A Hot Melt System (HMS), will need draining whenever a new type of glue is used in the system. Thorough drainage – which is simply releasing the glue from the tank via the main plug – flushing, and cleaning is recommended each time you do this, as failure to do so can lead to contamination of the new hot melt, and a build-up of char (degraded adhesive) in the system.
However, because hot melt dispensers are pressurised systems, and because of the high temperature of the adhesives involved, draining your system can involve a safety risk. In this article, we explain how to drain a hot melt adhesive system safely, in simple steps that can be applied to any make of hot melt system.
1) Depressurising The System
Your HMS must be depressurised before drainage is attempted, or there is a risk of an explosive release of hot adhesive when the drain valve is opened. To avoid this:
- Reduce the tank air pressure to 0, and verify this with a pressure gauge
- If the built-up pressure has been removed, once the drain valve is opened the glue should start leaking from the drain valve immediately
2) Removing The Old Hot Melt
Carefully increase the air pressure to around half a bar until the glue starts pumping out the drain valve at a manageable rate. Catch the hot melt adhesive by placing a metal receptacle directly under the drain valve. This glue can be over 150°C, so be very careful to avoid splashing – and never use a plastic or glass receptacle.
If the flow slows down or sputters, this is a sign that the tank is empty of Glue.
3) Flush And Clean The System
Once empty, the HMS can be filled with new hot melt or purging liquid. Add a small amount of hot melt to the system and use this adhesive to flush your HMS to remove blockages, old glue residue, and contaminants – which can cause blockages.
4) Use PPE!
You can never completely remove all risk when working with pressurised, high-temperature fluids. Hot melt that gets onto the skin or eyes can cause severe burns, so be sure to equip all personnel draining your HMS with the appropriate personal protective equipment (PPE). This should include long-sleeved overalls, Gauntlet-style rubber safety gloves and safety goggles. Long hair and beards should be safely covered and tied back.
At Adhesive Laundry, we provide a full spectrum of hot melt adhesive services, including the supply of new and refurbished hot melt equipment, spare parts, adhesive pellets/sticks, and a tank cleaning and rebuilding service. To find out more, please call 01480 869220 today.