Replacing a filter in a hot melt adhesive system (such as Nordson, Robatech or Valco Melton) is a precision job that requires safety has absolute priority. After all, you are working with temperatures of up to 200°C and systems that are under high pressure.
It is best to call on hotmeltservice.nl for this. This company is available 24/7 and provides technical service. It has a stock of parts and in-house technical expertise to keep your production running smoothly.
Would you like to know what we do there? Take a look below.
Here is a general step-by-step plan that can be applied to most standard adhesive units (tank filters).
⚠️ Important Safety Warning
Risk of burns and high pressure:
- Try never Replacing a filter while the pump is still running or the system is under pressure.
- The adhesive must be liquid (hot) in order to remove the filter, which means you are working on a hot machine.
- Always carry heat-resistant gloves, safety goggles and protective clothing (long sleeves).
We recommend having this done by an experienced technical expert! When removing the air pressure, there is often still residual pressure on the adhesive section! Due to the transmission in the plunger pump (often 14:1), 2 BAR of air pressure means 28 BAR of HOT ADHESIVE PRESSURE!
1. Preparation & Requirements
Ensure you have the following items ready before you begin:
- New filter set: Check that you have the correct mesh size (often 50, 100 or 200 mesh) and that the O-rings are included.
- Tools: Spanner or Allen key (depending on your unit).
- Heat-resistant grease: O-ring lubricant (e.g. silicone grease) that is resistant to high temperatures.
- Drip tray: For leaking glue.
- Cloths: Lint-free cloths for cleaning the housing.
2. Step-by-step plan for replacing the filter
Step 1: Switch off the system and release the pressure (Crucial)
- Ensure that the adhesive is at the correct temperature (otherwise the filter will be stuck).
- Switch on the glue pump out.
- Printing: This is the most important step. Turn the system ‘pressureless’. This can often be done by:
- Close the air pressure supply to the pump.
- Activate the glue gun manually (in a tray) until nothing more comes out.
- Or use the specific drain valve on the tank if your unit has one.
Step 2: Unscrew the filter
- Locate the filter housing (usually a hexagonal nut or cap on the adhesive block/manifold).
- Slowly unscrew the cap. Please note: There may still be residual pressure, which could cause hot glue to spray out. First, loosen the cap slightly and wait a moment for any air/glue to escape before unscrewing it completely.
- Remove the filter holder and the old filter.
Step 3: Cleaning and Inspection
- Remove the old filter element (often a gauze pad).
- Discard old O-rings; use never Replace old O-rings, as these are often deformed by heat.
- Inspect the filter housing. Is there a lot of burnt adhesive (black carbon) in it? If necessary, flush this out by running the pump very briefly without the filter (do this with extreme caution and collect the adhesive).
Step 4: Install new filter
- Take the new filter and the new O-rings.
- Lubrication: Lightly grease the new O-rings with heat-resistant grease. This ensures a good seal and makes sure you can remove them again next time.
- Place the filter in the holder/cap.
- Screw the filter cap back onto the adhesive block. Tighten it by hand and then give it a little tap with the spanner. Not too tight, Due to the expansion of the metal when heated, it may become stuck fast.
Step 5: Start-up
- Put the air pressure back on the pump.
- Immediately check for leaks around the filter cap.
- Pump a small amount of adhesive through the system to remove air bubbles before resuming production.
Frequency of maintenance
- Tank filters: Replace these preventively every 6 to 12 months, or after approximately 1,000 operating hours.
- Inline filters (in the hose/gun): These are smaller and become clogged more quickly. Replace them more often (e.g. every 3 months).
- When earlier? If you notice that the adhesive pressure at the head is decreasing, or if you see a lot of ‘burnt’ particles in the adhesive.
Here is a video that clearly shows the process on a common system:
… Nordson ProBlue filter replacement instructions …
This video is relevant because it shows step-by-step how to safely replace a tank filter on a Nordson unit, which is the industry standard for many adhesive installations.
APPLIED How to Change a Filter on a Nordson® ProBlue® – YouTube
English 
Dutch 
German