You mean that heater bands just burn out? False. According to some band heater supplier, environmental conditions typically result in short circuits, hot spots, or forcing band heaters over their usual working temperatures, which leads to early failures and the need for frequent replacements.
Pollution
The most common reason for band heater failure is contamination. Hydraulic oil, plastic, and moisture are the three primary pollutants. Contamination of the lead wire, rather than impurities inside the band, is the main reason for the failure of band heaters. Heaters resistant to contaminants don’t stop lead wire corrosion.
Invest in inexpensive band warmers and make regular replacements. Verify that the machine barrel where the heater is mounted is clear of scale and grit. Scale can change the heater’s heat-conduction route and create a hot spot.
Inadequate Contact
As conductive heaters, mica, high watt density, and extruded aluminum bands must fit tightly. Resistance wire failures may result from localized hot spots that form if the fit isn’t tight enough. The fit becomes more crucial as operating temperatures rise. With a ceramic band, a snug fit is not as important. Because of their serrated edges, ceramic band housings permit complete expansion while being installed.
Verify the OD of the machine barrel and place an order for band heaters that have the same dimension. Adhere closely to the tightening and installation instructions. Whenever feasible, designate clamping mechanisms in the strap style. They can assist in keeping the heater firmly on the barrel while it is operating since they have a lower CFTE rate than the heater.
Density of Watts
The band heater’s wattage is significantly more than needed for operation, and heaters are frequently sized to heat the press as rapidly as possible. This can reduce the life of the heater by raising interior temperatures during the molding process.
Select a watt density that, while accounting for a suitable safety factor, is as near to the required load as feasible. The leading band heater provider may assist you in determining the appropriate wattage for a particular application.
Misuse of Barrel Blankets
Blankets can make conductive heaters run hotter if their watt density is approaching their intended limit, putting more strain on the element wire and the dielectric materials.
To find out the maximum watt density values, contact your heater provider. If using blankets, lower the band’s intended watt density by at least 25%. This might not always be achievable with fast-cycling machines since the heater needs to provide adequate make-up heat for the process to function properly.
Control of Temperature
Runaway temperature commands often happen when a sensor, such as an RTD or thermocouple, loosens or disconnects and fails to establish firm contact with the surface that needs to be measured. Although the process is already at the proper temperature, faulty input that the control device receives causes the heater to run continuously. Overshooting the temperature is another issue.
Think about using a control that offers a gradual or gentle starting. To enable the generated wattage to seep into the barrel, a soft-start control will alternately turn on and off the heater.
Note: The purpose of soft-start controls is to prevent a heater from going to the ground due to moisture intrusion. Some will gradually raise the voltage percentage applied to the heater.