Reasons for Low Vacuum Degree during De-gassing Process of VAC-V1

VAC-V1 Gas Permeability Tester may encounter problems of vacuumization failure or inferior vacuum degree, and correspondingly, would lead to great errors in testing results, or even test failure. Hereafter, we would introduce several causes for low vacuum degree and relevant solutions.

1. Insufficient Gas Pressure
A Pneumatic valve is in VAC-V1. This valve requires a pressure among 0.5MPa-0.7 MPa from the cylinder. Therefore, if the gas source is less than 0.5MPa, or no pressure, the pneumatic valve would not open, and the gas inside cell and sensor can not be vacuumized. Thus, the low vacuum degree or vacuum failure would make the test impossible.
Solution: check whether the cylinder gas pressure is within regulated scope. If not, change a new cylinder or increase output pressure of the pressure output valve.

2. Vacuum Pump Breakdown
Check with the vacuum pump is on and in good working condition. Check the joint point between the pump and the instrument, and the connector between vacuum pipe and the pump.
Solution: screw down clamping band for better sealing performance.

3. Specimen Inspection
●Check the evenness of the specimen. The specimen should be even, and the uneven and rigid crease would lead to sealing failure of the sealing ring. Thus, the outer gas would come to the chamber from the cracks, and would lead to difficulty in vacuumization.
Solution: choose even specimen.
●Check Whether Specimen is Thick or with Rigid Fiber
Thick specimen can not be pressed firmly by the sealing ring. Paper and textile materials with crude fibers would lead to lateral gas transmission and incomplete vacuum.
Solution: place more vacuum grease on the edge of the specimen for better sealing performance.
● Specimen is Fragile
Some specimens are very fragile, and would be broken when being clamped.
Solution: take care of the specimen. When placing it, vacuum the lower chamber first so that the specimen can complete stick to the lower chamber. Close the upper chamber slowly and gently. During testing, there is pressure difference between the upper and lower chambers, and there is vacuum grease sealing; therefore, there is no need to seal with great strength.
● Check Whether Specimen is Placed in the Center Part
There are two sealing rings in the upper chamber of the instrument. The inner ring is for testing area confirmation and out gas impediment. The outer ring is for edge sealing. Thus, if the specimen is placed deviated from the center, the ring can not fully press on the specimen and lead to leakage.
Solution: apply the specimen placement ring and place the specimen in the center.