Modern drycleaning machines are designed to ensure safe operation and to minimise the risk of leaks or vapour escapes but staff who operate the still must be properly trained. The main risks with still cleaning are:-
• residue in still door seals, which can result in serious solvent leaks;
• cracked door seals;
• failure to close the door properly;
• finding large unexpected volumes of solvent in the still when the door is opened – this is one of the most common risks;.
• faulty still door switches which may stick in the closed position. If still residue is spilt on the switch and the door is left open the machine thinks it is closed.
Serious spillages, which can lead to the emergency services being called, are almost always associated with failure to follow safety rules during cleaning. To minimise the risks I advise following these guidelines.
1. Stills should always be cleaned when they are cold.
2. Once the still door has been opened, the still cleaning process must be completed without any interruptions. The operator that starts the task must always finish it.
3. As far as possible make sure the still is empty (except for residue) before proceeding to open the still door. Visual access through the still sight glass is often restricted by dirt and debris.
4. When opening the still door, slacken the nut and ease it open slowly keeping the hasp closed – if there is solvent in the still the door can then be easily be closed thus avoiding large amounts escaping uncontrolledly.
5. Before closing the still door make sure that the gasket is in good condition, that the sealing surfaces are clean and if possible clean the still sight glass.