Chromatography Forum

53mtorr is the foreline pressure indicate on the msdchemstation.
You need to have 300mtoor with your Mechanical pump to start the diffusion pump.
With ion gauge, the reading is 4x10'-5 torr

You are ok Don, no problem.
53mtorr is a good foreline pressure and the diffusion pump is supposed to start......so, it's important to verify manually if the diffusion pump is running.
Rick

I guess my question is more directed at Rick, who has stated
"If your pressure is 53mtorr,your mechanical pump is ok and your diffusion pump is ok"
"53mtorr is a good vacuum, so, i think that your diffusion pump is running"
"If you have a foreline vacuum of 53mtorr, your diffusion is ok"

I don't understand why the diffusion pump is assumed to be operating properly. Everything that I see indicates that the diffusion pump heater is NOT on and therefore the diffusion pump is not operating.

The first thing I would do is see if voltage is getting to the diffusion pump heater. If it is, the heater has gone out or there is a problem in the connector, if not, something is preventing the pump from being turned on - safety interlock, blown fuse, bad electrical connection, or other electrical failure

hi

today i test the pump. its cold. the fluid level is on cold position.
During the automatic pump down process once the MSD starts up,I have the following message <high Vacuum Pump Off, vent in progress> but the pump down process goes on unable to complete it.

if i try to activate the pump down manually from the msd menu (maintenance --->pump down?--->yes) after twenty minutes i have the message <error in pump down>.

Rick, the connection between MSD and Diffusion pump seems to be ok.
bhuvfe, i have had power failures in my lab recently.

during the normal pump down the temperatures are on setpoint. during my pump down the temperatures are 25 Celsius. why?

hi

today i test the pump. its cold. the fluid level is on cold position.
During the automatic pump down process once the MSD starts up,I have the following message <high Vacuum Pump Off, vent in progress> but the pump down process goes on unable to complete it.

if i try to activate the pump down manually from the msd menu (maintenance --->pump down?--->yes) after twenty minutes i have the message <error in pump down>.

Rick, the connection between MSD and Diffusion pump seems to be ok.
bhuvfe, i have had power failures in my lab recently.

during the normal pump down the temperatures are on setpoint. during my pump down the temperatures are 25 Celsius. why?

Because you get a pop-up window from chemstation to set the T of the ion source and quadrupole only after the MS is pumped down (and when the diffusion pump is working). Before that what you have are the previous T of your detector (in your case, ambient T).

Have you tried to switch off the msd using the on/off button. Then waiting 2-5 seconds and trying the pumpdown procedure? I've checked on the manual of my instrument and, beside calling Agilent for help, what was mentioned is the procedure above (power cycle of the MSD).

And what about pumping down without chemstation (it's a long shot but it's easy to do..)?

bhuvfe, i have tried all that you have mentioned before but nothing...

Try this.....
http://www.chem.agilent.com/Library/Sup ... A20346.pdf

bhuvfe, i have tried all that you have mentioned before but nothing...

Too bad
Then I'm afraid that only an Agilent service engineer will be able to help you..
Likely changing some boards or sensors.

RICK, from pdf file..

If the vented air feels cool and the foreline pressure is good (below 300 mtorr), it could indicate that the diffusion pump heater has burned out or problems with the electronics controlling power to the diffusion pump heater.

but how can i test the diffusion pump heater??

Make sure that power to the diffusion pump is off.
Disconnect the electrical connector from the diffusion pump.
Get an ohmmeter.
Measure the resistance across the contacts of the diffusion pump heater.
I don't know the exact value that it should read, but it will probably be in the tens to hundreds of ohms.
It most definitely should NOT be in the thousands of ohms or higher.

If the resistance reads OK, do a physical inspection of the connector and all wiring going to the connector. Wiggle the connector. Look for loose screws/nuts. Look for loose wires. Look for frayed insulation.

If everything looks OK, switch the meter over to read voltage. Connect the meter leads to the diffusion pump supply wiring (what you have just been inspecting). Power up the system to the point that the diffusion pump should turn on and watch the meter. You should see the supply voltage, which will probably be between 100 and 250 volts. Without seeing the schematic of your instrument it's hard to be more exact.

Surely, one of those tests will show something wrong. Either your heater is burned out, the connector/wiring is bad, or no voltage is getting to the heater.

Let us know the outcome.

Hi Nicolas!
Follow the step give by Don
Rick

I bet you its the diffusion pump heater...the thing is turning on but the heater element is faulty. The diffusion pump has to basically boil its oil to work but you don't want it starting to do that unless the rough pump is down to an acceptable level (53 mTorr or so is good). IF you did then oil would get up into the source and everywhere else.

Take a multi-meter and check if the heater is OK. Open circuit means the heater's element has a break in it. Timothy

I have had a diffusion pump heating element fail. Replaced it and back to work we go....

Don,

today i haven't got enough time to check out the diffusion pump heater like you told me.
i spend five minutes trying to disconnect the high vacuum pump wire on the back side of MSD but i renounced.Each step is difficult. But i will never give up!:)
I will try better the next week after understanding this particular connection.

Nicolas.

<thank you everyone for all your messages of support!!>