Many people probably associate the word "spraying" primarily with graffiti, yet this ignores the diverse industrial applications for coating of a wide range of products. The automotive industry, machine tool manufacturers and makers of other mass-produced consumer products, for example, make use of stationary electrostatic spray systems which require no operator to be present in the paint booths during operation. It was therefore easy to improve the efficiency of such systems: by increasing the concentration of the coating and solvent and by increasing the discharge energy and the high-voltage current during the painting in the closed spray booth. However, hand-held spraying equipment is increasingly the medium of choice for products which are too large for paint booths or painting lines - in shipbuilding, for example - or for small production runs right down to individual products.
If the intention is to make portable spraying equipment more energy and resource-efficient and thus more environmentally friendly, the above options are of very limited use. The operators hold the spray gun in their hand and stand directly in the spray area, meaning that they are directly exposed to the potential hazard. The potential hazard of dangerous electric shocks, in particular, needs to be considered.
Such deliberations are based on the DIN-IEC pre-standard "Effects of electric current on human beings and livestock" which stipulates maximum limit curves for dangerous body currents. The Physikalisch Technische Bundesanstalt (PTB) carried out a series of experiments to investigate whether the electrostatic spray guns currently used were keeping within these limit curves. It was found that the limit curves of the pre-standard were being kept well within. This means that it is possible to increase the operating current of the spray guns to increase their efficiency. Yet it is still possible to stay well within the limit curves to avoid any risk to the operator.
These findings are to be communicated to the other national committees in the coming deliberations of the relevant technical body at the European level in an effort to raise the acceptance of this new approach and to have it taken it into account in future work.