Galvanized Steel Tubes Research Articles

Experimental characterization of bond between concrete and HDG steel tubes for mixed steel-concrete structures

Bond between concrete and reinforcement material is crucial for the structural behaviour and design of reinforced concrete or mixed steel-concrete structures. When considering applications in harsh environments, such as severe marine exposure or submerged conditions, hot-dip galvanized (HDG) steel seems to be a promising solution, as part of new mixed steel-concrete structural systems. Although it is essential to guarantee an effective composite response, the interaction and bond behaviour between materials is not yet sufficiently well understood. This experimental investigation aimed to study the bond behaviour between concrete and HDG steel tubes, including the influence of adopting concrete pin connectors by creating holes in the tube profile, and also the influence of the galvanic surface state. The impact of bond length on the bond behaviour of the galvanized steel tube embedded in different concrete mixtures was analysed. Pushout tests were conducted to obtain the load end versus slip responses, as well as the failure modes. The results showed that the embedment lengths and the concrete compositions had no relevant effect on the overall shape of the pushout experimental responses, with the exception of the specimens that include the concrete pin connector. However, both variables clearly influenced the bond stress, dissipated energy during pushout until failure, and residual pushout force. The addition of the concrete pin significantly improved the adherence mechanism, while the contamination of the galvanic surface showed to significantly reduce the bond strength.

Investigation on Interfacial Bond Strength Characteristics of Concrete Filled in Galvanized Steel Tubes Utilizing Statistical Analysis and Advanced Prediction Techniques

Investigation on Interfacial Bond Strength Characteristics of Concrete Filled in Galvanized Steel Tubes Utilizing Statistical Analysis and Advanced Prediction Techniques

Identifying fouling mechanism in a novel hybrid cooling tower's bundles: Application in concentrated solar power (CSP) plant

In this paper, structural, chemical, and thermos-physical characteristics of fouling and tube materials for hybrid cooling tower bundles in Concentrated Solar Power (CSP) facilities are addressed. Toward an in-depth understanding and a comparison of the fouling mechanism on galvanized steel and polymer tubes, results obtained from the characterization studies and the experimental test correlations were used to calculate the sticking probability (P) and deposit bond strength (ξ) based on the Kern-Seaton model. According to the data, the polymer tube had three times higher the adhering probability of the galvanized steel tube with a value of PPf = 3.15*102 Ns/m2, whereas the deposit bond strength was two times lower with a value of ξPf = 3.49*10−8. The results revealed that when it comes to polymer tubes, the ones with a finer surface structure tend to attract foulants from deluge water more readily. However, once foulants are attached to the heat transfer surface, it's simpler to be removed. The substantial increase in kaolinite and gypsum phases can explain this occurrence. On the other hand, galvanized tubes, exhibit the opposite behavior. It is anticipated that this constructive study will shed light on performance-enhancing fouling mechanisms and offer a scientific basis for thermal engineers.

Corrosion Behavior in Volcanic Soils: In Search of Candidate Materials for Thermoelectric Devices.

Thermoelectric generators have emerged as an excellent solution for the energy supply of volcanic monitoring stations due to their compactness and continuous power generation. Nevertheless, in order to become a completely viable solution, it is necessary to ensure that their materials are able to resist in the acidic environment characteristic of volcanoes. Hence, the main objective of this work is to study the resistance to corrosion of six different metallic materials that are candidates for use in the heat exchangers. For this purpose, the metal probes have been buried for one year in the soil of the Teide volcano (Spain) and their corrosion behavior has been evaluated by using different techniques (OM, SEM, and XRD). The results have shown excessive corrosion damage to the copper, brass, and galvanized steel tubes. After evaluating the corrosion behavior and thermoelectric performance, AISI 304 and AISI 316 stainless steels are proposed for use as heat exchangers in thermoelectric devices in volcanic environments.

Experimental Study of Fouling in Hybrid Cooling Tower Used in CSP Plants: Effects of the Polymer and galvanized steel tubes

Concentrating solar power (CSP) plants require cooling systems, which are typically operated using either water resources that are scarce in arid regions or dry cooling which impacts the overall efficiency of the system. To ensure a higher sustainability of solar-electric facilities, hybrid cooling is promising solution for higher system efficiency with lower water consumption. However, fouling of cooling components can contribute to several operation issues, such as the reduction of heat transfer, precipitation on heated tubes, and increasing the maintenance cost. It can also be influenced by many parameters, namely the surface proprieties, and operating conditions (such as temperature, water and air flow rates, relative humidity….). To assess the fouling process in the hybrid cooling system, a fouling test facility with a dynamic monitoring system was built its operational performances were experimentally investigated on the basis of a long-term test of 108 days. To explore the influence of the surface materials, the hybrid towers were equipped with polymer and galvanized steel tubes. Based on fouling data, test results indicated that the influence of the tubes positioning on fouling deposition was at least as significant as the influence of tube materials. Generally, the heated tubes at the bottom positions in the test facilities were subject to severe fouling for both tube’s materials. As for the polymer heated tubes, an asymptotic fouling resistance value was achieved 22 days before the galvanized ones. Finally, the cleaning method showed that the fouling deposits on polymer tubes were cleaned easily compared with the galvanized tubes.

Quality analysis of galvanized pipes applied to natural gas installations in civil construction

Some natural gas distributors for residential and commercial buildings in Brazil use galvanized steel tubes and fittings manufactured by the hot-dip zinc process that are supported by the specifications contained in the Brazilian Standards. Zinc coating is one of the most widely used methods to provide protection against corrosion. It is therefore essential that national and international tube manufacturers and installation and maintenance companies in civil construction also meet the defined national and international standards, especially when the tubes and fittings are used for natural gas in residential buildings. This two-way communication could eliminate most issues that delay or prevent superior galvanizing quality. Low standards lead to the deterioration of the zinc coating and the metal base of the pipes, which may lead to leaks, such as fluids, flammable gases, and other toxic products, and potentially jeopardise residential and commercial buildings. Here the importance of ensuring the quality of zinc-coated pipes is demonstrated through a series of analyses on natural gas pipe corrosion used in civil construction in Brazil. Based on Brazilian standards, the zinc mass determination per square meter, uniformity tests (Preece test) and metallographic evaluation of the deposited zinc layer were carried out on samples of galvanized tubes for natural gas. An experiment was also developed to reproduce the same conditions of subfloors (mortar beds) where there is penetration of water and humidity reaching the galvanized pipes. Metallographic analysis showed that samples of galvanized tubes by the hot-dip zinc galvanizing can have discontinuities and defects in zinc layer. Such defects associated with penetration and/or permeation of the water and humidity in the subfloor favor the corrosive process and consequently can cause gas leaks and probable accidents in residential buildings. Keywords: Corrosion, galvanized steel, zinc coating, quality, natural gas pipes, civil construction.

Study of the Torsional Behavior of Aluminum Foam-Filled Galvanized Steel Tubes after High Temperature

Torsional test of aluminum foam-filled galvanized steel tube before and after high temperature is performed. The influence of temperature, porosity of aluminum foam and steel ratio on torsional behavior of aluminum foam galvanized steel tubes were analyzed. Experimental results showed that torsional curves of aluminum foam-filled galvanized steel tube before and after high temperature is similar, and can be divided into four stages: the elastic torsional stage, yield platform stage, descent stage and hardening stage; Its torsional load capacity decreases with increasing porosity of aluminum foam and increases at a higher steel content and slenderness ratio; after high temperature, torsional load capacity of galvanized steel tube decreased significantly. It was found that the strength reduction factor ratio under the elevated test temperature is higher than that recommended by British ECCS, Australian AS4100 and Chinese CECS 200-2006.

Behavior of galvanized steel tube subjected to web crippling

The details of a research study of galvanized steel tube under web crippling were presented. A total of 48 galvanized steel square hollow sections with different boundary conditions, loading conditions, bearing lengths and web slenderness were tested. The experimental scheme, failure modes, load-displacement curves and strain intensity distribution curves were also presented. The investigation was focused on the effects of loading condition, bearing length and slenderness on web crippling ultimate capacity, initial compressive stiffness and ductility of galvanized steel tube. The results show that web crippling ultimate capacity increases linearly with the increase of the bearing length under EOF and IOF loading condition. In the end-flange and ITF loading conditions, strain intensity of the centerline of web reaches the peak and decreases progressively from central web to flanges. Finite element models were developed to numerically simulate the tests in terms of failure modes and ultimate capacity. Web crippling strength of galvanized steel tube increases linearly with the increase of the ratio of the bearing length to web thickness and decrease of web slenderness. The effect of ratio of galvanized layer thickness to web thickness on web crippling strength is small. Based on the results of the parametric study, a number of calculation formulas proposed in this work can be successfully employed as a design rule for predicting web crippling ultimate capacity of galvanized steel tube under four loading and boundary conditions.

Web crippling of galvanized steel tube strengthened by CFRP sheets

Web crippling is the major failure mode of galvanized steel tube members when they are subjected to concentrated loads or reactions. Carbon fibre-reinforced polymer (CFRP) sheets were found to be promising for strengthening metallic structural members. This paper presents a test program on strengthening of high strength galvanized steel tubular structural members using externally bonded CFRP sheets. The results of 16 web crippling tests were presented, with 8 tests conducted on galvanized steel square hollow sections without CFRP sheets strengthening and 8 tests conducted on galvanized steel square hollow sections with CFRP sheets strengthening. The experimental scheme, failure modes and load–displacement curves were also presented. The investigation was mainly focused on the effects of boundary condition, loading condition and CFRP sheets layers for the strengthening of galvanized steel square hollow sections against web crippling. Significant increase in web crippling ultimate capacity was obtained due to CFRP sheets strengthening. Enhancement of web crippling ultimate capacity was not obvious when CFRP sheets layers exceeds 3 layers. Finite element models were developed to numerically simulate the experimental results. Based on the results of the parametric study, a number of design formulas proposed in this paper can be successfully employed as a design rule for predicting web crippling ultimate capacity of galvanized steel tubular sections strengthened by CFRP sheets under four loading and boundary conditions.

Corrosion behaviour and biocorrosion of galvanized steel water distribution systems

Galvanized steel tubes are a popular mean for water distribution systems but suffer from corrosion despite their zinc or zinc alloy coatings.First, the quality of hot-dip galvanized (HDG) coatings was studied. Their microstructure, defects, and common types of corrosion were observed. It was shown that many manufactured tubes do not reach European standard (NBN EN 10240), which is the cause of several corrosion problems. The average thickness of zinc layer was found at 41μm against 55μm prescribed by the European standard.However, lack of quality, together with the usual corrosion types known for HDG steel tubes was not sufficient to explain the high corrosion rate (reaching 20μm per year versus 10μm/y for common corrosion types).Electrochemical tests were also performed to understand the corrosion behaviours occurring in galvanized steel tubes. Results have shown that the limiting step was oxygen diffusion, favouring the growth of anaerobic bacteria in steel tubes.EDS analysis was carried out on corroded coatings and has shown the presence of sulphur inside deposits, suggesting the likely bacterial activity.Therefore biocorrosion effects have been investigated. Actually sulphate reducing bacteria (SRB) can reduce sulphate contained in water to hydrogen sulphide (H2S), causing the formation of metal sulphides. Although microbial corrosion is well-known in sea water, it is less investigated in supply water. Thus, an experimental water main was kept in operation for 6months. SRB were detected by BART tests in the test water main.

Experimental investigation into the thermal-flow performance characteristics of an evaporative cooler

Abstract This study investigates the thermal-flow performance characteristics of an evaporative cooler. The derivation of the Poppe [1] and Merkel [2] analysis for evaporative coolers are presented and discussed. Performance tests were conducted on an evaporative cooler consisting of 15 tube rows with 38.1 mm outer diameter galvanized steel tubes arranged in a 76.2 mm triangular pattern. From the experimental results, correlations for the water film heat transfer coefficient, air–water mass transfer coefficient and air-side pressure drop are developed. The experimental tests show that the water film heat transfer coefficient is a function of the air mass velocity, deluge water mass velocity as well as the deluge water temperature, while the air–water mass transfer coefficient is a function of the air mass velocity and the deluge water mass velocity. It was found that the correlations obtained for the water film heat transfer coefficient and the air–water mass transfer coefficient compare well with the correlations given by Mizushina et al. [3] . Relatively little published information is available for predicting the air-side pressure drop across deluged tube bundles. The present study shows that the pressure drop across the bundle is a function of the air mass velocity and the deluge water mass velocity.

Advantages of Steinmetz Circuit Theory Over Schelkunoff Transfer Impedance Theory

This paper presents induced voltage measurement results along a conductor pair inside a 4.5", 9-m-long galvanized steel tube, with an intermediate screwed joint. The excitation was done by an external parallel conductor where a 60-Hz current flows, followed by an impulsive current (5 kA, 8/20 mus). Some measurements with the external joint short-circuited cast a great doubt about the validity of all Schelkunoff transfer impedance concept. The paper focuses also the recommended calculation procedures using Circuit Theory. This paper also shows that there are strong evidences that the classical Maxwell equations were developed to represent wireless propagation such as light and wireless communication. The paper suggests as well the convenience of a deeper verification on the validity of applying Maxwell equations to solve metallic circuit problems.

Korrosionsschäden in Verbindung mit gelöteten Plattenwärmeübertragern aus nichtrostendem Stahl

With increasing time of operation the number of damage to brazed plate heat exchangers made of stainless steel for heating of drinking water as well as to galvanized steel tubes behind the exchangers increase. The heat exchangers suffered from leakages and bulgings. Tubes are assumed to suffer from copper induced pitting. The cause for the damage to the exchangers is galvanic corrosion of copper braze. Investigations of copper contents in the hot water behind the exchanger and in the surface layer of tubes gave no clear results. But the analyses show that pitting of galvanized tubes can possibly be accelerated by liberating copper from the braze to the water.

Nonbiological Nitrous Oxide Production from Vadose Soil Catalyzed by Galvanized Steel Tubing

AbstractStudies of microbial processes in the vadose zone are hampered by difficulties in obtaining uncontaminated samples. We initiated a study in 1985 to quantify microbial denitrification in the vadose zone of agricultural land located in the Atlantic Coastal Plain. In the initial stages of this study, deep soil cores (360 cm) were collected and subcored with sterile galvanized steel tubes to eliminate contamination by surface soil. We observed N2O production from subsoil incubated with C2H2 in galvanized tubes, but in the same soil incubated anaerobically with added glucose and NO−3, denitrification activity was not detected. Subsequent comparisons of N2O production in surface and subsurface soil incubated in galvanized and plastic tubes indicated that chemodenitrification was the likely mechanism responsible for the N2O production observed in soil contained in galvanized steel tubes. These results suggest that, in field or laboratory experiments designed to investigate soil‐N transformations, galvanized steel enclosures should be used with caution.

A new crush-cage with rotating squeeze-back for restraining large primates.

113 The restraint of large primates such as baboons for the purposes of research can prove traumatic for both animal and operator. Restraining cages are usually used, but tend to be difficult to manipulate due to the size and weight of the squeeze-back, which is generally the same internal width and height as the cage. Design and construction The cage is 1150 x 825 x 2000 mm high although other sizes are possible. It is constructed of galvanized welded wire mesh (50 mm square) over a frame of galvanized steel tubing (34 mm diameter). The squeeze-back has been reduced in size to about half the internal height of the cage, with a consequent reduction in weight. The effort required to restrain the animal has been further decreased by a system of counterweights and pulleys. The squeeze-back consists of galvanized welded wire mesh (25 mm square) welded to 25 mm square section galvanized steel tube. It rotates about a point P (Fig. 1) and is angled 100