Agilent Technologies 5975T LTM GC/MSD, Troubleshooting And Maintenance Manual

Page: 195 / 270

Vacuum System
12
Troubleshooting and Maintenance Guide 195
Turbo Pump and Fan
The turbo pump is clamped directly to the bottom of the
analyzer chamber.
The turbo pump has a cylindrical body with its inlet open to the
interior of the analyzer chamber. Inside the pump body is a
central shaft or cylinder. Sets of small blades (airfoils) radiate
from the central shaft. The shaft spins at up to 90,000 rpm in
the standard turbo pump.
Turbo pumps move gas by momentum transfer. The turbine
blades are angled so that when they strike a gas molecule it is
deflected downward. Each set of blades pushes the gas
molecules further down toward the pump outlet.

The foreline pump is connected by a hose to the outlet of the
turbo pump.

It removes the gas molecules that reach the outlet.
A controller regulates current to the pump and monitors pump
motor speed and temperature. A cooling fan is located between
the turbo pump and the front panel of the MSD. The fan draws
air from outside the MSD and blows it over the pump.
The turbo pump turns on automatically when the MSD power is
switched on. The system allows the analyzer to be turned on
when the turbo pump is greater than 80% speed, but the pump
normally operates at 100% speed. The turbo pump maintains an
indicated pressure below 8 × 10
-5
Torr for helium column flows
up to 2 mL/minute. Pressure (vacuum) can only be measured if
your MSD is equipped with the optional gauge controller.
The turbo pump spins up (starts) and spins down (stops)
quickly. This simplifies pumpdown and venting. From initial
power-on, the system can pump down to operating pressure in 5
to 10 minutes.
See Also
• To pump down the MSD
• To vent the MSD
• Turbo pump control , page 220 .