GB611610A - Methods of and apparatus for electrolytically cleaning or descaling the internal surface of a hollow metal article, such as the internal surface of a hollow metal valve - Google Patents

Abstract

611,610. Electrolytic cleaning. THOMPSON PRODUCTS, Inc. March 14, 1944, No. 4721. Convention date, April 9, 1943. [Class 41] [Also in Group XXVII] The internal surface of a hollow metal valve is descaled electrolytically to form a surface having a high rate of heat transfer to the metal coolant such as sodium. The valve 14 is fixed vertically in a clamp 13 from which it is insulated at 19 and a hollow conductor 25 passes down the valve stem through insulating spacers 28, 29 and clamp 26 insulated at 27 which hold it respectively inside and outside the valve. Also passing through spacers 28, 29 is a wire 41 which is connected at its lower end to the end of the tube 25 by two wire links 37, 38 hinged at 36, 39, 42. By pulling up the upper end of the wire 41, links 37, 38 are collapsed into a straight-line position (Fig. 3), thus allowing their insertion into and removal from the valve 14 with the tube 25, or extended into the position shown in Fig. 2, which conforms with the internal shape of the valve head 15. An electrolyte which may be an aqueous solution of orthophosphoric acid, is passed from a reservoir (not shown) down the tube 25 and overflows, passing through apertures 32, 31 in spacers 29, 28. A positive connection 47 is made to the valve 14 which forms the anode and current passes through the electrolyte to the links 37, 38 which form the cathode and together with wire 41 are of stainless steel, and thence along the tube 25, which is coated with a stop-off lacquer to prevent electrolytic action at its surface, to a negative connection 48. To produce an even descaling of the valve head relative rotation is arranged between the valve and cathode, preferably by rotating the valve through about 45 degrees every 5 minutes. After emptying and washing the surface will be bright but pitted, and for polishing a small current might be used as described more fully in Specification 611,609. Sulphuric acid or a mixture of sulphuric and phosphoric acids may be used as electrolytes whilst the valve may be made of alloys containing nickel, chromium, iron, molybdenum, cobalt or tungsten. Instead of D.C., interrupted D.C. or A.C. may be used.