Flame cleaning

Flame Cleaning Now little used as a preparatory method, flame cleaning is a process whereby an intensely hot oxyacetylene flame is played on the surface of the steel. In theory, differential expansion causes millscale to detach. In practice, there is evidence that the treatment may not remove thin, tightly adhering millscale. Also, steel less them 5 mm thick can buckle. Finally, the process can burn in chemicals deposited on the surface, causing premature paint failure. 

Mechanical action might involve such activities as abrasion, deformation, heat or flame cleaning, and electrocleaning, which involves direct current hydrogen scrubbing at the cathode. Metal-bearing wastes associated with these actions would be due to the metalbearing contamination removed in the process as well as any of the metal substrate removed. 

As regards adjustments, the following factors ii proved combustion and flame clean nozzle, strong swirl, intense symmetrical flame, pressure air atomisation compared to steam), increase of air coefticient and combustion power (having enough residence time though), suitable atomisation viscosity (abt 15-20 cSt). At the optimum adjustments of this combustion system, the mean conibustion results and emission values of typical pyrolysis oils were as follows O2 3 5 vol%, NO 88 mg/MJ, CO 4.6 mg/MJ, hydrocarbons 0.1 mg/MJ, soot 2.4 Bac., and particles 86 ing/MJ. 

In the case of Pt(l 11), voltammograms for flame-cleaned electrodes were obtained under UHV conditions [53] providing evidence that such voltammograms correspond to well-ordered (lxl) structures. Since the same voltammetric features were obtained with various surface preparation procedures, there is a large stability of the (111) (lxl) structure [60], Conversely, UHV studies have shown the existence of various surface structures for Pt(100) [42] or Pt(110) [61]. Such structural changes may influence the electrochemical response of these orientations. Similar to Pt(lll), voltammograms obtained with Pt(100) electrodes have been found to depart on the electrolyte composition that is, a decrease of the anion-specific adsorption shifts the hydrogen adsorption states to more positive potentials. 

The electrolysis is conducted in a cylindrical vessel (95 mm. I. D. and 100 mm. high) in which a porous clay cell (50 mm. I. D. and 80 mm. high) is set. The cell is held in place by a paraffin-soaked cork ring in such a way that it touches the bottom of the cylinder. The anode is a strip of transformer iron sheet (0.3% Mn 27 x 3.7 cm. = 100 cm. of surface on each side) which adheres closely to the outer wall. The cathode consists of a screen of iron wire rolled into a cylinder and placed inside the cell. The anode is welded to a thick, acetylene-flame-cleaned iron wire, which passes through the cork ring and is sealed in... 

Burner flame is impinging directly on temperature sensor. Thermowell is damaged due to flame. Check burner installation, tertiary air distributor, and atomisation of fuel oil which can cause this problem. Provide additional view glasses on furnace shell to observe the flame. Clean strainer in fuel oil pipe. 

Descaling n. Removal of mill sale or caked rust from steel by chemical and/or mechanical means, sometimes assisted by flame cleaning. 

Flame cleaning n. Impingement of an intensely hot flame to the surface of structural steel resulting in the removal of mill scale and the dehydration of any remaining rust, leaving the surface in a condition suitable for wire brushing followed by the inunedi-ate application of paint. 

Immediately after flame-cleaning the gold surface, water will adhere to the surface when the slide is dipped in water. If this water is cleaned off the slide and the slide is allowed to sit in the air for several minutes, water will no longer adhere to the surface when the shde is rinsed in water. Explain why. 

Figure 10.1 Cyclic voltammograms of flame-cleaned (H2 -t- Ar atmosphere) (A) Pt(111), (B) Pt(lOO) and (C) Pt(l 10), all in 0.5 M H2SO, at 50 mVs . Reproduced with permission from Ref [9], Societe Chemique de France.

The process of flame cleaning has found greater favor in Europe than in America. A wide oxy-acetylene flame is played on the surface of steel parts to produce two effects. First, the heavier portions of rust scale or mill scale will pop from the surface because of the thermal expansion difference between the scale and the substrate. Secondly, the surface is freed of moisture if sufficient heat is applied to the substrate. Removal of loose rust particles after the treatment, followed by prompt coating can produce an adequate coating procedure for certain applications. When using an open flame for cleaning, extreme caution must be used to prevent fires and explosions. 

Chromate Dyed Glass Cloth (Flame cleaned) Tab 70 0/20 M-D... 

Surface Preparation Specification No. 4 (SSPC-SP 4) Flame Cleaning... 

Flame cleaning should not be specified for removal of mill scale in a new unbroken state from steel. 

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