PRIOR TO START UP

1. The liquid distributor and the atomiser wheel must be correctly mounted, having the specified distance between them. Check that the vaned wheel freely rotates

2. Check all duct connections for tightness. All gaskets must be correctly mounted. No false air must be sucked into the drier system due to air leakage around the duct connections

3. Check that the glass jar under the cyclone is securely fastened. The glass jar must be clean and dry. It is recommended to preheat (warm) the glass jar to prevent condensation occurring in the jar during the early stages of the drying

4. Check that the silencer is mounted on rotary atomiser

START UP

With the power switched on to the unit, the chamber light and the panel live indicator lamp will light up. Turn the switch to I, II or III depending on the inlet air temperature required. Use the percentage timer to adjust the air temperature until the disired inlet air temperature is obtained

With the heater on and the fan started, start the atomiser by completely opening the blue valve on the instrument panel. The atomiser will accelerate rapidly with a squealing sound, which will gradually decrease until it becomes almost inaudible at full speed. The air pressure is indicated on the pressure gauge and this must be kept constant. The atomiser will, of course loose speed if the pressure decreases. It is essential that the speed is kept constant in order to obtain and efficient liquid atomisation

The atomiser will reach top speed after 30 seconds. Then pass distilled water to the atomiser until the required outlet air temperature is obtained. This temperature depends on the product to be dried. For many products about 85ºC will be suitable

When the outlet temperature has been obtained and is maintained constant, switch from the water supply to the liquid feed.

The drying operation now commences

Note: The unit is designed to operate with an inlet air temperature of max 350ºC and outlet temperature of max 120ºC

DRYER CONTROL

The drying operation is controlled by maintenance of the required outlet air temperature at a constant inlet temperature. For a given feed liquid of constant physical properties, the outlet air temperature is related directly to the moisture content of the dried powder. Increase in outlet temperature reduces the moisture content, decreasing the temperature increases the moisture content. Once the outlet temperature range to obtain dried product from the drying chamber has been established, the outlet temperature can be precisely adjusted to obtain the required moisture content. During the drier operation it is most important to keep the outlet air temperature constant so as to maintain the moisture content level

This is carried out by regulating the rate of feed. Usually the outlet air temperature does not change, once the feed rate has been adjusted. Alterations of the viscosity and the solids content of the product will influence the outlet air temperature

If the feed rate is too large, it is likely that the powder, already in the chamber, will absorb moisture and stick to the chamber wall. Any adjustments must take place very slowly, with intervals of sufficient length to enable the resulting effects to be registered on the thermometer

The powder is collected in the glass jar mounted under the cyclone. It is important that the glass jar is exchanged before it becomes completely full as this will result in product losses from the cyclone

Products that are difficult to dry must be atomised at the highest possible speed of the vaned wheel. A low speed will give a coarser droplet size but may result in wet wall deposits. A high speed gives fine droplets which are retained in the chamber air flow thus dried before reaching the chamber wall

DRYER SHUT DOWN

Before the unit is shut down a change over of feed from product to distilled water must take place. The amount of water fed to the atomiser must be regulated so that the outlet air temperature does not decrease. This is most important as the powder in the drying chamber will absorb excess moisture

The unit is to run 10 - 15 minutes with water in order to flush clean the atomiser wheel and the feed pipe. The air heater is then switched off. After setting the percentage timer to 0 and the operation switch at M the water supply is turned off. Approximately 3 minutes later the atomiser is stopped

Draw cold air through the drier for 5 minutes of so. When the outlet air temperature is 50ºC the chamber is opened by means of the pneumatic lifting device. If powder is retained in the chamber, it can be swept down. Switch the fan on during this operation

Finally turn the operation switch to position 0, which cuts the power supply

Note: If it is necessary to stop the spray drier suddenly, it is most important that the feed rate is stopped immediately

CLEANING

Before the lid is raised ensure the atomiser wheel has stopped rotating

Remove the atomiser wheel and the liquid distributor from the atomiser and clean immediately after use

For dry cleaning, lift the chamber roof and turn it vertically upwards. When the roof is in the upright position, insert the locking pin. This is a safety precaution. Brush down the powder from the chamber walls and roof. Leave the fan running. All powder will be collected in the glass jar under the cyclone. Hygroscopic powders must always be swept down immediately

For wet cleaning the fan must be stopped and the electrical power supply switched off. Disconnect the duct at the chamber base. Hose down the interior of the chamber

It is best to dismantle the ducts and cyclone for thorough cleaning

Never spray water on the instrument panel or the light fixture

For cleaning synthetic washing powders, industrial cleaners, and soap solutions are recommended as cleaning media. Rinsing with water must take place after their use

Following cleaning the spray drier must be assembled correctly. All connections must be tight and all parts dry. Drying-out of the drier may be done by drawing hot air through the unit for some time before start-up

It is recommended that regular inspection and cleaning of the fan is carried out. Deposits on the impeller of the fan may cause vibrations and may cause irregularity in the spray drier operation