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FLAME CLEANING STEEL STRUCTURES

FLAME CLEANING STEEL STRUCTURES The conditions necessary for a satis­ protective finish, since they permit the cleaning was noted. It has been found factory protective coat on steel, whether it primer to give false cover by cloaking that flame cleaning is best carried out is new or old, are twofold: the surface instead of penetrating the cavities. The using an oxy-acetylene flame. This is the must be completely clean and it must be warmth of the plate has another advantage hottest of oxygen-fuel gas flames, and is completely free from moisture. Paint in this respect since it tends to lower the most effective in rapidly heating the surface applied to a surface prepared in this natural viscosity of the paint and enables with the minimum of heat spread through manner makes a 100% bond with the it to penetrate more easily into minute the plate or structure. The ideal is the metal. surface irregularities, so creating the most intense heat over the shortest period; intimate bond which is essential for the slow flame will give unwanted heating Construction and maintenance engineers primer coat. through the plate before the required will be well aware of the difficulty of ensuring that the two essential conditions surface temperature is attained. Due to For the best results the primer should are obtained; indeed, using the customary the use of multiple burners for rapid heat­ be applied immediately after brushing away methods, even conscientious workmanship ing and reasonable coverage, the equipment the oxide dust; subsequent protective in operation requires larger quantities of will not achieve the desired result unless coats should be put on as rapidly as drying both oxygen and acetylene than can be the job is also favoured with ideal weather. permits. readily supplied by standard-size cylinders. Flame cleaning, however, does provide In the case of very heavily scaled plates Consequently, couplers are provided with the two essentials for efficient application it may be found more economical to chip the B.O.C. equipment so that two or more of paint coats. The process is brief, con­ prior to flame cleaning. It is important cylinders of each gas may be coupled sisting of passing a high-temperature flame to assess the requirement on each job so together. over the surface of the metal at a speed as to use the process to its best advantage. determined by the heaviness of corrosion Last month in 'Corrosion Commentary' The rapid heating action required for or scale and the plate thickness. The flame cleaning is produced by specially some of the applications of flame cleaning operation is facilitated by providing the designed multiple-jet nozzles: flat, round, were mentioned, ranging from railway blowpipe with suitably shaped nozzles, bridges to ships' hulls. Considerable semi-circular and circular. e.g. flat nozzles which give a brushlike experience has been gained in cleaning The flat nozzle is used for cleaning flat flame pattern for flat surfaces and large plates of new tankers using British Oxygen surfaces free from projections; the round areas and round nozzles for small sections Co. equipment. In another sphere, gas nozzle is used for all riveted and bolted and awkward corners. undertakings are using the process to clean areas, plate edges, corners, recesses and In the case of relatively new metal, mill gasholders without emptying. In this case, other places where it is not possible to the plates are much thinner than those scale is removed by reason of the differing operate a flat nozzle effectively. Semi­ encountered in construction work and ship expansion set up between the scale and circular and circular nozzles are used for building, yet no disturbance due to flame cleaning tubular sections. the base metal due to the application of local heat. The products of corrosion are loosened by dehydration and the rust Stress-corrosion cracking in welded gas mains particles are converted to powder which can be brushed away. possible corrosive agents, in which strained To explain the mechanism of stress The penetrative power of flame cleaning corrosion cracking; to find the corrosive specimens are examined for attack at the enables the flame to enter and explore the agent responsible, and to assess its preva­ grain boundaries, a fairly wide range of H S/NH /HCN mixtures has been most minute pits and craters in the metal lence in British gas plants are problems 2 2 examined without positive results. So far and, in addition to the removal of solids, investigated by the Committee on cracking 41 visits have been made to gas plants it is effective in dissipating chemical bar­ in welded gas mains, set up by the British experiencing trouble from stress-corrosion riers such as moisture, which would pre­ Welding Research Association. Assessment cracking. Relevant data has been recorded, vent the overall and intimate contact of possible corrosive agents by examining required between the first paint coat and the attack at grain boundaries, a survey of and the results incorporated in two com­ mittee reports. Some progress has been the underlying metal. stress-corrosion in British gas plants, and made in the theoretical aspects of the work, theoretical work on the mechanism of stress- Unless these minute surface irregulari­ and in particular on the evaluation of the corrosion cracking have been continued. ties are thoroughly cleaned they form a possible role of hydrogen. potential source of breakdown in the later Using a method for a rapid survey of CORROSION TECHNOLOGY, December 1954 391 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Anti-Corrosion Methods and Materials Emerald Publishing

FLAME CLEANING STEEL STRUCTURES

Anti-Corrosion Methods and Materials , Volume 1 (10): 1 – Oct 1, 1954

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Publisher
Emerald Publishing
Copyright
Copyright © Emerald Group Publishing Limited
ISSN
0003-5599
DOI
10.1108/eb019001
Publisher site
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Abstract

The conditions necessary for a satis­ protective finish, since they permit the cleaning was noted. It has been found factory protective coat on steel, whether it primer to give false cover by cloaking that flame cleaning is best carried out is new or old, are twofold: the surface instead of penetrating the cavities. The using an oxy-acetylene flame. This is the must be completely clean and it must be warmth of the plate has another advantage hottest of oxygen-fuel gas flames, and is completely free from moisture. Paint in this respect since it tends to lower the most effective in rapidly heating the surface applied to a surface prepared in this natural viscosity of the paint and enables with the minimum of heat spread through manner makes a 100% bond with the it to penetrate more easily into minute the plate or structure. The ideal is the metal. surface irregularities, so creating the most intense heat over the shortest period; intimate bond which is essential for the slow flame will give unwanted heating Construction and maintenance engineers primer coat. through the plate before the required will be well aware of the difficulty of ensuring that the two essential conditions surface temperature is attained. Due to For the best results the primer should are obtained; indeed, using the customary the use of multiple burners for rapid heat­ be applied immediately after brushing away methods, even conscientious workmanship ing and reasonable coverage, the equipment the oxide dust; subsequent protective in operation requires larger quantities of will not achieve the desired result unless coats should be put on as rapidly as drying both oxygen and acetylene than can be the job is also favoured with ideal weather. permits. readily supplied by standard-size cylinders. Flame cleaning, however, does provide In the case of very heavily scaled plates Consequently, couplers are provided with the two essentials for efficient application it may be found more economical to chip the B.O.C. equipment so that two or more of paint coats. The process is brief, con­ prior to flame cleaning. It is important cylinders of each gas may be coupled sisting of passing a high-temperature flame to assess the requirement on each job so together. over the surface of the metal at a speed as to use the process to its best advantage. determined by the heaviness of corrosion Last month in 'Corrosion Commentary' The rapid heating action required for or scale and the plate thickness. The flame cleaning is produced by specially some of the applications of flame cleaning operation is facilitated by providing the designed multiple-jet nozzles: flat, round, were mentioned, ranging from railway blowpipe with suitably shaped nozzles, bridges to ships' hulls. Considerable semi-circular and circular. e.g. flat nozzles which give a brushlike experience has been gained in cleaning The flat nozzle is used for cleaning flat flame pattern for flat surfaces and large plates of new tankers using British Oxygen surfaces free from projections; the round areas and round nozzles for small sections Co. equipment. In another sphere, gas nozzle is used for all riveted and bolted and awkward corners. undertakings are using the process to clean areas, plate edges, corners, recesses and In the case of relatively new metal, mill gasholders without emptying. In this case, other places where it is not possible to the plates are much thinner than those scale is removed by reason of the differing operate a flat nozzle effectively. Semi­ encountered in construction work and ship expansion set up between the scale and circular and circular nozzles are used for building, yet no disturbance due to flame cleaning tubular sections. the base metal due to the application of local heat. The products of corrosion are loosened by dehydration and the rust Stress-corrosion cracking in welded gas mains particles are converted to powder which can be brushed away. possible corrosive agents, in which strained To explain the mechanism of stress The penetrative power of flame cleaning corrosion cracking; to find the corrosive specimens are examined for attack at the enables the flame to enter and explore the agent responsible, and to assess its preva­ grain boundaries, a fairly wide range of H S/NH /HCN mixtures has been most minute pits and craters in the metal lence in British gas plants are problems 2 2 examined without positive results. So far and, in addition to the removal of solids, investigated by the Committee on cracking 41 visits have been made to gas plants it is effective in dissipating chemical bar­ in welded gas mains, set up by the British experiencing trouble from stress-corrosion riers such as moisture, which would pre­ Welding Research Association. Assessment cracking. Relevant data has been recorded, vent the overall and intimate contact of possible corrosive agents by examining required between the first paint coat and the attack at grain boundaries, a survey of and the results incorporated in two com­ mittee reports. Some progress has been the underlying metal. stress-corrosion in British gas plants, and made in the theoretical aspects of the work, theoretical work on the mechanism of stress- Unless these minute surface irregulari­ and in particular on the evaluation of the corrosion cracking have been continued. ties are thoroughly cleaned they form a possible role of hydrogen. potential source of breakdown in the later Using a method for a rapid survey of CORROSION TECHNOLOGY, December 1954 391

Journal

Anti-Corrosion Methods and MaterialsEmerald Publishing

Published: Oct 1, 1954

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