Sterling Dehumidifier STT40 User Manual

Operation Instructions  
Dehumidified air dryer  
STT40  
STT70  
Sterling Material Processing  
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STT40 / STT70  
Sterling Material Processing retains all rights to change the information in these operation  
instructions at any time without notice.  
We assume no liability for any errors from direct or indirect damage resulting in context with these  
operation instructions.  
Copying, translation or publication in any form except for personal use by the purchaser requires  
approval from Sterling Material Processing.  
All rights reserved.  
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Table of contents  
1. General Information.................................................................................................1-1  
1.1. Warnings and symbols..........................................................................................1-1  
1.2. Explanations and information...............................................................................1-3  
1.3. Legal basis ............................................................................................................1-3  
1.4. Field of application ...............................................................................................1-3  
1.5. Notes on Usage .....................................................................................................1-3  
2. Safety instructions....................................................................................................2-1  
2.1.1. Assembly......................................................................................................2-3  
2.1.2. Operation .....................................................................................................2-3  
2.1.3. Maintenance.................................................................................................2-4  
2.2. For the safety of the device...................................................................................2-5  
3. Start up.....................................................................................................................3-1  
3.1. Initial Operation....................................................................................................3-2  
3.1.1. Switching on the Dryer................................................................................3-2  
3.2. Continuous Operation...........................................................................................3-4  
3.2.1. Switching the Dryer on................................................................................3-4  
3.2.2. Setting the Drying Temperature...................................................................3-5  
3.3. Switching the Dryer off ........................................................................................3-7  
4. Error and error correction ........................................................................................4-1  
5. Maintenance.............................................................................................................5-1  
5.1. Maintenance schedule...........................................................................................5-3  
5.2. Preventative Maintenance.....................................................................................5-4  
5.2.1. Servicing Process Air Filters .......................................................................5-4  
Cleaning or Replacing the Return Air Filter............................................................5-5  
5.2.3. Servicing the Dew Point Monitor ................................................................5-6  
5.3. Corrective Maintenance........................................................................................5-7  
5.3.1. Symptoms of Worn Desiccant .....................................................................5-7  
5.3.2. Replacing Worn Desiccant ..........................................................................5-8  
5.4. Disposing of Drying Agents .................................................................................5-9  
5.5. Replacing the Process Heater..............................................................................5-10  
5.5.1. Replacing/Cleaning the Cooling Coils ......................................................5-11  
5.5.2. Replacing the regeneration heating coil.....................................................5-12  
5.6. Cleaning the Drying Hopper...............................................................................5-13  
6. Functional description............................................................................................6-15  
6.1. General Information............................................................................................6-16  
6.2. Drying Hopper (Optional)...................................................................................6-19  
6.2.1. Hopper Heater............................................................................................6-20  
6.3. Connection to a Pneumatic Conveying System (Optional) ................................6-22  
6.4. Return Air Cooler (Optional)..............................................................................6-22  
7. Transporting, Assembly and Storage.......................................................................7-1  
7.1. Transporting and Packing .....................................................................................7-2  
7.2. Assembly...............................................................................................................7-3  
7.3. Storage ..................................................................................................................7-3  
8. Assembly instructions..............................................................................................8-1  
8.1. Installation of the exhaust fan for regeneration of exhaust air..............................8-2  
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8.2. Grounding the equipment against electrostatic charging......................................8-2  
8.3. Electrical Connection............................................................................................8-3  
8.4. Connection of Return Air Cooler (Optional)........................................................8-4  
9. Troubleshooting.......................................................................................................9-1  
9.1. Introduction...........................................................................................................9-1  
9.2. Determining Temperature Controller Errors or Sensor Errors .............................9-4  
Using a Thermocouple.............................................................................................9-4  
Using a Platinum Resistance Thermometer.............................................................9-4  
10. Technical data........................................................................................................10-5  
10.1. STT40 ...............................................................................................................10-5  
10.2. STT70 ...............................................................................................................10-5  
10.3. Dimension Sheet...............................................................................................10-6  
11. Spare parts list........................................................................................................11-1  
12. Electrical manual ...................................................................................................12-1  
13. Accessories ............................................................................................................13-1  
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1. General Information  
These operation instructions are addressed to all users of this  
device.  
These operation instructions must be followed by every person  
working on or with the unit.  
1.1. Warnings and symbols  
The following warnings and symbols are used in these operating instructions:  
This symbol indicates danger to life! Fatal or serious injury is  
possible if the corresponding instructions, regulations or  
warnings are not observed.  
/
This symbol indicates that serious injury is possible if the  
corresponding instructions, regulations or warnings are not  
observed.  
)
This symbol indicates that extensive damage to equipment is  
possible if the corresponding instructions, regulations or  
warnings are not observed.  
This symbol indicates that information is important for becoming  
familiar with the equipment, i.e. technical specifications.  
This symbol indicates that a technical term is explained at this  
point.  
General Information 1-1  
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When disposing of drying agents / batteries / oil, observe all  
official rules.  
Caution: High noise pollution !  
For anyone working on the equipment, hearing protection  
should be worn.  
Avoid impairment of hearing!  
Caution: Danger of being crushed !  
Disconnect the equipment from the main power supply before  
starting maintenance procedures. All compressed air pipes on  
the equipment should be depressurized before starting  
maintenance work.  
Caution: Danger, surface is hot !  
Before starting any work, wait until all parts have cooled down  
sufficiently. Avoid touching any of these parts!  
Caution: Danger, surface is slippery !  
Remove any granules remaining on the ground.  
Caution: Danger, electrical shock hazard !  
Observe that the control system is still under voltage even  
when the main power switch is switched off.  
General Information 1-2  
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1.2. Explanations and information  
Various terms and designations are used in these operating instructions to ensure clarity.  
Therefore please note that the terms used in the text stand for the corresponding explanations  
listed below.  
Equipment: ”Equipment” can mean an individual unit, a machine or an installation.  
Operating personnel: The ”operating personnel” are persons operating the equipment under  
their own responsibility or according to instructions.  
Operator: The ”operator” of the equipment (production manager, foreman, etc.) is the person  
responsible for all production sequences. The operator instructs the operating personnel  
what is to be done.  
Operating instructions: The ”operating instructions” describe the interaction of the equipment,  
production sequences or methods. The operating instructions must be compiled by the  
operator of the equipment.  
Equipment foreman: When several operating personnel work on one machine, the  
”equipment foreman” coordinates the operating sequences. The equipment foreman must be  
appointed by the operator.  
Trained personnel: ”Trained personnel” are persons whom, due to their training, are  
authorized to carry out the required work.  
1.3. Legal basis  
See “Manufacturer’s Certificate” resp. “Certificate of Conformity”.  
1.4. Field of application  
This dryer has been manufactured to dry thermoplastic granules and regrind before processing.  
This machine removes all remaining moisture from the granules both inside and out, regardless  
of climate or ambient air conditions.  
1.5. Notes on Usage  
Experienced operators can begin directly with the chapter on “Start-up” if the unit has been  
properly installed.  
If the unit has not been installed yet, observe the instructions in the chapter on “Assembly  
Instructions” and “Transport, Assembly and Storage”.  
General Information 1-3  
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2. Safety instructions  
These safety instructions apply to all persons around the  
operating equipment.  
Please inform all persons around the operating equipment of the  
direct and indirect hazards connected with it.  
These operation instructions are to be used by all persons  
assigned activities connected with the equipment.  
Knowledge of the English language is a prerequisite.  
For your safety, ensure that the operating personnel are familiar  
with the operating instructions and the function of the equipment.  
Safety instructions 2-1  
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2.1 General  
The operating personnel of this equipment must be at least 16 years old.  
Please read these operation instructions carefully before operating the equipment for the first  
time. Contact us should questions arise. This avoids injury and damage to equipment!  
These operation instructions must be kept available at all times at the place where the equipment  
is operating. Improper operation results in danger of accidents!  
Please note that not all conceivable cases regarding operation or maintenance of the equipment  
can be covered in these operating instructions.  
Please observe all safety instructions and warnings on the equipment. This avoids injury and  
damage to equipment!  
All work on the equipment must be carried out by persons whose qualifications are specified in  
the pertaining chapters of the operation instructions. Improper operation results in danger of  
accidents!  
The proper work clothes must be worn during any work on the equipment is performed. This  
avoids injury!  
The local regulations and requirements pertaining to this equipment must be observed.  
Disconnect electrical components from the main power supply before working on them. Caution:  
Danger, electrical shock hazard!  
Compile a detailed sequence of operating procedures to be carried out on this equipment based  
on this Operation Instruction Manual. Improper operation results in danger of accidents!  
Observe that the control system is still under voltage even when the main power switch is turned  
off. Caution: Danger, electrical shock hazard!  
Safety instructions 2-2  
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2.1.1. Assembly  
Compare the connected loads with those of the main power supply. Danger, electrical shock  
hazard!  
When using lifting gear, please observe the pertaining regulations. Caution: Danger of accidents!  
Do not modify, add other equipment or change the design of the equipment without the approval  
of the manufacturer. Caution: Danger of accidents!  
Attachments not supplied by Sterling must be manufactured in accordance with safety regulation  
EN 294. Danger of accidents!  
The equipment may only be operated when all the associated components are properly  
connected in accordance with the relevant regulations. This avoids injury and damage to  
equipment!  
Operate the device only if all its components are grounded. Danger, electrical shock hazard!  
Please note for installation that the equipment is top-heavy. Danger exists that it may topple over!  
Take care that the device is not standing on the main power cable. This will prevent danger to  
people and material!  
2.1.2. Operation  
Appoint a foreman to be responsible for the equipment.  
Ensure that the operating personnel are provided detailed instruction in the operation of the  
equipment. Improper operation results in danger of accidents!  
When the main power switch is turned off for reasons pertaining to safety, it must be secured  
against unauthorized activation. Caution: Danger of accidents!  
Repair work must be carried out by trained personnel only. Caution: Danger of accidents!  
Never operate the equipment when partially dismantled! Danger! Limbs may be caught in  
machinery! Electric shock!  
In case of malfunction, shut down the equipment immediately. Have malfunctions corrected  
immediately. Danger of accidents!  
This machine is intended only for the drying of granulated plastics. Any other use is contrary to  
specifications.  
This equipment is not suitable for food processing.  
The safety instructions of any connected machines must be followed.  
Please note that sound levels exceeding 85 db(A) may cause long term damage to your health.  
Use the appropriate ear muffs. This avoids impairment of hearing!  
Please note that the drying cells, drying hoppers and piping grow hot during use. Avoid touching  
any of these parts! Danger: Injury through burns!  
Never operate the dryer without side panels. Danger: Limbs may be caught in machinery! Injury  
through burns!  
When drying plastics which emit gases dangerous to human health, take care that the  
regeneration exhaust air is disposed of without polluting the environment. This will prevent danger  
to people and material!  
Safety instructions 2-3  
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2.1.3. Maintenance  
Before starting maintenance work, appoint a supervisor.  
Inform personnel responsible for the system before beginning maintenance work. Caution:  
Danger of accidents!  
Disconnect the equipment from main power supply before starting maintenance procedures to  
ensure that it cannot be switched on unintentionally. Caution: Danger of accidents!  
All pipes, hoses and connections should be checked regularly for leaks and damage. Any faults  
which arise should be corrected immediately. Danger of accidents!  
Depressurize all compressed air piping before starting maintenance work. Danger of accidents!  
Air filters should only be cleaned/replaced when the the main power switch is off and the blower  
has stopped. This avoids injury and damage to equipment!  
Any maintenance work on the equipment should only be started when the main power switch is  
off and the blower has stopped. This avoids injury and damage to equipment!  
Check the v-belts of the blower only when the main power switch is turned off and the blowers  
have stopped. Caution: Danger of accidents!  
Open drying hoppers only if they are completely empty. Danger of accidents!  
Never open drying hoppers while the device is in operation. Danger: Injury through burns!  
Open drying hoppers only if they have been sufficiently cooled down. Danger: Injury through  
burns!  
Before beginning maintenance work, wait until the drying cells, drying hoppers and air piping  
have cooled down sufficiently. Avoid touching any of these parts! Danger: Injury through burns!  
Remove any granules remaining on the ground. Danger of accidents!  
Lock the wheels in place after installation if the dryer is mounted on a movable frame. This will  
prevent danger to people and material!  
Safety instructions 2-4  
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2.2. For the safety of the device  
Never change settings without carefully assessing the consequences.  
Use only original Sterling spare parts.  
Observe the maintenance instructions.  
Keep a record of all maintenance work and repairs.  
Please note that electronic components can be damaged by static discharge.  
Before initial operation and at regular intervals, make sure that no electrical connections are  
loose.  
Never readjust sensors without exactly knowing their functions.  
Please ensure that the storage temperature is between 32 to +131 °F (0 and +55 °C).  
Please ensure that the operation temperature is between 32 to +113 °F (0 and +45 °C).  
Check the rotation direction of the blowers after the electrical connections have been made (see  
rotational direction arrow).  
Clean the drying hoppers before filling them for the first time.  
Follow the material manufacturers’ instructions for maximum drying temperature.  
Follow the material manufacturers’ drying instructions.  
Ensure that the drying hoppers are always completely filled and that the retention period is  
respected if material is continually being removed.  
Note that if too much material is taken from the drying hopper, it will lead to insufficient drying of  
the material.  
Close the air stop valves of the drying hoppers which are empty or have not been used.  
Write down all data which you have entered into the control system.  
The password is to be given to authorized personnel only.  
Please note that the temperature of the dryer heating system must always be set lower than that  
of the supplementary heaters.  
When you dispose of drying agents, observe all official rules and guidelines.  
Note that drying cells should be replaced or refilled only by Sterling if they are empty.  
When no material is continuously fed into the drying hopper (batch drying) and is continuously  
removed, the material level must not fall below 40% in the drying hopper. Close the throttle  
valves.  
Read the operating manuals of any machines connected to this dryer.  
Safety instructions 2-5  
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3. Start up  
This chapter is addressed to the operators of the machine.  
It assumes the operator has general skills with drying equipment  
and that the functional description has been read and  
understood.  
Ensure that the operators have the required experience.  
)
Make sure that the main switch is set to the “0" position.  
Check the drying hopper for cleanliness.  
Check to see whether the adhesive film on the drying hopper has  
been removed.  
If there is a return air cooler, switch on the coolant circuit.  
If there is a timer clock (optional), adjust it. Read the timer clock  
operating manual.  
Check whether the release switches for the “Timer” and the  
“Hopper” (ST1, ST2) are set to the ”0" position.  
The “trouble” signal lamp may flash shortly while the valve block  
is being changed.  
Start up 3-1  
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3.1. Initial Operation  
Check whether the inlet of the drying hopper is closed by a lid or whether a conveyor unit  
(optional) is installed.  
If not, manufacture a suitable lid and install it on the inlet of the drying hopper or install the  
optional conveyor unit.  
)
Attachments which are not supplied by Sterling must be  
manufactured according to the European Standard 294 safety  
regulation.  
Check whether the coolant circuit of the return air cooler (if a return air cooler is installed) is  
turned on.  
3.1.1. Switching on the Dryer  
1. Turn on the dryers’ main power switch.  
The “run” signal lamp lights up.  
2. For operation with timer clock (optional):  
Turn the “Timer” switch to the ON position:  
For operation without timer clock:  
Turn the “Timer” switch to the ON position:  
The blower is running.  
)
If the dryer has not been used for several months it must be run  
for 2 hours without material.  
Start up 3-2  
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Turn the “Hopper” release switches (ST1, ST2) to the “I” position.  
To set the drying temperature, turn the temperature controller to 176° F (+80 °C).  
Press the “PGM” key one time.  
Set the drying temperature to 176° F using the arrow keys.  
After 2 seconds, the display will flash and the value will be stored.  
Press the “EXIT” key (the setpoint value and the actual value  
of the drying temperature are displayed).  
After 2 hours, turn the “Hopper” release switches (ST1, ST2) to the “0” position.  
Turn the “Timer” switch to the OFF position:  
/
Wait until the blower has stopped.  
The blower will continue running for 10 minutes once it is turned  
off.  
If there is a return air cooler installed, turn off the coolant circuit.  
Turn off the dryers’ main power switch.  
The “power” signal lamp turns off.  
Note: The previous steps only need to be taken if this is the initial  
startup of the dryer, or if the dryer has been sitting for  
several months.  
Start up 3-3  
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3.2. Continuous Operation  
Note: To see a quick start guide for operation of this dryer see  
chapter 14.  
)
Fill at least half of the drying hopper with material.  
3.2.1. Switching the Dryer on  
Turn on the dryers’ main power switch to the on position.  
The “run” signal lamp turns on.  
For operation with the optional timer clock:  
Turn the “Timer” switch to the  
position.  
For operation without timer clock:  
Turn the “Timer” switch to the  
position.  
The blower is running at this point.  
Start up 3-4  
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3.2.2. Setting the Drying Temperature  
Turn the “Hopper” (ST1, ST2) release switches to the “I” position.  
For each drying hopper, set the required process drying temperature by using the corresponding  
temperature controller.  
Check whether the set process drying temperature is appropriate for the materials which have  
been placed in the drying hopper.  
Observe the instructions of the material manufacturer.  
After filling the drying hopper you must wait for the resonance time of the material to pass before  
using the material for making product.  
Observe the instructions of the material manufacturer.  
Use the following steps to set the temperature controller.  
Press the “PGM” key.  
By using the arrow keys, select the desired value for  
the drying temperature.  
After 2 seconds, the display will flash and the value is stored.  
Press the “EXIT” key (the setpoint value and the actual value  
of the drying temperature are displayed).  
)
After changing materials, immediately check and reset the drying  
temperature.  
Start up 3-5  
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Autotuning the temperature controller  
Press the “EXIT” key for at least 2 seconds.  
“tunE” flashes. Autotuning can take several minutes.  
If “tunE” stops flashing, Autotuning is finished.  
Press the “EXIT” key.  
Start up 3-6  
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3.3. Switching the Dryer off  
Turn the “Timer” switch to the  
position:  
/
Wait until the blower has stopped.  
The blower will continue running for 10 minutes once the dryer is  
turned off.  
If there is a return air cooler installed, switch off its coolant circuit.  
Turn off the dryer’s main power switch.  
The “power” signal lamp turns off.  
Note: For more detailed instructions on the shutting down of this  
dryer, see the quick start guide in Chapter 14.  
Start up 3-7  
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4. Error and error correction  
This chapter is directed at the operators of the equipment.  
It assumes the operator has general skills in dealing with drying  
systems and that the “start-up” description has been read and  
understood.  
Ensure in each and every case that the operators have the  
relevant skills in operating this equipment.  
)
Faults must be eliminated before the control system can start  
operating again.  
An alarm is indicated by the steady light of the “trouble” signal  
lamp.  
When the fault has been eliminated, the “trouble” signal lamp  
turns off.  
Error and error correction 4-1  
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The following errors can cause an alarm:  
Blower  
The blower pressure is too low.  
Check the blower.  
Vacuum sensor is defective.  
Regeneration heater 1  
The safety temperature limiter on regeneration heater 1 has been activated.  
Check the safety temperature limiter.  
Call the Sterling Service Department.  
Regeneration heater 2  
The safety temperature limiter on regeneration heater 2 has been activated.  
Check the safety temperature limiter.  
Call the Sterling Service Department.  
Hopper heater  
The safety temperature limiter on the hopper heater has been activated.  
Check the safety temperature limiter.  
Call the Sterling Service Department.  
Error and error correction 4-2  
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5. Maintenance  
This chapter is intended for persons having skills in electrical and  
mechanical areas due to their training, experience and supporting  
documentation.  
Personnel using the instructions in this chapter must be familiar  
with accident prevention regulations, operating conditions, safety  
regulations and their implementation.  
Ensure in each case that the personnel are informed.  
For maintenance work taking place at heights of over 6ft.  
(1829mm), use only ladders and working platforms or similar  
equipment intended for this purpose. At greater heights, the  
proper protective equipment against falling must be worn.  
Use only suitable lifting gear in proper working order and load  
suspension devices within the sufficient carrying capacity. Do not  
stand or work under suspended loads!  
Ensure that electric motors and controller cabinets are  
sufficiently protected against moisture.  
Use suitable workshop equipment.  
Before starting maintenance work, appoint a supervisor.  
Before beginning maintenance work on the system, inform the  
responsible personnel.  
Never operate the equipment when it is partially dismantled.  
Any maintenance and repair work NOT described in this manual  
may only be carried out by Sterling service personnel or by  
specialized staff authorized by Sterling.  
/
To ensure that it cannot be switched on unintentionally,  
disconnect the equipment from the main power supply before  
starting maintenance procedures.  
Before starting maintenance work, all compressed air pipes on  
the equipment should be depressurized.  
Maintenance 5-1  
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)
Please observe the maintenance schedule.  
Before starting maintenance work, clean the equipment of oil, fuel  
or lubricant.  
Ensure that materials and incidentals as well as spare parts  
required for operation are disposed of properly and in an  
environmentally sound manner.  
Use only original Sterling spare parts.  
Keep records of all maintenance and repair procedures.  
Maintenance 5-2  
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5.1. Maintenance schedule  
The checklist below contains a list of items which should be inspected and/or replaced to keep  
your Dehumidifying Dryer operating at peak efficiency. Perform each inspection at the regular  
intervals listed below.  
System model #  
Serial #  
Date/ Date/ Date/ Date/ Date/ Date/ Date/ Date/ Date/ Date/ Date/ Date/ Date/  
By By By By By By By By By By By By By  
Every week  
Inspect all filters for  
wear, replace/  
clean if dirty or  
worn.  
Check to make  
sure that all hose  
conections are  
air tight.  
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec  
Every  
month  
Lock out electrical  
power and inspect  
electrical wiring for  
integrity.  
Check main power  
switch and ensure  
that signal lamps  
are functioning  
properly.  
Check dew point  
and temperature  
tracking with an  
external dew point  
monitor and  
pyrometer.  
Visually inspect the  
shifting of the  
airflow valve during  
one cycle.  
Next scheduled  
inspection  
Actual inspection  
Date/By  
Next scheduled  
inspection  
Actual inspection  
Date/By  
Every year  
Inspect desiccant. Replace  
if brown or broken.  
Scheduled  
replacement date  
Actual replacement  
Date/Work done by  
Scheduled  
replacement date  
Actual replacement  
Date/Work done by  
Every two years  
Replace desiccant.  
Whenever the material is changed: The drying hopper and suction box must be cleaned.  
The service intervals provided above are based on a 3-shift  
operation.  
-Photocopy this page for your maintenance records –  
Maintenance 5-3  
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5.2. Preventative Maintenance  
This section describes maintenance procedures which will increase the longevity and efficiency of  
your dehumidifying dryer. Perform them at the regular intervals listed on the dryer checklist on  
the previous page.  
5.2.1. Servicing Process Air Filters  
Caution!  
Operating the dryer without the process air filter installed voids  
your warranty!  
Dehumidifying dryers have a single cartridge canister-type filter  
in the process air loop. The filter protects blowers from plastic  
fines drawn in from the drying hopper and prevents the desiccant  
from being contaminated. Regular filter cleaning is essential to  
keep your dryer operating at peak efficiency.  
You can blow or vacuum the dirt out of the filter with compressed  
air, but remember, it could become damaged from high-pressure  
blowing.  
Set the “Timer” release switch to the  
position.  
Recommendations for Cleaning and Replacing Filters  
Remove the threaded fastener securing the filter access cover, then remove the cover.  
Remove the nut on the center retaining rod to remove the filter cartridge.  
/
Wait until the blower has stopped.  
The blower will continue running for 10 minutes once the dryer is  
turned off.  
If there is a return air cooler installed, switch off the coolant circuit.  
/
Switch off the dryer’s main power switch (the “power” signal  
lamp turns off).  
Interrupt the main power supply so that the device cannot be  
turned on unintentionally.  
Clogged filters substantially reduce the amount of circulating air  
and lead to a production lag of your dryer. Clogged filters may  
also damage the heating elements.  
Maintenance 5-4  
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STT40 / STT70  
5.2.2. Cleaning or Replacing the Return Air Filter  
STT40 / STT70  
Figure 1: Air Filter Location & Disassembly  
Detach the screw on the housing of the return  
air filter and remove the housing cover.  
Return Air Filter  
Remove the nut of the filter cartridge.  
Remove the filter cartridge.  
Clean the inside of the return air filter housing.  
Use non-fibrous cleaning cloths or an industrial  
type vacuum cleaner.  
Vacuuming - Try vacuum-cleaning a soiled filter  
first. Vacuuming removes most large particles  
and surface contaminants, and may suffice for  
the first time you clean a filter. Use a  
commercial-duty (recommended) or household  
vacuum cleaner. Vacuum the filter from the air  
intake (dirty) side only.  
Cleaning with Compressed Air - Blow clean, dry  
compressed air up and down the pleats, blowing  
from the inside out. Remove loose dirt from the  
filter with compressed air or vaccum from the  
outside.  
)
DO NOT clean/wash filter with water!  
After each cleaning:  
Inspect the filter element. Briefly hold a light bulb behind the element and look for  
any fatigued paper or residual dirt. Inspect for holes and tears by looking though  
the filter toward a bright light. Check for damaged gaskets or dented metal parts.  
Do not re-use a damaged filter!  
Check the gasket for damage. A damaged gasket allows contaminants into the  
process. Replace as needed.  
Re-install the cleaned/new filter cartridge.  
Rethread the nut that holds the filter in place.  
Install the lid of the return air filter housing.  
)
Never operate the dryer without a return air filter.  
Purchase order numbers for a return air filter on the STT40/70  
dryer are:  
when operating without return air cooler: ID 83957  
when operating with return air cooler:  
ID 83956  
Maintenance 5-5  
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STT40 / STT70  
5.2.3. Servicing the Dew Point Monitor  
The accuracy of the dew point monitor on mini dryer systems depends on proper operation of the  
dew point sensor and the control board. The dew point sensor is in the process air stream and is  
therefore susceptible to contamination.  
Dew point sensor life depends on:  
Air temperature and flow passing over the sensor.  
The amount of fines (dust) in the process air.  
The amount of plasticizer vapor in the process air.  
Once every six months, the dryer operator should monitor the initial dew point sensor readings  
and establish a periodic replacement schedule as needed.  
Do not attempt to check the continuity or resistance of the dew  
point sensor.  
The sensor will be destroyed!  
Maintenance 5-6  
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STT40 / STT70  
5.3. Corrective Maintenance  
This section provides you with the information necessary to correct or repair any issues which  
might appear during the normal operation of your dehumidifying dryer. Although we have listed  
how to perform these procedures, it is recommended that you call the Service Department to  
have any in-depth maintenance performed.  
5.3.1. Symptoms of Worn Desiccant  
The moisture absorption capacity of the desiccant used in your dehumidifying dryer degrades  
after an indefinite period of time. Useful life depends on variables such as material moisture  
content, plasticizer vapors in the return air, and number of regeneration cycles.  
Your dryer may need new desiccant if it exhibits any of the following symptoms:  
The process air dew point measured with a portable dew point monitor is higher than  
-10°F (-23ºC) throughout the process drying cycle.  
Noticeable amounts of desiccant in the beds is a medium-brown color or darker.  
If you notice any of these signs, replace the desiccant in the desiccant beds. Desiccant  
replacement kits are available from the Parts Department. If you want, a technician can repack  
desiccant beds at your site.  
Handling desiccant material is HAZARDOUS.  
Wear an N-100 type safety filter mask or equivalent to avoid  
prolonged breathing of desiccant dust. Wear safety goggles  
and gloves to avoid contact with eyes and skin.  
Handle with adequate ventilation.  
Wash hands thoroughly after handling.  
FIRST AID ✚  
In case of eye contact, immediately flush eyes  
with plenty of water for at least 15 minutes.  
SEE A PHYSICIAN IMMEDIATELY IF IRRITATION PERSISTS.  
Maintenance 5-7  
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STT40 / STT70  
5.3.2. Replacing Worn Desiccant  
DESICCANT BEDS ARE HOT DURING OPERATION.  
To avoid burn hazard, make sure desiccant beds are sufficiently  
cool before replacing worn desiccant.  
To access the Desiccant Bed:  
1. Disconnect electrical power to the dryer.  
2. Remove dryer side panels.  
3. Remove any internal hoses that may be in the way.  
4. Use nut driver to remove clamps at top and bottom of the desiccant tank.  
5. Remove the Desiccant Cell leaving valve and Y-pipe attached to the dryer.  
6. With a shop vacuum or by dumping, carefully remove all desiccant from each  
tower.  
Figure 2: Desiccant Bed Location and Disassembly  
Remove  
Hose Clamps  
Remove  
Clamp  
7. Inspect each lower desiccant screen for tears or holes where desiccant  
burned-through. Replace as needed.  
8. After cleaning each chamber, add a level layer of half the 8 x 12 bead  
desiccant on top of the screen. Next, carefully add the full amount of bead  
desiccant specified per bed. Smooth the top level, and finally add another  
layer of the remaining bead desiccant to the top. Make sure this layer is level  
and smooth. (See following table for correct amount of desiccant required.)  
9. Repeat the previous step for the other bed.  
10. Inspect the gaskets on the valve assembly. Replace if necessary.  
11. Place the desiccant cell assembly back into the dryer and replace clamps.  
Maintenance 5-8  
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STT40 / STT70  
12. Replace any internal hoses that were removed to change desiccant.  
Figure 3: Required Desiccant Amounts  
Dryer  
8 x 12 bead Total  
model  
STT 40  
STT 70  
Part no.  
lbs.  
13.23  
28.76  
Kg  
6
13  
W00018051  
5.4. Disposing of Drying Agents  
Please note that drying cells are replaced or refilled by Sterling only if they are empty.  
When disposing of drying agents, observe all official rules.  
Since used drying agents may contain impurities from the dried  
materials, treat them as special waste.  
It is not possible for Sterling to take back the used drying agent  
or drying cells with used drying agents.  
Maintenance 5-9  
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STT40 / STT70  
5.5. Replacing the Process Heater  
The dehumidifying dryers utilize a thru-phase Calrod-type heater element. This heater element is  
mounted to the inlet of the drying hopper. Although the replacement procedure is the same for  
each heater, the wattage varies by model, voltage, temperature range, etc.  
Hazardous electrical current present.  
Disconnect and lock out power before you replace heater  
elements!  
Figure 4: Process Heater Location and Disassembly  
Remove Clamp  
Process Heater  
Procedures  
1. Remove access cover from the junction box located on the bottom of the  
heater.  
2. Remove the wiring from all terminals that are inside the junction box. (Note:  
Sketch all wiring locations so that you can properly re-install later.)  
3. Remove the clamp that is attaches the process heater to the hopper. Also,  
remove the hose from the heater.  
4. Place the process heater assembly on a workbench to begin disassembly.  
5. Carefully unscrew heater/junction box subassembly from the process heater  
housing. (You must replace both the process heater element and the  
junction box.)  
6. Replace with new heater element/junction box subassembly.  
Heater loops should not touch each other.  
“Hot spots” lead to premature heater failure!  
Maintenance 5-10  
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STT40 / STT70  
7. Re-clamp process heater assembly onto the drying hopper.  
8. Reattach wiring according to the sketch that was made previously.  
9. Replace the air hose to the process heater.  
10. Replace access cover on junction box of process heater assembly.  
5.5.1. Replacing/Cleaning the Cooling Coils  
Hazardous electrical current present.  
Disconnect and lock out power before you replace cooling coil!  
Figure 5: Cooling Coil Location and Disassembly  
Cooling Coil  
Location  
1. In order to gain access to the cooling coil, the cover plate on the side of the  
dryer must be removed.  
2. Remove cooler from the cooler housing.  
3. To clean the cooling coil, use compressed air or a steam cleaner to blow the  
dust off or clean any oily residue on the coil.  
4. Re-install the cooler in reverse order. Install new gaskets and securely  
tighten all fasteners.  
5. Secure the access cover on the side of the dryer.  
Maintenance 5-11  
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5.5.2. Replacing the regeneration heating coil  
Hazardous electrical current present.  
Disconnect and lock out power before you replace heating  
element!  
Figure 6: Heating Coil Location and Disassembly  
Heating Coil  
1. In order to gain access to the heating element, the cover plate on the side of  
the dryer must be removed.  
2. Remove the desiccant tank which has the faulty heater element from the  
dryer.  
3. Place desiccant tank onto a workbench and remove desiccant as stated  
earlier in the changing desiccant section of this manual.  
If the desiccant is old or damaged, you may discard it at this time. If it is  
undamaged, place it in a bag and save it for later.  
4. Unwire the heater that is located inside the bottom of the desiccant tank.  
Remove and replace the heater with a new heater.  
Rewire the heater and reassemble the desiccant tank.  
5. Pour desiccant back into the tank. Use either the saved desiccant in the bag  
or new desiccant if it is needed.  
6. Put the desiccant tank back into the dryer cabinet.  
7. Inspect the gaskets on the valve assembly. Replace if necessary.  
8. Place the desiccant cell assembly back into the dryer and replace clamps.  
9. Replace any internal hoses that were removed to change desiccant.  
Maintenance 5-12  
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STT40 / STT70  
5.6. Cleaning the Drying Hopper  
Set the “Timer” release switch to the  
position.  
/
Wait until the blower has stopped.  
The blower will continue running for 10 minutes once the dryer is  
turned off.  
If there is a return air cooler installed, switch off the coolant circuit.  
/
Switch off the dryer’s main power switch (the “power” signal  
lamp turns off).  
Interrupt the main power supply so that the device cannot be  
turned on unintentionally.  
)
Clean the drying hopper each time you change the materials to be  
dried.  
Make sure that the drying hopper is completely empty and has  
cooled down sufficiently.  
Remove any granules remaining on the ground.  
Maintenance 5-13  
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STT40 / STT70  
STT 25  
A
Open the toggle-type fasteners (A) at the hopper lid  
and fold the hopper lid upwards (if in use: remove  
before the single conveyor).  
Clean the drying hopper.  
Close the hopper lid and close the toggle-type  
fasteners (A) (if in use: re-mount the single  
conveyor).  
Figure 7: STT 25  
)
When cleaning, remove any granules remaining in the hopper lid.  
STT 60 - 100  
Open the door of the drying  
hopper: Lift and turn the  
handle (A) to open the lock (if  
in use: remove before the  
single conveyor).  
Clean the drying hopper.  
Close the door of the drying  
hopper: Turn the handle (A)  
until the door is locked and  
then close the handle (if in  
use: re-mount the single  
conveyor).  
Figure 8: STT 60 - STT 100  
)
When cleaning, remove any granules remaining in the hopper  
door.  
Maintenance 5-14  
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STT40 / STT70  
6. Functional description  
This functional description is addressed to the operators of the  
equipment.  
This functional description assumes the operator has a general  
familiarity with drying equipment.  
Verify that the operators have the appropriate skills.  
Functional description 6-15  
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STT40 / STT70  
6.1. General Information  
The dehumidified air dryers were developed for drying plastic granules. Due to their compact  
construction, they can be utilized for drying next to the processing machine (drying hopper on the  
processing machine) or with one or more drying hoppers as a movable facility (compact facility).  
The dryers work according to the dehumidified air principle, i.e., the air is not only heated but also  
dehumidified before it flows through the drying hopper.  
In this manner, plastic granules can be dried down to a very small residual moisture content.  
The drying temperature can be adjusted, if necessary, up to a maximum of 356°F (+180 °C)  
(upper limit) (When drying above 250°F process temperature, a return air cooler is required.).  
Due to the heat that is released during water absorption in the drying cells, the lower limit of the  
dehumidified air temperature is approx. 140°F (+60 °C).  
Drying takes place continuously, i.e., there are no rest periods due to regeneration of the drying  
agent.  
)
The dryer is rated for continuous operation.  
The dryer may only be put into operation if the drying hopper is  
filled.  
Functional description 6-16  
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STT40 / STT70  
Figure 9: Functional diagram of STT40 / STT70  
All functions are fully automatic.  
The dryer is equipped with two drying cells. One drying cell is part of the drying cycle; the other  
drying cell is regenerated simultaneously.  
Part of the dehumidified air is used for regenerating the moist drying cell. At the beginning of  
regeneration, it is heated by the regeneration heater. After the end of the heating period, the  
drying cell is cooled off by using dehumidified air. After the switch-over time is reached, the  
regenerated drying cell is included in the drying cycle, and the cycle starts again.  
1 Drying cell  
2 Regenerating heater  
3 Drying hopper  
4 Diaphragm  
5 Return air filter  
6 Blower  
7 Valve  
8 Drying heater  
9 Suction box  
Functional description 6-17  
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STT40 / STT70  
A digital display of the current dew point temperature can be supplied as additional equipment.  
An optional timer clock can also be supplied which switches the dryer on or off at preselected  
times.  
)
Read the timer clock operating manual.  
2
4
3
1
6
5
7
8
1 = “hopper” release switch STT1, STT2 (STT2 only STT70)  
2 = dew point display (op tional)  
3 = “power” signal lamp  
4 = “trouble” signal lamp  
5 = main power switch  
6 = “Timer” release switch  
7 = timer clock (op tional)  
8 = temperature controller “drying hopper” STT1, STT2 (STT2 only STT70)  
Figure 10: Operating unit  
Functional description 6-18  
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STT40 / STT70  
6.2. Drying Hopper (Optional)  
The material is dried in the drying hopper. The  
dehumidified air is heated and then conducted  
through the material in the drying hopper and  
removes moisture. Drying hoppers must have the  
appropriate dimensions for their specific use so  
that the desired final moisture content is reached.  
When refilling a drying hopper, the material must  
be dried completely before material can be taken  
out for the first time. Time needed to do this is  
equivalent to the resonance time (of that material).  
If material is taken out continuously, there must  
also be a continual addition of material into the  
drying hopper (continuous drying process). New  
(moist) material is conveyed into the upper  
opening of the drying hopper and slowly reaches  
the material outlet at the lower end. On its way  
from the upper to the lower end, the material is  
dried down to the final moisture content.  
In order to guarantee a continuous drying process,  
we recommend that you always keep the drying  
hopper filled completely.  
Figure 11: Drying Hopper  
Functional description 6-19  
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STT40 / STT70  
6.2.1. Hopper Heater  
Each drying hopper has its own heater. The temperature of the dehumidified air is adjusted by  
means of the temperature controller. The setting range is from +140°- +356°F (+60 - +180 °C).  
The current temperature can be read off the digital display (= actual value). If you are drying at a  
process temperature above 250°F you must use a return air cooler.  
)
The temperature controller is factory-programmed. Nevertheless,  
you have to set specific values which are dependent on the  
processed material.  
Process display  
drying temperature  
Setpoint display  
drying temperature  
“EXIT” key.  
Aborting the input  
“PGM” key. Selecting  
operating level or  
parameter selection  
Increasing setpoint value  
Reducing setpoint value  
Figure 12: Temperature  
controller  
Functional description 6-20  
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STT40 / STT70  
DEFAULT SETTINGS FOR JUMO TEMP. CONTROLLER  
Model number: dTRON 16.1 B 70.3011  
Contact information:  
Germany  
USA  
MoltkestraBe 13-31  
36035 Fulda, Germany  
Ph: +49 661 60 03-7 27  
Fax: +49 661 60 03-5 08  
885 Fox Chase, Suite 103  
Coatesville, PA 19320, USA  
Ph: 610-380-8002 or 1-800-554-JUMO  
Fax: 610-380-8009  
PARAMETERS THAT ARE CHANGED IN TESTING AREA  
CELSIUS  
FACTORY DEF. ACS VALUE  
FAHRENHEIT  
ACS VALUE DESCRIPTION  
C112  
SPL  
SPH  
SPH  
AL1  
2 0 0 0 C  
2 0 0 0 = C  
40 Deg. C  
140 Deg. C  
180 Deg. C  
20 Deg. C  
5
2 0 3 0 = F  
104 Deg. F  
284 Deg. F  
356 Deg. F  
68 Deg. F  
19  
NOTE: DEG. C TO DEG. F CONVERSION  
LOW TEMP LIMIT  
HIGH TEMP LIMIT (STANDARD)  
HIGH TEMP LIMIT (REQUIRES AFTER COOLER)  
HIGH TEMP ALARM BAND  
RAMP GRADIENT  
-200  
850  
850  
0
rASd  
0
PARAMETERS THAT ARE NOT CHANGED (FACTORY DEFAULTS)  
SCL  
SCH  
OFFS  
AL2  
Pb1  
Pb2  
dt  
0
100  
-200  
0
0
0
80 s  
350 s  
20.0 s  
20.0 s  
0
0
100  
-200  
0
7
0
9 s  
36 s  
7.4 s  
20 s  
0
START VALUE RANGE FOR STD. SIGNALS  
END VALUE RANGE FOR STD. SIGNALS  
PROCESS VALUE CORRECTION (OFFSET)  
LIMIT FOR LIMIT COMPARATOR 2  
PROPORTIONAL BAND 1(CONTROLLER OUT 1)  
PROPORTIONAL BAND 2(CONTROLLER OUT 2)  
DERIVATIVE TIME  
rt  
RESET TIME  
Cy 1  
Cy 2  
db  
SWITCHING CYCLE TIME(CONTROLLER OUT 1)  
SWITCHING CYCLE TIME(CONTROLLER OUT 2)  
CONTACT SPACING  
HYS 1  
HYS 2  
y.0  
y.1  
y.2  
1
1
0%  
100%  
-100%  
0.6 s  
1
1
SWITCHING DIFFERENTIAL1(CONTROLLER OUT 1)  
SWITCHING DIFFERENTIAL2(CONTROLLER OUT 2)  
WORKING POINT  
OUTPUT LIMITATION: MAX OUTPUT  
OUTPUT LIMITATION: MIN OUTPUT  
FILTER TIME CONSTANT FOR ADAPTATION  
RAMP GRADIENT  
0%  
100%  
-100%  
1.2 s  
9
Df  
raSD  
SP1  
SP2  
C111  
C113  
C114  
0
Process Temp  
Process Temp  
0 0 0 0  
0 5 3 4  
1 0 0 1  
Process Temp SET POINT FOR PROCESS TEMPERATURE  
Process Temp USED FOR SECOND HEATER  
0 0 0 0  
0 5 3 4  
1 0 0 1  
PARAMETER SETTINGS  
PARAMETER SETTINGS  
PARAMETER SETTINGS  
Note: 1) Please consult the JUMO dTRON temperature controller O&I manual for  
further explanation of the above parameter settings.  
2) Some factory default settings may change as the unit is run continuously.  
Functional description 6-21  
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STT40 / STT70  
6.3. Connection to a Pneumatic Conveying System (Optional)  
Your dryer works best in combination with a  
pneumatic conveying system. When  
assembled this way, your drying hopper will  
always be supplied with sufficient material.  
The dryer will only take as much material as is  
required by the processing machines.  
Therefore, the drying result will remain  
consistent.  
Sterling drying hoppers are equipped with a  
suitable flange for adding a Sterling pneumatic  
conveyor.  
Suction boxes with one or three suction tubes  
can be supplied as well (optional). These  
suction boxes are developed specifically for  
this type of hopper.  
A
The loading of material into the conveying line  
is adjusted by closing or opening the control  
cover (A).  
Figure 13: Suction Box  
6.4. Return Air Cooler (Optional)  
)
A RETURN AIR COOLER MUST BE EMPLOYED IF THE RETURN  
AIR TEMPERATURE IS HIGHER THAN +65 °C (149°F).  
A return air cooler improves the efficiency of the drying cells.  
The lower the return air temperature, the better the efficiency of  
the drying cells.  
The return air cooler can be connected to a coolant circuit or to the water main network.  
Functional description 6-22  
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STT40 / STT70  
7. Transporting, Assembly and Storage  
This chapter is intended for all operating personnel of the  
equipment.  
Personnel using these instructions must be knowledgable in the  
regulations for the prevention of accidents, the operating  
conditions, safety regulations and their implementation.  
Ensure that the operating personnel are sufficiently informed.  
Please inform all persons around the operating equipment of the  
direct and indirect hazards connected with it.  
Please observe all safety regulations for the operation of lifting  
equipment.  
Transporting, Assembly and Storage 7-1  
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STT40 / STT70  
7.1. Transporting and Packing  
Please ensure that the lifting equipment has an adequate carrying  
capacity.  
Note that the dryer system is top-heavy. Risk of toppling!  
)
The machine must not be tilted or laid on its side.  
The equipment has undergone a rigorous operating test in the factory and is packed carefully to  
avoid transport damage.  
Please check packing materials upon delivery for transport damage.  
The inlet and discharge flanges are sealed with plugs so that no dirt can enter during transport.  
Remove the plugs before assembly.  
Packing materials should be disposed of according to environmental laws or reused.  
The dryer or the compact unit is delivered on a pallet.  
The dryer should only be moved by means of the appropriate lifting equipment (e. g. a fork lift  
truck or a workshop crane).  
Fasten the transport cables to the eyelets of the control cabinets.  
When transporting the dryer to another location, it must be shock-proofed and free from  
vibrations.  
Transporting, Assembly and Storage 7-2  
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STT40 / STT70  
7.2. Assembly  
Please ensure the lifting equipment has an adequate carrying  
capacity.  
Check the load capacity where the dryer is to be installed,  
particularly if it is to be installed on a platform.  
The place selected for installation should be as vibration-free as  
possible.  
The main power switch must be accessible.  
Ground the equipment against electrostatic charging.  
)
The machine must not be tilted or laid on its side.  
Because of its compact construction, the dryer can be installed directly beside the processing  
machine (drying hopper on the processing machine) or with one or more drying hoppers as a  
movable facility (compact facility).  
Special foundations are not necessary for installation.  
The dryer must be installed on a level surface and must not be exposed to excessive humidity.  
The maximum permissible ambient temperature is 45 °C (113°F).  
To facilitate servicing, the dryer should be installed in such a way that it is accessible from  
3 sides. Make sure that the air filters can be changed without problems.  
To conserve energy, keep the distance between dryer, hopper and processing machine as small  
as possible.  
The wheels of the compact unit should be locked to ensure stable operation.  
The foil skin should be removed from the drying hopper before operation.  
7.3. Storage  
The control system may only be stored at temperatures from 0 to +55°C (32 to +131 °F).  
Between delivery and machine commissioning, the equipment should be stored in a dry, dust and  
vibration-free room.  
Transporting, Assembly and Storage 7-3  
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STT40 / STT70  
8. Assembly instructions  
These installation instructions are intended for persons with  
skills in electrical and mechanical areas due to their training,  
experience and supporting documentation.  
Personnel using these installation instructions must be  
knowledgeable in the regulations for the prevention of accidents,  
operating conditions, safety regulations and their implementation.  
Ensure in each case that the personnel are informed.  
The installation and operation instructions apply to all connected  
equipment.  
Observe safety regulations with regard to handling lifting gear.  
All installation work must be carried out with the equipment  
disconnected from electrical power and compressed air supply.  
/
For installation work taking place at heights of over approx. 6 feet  
(1829mm), use only ladders or similar equipment and working  
platforms intended for this purpose. At greater heights, the  
proper equipment for protection against falling must be worn.  
Use only suitable lifting gear which is in proper working order and  
suspension devices within the sufficient load carrying capacity.  
Do not stand or work under suspended loads!  
Use suitable workshop equipment.  
)
Install the equipment such that all parts are easily accessible; this  
facilitates maintenance and repair work.  
Assembly instructions 8-1  
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STT40 / STT70  
8.1. Installation of the exhaust fan for regeneration of exhaust  
air  
When plastics are being dried that release harmful gases during the drying process, care must be  
taken that the regeneration exhaust air is disposed of in an environmentally sound way. At the  
same time the throughput of the regeneration blower must not be altered. It should be noted  
when assembling a disposal system (e.g. an exhaust system) that the regeneration exhaust air is  
very humid. Thus condensation may form, which must not under any circumstances return to the  
dryer.  
8.2. Grounding the equipment against electrostatic charging  
Considerable electrostatic charging may occur in the equipment during processing of the various  
materials. For this reason, all components must be sufficiently grounded, see grounding bolt dryer  
(A) and drying hopper (B).  
Ensure that all state and local electrical regulations are observed.  
Figure 14: Grounding the equipment  
Assembly instructions 8-2  
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STT40 / STT70  
8.3. Electrical Connection  
The electrical connection of the dryer and the hopper heaters may  
only be done by Sterling service staff or by qualified staff  
authorized by Sterling.  
Other persons are not permitted to perform any electrical  
connection.  
Observe the rules of the state and local electricity board.  
The main power switch must be freely accessible.  
Ground the equipment against electrostatic charging.  
The serial tag lists voltage, phase, and amp draw information:  
Line voltage must be within plus or minus ten percent (±10%)  
of the voltage listed on the serial tag, or damage may occur.  
Phase imbalance must be less than two percent (2%).  
Connect main power to the dryer at the disconnect or terminals in  
the lower position of the control enclosure.  
Install a fused disconnect with a lockout feature in the power  
main leading to the dryer.  
)
On a regular basis, make sure that none of the electrical or screw  
connections become loose.  
Ensure that the main power switch is at the “0" position before  
carrying out any electrical connection.  
The operating voltage is  
STT40: 230/1/60  
STT70: 480/3/60.  
Special voltages can be supplied on request.  
The connected loads* are  
STT40 max. 1.1 kW,  
STT70 max. 2.0 kW.  
*If hopper heaters are installed, the value of each hopper heater must be added to these  
connected loads (STT40: max. 1.5 kW, STT70: max. 3.0 kW).  
The fuse protection must have  
STT40 16 A,  
STT70 16 A.  
Assembly instructions 8-3  
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STT40 / STT70  
8.4. Connection of Return Air Cooler (Optional)  
)
A return air cooler must be used if the return air temperature is  
higher than 149°F (+65 °C).  
You can connect the return air cooler to a coolant circuit or to the water main network.  
The water flow rate in the water main network* is for:  
3
3
STT40 approx. 7.16 ft (0.2 m /h),  
3
3
STT70 approx. 14.13 ft (0.4 m /h)  
(*water temperature:42.8°F) (+6 °C)  
Rate your coolant circuit accordingly.  
Connect the coolant in- and outlets to the return air cooler.  
Observe the flowing direction of the coolant.  
Check the tightness of the connections.  
Connections are made with ½” NPT.  
Figure 15: Connection of Return Air Cooler STT40 (A) / STT70 (B)  
Assembly instructions 8-4  
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STT40 / STT70  
9. Troubleshooting  
9.1. Introduction  
The utmost in safety precautions should be observed at all times when working on or  
around the machine and the electrical components. All normal trouble-shooting must  
be accomplished with the power off, line fuses removed, and with the machine  
tagged as out of service.  
The use of good quality test equipment cannot be over-emphasized when  
troubleshooting is indicated. Use a good ammeter that can measure at least twice the  
AC and DC current that can be encountered for the machine. Be sure that the  
voltmeter has at least minimum impedance of 5,000 OHMS-per-volt on AC and  
20,000 OHMS-per-volt on DC scales. Popular combination meters, VOM and  
VTVM can be selected to provide the necessary functions.  
Before making haphazard substitutions and repairs when defective electrical  
components are malfunctioning, we recommend that you check the associated  
circuitry and assemblies for other defective devices. It is common to replace the  
obviously damaged component without actually locating the real cause of the trouble.  
Such hasty substitutions will only destroy the new component. Refer to wiring  
diagrams and schematics.  
Locating mechanical problems, should they occur, is relatively straightforward.  
When necessary, refer to the parts catalog section.  
Problem  
Possible cause  
Corrective action  
Dirty filter.  
Clean or replace filter.  
Desiccant beds are contaminated  
by material or plasticizer leaking  
into the system.  
Replace desiccant. See Page 42  
for more information.  
Little or no air coming from  
the process delivery tube.  
Fix the problem and reset the  
overload.  
Blower overload has tripped.  
Blower fins filled with dust or  
contaminants.  
Remove blower side plate,  
clean baffles, replace.  
Stop the dryer.  
If the dryer was connected to  
the drying hopper, check to see  
if the desiccant and process air  
Phase is reversed on power drop heater has been contaminated  
Suction in delivery tube,  
pressure from the return tube.  
coming into the dryer.  
(Note: on STT 70 only)  
with resin.  
If so, replace the desiccant and  
remove any resin carry-over.  
Otherwise, change the phase of  
two legs of the three-phase  
power drop.  
Troubleshooting 9-1  
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STT40 / STT70  
Problem  
Possible cause  
Corrective action  
Check for open heaters. Replace  
if required.  
Process heaters are faulty.  
Solid-state temperature  
controller faulty.  
Replace.  
Loss or reduction of process air  
temperature.  
Make sure that plant personnel  
are aware of the proper  
temperature set point. Post an  
appropriate sign next to the  
controller.  
Process temperature was  
adjusted in error by plant  
personnel.  
Process heaters are faulty.  
Desiccant beds are  
contaminated.  
Replace.  
Replace desiccant.  
Drying systems are designed for  
the material which was  
originally specified. Different  
materials may need a longer  
residence time or a different  
drying temperature.  
Material being dried differs  
from material specified at the  
time of purchase.  
Loss or reduction in drying  
capacity.  
Break in flex hose to/from  
drying hopper.  
Inspect for air leaks; replace as  
needed.  
Check for proper operation of  
valve actuators. Repair or  
replace if necessary.  
Airflow valve sticking or failing  
to shift.  
Remove blower side plate,  
clean baffles, replace.  
Replace filter elements.  
Check power supply and power  
wiring to PLC.  
Blower fins filled with dust or  
contaminants.  
Insufficient power to PLC  
(Power LED is off).  
PLC Regeneration Bed LED  
indicators both off.  
Faulty PLC (PLC Power light is  
on, Run light is off, and/or Error Replace PLC.  
light is on).  
Regenerating bed cooldown.  
None.  
Verify that blower contactor is  
on. Check input wiring to PLC.  
Blower Input indicator is off.  
Process air in high-temperature  
condition.  
Insufficient power to PLC  
(Power light is off).  
PLC Regeneration Heater  
Left/Right output indicators both  
off.  
None.  
Check power supply and power  
wiring to PLC.  
Faulty PLC (PLC Power light is  
on, Run light is off, and/or Error Replace PLC.  
light is on).  
Troubleshooting 9-2  
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STT40 / STT70  
Problem  
Possible cause  
Corrective action  
Check resin manufacturer’s data  
sheet for proper drying  
Process temperature set too high temperature. Make sure plant  
due to operator error.  
personnel are aware of the  
correct process temperature set  
point.  
High temperature alarm not set  
properly.  
Process set point is out of  
acceptable range.  
Reset high temperature alarm.  
Material in drying hopper cakes,  
or meltdown occurs.  
Restore temperature controller  
to factory pre-sets.  
Function set for degrees Celsius  
(ºC), set point at degrees  
Fahrenheit (ºF).  
Verify correct Celsius or  
Fahrenheit settings.  
Verify that the thermocouple is  
properly installed in the inlet  
tube.  
Process thermocouple not in  
airflow.  
Burned out regeneration heater.  
Contaminated or worn out  
desiccant.  
Repair or replace.  
Replace.  
Leaking process air hoses.  
Dryer operates beyond its  
capacity.  
Repair or replace.  
Check dryer and drying hopper  
sizing.  
Poor dew point performance.  
Bad dew point sensor.  
Fouled dew point sensor  
manifold.  
Replace.  
Clear obstruction. Air should  
flow freely through sensor.  
Clean or replace filter element.  
Dirty filter.  
The internal mechanism is not  
inserted properly into the  
housing.  
Properly insert the internal  
mechanism into the housing.  
The power supply is not  
connected to its terminals  
properly.  
Properly connect the power  
supply to the power supply  
terminals.  
No power is supplied, or the  
supplied power is not within the VAC to the power supply  
specified range.  
Supply a voltage of 85 to 125  
Nothing displays when the  
controller is turned on.  
terminals of the controller.  
Check control power fuse for  
continuity. Turn disconnect  
switch and control power switch  
ON.  
Disconnect switch or Control  
Power switch not set to ON.  
Control Power fuse blown.  
Hopper release switch is not in  
the “I” position.  
Turn the hopper release switch  
to the “I” position.  
Troubleshooting 9-3  
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STT40 / STT70  
Problem  
Possible cause  
Corrective action  
No setting change possible on  
temperature controller.  
The key protection switch is set  
to ON.  
Set the key protection switch to  
OFF.  
Input polarity on thermo-couple  
is wrong or connection is wrong.  
Properly wire the terminals.  
Properly set the input with the  
input-type selector rotary  
switch.  
Input-type setting is incorrect.  
No compensating lead wires  
used for extension of the  
thermocouple.  
Use proper compensating lead  
wires and terminals.  
Use a dedicated thermocouple  
Thermocouple and controller are connector. If a connector is a  
connected by wires other than  
proper lead wires.  
metal different from the  
thermocouple and controller, a  
temperature error may result.  
Verify that the thermocouple is  
properly installed in the inlet  
tube.  
Process value is abnormal or  
not obtained.  
Process thermocouple not in  
airflow.  
Sensor is broken or short-  
circuited.  
Replace with a good sensor.  
Separate input wires as far as  
possible from the origin of the  
noise.  
The controller is influenced by  
noise or other induction.  
Celsius temperatures used  
instead of Fahrenheit or vice  
versa.  
Check to see that proper  
temperature setting is in the  
temperature controller.  
9.2. Determining Temperature Controller Errors or Sensor Errors  
Using a Thermocouple  
If the controller displays a temperature that is close to room temperature (70ºF/21ºC)  
when you short-circuit controller input terminals, the controller is normal and the  
sensor is probably broken, short-circuited, or incorrectly wired.  
Using a Platinum Resistance Thermometer  
If the controller displays a temperature of about 0.0°C (32ºF) when you insert a 100-  
ohm resistor between terminals A and –B of the controller, and you short-circuit  
controller terminals +B and –B, the controller is normal and the sensor is probably  
broken, short-circuited, or incorrectly wired.  
Other service problems or questions can be answered by contacting the Service  
Department.  
Troubleshooting 9-4  
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STT40 / STT70  
10. Technical data  
10.1. STT40  
amount of dehumidified air:  
3
3
max. 1,412.69 ft /h, (40 m /h)  
operating voltage:  
230 V/AC/50 Hz  
special voltages can be supplied upon request  
connected load:2.6 kW  
calorific output (drying)*:max. 1.5 kW  
*depending on the equipment with hopper heaters  
calorific output (regenerating): 0.7 kW  
driving power (drying, regenerating):  
0.37 kW  
drying temperature: max. 356°F (+180 °C)  
width: 11.8 in. (300 mm)  
depth: 27.5 in. (700 mm)  
height: 35.5 in. (900 mm)  
weight: approx. 149.9 lbs (68 kg)  
noise: approx. 61 dB (A)  
options:timer clock  
dew point display  
return air cooler  
Return Air Cooler (optional)  
3
3
water flow rate in the water main network*: approx. 7.16 ft /h (0.2 m /h)  
(*water temperature: 42.8°F) (+6 °C)  
Ø pipe connection:  
0.5 in. (12 mm)  
10.2. STT70  
amount of dehumidified air:  
3
3
max. 2,472.03 ft. /h (70 m /h)  
operating voltage: 400 V/3 AC/50 Hz  
special voltages can be supplied upon request  
connected load:5.0 kW  
calorific output (drying)*:max. 3.0 kW  
*depending on the equipment with hopper heaters  
calorific output (regenerating): 1.2 kW  
driving power (drying, regenerating):  
0.75 kW  
drying temperature: max. 356°F (+180 °C)  
width: 15.7 in. (400 mm)  
depth: 35.5 in. (900 mm)  
height: 35.5 in. (900 mm)  
weight: approx. 227.17 lbs. (103 kg)  
noise: approx. 66 dB (A)  
options:timer clock  
dew point display  
return air cooler  
Return Air Cooler (optional)  
3
3
water flow rate in the water mains network*:  
approx. 14.13ft. /h (0.4 m /h)  
(*water temperature: 42.8°F (+6 °C)  
Ø pipe connection:  
0.5 in. (12 mm)  
Technical data 10-5  
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STT40 / STT70  
10.3. Dimension Sheet  
STT 40  
STT 70  
A
B
C
D
27.5” (700 mm)  
3.2” (80 mm)  
35.5” (900 mm)  
11.8” (300 mm)  
35.5” (900 mm)  
3.2” (80 mm)  
35.5” (900 mm)  
15.7” (400 mm)  
Dimensions in inches (mm). Specifications may be subject to change without notice.  
Technical data 10-6  
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STT40 / STT70  
11. Spare parts list  
This spare parts list must be used only by trained personnel.  
Other persons are not permitted to modify or repair the  
equipment.  
Spare parts list 11-1  
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STT40 / STT70  
STT40  
Pos. ID-number  
Description  
1
valve stem  
31940  
31938  
36212  
84130  
shaft  
housing  
disc with bush  
disc flywheel DU  
filter cartridge, when operating without  
return air cooler  
filter cartridge, when operating with  
return air cooler  
blower STT40  
guide roll with fixing device  
guide roll  
seal  
hose clamp  
seal  
tension ring  
2
83957  
83956  
3
4
5
6
84129  
85819  
85820  
94233  
93298  
85690  
85691  
96196  
96353  
92361  
7
8
9
desiccant (6 kg) (13.23 lbs.)  
seal  
tension ring  
Return air cooler (optional)  
33848  
83972  
return air cooler  
hose  
Spare parts list 11-2  
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STT40 / STT70  
STT70  
Pos. ID-number  
Description  
1
valve stem  
31940  
31938  
36212  
84130  
shaft  
housing  
disc with bush  
disc flywheel DU  
filter cartridge, when operating without  
return air cooler  
filter cartridge, when operating with  
return air cooler  
blower STT70  
guide roll with fixing device  
guide roll  
sealing ring  
tension ring  
sealing ring  
tension ring  
2
83957  
83956  
3
4
5
6
85677  
85819  
85820  
94233  
97677  
23917  
97677  
23533  
96196  
96353  
92361  
7
sieve  
8
9
desiccant (13 kg)(28.76 lbs.)  
seal  
tension ring  
Return air cooler (optional)  
29786  
83972  
return air cooler  
hose  
Spare parts list 11-3  
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STT40 / STT70  
Operating unit  
Pos. ID-number  
Description  
1
2
82368  
82394  
82393  
82495  
82494  
82392  
82495  
26207  
82395  
82490  
87454  
85241  
83646  
main switch  
LED element, green  
cap  
fixing adapter  
LED element, white  
cap  
3
fixing adapter  
4
5
dew point display (optional)  
selector switch actuator  
contact element  
temperature controller TT1, TT2  
timer clock (optional)  
seal  
6
7
Spare parts list 11-4  
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STT40 / STT70  
Control unit STT40  
85280 motor  
84131 radiator 0.7 kW  
83339 pull-button  
87440 contact element  
83411 controller  
82516 temperature limiter  
88440 contactor  
85941 terminal  
85940 fuse  
99102 fuse  
88806 relay holder  
88816 relay  
84510 thermal breaker  
Hopper heater  
85688 radiator 1,5 kW  
85652 safety temperature limiter  
Control unit STT70  
85279 motor  
85676 radiator 1.2 kW  
95816 pull-button  
87440 contact element  
83329 controller  
85275 temperature limiter  
88914 contactor  
85254 power supply  
88907 terminal  
99815 fuse  
88806 relay holder  
88849 relay  
83624 terminal  
84512 thermal breaker  
84159 control switch  
Hopper heater  
85343 radiator 1,5 kW  
84512 thermal breaker  
85652 safety temperature limiter (= STB)  
85338 radiator 3 kW  
84510 thermal breaker  
85652 STB  
Spare parts list 11-5  
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STT40 / STT70  
12. Electrical manual  
This electrical manual is intended to be used by Sterling service  
personnel and trained personnel authorized by Sterling only.  
Other persons are not permitted to modify or repair the  
equipment.  
Connection diagram no.: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  
Currently not available; will be delivered at a later date !  
Electrical manual 12-1  
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STT40 / STT70  
13. Accessories  
Basic setting on temperature controller  
Digital timer  
Spare parts list Drying Hoppers ST 25 - ST 6400  
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  
Accessories 13-1  
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STT40 / STT70  
Basic temperature controller settings STT40  
This information is intended to be used by Sterling service  
personnel and trained personnel authorized by Sterling only.  
Other persons are not permitted to modify or repair the  
equipment.  
Settings, if temperature is displayed in F°  
Code  
C111  
C112  
C113  
C114  
SPL  
0
2
0
1
0
0
0
0
5
0
1
2
0
3
3
0
0
8
0
0
4
1
4
4
SPH*  
* with return air cooler in use: 0 3 5 6  
Parameter  
AL1  
HYS1  
Parameter set 1  
68.0  
1
rASd  
19.0  
Settings, if temperature is displayed in C°  
Code  
C111  
C112  
C113  
C114  
SPL  
0
2
0
1
0
0
0
0
5
0
0
1
0
0
3
0
4
4
0
0
4
1
0
0
SPH*  
* with return air cooler in use: 0 1 8 0  
Parameter  
AL1  
HYS1  
Parameter set 1  
20.0  
1
rASd  
5.0  
Accessories 13-2  
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STT40 / STT70  
Basic temperature controller settings STT70  
This information is intended to be used by Sterling service  
personnel and trained personnel authorized by Sterling only.  
Other persons are not permitted to modify or repair the  
equipment.  
Settings, if temperature is displayed in F°  
Code  
C111  
C112  
C113  
C114  
SPL  
0
2
0
1
0
0
0
0
5
0
1
2
0
3
3
0
0
8
0
0
4
1
4
4
SPH  
* with return air cooler in use: 0 3 5 6  
Parameter  
AL1  
HYS1  
Parameter set 1  
68.0  
1
rASd  
19.0  
Settings, if temperature is displayed in C°  
Code  
C111  
C112  
C113  
C114  
SPL  
0
2
0
1
0
0
0
0
5
0
0
1
0
0
3
0
4
4
0
0
4
1
0
0
SPH  
* with return air cooler in use: 0 1 8 0  
Parameter  
AL1  
HYS1  
Parameter set 1  
20.0  
1
rASd  
5.0  
Accessories 13-3  
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14. Quick Start Guides  
14.1. for STT 40 Dryer  
1. Check all wiring connections to ensure that they are in the correct place and have a good  
tight connection.  
2. Hook up main single-phase power and ground. The following picture shows the correct  
location.  
Main power High Temp Safety  
Heater Connection Thermocouple  
Main Power Connection  
3. Turn the disconnect switch to the “ON” position as shown. The green run light should light  
up.  
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4. Turn the dryer operation switch to the desired position. If you have a seven day timer  
installed, set it to “On with timer” position, otherwise set it to “On without timer” position. The  
blower will start. An explanation is given in the following diagram.  
OFF  
On with timer  
On without  
timer  
5. Turn the hopper heater switch to position “I”  
Position “O”  
Position “I”  
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6. Once in position “I”, temperature controller will display as shown below. Blower must be  
running for temperature controller to be on. Temperature setting will vary as the processed  
desired temperature is changed. Also, a description of the buttons are listed below.  
Note: For initial start-up or if the dryer has not run for an extended  
period of time, turn the hopper heater switch to position “O”.  
Wait 2 hours for both beds to regenerate (without material in the  
hopper). If there are two hoppers, switch both to position “0”. If  
this is not an initial start-up, use position “I” and continue.  
Process Display  
Set Point  
LED “Status”  
LED Ramp/Program  
PGM  
EXIT  
Arrow down  
Arrow up  
Use the following steps to adjust the process temperature set point.  
a.) Press “PGM” key one time.  
b.) Use arrow up or down to set the preferred process temperature.  
c.) The set point will flash after 2 seconds, and then it will be accepted and stored.  
d.) Press “EXIT” key one time to return to the original screen.  
e.) Observe actual and set point temperatures, both will ramp up or down  
momentarily to the desired set point temperature.  
Note: Due to the following circumstances:  
- initial dryer start-up  
- dryer not running for long period of time  
- dryer has been unplugged and moved to a different location  
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It is recommended that the dryer be Self-Optimized. The following steps should be taken to self  
optimize the dryer:  
a.) Press and hold the “EXIT” button for at least 2 seconds.  
b.) “tunE” will flash while self-optimization is in progress (can take several minutes)  
c.) When “tunE” stops flashing; self-optimization is completed.  
d.) When self-optimization is complete press “EXIT” key once.  
e.) At this point the dryer is ready to run continuously.  
Note: If for any reason the “FAULT” orange light goes on, please go to  
Chapter-4 in this operation manual for troubleshooting  
instructions.  
(CAUTION: DO NOT TURN MAIN POWER DISCONNECT TO  
THE OFF POSITION WITHOUT FIRST TURNING  
THE BLOWER SWITCH TO THE OFF “0”  
POSITION. WAIT UNTIL THE BLOWER HAS  
TIMED OUT PRIOR TO DISCONNECTING MAIN  
POWER.)  
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14.2. Proper Shut-down Guide for STT 40 Dryer  
1. Turn the hopper heater switch to position “0”  
Position “O”  
Position “I”  
OFF  
2. With the main disconnect power in the “ON” position, turn the dryer operation switch  
to the “OFF” position, this will automatically enable the system to go into cool down  
mode. That means the blower will run for 10 minutes.  
Note: This time is utilized to cool down the regeneration heater/cell.  
3. After 10 minutes of run time, the blower will turn off but the green light remains lit.  
That means the system is off but the power is still on.  
4. Turn the disconnect switch to the “OFF” position as shown. The green run light  
should turn off.  
(CAUTION: DISCONNECT POWER BEFORE  
SERVICING DRYER UNIT).  
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14.3. Quick Start Guide for STT 70 Dryer  
1. Check all wiring connections to ensure that they are in the correct place and have a good tight  
connection.  
2. Hook up main three-phase power and ground. The following picture shows the correct  
location.  
Main power High Temp Safety  
Main Power Connection  
Heater Connection Thermocouple  
3. Turn the disconnect switch to the “ON” position as shown. The green run light should light up.  
4. Turn the dryer operation switch to the desired position. If you have a seven day timer  
installed, set it to “On with timer” position, otherwise set it to “On without timer” position. The  
blower will start. An explanation is given in the following diagram.  
OFF  
On with timer  
On without  
timer  
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5. Turn the hopper heater switch to position “I”  
Position “O”  
Position “I”  
6. Once in position “I”, the temperature controller will display as shown below. Blower must be  
running for temperature controller to be on. Temperature setting will vary as the processed  
desired temperature is changed. Also, a description of the buttons is listed below.  
Note: For initial start-up or if the dryer has not run for an extended  
period of time, turn the hopper heater switch to position “O”.  
Wait 2 hours for both beds to regenerate (without material in the  
hopper). If there are two hoppers, switch both to position “0”. If  
this is not initial start-up, use position “I” and continue.  
Process Display  
Set Point  
LED “Status”  
LED Ramp/Program  
PGM  
EXIT  
Arrow down  
Arrow up  
Use the following steps to adjust the process temperature set point.  
a.) Press “PGM” key one time.  
b.) Use arrow up or down to set the preferred process temperature.  
c.) The set point will flash after 2 seconds, and then it will be accepted and stored.  
d.) Press “EXIT” key one time to return to original screen.  
e.) Observe actual and set point temperatures, both will ramp up or down momentarily  
to the desired set point temperature.  
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Note: Due to the following circumstances:  
- initial dryer start-up  
- dryer not running for long period of time  
- dryer has been unplugged and moved to a different location  
It is recommended that the dryer be Self-Optimized. The following steps should be taken to self  
optimize the dryer:  
a.) Press and hold the “EXIT” button for at least 2 seconds.  
b.) “tunE” will flash while self-optimization is in progress (can take several minutes)  
c.) When “tunE” stops flashing; self-optimization is completed.  
d.) When self-optimization is complete press “EXIT” key once.  
e.) At this point the dryer is ready to run continuously.  
Note: If for any reason the “FAULT” orange light goes on, please go to  
Chapter-4 in this operation manual for troubleshooting  
instructions.  
(CAUTION: DO NOT TURN MAIN POWER DISCONNECT TO  
THE OFF POSITION WITHOUT FIRST TURNING  
THE BLOWER SWITCH TO THE OFF “0”  
POSITION. WAIT UNTIL THE BLOWER HAS  
TIMED OUT PRIOR TO DISCONNECTING MAIN  
POWER.)  
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14.4. Proper Shut-down Guide for STT 40 Dryer  
1. Turn the hopper heater switch to position “0”  
Position “O”  
Position “I”  
OFF  
2. With the main disconnect power in the “ON” position, turn the dryer operation switch to the  
“OFF” position, this will automatically enable the system to go into cool down mode. That  
means the blower will run for 10 minutes.  
Note: This time is utilized to cool down the regeneration heater/cell.  
3. After 10 minutes of run time, the blower will turn off but the green light remains lit. That means  
the system is off but the power is still on.  
4. Turn the disconnect switch to the “OFF” position as shown. The green run light should turn  
off.  
(CAUTION: DISCONNECT POWER BEFORE SERVICING  
DRYER UNIT).  
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Parts Department  
[
]
[414]  
Call toll-free 7am–5pm CST 800 423-3183 or call 354-0970, Fax [414] 354-6421  
The ACS Customer Service Group will provide your company with genuine OEM quality parts manufactured  
to Sterling engineering design specifications, which will maximize your equipment’s performance and  
efficiency. To assist in expediting your phone or fax order, please have the model and serial number of your  
unit when you contact us. A customer replacement parts list is included in this manual for your convenience.  
ACS welcomes inquiries on all your Sterling parts needs and is dedicated to providing excellent customer  
service.  
Service Department  
[
]
[
] 3  
Call toll-free 8am–5pm CST 800 657-4679 or call 414 54-0970  
[
]
Emergencies after 5pm CST, call 847 439-5655  
Sterling has a qualified service department ready to help. Service contracts are available for most Sterling  
products.  
Sales Department  
[414]  
Call  
354-0970 Monday–Friday, 8am–5pm CST  
Sterling products are sold by a world-wide network of independent sales representatives. Contact our Sales  
Department for the name of the sales representative nearest you.  
Contract Department  
[
]
Call 414 354-0970 Monday–Friday, 8am–5pm CST  
Let Sterling install your system. The Contract Department offers any or all of these services: project  
planning; system packages including drawings; equipment, labor, and construction materials; and union or  
non-union installations.  
Sterling  
5200 W. Clinton Ave  
Milwaukee, WI 53223  
[
]
[414]  
354-6421  
414 354-0970 Fax  
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