Chromatography Forum

I am using this Edwards pump and it has been fitted with a rebuild kit. Pretty much all consumables are new in it. I used Ultragrade 19 type oil in the pump. It reaches around 230mtorr in operation (the needed spec is around 300). After an hour and a half or so the pressure rises to around 400-450 mtorr. If I let it cool down and re-turn it on it works well again, and then back to the high pressure. I am puzzled. What could be wrong?

thanks in advance

Should be doing better. I use an E2M1.5 and get down to below 70 mtorr withing a minute or two. Check for leaks. Use a rubber stopper to plug the inlet of the pump, let it go for a minute then see if their is any flow out the exhaust. After the initial evacuation of residual air in the inlet there should be none.

After checkign to see if something is leaking - and this can be a foreline connection - either end - if that is not helping you, then:

Was the container of pump oil freshly opened by you? If a pump oil with a higher vapor pressure was mixed into the oil - like put "back" into the wrong container, you can have a problem obtaining the vacuum you need when the pump warms up...

We typically use Inland 45 oil with these types of pumps. Can't speak to their performance with the oil you have in it.

Was there a type of oil specified for your system? Properties of oils do differ note: http://www.inlandvacuum.com/index_files/mechanical.htm and http://www.tedpella.com/vacuum_html/Vac ... erties.htm The vapor pressure at operating temperature is the critical item, by the way - and it would take further digging to come up with the vapor pressure of inland 45 at an elevated temperature.

I agree with MSChemist. You should be seeing WAY better than 230 mTorr with an E2M2 on a GC-MS. If you are using it on an LC-MS then you desperately need to change pumps, as the E2M2 is badly undersized for a LC-MS.

If you are on a GC-MS then you have what amounts to a massive leak somewhere in your vacuum system.

Was there a type of oil specified for your system? Properties of oils do differ note: http://www.inlandvacuum.com/index_files/mechanical.htm and http://www.tedpella.com/vacuum_html/Vac ... erties.htm The vapor pressure at operating temperature is the critical item, by the way - and it would take further digging to come up with the vapor pressure of inland 45 at an elevated temperature.

We always use Inland45, and from that chart the vapor pressure @25c has a difference of 1x10^-5 torr for Inland19 versus 1X10^-7torr for Inland45. I would think his Ultragrade 19 oil would be similar to the Inland19.

Try some Inland45 in the pump and see what happens. I get 70mtorr or less with 1ml/min flow through the MS on my E2M2 once it is warmed up.

I had this problem in 2003.
The shaft seal is probably not properly install......not the shaft seal near motor but the other.