Install hot melt hoses correctly: tips from a professional

author Robert Seiferth, Technical Account Manager and Trainer at Robatech Germany
Hot melt hoses are probably the most inconspicuous component in an adhesive application system, which is why they often do not receive much attention. Only when the adhesive stops flowing and the machine comes to a standstill due to a coked hose or a defective heating conductor does it become clear what a key role they play. Handling hot melt hoses correctly is not difficult, but it makes a big difference.

Enduro heated hose

Heated hoses have a complex design. The heating conductor, which wraps around the entire length of the hose core, is a particularly sensitive component. We are talking about a very thin wire that is stretched by forces such as tensile or torsion, thereby changing its resistance value. As a result, the temperature is increased locally: the heated hose overheats. On the one hand, this shortens the service life of the heating conductor – and thus that of the hot melt hose. On the other hand, overheating also leads to coking of the adhesive, which clogs not only the application head but also the hose. Care when handling hot melt hoses is essential to prevent the entire adhesive application system from coming to a standstill.

  Design of a hot melt hoseCaution sensitive parts: do not bend, pull or twist the high-pressure hose and heating conductor!

Hot melt HOSES: KEEP EVERYTHING FLOWING

A few simple rules ensure that your heated hoses reliably transport the adhesive from the adhesive melter to the application head for many years. Regardless of whether you are rolling up the hose for transport or installing it in a machine, please note the following:  

  • No bends: Do not fall below the specified minimum bending radius of the hot melt hose! If the high-pressure hose surrounding the hose core is bent, this can lead to a leak in the hose core over time. This also overstretches heating conductors and electrical cables which, in turn, significantly shortens their service life.

  • No torsion or tensile load: Heated hoses must not be twisted or stretched so as not to tear the internal high-pressure hose and the heating conductor wound around it. Hot melt adhesive hoses must be moved in a line, especially in dynamic applications. Use swivel connectors as torsion protection.

  • The right mounting: Cable ties are not suitable for mounting hot melt hoses. They cut into the insulation of the hose and cause bends. Use special hose holders for gentle mounting.

  • Be careful with water: Most heated hoses are not watertight unless they are marked as such. For this reason, do not use water to clean the outside of heated hoses. If moisture penetrates the hose, the electrical contacts may oxidize or be damaged by a short circuit. Heated hoses must therefore be stored in dry rooms and away from sunlight. 

Mounting two hot melt hoses: Bad example with cable ties, correct example with EasyFix hose holders from Robatech ❌ Cable ties are not a good choice for mounting hot melt hoses
✔️ EasyFix hose holders from Robatech not only ensure the perfect distance between the hot melt hoses, but also prevent them from bending

Heated HOSES: A HOT ISSUE

When installing the hot melt hoses, you should also give some thought to the thermal system. Although hot melt hoses are insulated, they release heat to the outside. If several heated hoses are installed next to each other, it is important to keep a distance of at least 25 mm so that they do not heat up eachother.  In addition, you should not arrange the hoses directly on top of each other, as otherwise the waste heat from the lower hoses will heat the hoses above. 

Heated hoses with and without safety distance > 25 mm, diagramAlways install hot melt hoses at a distance to avoid overheating

If you notice that the adhesive is becoming darker and darker, this is a sign of local overheating. How can this happen? The temperature sensor that monitors the heat output in the hose measures the temperature at a single point, namely just before the application head. The control system uses this information to regulate the heat output, which is identical for the entire hose length. Cold drafts or a lack of air circulation change the local temperature of the hose without the temperature sensor registering it. To prevent this from happening, make sure that the same thermal conditions are present for the entire length of the hose. 

  • Do not install hot melt hoses directly on top of each other. Waste heat from the lower hoses can overheat the hoses above.
  • Protect heated hoses from drafts, otherwise the heat output will increase unnecessarily and the heated hose will overheat.

  • Do not encapsulate hot melt hoses. Heat must be able to escape.

As you can see, with just a few simple tips, you can create the best conditions to ensure your hot melt hoses last for years to come. These tips also ensure that the adhesive application works smoothly as the heated hose can perform its function reliably. 

 
author

Robert Seiferth, Technical Account Manager and Trainer at Robatech Germany

Robert Seiferth is a Technical Account Manager and Trainer at Robatech Germany. For the past 12 years, he has overseen the service hotline, supporting customers from a wide range of industries with technical problems. He passes on his know-how to customers in user training courses.

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