Sometimes we have such a problem: The vacuum pump works perfectly to reach required vacuum pressure in a vacuum chamber during operation. When we turn off the pump and then turn on the pump again, the pump doesn’t start. Some oil can be found in the chamber. So, what’s wrong with the vacuum pump?
It is because the anti-suckback valve of the vacuum pump is not effective or missing. The non-return valve is composed of two lightweight aluminum parts and one spring. The construction is simple but very important. It’s designed to protect the vacuum pump in the event of sudden stop. The anti-suckback valve closes when the pumping is stopped, so that the air will not be sucked back into the vacuum chamber.
Without this valve, the pressure in the vacuum pipeline is higher than that in the vacuum chamber while the pump stops, and the air (or gas) enters the chamber through exhaust port immediately. The vacuum oil or particles will go into the evacuated vacuum chamber to contaminate it.
Function of anti-suckback valve
The function of the anti-suckback valve is to balance the pressure inside and outside the pump by closing when the pump stops working. The valve opens when the pressure inside the pump achieves the vacuum level in the vacuum chamber after the pump operates for a while. In this way, the oil will not be sucked back.
In case the pump employs no anti-suckback valve, it’s considerable to assemble a solenoid valve outside to realize the same function. Even for vacuum pumps with anti-suckback design, it’s common to use solenoid valve as an extra device.