At Godfrey & Wing, we are often asked this question and wanted to provide some explanation in this article. Some manufacturers state that sealant consumption is 10 grams per impregnated kilogram. Other manufacturers state 5 grams and some even say less than 2 grams. All of these numbers may be correct.
There is not just one answer to this question as sealant consumption is related to many variables including the work pieces, the process, the sealant, the workload and the equipment.
Of course sealant consumption will be different if you impregnate a single large motor block weighing 40 kg without a basket (direct part handling) or a batch of a large amount of small work pieces in a basket with a lot of dividers.
In the Godfrey & Wing Continuous Flow Impregnation (CFi) system, we have achieved a sealant consumption of 2.8 grams with conventional sealant for a motor block.
What is sealant consumption?
Sealant consumption is the amount of sealant which has to be added over time because sealant is carried over with the workload out of the autoclave/sealant reservoir. But then where is the sealant? Is all the sealant in the porosity or on the surface of the work piece? Sealant consumption is a volume which consists of three different parts:
1. Amount of sealant which is needed to fill the voids/porosities within the work pieces
This is directly related to the volume of porosity within the work piece which may be filled during the impregnation process. The more sealant that can be penetrated into the work piece structure/voids, the better the sealing results.
2. Amount of sealant which is lost due to handling (from the autoclave to the wash tank) or stuck to baskets and dividers
This is related to the equipment and is a result of the fixture design, how parts are placed in the fixture and the effectiveness of the sealant recovery station.
To avoid losses during handling/manipulating of the workload, it is good to add some dripping time to collect the dripped off sealant and to transport it back to the sealant reservoir for reuse. The most effective way to recover the adhered sealant is to use a centrifuge.
With a well-designed centrifuge you will be able to recover nearly 100% of the adhered, pure sealant before it comes in contact with contaminants (like water, oil, grease, etc.). If the centrifuge is installed directly inside the autoclave, there will be a minimum loss of sealant as all the sealant stays where it is needed.
3. Amount of sealant that will be washed away in the wash station
This is simple. The smaller the amount of sealant that reaches the wash tank, the smaller the amount that is lost.
Normally you are not able to recover the introduced sealant into the wash solution as all conventional sealants will emulsify in the wash water. Because of this, you need to change the wash tanks regularly to be able to guarantee clean parts.
If you have a sealant recovery rate of nearly 100% in the centrifuge, you can prolong these changing intervals as you will not introduce any contaminants into the wash water. With these recovery rates there is no need to use recycling sealants.
For more details, please contact us online or by calling 330.562.1440.