/ep_edm/en/contect_615.html SHINI PLASTICS TECHNOLOGIES, INC.

Special Reports

2012 Quarter 2 Issue 11

Maintenance of Dehumidifiers

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Plastic products will have lot of quality problems including bubbles, crazes, cracks, flow marks and bad transparency, etc. One main reason of these problems is that plastic materials are not fully dried before molding. Engineering plastic such as PA, PC, PBT, PET and NYLON, etc. are all hygroscopic good. Material cannot be fully dried by the traditional dryer because it uses air with moisture to dry the material which can not dry the internal plastic particles. It has been proved that only by reducing the process air dew point to lower than-40℃ and the control the heat to blow over the moisture material, can we make the moisture content dropped to below 0.02% before molding.

 

With the widely use of engineering plastics, dehumidifying type dryers have gradually replace the traditional hot air dryers.

 

Honeycomb rotor dehumidifiers series are the most common type which with ceramic fiber made honeycomb rotor as the core to ensure the best effects. The process air provided by the dehumidifier can easily and stably reach the dew point 40℃ below zero or even 50℃ below zero ideally to ensure the product quality. The series adopt P.I.D standard temperature controller, and PLC touch screen controller and dew-point monitor are optional. With the advantages of multifunctional, better dehumidifying effects, no pollutions, high quality, high speed and energy-saving, etc., the series has a service life which can be prolonged under good maintenances.

 

Use the operation instruction of the machine for reference for better maintenance. Pay attention to the instruction part and safety regulations. Maintenance must be done according to the specifications listed in the manual and the maintenance schedule must be completed.


1. Safety Regulations


The machine must be placed indoors with the maximum temperature of +45℃ and humidity of less than 80%, as well as the air outlet with no blockings. Do not use the machine in the following conditions:


1) If it is with a damaged cord.
2) On a wet floor or when it is exposed to rain to avoid electrical shock.
3) If it has been dropped or damaged until it is checked or fixed by a qualified serviceman.
4) This equipment works normally in the environment with altitude within 3000m.
5) At least a clearance of 1m surrounding the equipment is required during operation. Keep this equipment away from flammable sources at least two meters.
6) Avoid vibration, magnetic disturbance at the operation area.

 

2. Operations for accurately use and maintain the dehumidifier


2.1 Dehumidifying drying machine should be placed a flat surface without tilt or GoProne, so any failure or abnormalities can be avoided. Never use thin rods or iron wire to draw out within the machine, for faults or danger may be caused.

 

2.2 Correctly adjust the dry temperature, regeneration temperature, runtime and mode of the dehumidifier according to the materials and operation instruction, so as to material can be fully dried energy can be saved and at the same time the machine can be maintained.

 

2.3 Regular cleaning is necessary: regularly dismantling and clean the dehumidifier filters, when cleaning up the body, wipe gently with wet cloths rather than directly splash water on it to avoid destroying electrical insulation. Clean the body surface with soap water rather than gasoline, oil essence, solvents or pesticides spray to avoid paint stripping off or discolor; Regular cleaning can effectively improve the dehumidifier dedusting effect, and then improve air quality, and consequently improve the working efficiency of the dehumidifier.

 

2.4 Regular professional inspection is needed. After a long time running, units of the electrical lines and control elements inside the dehumidifier can have different degrees of aging which may cause damage to the unit or the human body. Therefore, regularly inspection by professionals can make the dehumidifier keep in good working condition.

 

2.5 Protection measures should be taken when the power goes out or the machine shuts down in a long term: please unplug the power cord to maintain machinery life; then cover the dehumidifier with a shield to avoid the weathered, dust deposition which may cause difficulty of cleaning and maintenance in the future.

 

3. The dry air volume and dew point are the most important two indicators to evaluate the drying capacity and effect of the honeycomb rotors. Honeycomb rotor, dry and regeneration electro-thermal, blower, cooler and filter are all important parts which can influence the air volume and the dew point, so the maintenance of these parts are imperative.


3.1 Honeycomb rotor is the core part of the rotor dehumidifier. The moisture absorption performance influence the dew point, unobstructed channels of the inside rotors can provide big volume of air flow, the performance of the honeycomb rotor is directly related to the dehumidifying ability and effect. When the dew point gets high and air volume reduces, the first thing to do is to check the honeycomb rotor. Maintenance and repair methods are as below:


1) Use high pressure air to clear the dusts on the surface of honeycomb-rotor.

2) If there are dusts inside of honeycomb-rotor, use high pressure air to blow away the dusts.

3) If there are sticky dirt on the inner surface of the rotor:

a. Blow wet air, relative humidity at 60%, into the rotor to make it saturate with moisture. If the current air humidity has come to 60%, you can turn off the regeneration motor, but keep running of the process motor and rotor motor make honeycomb-rotor wet with moisture. If the air is too dry, please use a humidifier to adjust the humidity. This process may take one hour.

b. According to different kinds of dirt, you can dip the rotor into water or a kind of solvent, such as solvent of dimethyl benzene. If it is grease or oil, detergent PH value less than 7 can be used. Using detergent of high PH value would damage silica gel of the rotor. Shake the rotor up and down for 15 minutes to get rid of the dirt.

c. Take out the rotor from the detergent and lay it upright for 5 minutes to make the detergent flow out of the rotor.

d. Use high pressure air to blow away the detergent remained in the honeycomb rotor.

e. Install the rotor back to the machine and start the regeneration blower and keep it running for one hour. (Temp. between 100℃ and 140℃)

 

3.2 Dry and regeneration electro-thermal

 

The dehumidified air from the honeycomb rotor is heated up to its setting temperature by the dry electro-thermal and then enters into the material tank for dehumidifying and drying. The role the regeneration electro-thermal plays is to renew the moisture absorption function of the honeycomb rotor. From which we can see that both dry and regeneration electro-thermal a key role ensuring good drying effects. Hence, the maintenance and repair are very necessary. Make sure the overtemperature protector can work normally. The electro-thermal belongs to the vulnerable product with a service life of 1 to 2 years, replacement is always necessary.

 

3.3 Blower


There are dry blower and regeneration blower in the rotor dehumidifier. Dry blower provides sufficient air dehumidified by the honeycomb rotor and dried by the dry electro-thermal for the dehumidifier to made raw material dehumidified and dried; Regeneration blower blows the vapor in the honeycomb rotor out. Maintenance and repair methods are as follows:

1) Under normal operation, the blowers will generate high temperature. Do not touch blowers case to avoid any physical injury.

2) Under normal operation, the blower motors current loading will increase or reduce according to air pressures change accordingly. While installation, an adequate motor overload protection switch should be installed with full loading test, to ensure operating safely under full-loading to avoid motors damage.

3) To avoid any block materials, dust, powder, fiber particles and water drops entering the blower, and hence cause the deficiency of its performance. This machine is well designed with air filters, so please clean up the filter with any foreign particles (recommended to clean up this filter weekly).

4) Clean the blowers both internal and external parts (especially for the fan cooling path), and remove surface dust if necessary. If more dusts are accumulated, it will cause deficiency for ventilation, temperature rising, vacuum power reduced, vibration increased and so it will cause machine broke down.

5) Ball bearing, oil seal and soundproof are belonging to consumable parts and so it has a life period and requires regular replacement. Meanwhile, blade, external case, and metallic screen etc. should be replaced regularly for best performance.

6) Under normal operation, if the blowers are not running smoothly or abnormal noise appeared. Please immediately shut down the machine for repair.

 

3.4 Filter


Before entering the blower and honeycomb rotor, the air must be filtered through the filter to avoid bad effects caused by hard object, dust, powders, fibers and water droplets. Filter plays a very important role ensuring dehumidifying and protects the main parts of the machine. Please periodically clean the dust on the air filters, once per week.

Cleaning steps:


1) Take out the air filter carefully.
2) Blow off the dust on the air filter screen and the cover with pressure air.
3) Wipe off the barrel wall of air filter with dishcloth.
4) After cleaning, place all parts in reversed order carefully.

 

3.5 Cooler


To make the honeycomb rotor work to its best, a lower temperature environment must be ensured. High temperature return air should pass through the cooler to get itself cooled and dehumidified. Cooler need regularly eject dew and clean. Monthly cleaned are suggested when using cooling water while using room temperature water, once every quarter is your best choice.

Cleaning steps:


1) Disassemble the coolers pipe and screw, and remove the cooler out of the chiller.

2) Release the fixed screw on the upper and lower cover of cooler and disassemble the cover.

3) Use brushes compressed air or low pressure water to clean the dust and sundries on the cooler fan and copper pipe. Notes: water residue on the cooler fan and copper pipe should be dried with compressed air.

4) Make the coolers upper and lower cover junction clean enough and smear the silica gel then fixed the covers with screws.

5) Put the cooler on the air at least 4 hours to make the silica gel drying enough then fix the cooler on the chiller and connect all pipes.

 

The cleaning work of Y-type cooler should be done according to the condition of cooling water dust. Clean it in time in such situations, such as hot air and insufficient cooling water flow.