Edwards EXT200/200H Not Pumping to Full Speed
Posted: Tue Mar 19, 2019 6:44 pm
Hi everyone, the post title sums up the problem pretty well, and I have tried so many things to fix this problem but you guys are probably quite a bit more knowledgeable than I am when it comes to vacuum systems.
My thing is mass spectrometry. The turbo pump in question is housed in a Waters ZQ single quadrupole mass spectrometer that I won from a university disposition auction and is in my garage. When everything is plugged in (I rent a house, so the ZQ and roughing pump are plugged into 110->220 transformers drawing from wall outlets on two different 20 amp breakers), everything starts flawlessly. The foreline pump is an Agilent MS40+, which is designed to be used as a mass spec roughing pump. It pulls about 25 cfm and down to 30 microns at the inlet. Monitoring the diagnostics on the instrument, the pirani gauge showed about 4 torr (either due to it not being calibrated well, or vacuum loss somewhere). I then press 'pump' to turn on the turbo. This is where the problem is. The turbo gets to about 36-40% speed fine, sounds great, but for some reason it appears that there is no further decrease in pressure, according to the Pirani gauge. I tried twisting the calibration screws on the Pirani gauge to see if the reading from that controls the turbo speed. Didn't do anything. I guess what confuses me the most is that the reading from the Pirani doesn't change regardless of whether the turbo is at 0 or 40%. It is crazy!
I am pretty sure all the seals are good in the mass spec. When the turbo returns to 0, and the instrument and the foreline pump are turned off (don't worry, the MS40+ pump has an isolation valve that closes to prevent oil from going into the mass analyzer), I can hear a very quiet hissing sound, which I assume to be the vent valve at the bottom of the turbo.
Do you guys think I am missing anything? Could it be a voltage problem? Or do you thing there is something wrong with the turbo?
Thanks,
Dean
My thing is mass spectrometry. The turbo pump in question is housed in a Waters ZQ single quadrupole mass spectrometer that I won from a university disposition auction and is in my garage. When everything is plugged in (I rent a house, so the ZQ and roughing pump are plugged into 110->220 transformers drawing from wall outlets on two different 20 amp breakers), everything starts flawlessly. The foreline pump is an Agilent MS40+, which is designed to be used as a mass spec roughing pump. It pulls about 25 cfm and down to 30 microns at the inlet. Monitoring the diagnostics on the instrument, the pirani gauge showed about 4 torr (either due to it not being calibrated well, or vacuum loss somewhere). I then press 'pump' to turn on the turbo. This is where the problem is. The turbo gets to about 36-40% speed fine, sounds great, but for some reason it appears that there is no further decrease in pressure, according to the Pirani gauge. I tried twisting the calibration screws on the Pirani gauge to see if the reading from that controls the turbo speed. Didn't do anything. I guess what confuses me the most is that the reading from the Pirani doesn't change regardless of whether the turbo is at 0 or 40%. It is crazy!
I am pretty sure all the seals are good in the mass spec. When the turbo returns to 0, and the instrument and the foreline pump are turned off (don't worry, the MS40+ pump has an isolation valve that closes to prevent oil from going into the mass analyzer), I can hear a very quiet hissing sound, which I assume to be the vent valve at the bottom of the turbo.
Do you guys think I am missing anything? Could it be a voltage problem? Or do you thing there is something wrong with the turbo?
Thanks,
Dean