When talking about daily maintenance issues, though, all thermoplastic equipment manufacturers emphasize the main concern is safety.
"When operating a thermoplastic handliner or any piece of equipment, safety should be foremost on any operator's mind," says Tom Waxler, president of Advance Striping Equipment. "The plastic has to be maintained within safe temperatures, between 400°F and 440°F for application. Thermostats have to be routinely checked on the kettle and the hand applicator to ensure they're working. All of our kettles have an additional safety features called a Hi Temp Limit Switch that shuts off the main gas line to the burner if the thermostat fails. If a thermostat goes bad, your kettle won't know that is should shut down.
"There are not many moving parts on a handliner, but there are a few bearings and they should be lubricated. Also, it may sound simplistic, but make sure the handliner has a full tank of LP gas before you start out in the morning. Then, always drain the handliner at the end of the day. If you don't, the plastic will freeze up like ice cream overnight and make startup difficult the next morning."
Adds Mayle, "Make sure you close the main material valve after draining the container. Operators have been known to load their handliner from a kettle melter and then helplessly watch the thermoplastic run right on the ground."
Mayle notes that thermoplastic has been used in this country since the late 1950s with continuing good results. That material contains binder, pigments, fillers, and glass beads which turn to liquid when heated. There are two types of thermoplastic: hydrocarbon and alkyd. Hydrocarbon is made from petroleum-derived resins and alkyd is made from wood-derived resins.
He offers this advice when heating the material in a melter. Calibrate the kettle's material temperature gauges periodically (weekly is suggested) by using a reference thermometer. Fill the melter to 30% capacity. After the thermoplastic becomes liquid, gradually add the remaining material to fill the melter to capacity.
Mayle advises transferring thermoplastic from the melter to the handliner 30 minutes after its temperature reaches operating range (400°F to 430°F). During transfer, thermoplastic should pass through a 1/4-inch mesh screen. Add more thermoplastic when two-thirds of the liquefied material has been used. The new material will be ready for transfer 30 minutes after reaching operating temperature range. Cease agitation during cool-down after the thermoplastics' temperature cools to 275°F.
"Do not hold thermoplastic above 400°F for more than six hours, and it should never exceed 450°F," Mayle says. "Granular thermoplastic can be reheated a maximum of three times and block material only twice. A color change in the thermoplastic indicates the material is overheated and beginning to scorch. Schedule the melter for cleaning if charred or burned particles remain on the screen after transfer and completely flush the system when changing from alkyd to hydrocarbon or vice versa.
"Avoid completely draining the kettle during overnight shutdown unless material must be replaced. Keep the kettle closed to protect against moisture and other contaminants."
Advanced Striping Equipment's Waxler has one final note for anyone operating a kettle and handliner. "Operators need to understand the operation of their equipment before they attempt to do any striping or maintenance. They should read the operator's manual in its entirety and familiarize themselves with the thermoplastic striping process."
Safety First with Thermoplastics
From M-B Companies