TPT September 2007

Furthermore, it is absolutely necessary to invest in research of advanced cleaning technologies to take into account a range of important issues. These include worker safety and health, environmental protection, reduction of water and electricity consumption, reduction of waste and use of ecologically compatible chemical detergents. For this reason, it is necessary to always develop machines with a totally closed cycle. It is also important to develop accessories for cleaning equipment in order to avoid any dispersion and to recover, filter and treat all fluids and vapours produced by the cleaning process. The excellent performance of a cleaning machine depends on the coexistence of certain conditions. These conditions are advanced technical features, an effective cleaning cycle, optimum working temperature, and efficient chemical detergents. However, one technology that can substantially improve performance is ultrasonic technology. In order to obtain the most effective ultrasonic action it is necessary, first of all, to choose the best type of ultrasonic technology (eg magnetostrictive or piezoelectric). Once this has been selected, it is necessary to establish, for each particular case, the best setting frequency, power, ultrasonic transducer shape, and ultrasonic transducer dimension/position. These settings must all be achieved according to liquid density and tube weight and shape. 3. The definition of tube ‘super-cleaning’ The main problem faced by all producers of industrial cleaning systems, is the penetration of the superficial boundary layer on tubes to be cleaned. This procedure is otherwise known as ‘super- cleaning’. Contaminants are usually bound to the tube surface by hard cohesion stresses, which are due to electrostatic phenomena and contaminant chemical composition. The smaller the contaminant particles, the more difficult it is to remove them. There are only a few renowned methods used to penetrate the boundary layer. The most effective are ultrasound technology or the use of special fluids (eg carbon dioxide). In both cases, the contaminant particles acquire the necessary energy to detach themselves from the tube surface. However, this mechanical removal action has to be added to a thermal action (either heat or cold helps remove the contaminant). Super-cleaning is gaining increasing benefit from the development and implementation of mechanical actions such as ultrasound, agitation, rotation, balancing, hydrokinetics, and spraying. In addition, research and development into alternative detergent solutions is also improving the effectiveness of super-cleaning, especially since traditional solvents are regarded as dangerous for health and the environment.

Panel 1: Examples of very difficult tube cleaning processes In the panels on pages 163, 164 and 165 are cases of tubes and tube cleaning machines representing the most difficult and actual cleaning problems. In the first panel (figures 11, 12, 13 and 14) the problem and solution concerns the achievement of premium tube cleaning under a high productivity output. The cleaning operations have to be totally automatic and the machine is inline, strictly connected with the manufacturing machine. The goal is more difficult when the main manufacturing line has a high output per hour and the cleaning cycle cannot delay production. Therefore, the cleaning machine has to reach the best performance in a very short time.

€fi Figure 11-12 :

Automatic equipment (outer and inner) for ultrasonic cleaning, rinsing and drying of aluminium tubes for fumes discharge of house heating plant (productivity of 1 tube every 30 seconds)

€fi Figure 13-14 :

Automatic high productivity equipment (outer and inner) for ultrasonic cleaning, rinsing and drying of stainless steel tube for pipelines.This machine is automatically connected with the manufacturing equipment

4. Precision requirements of medical tube cleaning

The cleaning of medical tubes, needles and cannulae represents a very complex and difficult washing problem, comparable with human body prosthesis cleaning. During drawing and subsequent manufacturing operations, the tube becomes dirty with oil and grease, while metal porosity is also a problem. A number of tests have proved that a washing cycle activated by ultrasound permits

163

S eptember /O ctober 2007