Cleaning ampoules the ultrasonic way

Cleaning ampoules the ultrasonic way

Natarajan Iyer

In an injectable plant, sterile liquids are filled in vials, ampoules and pre-filled syringes. Each one of the above has certain advantages and disadvantages. Since the opening of an ampoule is very small, internal cleaning becomes very difficult, as it cannot be cleaned manually. To properly clean an ampoule, ultrasonic waves are used. Therefore, it becomes very important to know the basics of ultrasonic cleaning to validate ultrasonic ampoule washing machines. This article is trying to throw light on ultrasonic validation for ampoule washing machine. An ampoule washing machine cleans the ampoules with a jet of water and by applying ultrasonic waves. Ultrasonic waves are used to loosen particles that stick to the ampoules.

Ultrasonic cleaning offers several advantages over conventional methods. Ultrasonic waves generate and evenly distribute cavitation implosions in a liquid medium. The released energies reach and penetrate deep into crevices, blind holes, and areas that are inaccessible by other cleaning methods. The removal of contaminants is consistent and uniform, regardless of the complexity and geometry of the part being cleaned. Cleaning is usually completed in one to three minutes.

An ultrasonic cleaning system has three components—ultrasonic generator, transducer and the vessel, where it is attached. The ultrasonic generator generally works on electrical power, which is usually 240 volt 50 Hertz, and converts it into a higher voltage and faster cycle to activate the transducer, usually 2,000 volts at 40,000 Hertz, for a cleaning system.

The function of a transducer in an ultrasonic cleaning system is to convert electrical pulses from the generator into a sound wave or pressure wave. This pressure wave travels through liquid and forms cavitation, which works as a scrubbing force in an ultrasonic cleaning system. The transducer is bounded to sides or bottom.

Constructional aspects of transducer

Ultrasonic transducers are made up of a number of materials, the most common one being a piezoelectric material used in ceramic, called lead zirconate titanate. During the manufacture of ceramic, it is subjected to high potential difference, which causes polarisation. When this is put in service and has an electrical potential applied to it from the ultrasonic generator, it swells and changes dimension. When the electrical potential is removed, it reverts to its normal dimensions.

By cyclic application of voltage, the transducer expands and emits a pressure wave. The frequency of the pressure wave is decided by the frequency of the transducer and output frequency of the generator.

Magnetostrictive transducers are generally less efficient than their piezoelectric counterparts. This is primarily due to the fact that the former requires a dual energy conversion from electrical to magnetic, and then from magnetic to mechanical. Some efficiency is lost in each conversion. A magnetic hysteresis effect also detracts from the efficiency of the magnetostrictive transducer. On the other hand, piezoelectric transducers expand and contract when potential difference is applied. There is no conversion from one form of energy to another.

Fixing of the transducer

Transducers are bounded either to the surface or immersed in the liquid. In both the cases, if it is a piezoelectric transducer, they are attached by epoxy, and if it is a magnetostrictive transducer, which is heavier, they are attached by brazing to the wall of the equipment.

Magnetostrictive

Fig 7. Magnetostictive transducer

Magnetostrictive transducers utilise the principle of magne