave speed, which, in this study, is achieved by using a tapered membrane under tension. A high noise attenuation rate is possible with the usual viscoelastic materials such as rubber. The transmission loss has a broadband spectrum, and it offers an alternative to conventional duct lining where a smooth air passage is desired and nonacoustical considerations, such as chemical contamination or cost of operation maintenance, are important. Another advantage of the tapered panel is that, at very low frequencies, typically 5% of the first cut-on frequency of the duct, sound reflection occurs over the entire panel length. This supplements the inevitable drop in sound absorption coefficient, and a high transmission loss may still be obtained at very low frequencies.

Optimizing the mill lining and the grinding media in tumbling mills

The grinding mill is probably the most common unit operation in mineral processing. There is, however, much that can still be done in the way of optimization. This paper discusses the results of a well-controlled pilot-scale test in which the performance of a tumbling mill equipped with a conventional rubber lining and lifter bars was compared to a tumbling mill equipped with a smooth rubber lining of the magnetic type. The results indicate that the smooth lining is about 14% more effective with respect to energy consumption. By optimizing the size of the grinding media, the mill capacity can be increased in many grinding operations. In this specific case, grinding with a −20-mm ball charge required 26% less grinding energy than grinding with a −30-mm ball charge. The energy savings can, in most cases, be converted to an increase in capacity. The wear of the grinding media is difficult to assess over a short test period, but the results suggest that the wear is somewhat less when a smooth lining is used. A determination of the wear of the linings was not included in this study, but it is generally accepted that the use of magnetic linings reduces the lining costs dramatically. Computer simulation using the Millsoft code developed by Mishra et al. confirms and explains the increased effectiveness of comminution when a smooth lining and smaller grinding balls are used.

An elastohydrodynamic analysis of a misaligned sterntube bearing

Steady load performance data are presented for a sterntube bearing lined with an elastic material, which is contained in a rigid housing and subject to angular misalignment. The analysis is thus applicable to oil-lubricated sterntube bearings in which reinforced resin liners are used as an alternative to conventional white metal lining. The hydrodynamic analysis method used satisfies flow continuity throughout the cavitation zone. A rigorous elastic model, accounting for inter-element and element-to-housing forces was developed. Results showed that a simplified approach neglecting element interaction was of acceptable accuracy. An effective oil viscosity based on a simple thermal balance calculation was used. A relaxation method was employed for the combined hydrodynamic and elastic deflection solutions, with over-relaxation applied to the former. The application of under-relaxation to the elastic deflection solution was necessary in order to obtain convergence. The most significant results are those for minimum film thickness which is shown to be reduced by liner elasticity in all cases. This reduction is shown to be a direct function of both specific bearing pressure and misalignment angle. The rigid bearing assumption is confirmed to be acceptable for white-metal-lined sterntube bearings.

Particle simulations of plasma and dielectric Čerenkov masers

A new particle simulation model has been developed to investigate Čerenkov masers. The novel aspects of the code are briefly described, and results of simulations of two types of Čerenkov masers are presented. The first device uses a conventional dielectric lining as its slow-wave structure. The second is a new type of Čerenkov maser in which a circular waveguide is partially filled with a dense annular plasma instead of a dielectric layer. Both simulations agree well with experimental results and linear theory calculations. Saturation of the instability is shown to be due to trapping of the beam electrons. The relative merits of each system are discussed.