JP2003013884A - Corrosive melt preventing structure for impeller fixing end face in underwater rotary machinery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a corrosive melt preventing structure for the end face where to an impeller of an underwater rotary machinery is fixed so that the impeller can play the role fully as a consumable positive electrode and exert an electric corrosion preventive effect for the main shaft. SOLUTION: The impeller 2 is made of a metal having a baser natural potential than the rotary main shaft 1, and an electric insulating oxide film 7a or any electric insulating member is interposed on the shaft hole tail fixing end face 5a where the impeller 2 contacts with the rotary main shaft 1 while an electric insulating oxide film 7b or an electric insulating member is interposed on the shaft hole front extremity fixing end face 5b contacting with an impeller fixture 3 made of metal.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a structure for preventing corrosion and dissolution of an impeller fixed end face in an underwater rotating machine such as a stirring device. [0002] In an underwater rotating machine such as a submersible pump, the main shaft is easily corroded by the action of a corrosion battery formed on a metal surface. As a countermeasure, a proposal has been made to avoid electric corrosion of the main shaft by using an impeller as a sacrificial anode. If it can be gradually and uniformly dissolved from the outer surface of the impeller such as a blade plate or shroud, the impeller will serve as a sacrificial anode, and the effect of preventing the main shaft from electric corrosion will be obtained. In reality, however, corrosion and dissolution proceed rapidly and vigorously from a specific portion of the impeller that becomes a contact portion with a different metal. That is, as shown in FIG. 1, the rear end fixed end surface 50a of the shaft hole 40 where the impeller 20 contacts the main shaft and the front end fixed end surface 50b of the shaft hole 40 which contacts the impeller fixing bracket are reversibly flat and have a gap. Therefore, the surface oxide film on the surface is scraped off, and the corrosion dissolution proceeds more rapidly than the other portions. Accordingly, when the impeller 20 is made of a metal that is baser than the main shaft, the fixed end faces 50a and 50b are significantly corroded and dissolved, and a gap is formed between the main shaft and the impeller fixing bracket, so that The rotation balance is lost, the rotation main shaft is worn by the rear end fixed end surface 50a, and the bearing may be damaged. Further, the rotation main shaft may be broken, and the impeller 20 may be loosened by the looseness of the impeller fixing bracket. Sometimes it falls out. SUMMARY OF THE INVENTION An object of the present invention is to provide an underwater rotating machine such as an underwater electric pump in which an impeller made of a base metal having a natural potential with respect to the rotating main shaft serves as a sacrificial anode. An object of the present invention is to provide a structure for preventing corrosion and dissolution of the impeller fixed end face so that the main shaft can be prevented from electrolytic corrosion. In the structure for preventing corrosion and dissolution of the impeller fixed end face in an underwater rotating machine according to the present invention, the impeller is made of a metal having a lower natural potential than the rotating main shaft, and the impeller is connected to the rotating main shaft. An electrically insulating oxide film or an electrically insulating member was interposed between the shaft hole rear end fixed end surface in contact with the shaft hole front end fixed end surface in contact with the impeller fixing bracket. DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments will be described below with reference to the drawings. Numeral 1 is a rotating main shaft made of a steel material such as stainless steel, 2 is an impeller mounted on a lead-out portion of the rotating main shaft 1, and a metal whose natural potential in seawater is lower than that of the rotating main shaft 1. It is made with. Reference numeral 3 denotes an impeller fixing bracket including a washer and a nut. Reference numeral 4 denotes a shaft hole drilled in the center of the boss portion of the impeller 2, and the rear end fixed end surface 5a is coated with an electrically insulating oxide film 7a, or an electrically insulating member 8a is interposed to rotate the rotating spindle 1 And the shaft hole 4
The front end fixed end face 5b is coated with an electrically insulating oxide film 7b, or brought into pressure contact with the impeller fixing bracket 3 with an electrically insulating member 8b interposed therebetween. The member 8
a and 8b may be sheet-like or sleeve-like. Since the impeller 2 has a lower natural potential than the rotating spindle 1, the anticorrosion current is transmitted from the outer surface of the impeller 2 regardless of whether it is rotating or stopped. Thus, anticorrosion of the rotating spindle 1 in water is realized.
The shaft hole rear end fixed end face 5a is electrically insulating oxide film 7
a or the electrically insulating member 8a, and the shaft hole front end fixed end surface 5b is insulated by the electrically insulating oxide film 7b or the electrically insulating member 8b. The other outer surface is gradually and uniformly dissolved and dissolved, and the rotational balance of the impeller 2 in water is maintained throughout. According to the structure of the present invention, the shaft hole front end fixed end surface and the shaft hole rear end fixed end surface of the impeller are not corroded and dissolved gradually from the remaining outer surface. Because the impeller is uniformly corroded and dissolved, the rotation balance of the impeller in water is not lost, there is no risk of damage to the bearings and the rotating spindle, and whether it is rotating or stopped The anticorrosion current flows into the rotating main shaft from the outer surface of the impeller, and the electric corrosion of the rotating main shaft in water can be effectively prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal side view of an impeller without a structure of the present invention. FIG. 2 is a longitudinal side view of an impeller having a structure of the present invention, showing an example in which an electrically insulating oxide film is applied to a fixed end surface of an end portion of a shaft hole. FIG. 3 is a vertical sectional side view showing a main part of an example in which the impeller of FIG. 2 is mounted on a lead-out portion of a rotary main shaft. FIG. 4 is a longitudinal sectional side view showing a main part of the structure of the present invention,
An example where the electrically insulating member is a sheet. FIG. 5 is a longitudinal sectional side view showing a main part of the structure of the present invention,
An example where the electrically insulating member is sleeve-shaped. [Explanation of Symbols] 1 Rotating main shaft 2 Impeller 3 Impeller fixing bracket 4 Shaft hole 5a Rear end fixed end surface 5b Front end fixed end surface 7a Electrical insulating oxide film 7b Electrical insulating oxide film 8a Electrical insulating member 8b Electrical insulation Sexual member

Claims (1)

What is claimed is: 1. An impeller is made of a metal having a lower natural potential than a rotating main shaft, and a shaft hole rear end fixing surface that contacts the rotating main shaft and a shaft that contacts an impeller fixing bracket. An anti-corrosion dissolution structure for an impeller fixed end face in an underwater rotating machine, wherein an electrically insulating oxide film or an electric insulating member is interposed on a front end fixed face of a hole.