STP-301/451 Series Instruction Manual
4-12
Installation
4.3.4 Vacuum Piping
◇ DO NOT open the STP pump through the flange to atmospheric air while the STP
pump is running.
If atmospheric air flows into the STP pump, it may not function normally.
◇ Depending upon the type of the backing pump used, atmospheric air may reverse
flow into the STP pump when the backing pump stops.
Attach a vacuum valve to the middle of the piping between the STP pump outlet
port flange and the backing pump, and close the vacuum valve when the backing
pump stops.
In order to let the STP pump bring its performance into full play, follow the precautions
below:
1) Be careful not to scratch the flange of the STP pump.
Before installing the STP pump, check whether or not there are scratches on the surface.
2) Use steel or aluminum tubes with a low gas loss to connect the vacuum equipment to the
STP pump.
3) Take measures for minimizing leakage. It is also necessary to degrease the tubes as
regularly as possible to keep the gas loss as low as possible.
4) It is recommended to use an backing pump of pumping speed 240 L/min or more.
However, the pressure at the inlet and outlet ports varies with the flow rate of gas,
capacity of the vacuum equipment, length and material of the piping. Select an backing
pump in accordance with the capacity and starting method (simultaneous starting,
starting after generating roughing vacuum) suitable for the vacuum equipment you use.
5) Connect the STP pump and the backing pump using stainless steel or aluminum alloy
tubing, flexible tubing, vacuum rubber or Teflon tubing, and other.
The following measures can be used to avoid the transmission of the vibration of the
backing pump to the STP pump and the vacuum equipment.
• DO NOT place the backing pump on the same floor as the vacuum equipment.
• Locate the backing pump on a vibration-proof table.
Attain 1/3 or less of the rotational speed of the backing pump, when adjusting the
inherent frequency of the backing pump installed on a vibration-proof table.
• Attach a weight to the piping from the backing pump, or secure the piping to a rigid,
heavy object free of vibration.
• Use a tube of high flexibility.
6) Depending upon the type of the backing pump used, oil may contaminate the inside of
the STP pump. Some oil viscosity could cause a malfunction when there is a strong
reverse flow of oil.
Take the following measures to ensure the correct flow of oil:
• Attach a vacuum valve to the middle of the piping between the STP pump outlet port
flange and the backing pump.
• Attach an absorption trap adjacent to the vacuum valve.
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