Chromatography Forum

Hi,
I am using Agilent MSD 5975C with GC7890A. I am having some issues with turbo pump. Whenever I try to pump down I get an error saying "High vacuum pump not ready". I have checked for leaks and also for foreline pump (oil etc). I also checked for loose electronic connections. The only other option left is faulty turbo pump (according to agilent manual). Is there anything we can check conclude the same. ? or in other words what are the things that we can check to see if the turbo pump is faulty ?
One more thing to mention, even if the vacuum reading on the console is 9.99 E1 torr I can hear air flowing in when I open the vent valve (Does that mean the gauge is faulty? )

Maybe the mechanical pump is not working; the Turbo needs a rough vacuum to start up. Vent the MSD, disconnect the vacuum tube from the pump and start it. Check that it is pumping by placing you hand over the hole in the pump, you should experience a sucking feeling. Good luck

If you do not get a rough vacuum of 300mTorr or less then the turbo pump controller will shut down the turbo pump to protect it.

One quick way to check if the turbo pump is bad. Vent and open the analyzer. Take a can of Dustoff, or other "canned air" used for cleaning electronics(you don't want too much pressure just good flow so don't use an air compressor and blow gun). Spray the top rotor of the turbo pump with an indirect flow from the can, it should spin up very quickly and continue to spin for 20-60 seconds easily. If it does not spin, or spins slowly and stops quickly, then the bearings are bad in the turbo pump.

Another way to check if you have the turbo pump out of the instrument and on the bench is to hold it in your hands with the rotor at the top, then rotate the body quickly. You should be able to turn the body of the pump without the rotor turning much at all if the bearings are good. This is how I do a quick check on replacement pumps before installing them. The bearings in these pumps are so good that turning the outside of the pump transfers very little momentum to the rotor itself. But I would not suggest this until you are ready to replace the pump, and practice with the broken one so not to break the new one if you don't have experience with it

We had a similar situation a few years ago.The 5975C has a Pfeiffer turbopump which shuts down in about 8 minutes after you restart the MS if the system does not read the right pressure. Our ion gauge had stopped working. We turned off the system, disconnected the ion gauge from the MS and restarted the system and problem was solved. Good luck.

Thank you for the replies. Pump problem is fixed. It was just an electronic communication problem. However we have another problem on the same system.
The system does not give proper air and water check. (N2 % > 15). We have done various trouble shooting checks.
1. Plug MS at the interface : Air water check passed (No leak in MS side)
2. Connect the transfer line column to the MS but plug the other end going into the splitter (Dean's switch) : Air water check passed (No leak in transfer line and interface nut)
3. Connect transfer line to the Dean's switch but plug all other outlets of the switch (viz GC column and FID). : Air water check failed. We start seeing N2 peak > 15-20 %
(and it varies with different runs) This made us conclude that there is a leak somewhere in Dean switch. But we could not identify the exact location by using Dust removal spray. So I have 3 options :

1. Go for on site agilent maintenance. (Very expensive and will take time)
2. Buy a new dean's switch. (Expensive and risky too as we are not 100% sure that it will fix the problem)
3. Continue with the small leak (around 15%) (Cheap but I dont know how will it affect our result and other parts of instrument)

Please, need advise.

If you do not get a rough vacuum of 300mTorr or less then the turbo pump controller will shut down the turbo pump to protect it.

One quick way to check if the turbo pump is bad. Vent and open the analyzer. Take a can of Dustoff, or other "canned air" used for cleaning electronics(you don't want too much pressure just good flow so don't use an air compressor and blow gun). Spray the top rotor of the turbo pump with an indirect flow from the can, it should spin up very quickly and continue to spin for 20-60 seconds easily. If it does not spin, or spins slowly and stops quickly, then the bearings are bad in the turbo pump.

Another way to check if you have the turbo pump out of the instrument and on the bench is to hold it in your hands with the rotor at the top, then rotate the body quickly. You should be able to turn the body of the pump without the rotor turning much at all if the bearings are good. This is how I do a quick check on replacement pumps before installing them. The bearings in these pumps are so good that turning the outside of the pump transfers very little momentum to the rotor itself. But I would not suggest this until you are ready to replace the pump, and practice with the broken one so not to break the new one if you don't have experience with it

thanks James!

How was the electronic communication problem fixed?

A few things to check with the Dean switch is check the nuts of all of the switch connections, and any gases that are connected to the line as well as any ferrules. Even though a connection may have positive pressure there can still be air that gets sucked in with the moving gases within the lines. There is a suggestion in the manual that says to heat it up to try and seal the ferrules a little more, but if the nuts are over tightened that can simply crush them and prevent a seal from ever forming. Remember, finger tighten plus a quarter to a half turn is a good rule of thumb.