Principle of single and double vacuum pump configuration

A. Function of double screw vacuum pump exhaust system

a) Eliminate the moisture of the material to make the product surface more smooth, no air bubble, and increase finished product ratio.

b) The construction and design of single and double vacuum air exhaust system is simple and easy to maintain.

c) Easily filter the impurities to extend the service life of vacuum pump.

d) The vacuum tank is big and takes long cleaning time. The diameter of vacuum pipe is big, air suction is even, vacuum operation is stable and reliable.

B. Principle diagram of single vacuum pump

Direction A: for cleaning use Direction B: for normal use

a) During the normal use, direction B is normal running status. At this time, value 1 is closed, value 2 and 3 remains open. After the exhaust air of main machine go through the pipework to the filter, part of the water, air and small quantity of impurities have been exhausted.

b) During the operation, when it is found that too much impurities in the filter or likely to be blocked, machine stoppage is not needed, just need to changeover the value, open valve 1, close valve 2 and valve 3 to clean the filter in time.

c) After the filter is cleaned, changeover the value, operate correctly based on step 1.

d) Check whether the vacuum pump infeed water remains open when start up the machine, when stop the machine, the infeed water valve of the vacuum pump must be closed.

C. Principle diagram of double vacuum pump

Direction A: for clean use Direction B: for normal use
a) During the normal use, direction B is at normal running status. At this time, Value 3 and 4 are closed, value 1 and 2 are open. Filter 1 is working, exhaust air of main machine go through the pipework to the filter, part of the water, air and small quantity of impurities have been exhausted.

b) During the operation, when it is found that too much impurities in filter 1 or it is likely to be blocked, it is not necessary to stop the machine, just need to changeover the switch. Open valve 3 and 4, close valve 1 and 2, the filter 2 is in normal working condition. The pipework route is through filter 2 and exhaust from the vacuum pump, at this time no need to clean filter 1, can do it when not busy to save time and labor.

c) When filter 2 need to be cleaned, then changeover the value, operate according to the 1st step.

d) Check whether the vacuum pump infeed water remains open when start up the machine, when stop the machine, the infeed water valve of the vacuum pump must be closed.

D. Reason analysis of surface bubble

a) The MC of calcium powder or other raw material is high.

b) The vacuum of the main machine is blocked or vacuum leak, so didn’t reach the requirement of vacuum.

c) The temperature of mould and barrel were set too high.

d) The stabilizer content in the recipe is small, slightly add more.

e) The quality of stabilizer is bad.

f) There is water leak for the water jacket between the bottom of double screw infeed and screw barrel.

g) There is water leak for the vacuum tank, water go inside from the air exhaust hole, wrong direction, the water pressure is too big.

h) Materials are not mixed well.

i) Recipe need to be adjusted and reset.

j) Showed temperature is different form actual temperature, need to measure with a temperature meter to see whether the temperature are correct.

k) Hot mixer inside or pipework leak water.

l) For the screw rod which has cooling construction in the core, screw rod leak oil and water, need to check whether the screw rod has cracks or holes.

E. Tips for machine start up：

Due to the high content of calcium powder in some products, the materials are not easy to be plasticized, so it is easy to have powder leak in the air exhaust, and it is easy to accumulate carbon in the air exhaust.

a) Regularly check whether the exhaust outlet is blocked, check once every 1 to 2 hours.

b) Clean the vacuum pump during shift hand over.

c) Check whether the material at the exhaust outlet is like cotton or cloud shape to verify whether it reaches the semi-plasticized condition.

d) Clean the carbon by the air exhaust in time, not allowed to use metal tool for cleaning.

F. Method of eliminating the causes of powder leak at double screw rod exhaust outlet.

a) A. If the feeding speed is too high, reduce the feeding screw revolution;

B. Increase the main machine speed but remain the same feeding until the exhaust outlet does not leak powder.

Note the current of the machine during running, it should not exceed 90% of its rated current!

Suggest to set the range of rated current for the operation of double screw operation, 60 ~ 85% of the motor rated current.

b) Clean the material and carbon around the the screw rod, take off the screw rod for cleaning and polishing.

c) Increase the temperature of heating zone of exhaust outlet and material out-feed, so that the material can be plasticized.

d) Set the temperature of the area behind exhaust outlet to be 10℃ lower than the front area to increase the friction ratio of materials.

（Front is start from the material infeed, behind is the transition piece direction.）