Pumps handle volatile, near-boiling solvents with ease

Withstanding the harsh conditions found in ultrasonic cleaning machines - including the need to transfer volatile, near-boiling solvents - has been a successful application involving Finish Thompson centrifugal pumps. The pump was supplied by Michael Smith Engineers to Guyson International for testing on a demonstration machine.

Guyson International's Kerry ultrasonic cleaning equipment includes both aqueous and solvent-based systems with applications in precision engineering, electronics, aerospace, metal finishing and medical manufacturing.

Ultrasonic cleaning works by introducing energy into a tank containing the cleaning solution and this causes minute bubbles to form and collapse within the solution. This cavitation results in a very gentle, yet highly effective scrubbing action on the component surface, loosening the contaminants. As a result of this, ultrasonic cleaning is acknowledged as a rapid and highly effective method of precision cleaning of components.

Pumping requirements

The pump, a magnetically-coupled centrifugal model in PVDF from the Finish Thompson DB range, was selected by Guyson following in-service reports that had identified the potential for failures of the main circulation pumps on some models of their solvent cleaning machines. Guyson had identified that the combination of handling volatile, near-boiling solvents with a very low suction head had resulted in very low pressures at the pump inlet, with NPSHa levels of typically less than one metre. On many other types of pump this would cause severe cavitation and inevitably lead to regular failures.

A DB pump was tested on a demonstration ultrasonic cleaning machine and found to perform very well without any failures under all test conditions. These operating scenarios included dry-running, starved suction by closing the suction valve and dead-heading by closing the discharge valve. After extensive running the pump was taken out, stripped and inspected for wear to the impeller, shaft, bearings and thrust rings. All were found to be in perfect condition.

John King, the Technical Support Manager at Guyson International, commented: "We had been searching for a suitable alternative pump for some time, so when our trials proved that the DB pump from Michael Smith Engineers was capable of withstanding the rigorous conditions found in our solvent cleaning equipment we were keen to incorporate them into our design. So far we have had no in-service failures since changing to these pumps."

The Finish Thompson DB range of centrifugal magnet drive pumps includes eight series of pumps handling capacities up to 50m3/hr and differential heads up to 43m. Their sealless mag-drive design makes them an excellent alternative to mechanically sealed pumps, particularly in corrosive duty applications. Superior run-dry capability helps to protect the pump from system upset or operator error and so eliminates expensive repairs and downtime.

Follow the link for more information about the Finish Thompson centrifugal pumps.