Backgrounds Plating
Presentations
The Problem: Clogged Pumps In Gold Plating
CHALLENGES WITH MAG-DRIVE PLATING PUMPS
Gold sulfite and gold thiosulfate solutions have been developed as an alternative to the highly toxic gold cyanide plating baths. A critical drawback to the use of cyanide-free alternatives is that bath stability is more difficult to control. It is imperative to avoid hotspots, dead-zones, extensive shear, rough surfaces, narrow gaps and fissures.
Magnetically driven plastic centrifugal pumps are widely used in metal plating because of their chemical resistance and leak-free design. In mag-drive pumps, the centrifugal rotor is driven by a magnetic coupling through the pump casing, enabling a seal-less design (Figure 1).
The principle limitation of the mag- drive design is the need of process lubricated slide bearings which are usually fabricated from carbon, silicon carbide or alumina ceramic. When operated with critical plating solutions such as gold sulfite, the metal tends to precipitate on the bearing surface. The precipitate ultimately fills the narrow gap between the stationary bearing spindle and the rotating bearing sleeve. In pump tests performed with gold sulfite solution at elevated temperatures, all mag-drive pumps failed within 3 to 17 weeks. In all cases, the slide bearings were completely clogged with gold which ultimately resulted in increased torque and complete bearing failure. Figure 2 shows the impeller and the bearing of a pump which ceased to function after only 3 weeks of operation.
THE SOLUTION: LEVITRONIX BEARINGLESS PUMPS
REVOLUTIONARY MAGNETICALLY LEVITATED CENTRIFUGAL PUMP
Compact Size And Highest Reliability
THE SMALLEST PUMP
Mag-drive pumps have an inherently complex design, consisting of an electrical motor, a mechanical coupling between the motor and the magnetic clutch, the magnetic clutch and the pump. Each of the rotating elements including the motor, the magnetic clutch and the impeller require a separate set of mechanical bearings. These elements wear out and fail.
Mag- drive pumps are also large compared to their hydraulic power. Levitronix pumps are 3-5 smaller than mag-drive pumps with comparable hydraulic performance (Figure 9 and 10). The highly integrated design of the pump and motor combined with the absence of mechanical bearings and bulky magnetic couplings, results in a system that greatly reduces the space requirements in your plating equipment.
Since there are no mechanical bearings to clog or wear out, Levitronix pumps can also be placed at locations which are not readily accessible. The high reliability and small size of the Levitronix pumps allows you further freedom in the placement of the pump.
