Active ULTRASONICS.....Providing Innovative Ultrasonic Solutions

Principle of operations:

High power ultrasonic transducers are strongly (mechanically and acoustically) coupled to the external cylindrical housing of the filter element. The active filter element inside of the housing is radially stimulated (360°) by intensive ultrasonic vibrations transmitted through the liquid or liquid slurry. With sufficient power and amplitude the ultrasonic vibrations will produce ultrasonic cavitation and streaming effects within the liquid and to the filter element. Oversized particles, powders, impurities, or other materials which usually fill or blind the fine filter structure are forced out of the active filter body. Flow rates are improved by a cleaner filter element plus the ultrasonic acoustic effects are actively working to reduce surface tension, cohesive forces, and or adhesive forces.

Coupling the high power ultrasonic transducer to the filter housing may be accomplished in two ways:

• A custom housing may be designed to allow a direct connection between the transducer and the filter housing. This coupling connection should be optimized to allow ultrasonic stimulation of the entire housing when possible. Coupling may be perpendicular or axial in orientation to the filter housing.

• A new Clamp-On technology allows easy adaptation to existing stainless steel cylindrical filter housing of nearly any size.

To achieve a uniform (surface and 3D) distribution of ultrasonic amplitudes and ultrasonic pressure our MMM ultrasonic generator performs frequency sweeping around the optimal resonant frequency of the resonating system (e.g. 35 to 45 kHz). The speed of applied frequency sweeping is in the range of 50 to 100 sweep intervals per second. Frequency sweeping also reduces the chance that some particles or areas of the filter body remain inactive (non-vibrated).

To eliminate the creation of standing waves and other vibration stationary (or stable) structures inside the filtering tube, low frequency, and full power On/Off pulsing is applied to the ultrasonic signals. This way, the applied pulse repetitive and transitory (mechanical) excitation is able to send shock pressure waves to the filter body. Pulsing shock pressure waves can be many times stronger than the effects of continuous operation. Such mechanical On/Off shocking also produces low frequency and very high vibration amplitudes that are superimposed and mixed with high frequency ultrasonic oscillations, thereby maximizing the effects of filter cleaning.

Programming, Regulating, and Operating Parameters:

Ultrasonically assisted filtration should operate at an optimized ultrasonic power level, meaning no more or no less power than is required. If the input power is more than necessary the ultrasonic transducers will produce excessive high thermal dissipation. If the power is insufficient the filter body will not be efficiently cleaned. When an optimal power regime is found the ultrasonic system should not produce overheating. This situation is closely related to the average liquid flow rate and average liquid temperature inside of the filter housing. Normally much of the delivered ultrasonic energy is dissipated and absorbed by the liquid, which passes through the filter housing. To reach the optimum operational conditions the output ultrasonic power and On-Off pulse-repetitive modulations should be carefully chosen and adjusted for every new application.

To better understand operational optimization it is useful to know that ultrasonic transducers are able to produce and accept significantly more power in a short pulse-repetitive regime than when they operate continuously. Therefore On-Off power modulation becomes an important variable and should be carefully adjusted. To address most any application the MMM technology offers a wide range of possible combinations of continuous or pulse power regulation, usually much more than will ever be required.

If the ultrasonically assisted filter system is overheating, this is usually a sign that the optimal operating power parameters such as pulsing Time-On and Time-Off as well as the output voltage of ultrasonic signal is not properly adjusted. In optimum set-up, after several hours, the temperature of the filter body should be several degrees of Celsius higher than the average temperature of input liquid. If the ultrasonic filter body and the ultrasonic transducers have operating temperature more than 10°C higher than input liquid temperature, it usually means that the system is not in the optimal operating regime. Therefore it should be modified, for instance by reducing the Time-On and widening Time-Off, or by reducing the output voltage to the transducers.

In normal applications the operating temperature of the filter system should never exceed 90°C. Temperatures in the range of 40°C to 60°C, or lower, are considered normal and acceptable for a stable and long operating life of the filter. For higher operating temperatures (higher than 100°C), the filter system and ultrasonics require a special design and cooling options to protect the ultrasonic equipment.

In the event of no-liquid or no-flow conditions, the ultrasonic system must be stopped. Continued operation in these state will cause ultrasonic transducer overheating resulting in subsequent inefficient operation or damage to the transducers. Production systems should be equipped with over-temperature and no-liquid-flow protection mechanism that will shut down ultrasonic generator.

Example: Transducer mounted directly to filter housing end. (Sintered metal filter)

Example: Clamp mounted Transducer to standard filter housing. (Sintered metal filter)

Example: Clamp mount Transducer systems allows easy adaptation to existing housings