Sterling STT70, STT40 manual Problem, Possible cause, Corrective action

STT40 / STT70

Problem	Possible cause	Corrective action
		Check resin manufacturer’s data
	Process temperature set too high	sheet for proper drying
		temperature. Make sure plant
	due to operator error.	personnel are aware of the
		correct process temperature set
		point.
	High temperature alarm not set	Reset high temperature alarm.
Material in drying hopper cakes,	properly.
or meltdown occurs.	Process set point is out of	Restore temperature controller
	acceptable range.	to factory pre-sets.
	Function set for degrees Celsius	Verify correct Celsius or
	(ºC), set point at degrees
		Fahrenheit settings.
	Fahrenheit (ºF).
	Process thermocouple not in	Verify that the thermocouple is
		properly installed in the inlet
	airflow.
		tube.
	Burned out regeneration heater.	Repair or replace.
	Contaminated or worn out	Replace.
	desiccant.
	Leaking process air hoses.	Repair or replace.
Poor dew point performance.	Dryer operates beyond its	Check dryer and drying hopper
	capacity.	sizing.
	Bad dew point sensor.	Replace.
	Fouled dew point sensor	Clear obstruction. Air should
	manifold.	flow freely through sensor.
	Dirty filter.	Clean or replace filter element.
	The internal mechanism is not	Properly insert the internal
	inserted properly into the
		mechanism into the housing.
	housing.
	The power supply is not	Properly connect the power
	connected to its terminals	supply to the power supply
	properly.	terminals.
Nothing displays when the	No power is supplied, or the	Supply a voltage of 85 to 125
	supplied power is not within the	VAC to the power supply
controller is turned on.
	specified range.	terminals of the controller.
	Disconnect switch or Control	Check control power fuse for
		continuity. Turn disconnect
	Power switch not set to ON.
		switch and control power switch
	Control Power fuse blown.
		ON.
	Hopper release switch is not in	Turn the hopper release switch
	the “I” position.	to the “I” position.

Troubleshooting 9-3