For several years, the idea among the manufacturers of industrial systems for metal washing was that the best solution to remove dirt and residues from the surface of the components was to use cleaning agents based on organic solvents.

The reasons behind this theory were several, including:

• high levels of final cleaning;
• repeatability of the result;
• ability to remove a large amount of contaminants;
• considerable reduction of the times associated with each washing cycle.

With the introduction of the European regulation EU1999 / 13 / C on the Directives on Solvent Emissions, all the traditional systems that envisaged the immersion of the components in liquids and / or vapors that could be freely released in the ‘atmosphere.

Before reaching this conclusion, several tests were carried out to try to identify the best configuration that allowed emissions to be reduced: in the end, at the light of the failures that happened, through the EuroNorm Standard 12921 (VOC Directive 2003/87 / EC) it was decided to limit the residual concentration of solvent inside the washing chamber to 1 gm / m3 before opening the loading door.

The VOC emissions legislation in Germany

In Germany, for example, a regulation very similar to the current VOC was introduced as early as 1990: to date the restrictions envisaged in this regard are far greater than the European, American and English legislation and the use of the solvent in the Country has reduced by 98%.

Solvents such as perchlorethylene, trichlorethylene, methylene chloride and modified alcohols can consistently achieve surface gravimetry levels of 3-5 mg / m2.

The solvent is constantly purified through the distillation and filtration units, in this way the contaminants are separated from the solvent and automatically transferred inside the tanks where the predetermined cleaning levels are reached.

Inside the washing chamber, by means of ppm control and vacuum drying, the activation of coal units ensure that all emissions are within the established standard.

Vacuum drying and ppm control inside the washing chamber, by means of an activated carbon recovery unit, ensure that all components are free from solvent residues before the end of the unloading phase.

The results of the FIRBIMATIC cleaning systems in terms of VOC

Tests and studies conducted on metal washing systems made by our company show emissions levels close to zero.

This important achievement is made possible by the use of drying systems with hermetic circuit technology which effectively eliminates the need for an emission chimney.

Both inside very small washing chambers and in large ones, it is possible to appreciate the result of high levels of surface cleanliness and the guarantee of long-term compliance with the directives on emissions.

The advantages of solvent-based degreasing systems

Alongside the more than positive results in terms of emissions, other important advantages related to the use of solvent-based metal washing machines are:

• the low surface tension causes the liquid to pass through complex geometric parts such as thin threads and blind holes carrying away contaminants;
• usually solvents allow to eliminate a wide range of contaminants compared to aqueous solutions which, on the contrary, result “specific” for a single contaminant;
• separate distillation within hermetically sealed solvent systems ensures that both pure steam and clean solvent are available for each washing cycle;
• the volatility of organic solvents ensures that the drying of the components is rapid and accurate: what has been said is verifiable by comparing the latent heat of evaporation of water at 2280 kj / kg with that of organic solvents equal to approximately 200-300 kj / kg;
• by applying the vacuum to the treatment chamber and reducing the boiling point, the residual heat of the particles will ensure instant vaporization allowing up to 10 washing cycles per hour;
• the solvent washing technology with hermetic cycle ensures that all contaminants are isolated in the distillation unit. Today, solvent suppliers offer the possibility of using special transfer systems that ensure the safe transfer of both the new solvent and waste residues within the closed circuit.

Solvent-based washing and degreasing systems: a small insight into SFK machines with modified alcohol or hydrocarbons

FIRBIMATIC’s hermetically sealed solvent-based washing and degreasing systems, which use non-halogenated solvents such as class A III hydrocarbons, allow for up to 8 washing cycles per hour with standard filtration from 1 to 100 microns.

The structure of hydrocarbon solvent plants for metals includes:

1. two to three indirectly heated vacuum solvent tanks;
2. one or two integrated vacuum distillation units;
3. washing chamber with doors equipped with automatic safety closure;
4. an integrated steam generator;
5. no exhaust chimney;
6. PLC control system for short programming (with an easy-to-use interface for the operator);
7. possibility of using baskets for static, rotating or oscillating components

The SFK series of machines for industrial metal washing perfectly complies with the emission standards envisaged at European level (including those of German legislation) and the EN12921 standard.

>> Find out more about the SFK FIRBIMATIC series

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