How to get the best from your impregnation plant
Checking Out The System – Sealant Condition
Sealant Condition
Ensure that your sealant is clean and free from contaminants such as swarf and similar debris. Remember that autoclave gel-ups invariably start with debris build up at the bottom of the autoclave/storage tank. So keep the system clean.
Check clarity of sealant to ensure no water/oil is present.
Some sealants are more prone to contaminants than others. If there is discoloration or a translucent appearance to the sealant it would be prudent to request your sealant supplier test a sample for contamination. Some contamination of oil may not unduly affect sealing performance but could affect temperature and/or chemical operational performance. Trace where the contamination is coming from and eliminate it.
Check that sealant is being correctly degassed before use.
Degassing cycles are often overdone on the basis that the more you degass, the better the sealant. This is not the case. The sealant requires dissolved air as this is part of the stability mechanism. Removing this by extended periods of degassing will make the sealant anaerobic and cause it to cure.
Absorbed air (as distinct from dissolved air) is the free air that is taken in from the atmosphere whenever the sealant is sitting at atmospheric pressure and this needs to be removed from the sealant before impregnation takes place. If not taken out, this free air causes significant exudation of sealant from the porosity during the curing cycle. The result is poor sealing.
The presence of this air can also have an inhibiting effect on the cure within the porosity. Link this with low catalyst level and you have a major curing problem. This free air generally comes off the sealant fairly quickly below 50 mbar and can normally be accommodated within the normal cycle time.
This applies to dry vacuum transfer systems only. Wet impregnation systems should have a separate degass cycle before impregnation commences.