Foreline backing pump & hose

[LALman]

Is it good practice to replace the backing pump hose periodically? My 5972 line has gone for 30 years. Do they get old and accumulate junk that off gases and makes it harder for the backing pump to do its job?

Thinking about the time I had some water vapor get aspirated into my transfer hose along with pump oil vapor...

At the low pressures in foreline pump inlets, the transfer must be molecular so, would it be a useful thing to warm the foreline pump transfer hose?

[James_Ball]

All of ours have the original hoses, many over 20 years old. Not sure if under that much vacuum there would be anything except some high boiling point contamination present since anything more volatile would pump out over time.

On mine I use the moisture traps at the foreline pump like what used to come on all the 5971 and prior models that are filled with molecular sieve. I especially use the traps on the ones running purge and trap volatiles since there is so much water in those, but it also helps catch any pump oil vapor that would backstream from the foreline pump is the valve leaks a little.

[benhutcherson]

If I walk into a lab and see a nice, sparkly clean hose it's almost always because it's a new instrument!

Most everyone I've used is cloudy with the typical opaque brown area near the pump. I still get as good of vacuum as I see on new instruments of similar specs.

BTW, for what really is a gigantic piece of Tygon with a spring in it, those hoses are surprisingly expensive.

[LALman]

Geoff at GVTS suggested my peak intensity variations might be caused by a vacuum problem due to poor backing performance. I ordered a new Edwards RV-3 foreline pump and was casting about for anything else that might affect foreline vacuum. Getting this 5972 system up and running is turning into a marathon.

[benhutcherson]

Well, you're in good hands with Geoff is all I can say.

He was the one who walked me through my 5972 upgrade, including supplying parts and software.

He also was the one who told me that he keeps an RV3 in his truck.

Hopefully Geoff can help you find some "sunshine" on your system(if he didn't use that phrase with you, he will).

[LALman]

Geoff did say it was unlikely that two top boards were misbehaving in identical fashion. So, he suggested getting vacuum right before looking for electronics failures.

[benhutcherson]

The top board I sent you came from him, and even though I didn't test it myself I'd trust his testing to be correct.

Did he give you his source cleaning lecture? Even though I thought I knew how to clean sources, he gave me some insight I'd never considered.

[LALman]

I followed what you related about his methods (especially about the draw out plate edges and the lip the draw out plate sits on) the last few times I've cleaned the source. All this breaking vacuum has gotten it dirty again judging from increased EV. So, its time to clean it yet again.

[benhutcherson]

A few things on vac even though you may well know this:

1. The seal between the top and manifold is a pain, to put it mildly. Make sure it's not nicked or has other issues. Brenda(local FSE) suggested a thin smear of Alpezion L on it. A former colleague said a smear of Santovac 5P is even better and is easier to apply. I've done both and didn't see any difference, although the Santovac is easier to apply.

2. I think I remember you saying you'd serviced your diff pump. If not, it might be good to do it.

3. I'd never thought of this or encountered it, but Geoff mentioned to me a few weeks ago(in a different conversation) that the giant KF flange that seals the diff pump to the manifold can be a pain to get seated absolutely correctly.

[James_Ball]

A few things on vac even though you may well know this:

1. The seal between the top and manifold is a pain, to put it mildly. Make sure it's not nicked or has other issues. Brenda(local FSE) suggested a thin smear of Alpezion L on it. A former colleague said a smear of Santovac 5P is even better and is easier to apply. I've done both and didn't see any difference, although the Santovac is easier to apply.

2. I think I remember you saying you'd serviced your diff pump. If not, it might be good to do it.

3. I'd never thought of this or encountered it, but Geoff mentioned to me a few weeks ago(in a different conversation) that the giant KF flange that seals the diff pump to the manifold can be a pain to get seated absolutely correctly.

I use the Apezion L grease on all of my MS units. I coat my fingers with a little and take the seal and rub the grease on it until it is coated well then wipe off all I can with a Kemwipe. Usually holding it with the Kemwipe in one hand while pulling it through with the other, just sliding the Kemwipe along the surface. It just needs to have enough there to seal any irregularities in the surface of the seal.

I also us it on the KF O-rings on the pump connections and where the pump attaches to the base of the manifold if I ever remove one.

[LALman]

A few things on vac even though you may well know this:

1. The seal between the top and manifold is a pain, to put it mildly. Make sure it's not nicked or has other issues. Brenda(local FSE) suggested a thin smear of Alpezion L on it. A former colleague said a smear of Santovac 5P is even better and is easier to apply. I've done both and didn't see any difference, although the Santovac is easier to apply.

2. I think I remember you saying you'd serviced your diff pump. If not, it might be good to do it.

3. I'd never thought of this or encountered it, but Geoff mentioned to me a few weeks ago(in a different conversation) that the giant KF flange that seals the diff pump to the manifold can be a pain to get seated absolutely correctly.

I use the Apezion L grease on all of my MS units. I coat my fingers with a little and take the seal and rub the grease on it until it is coated well then wipe off all I can with a Kemwipe. Usually holding it with the Kemwipe in one hand while pulling it through with the other, just sliding the Kemwipe along the surface. It just needs to have enough there to seal any irregularities in the surface of the seal.

I also us it on the KF O-rings on the pump connections and where the pump attaches to the base of the manifold if I ever remove one.

James I do this also. Although, I have to be careful not to squeeze with the kimwipe too hard. That tends to stretch the gasket and then its a pain to get it evenly in place without a ripple. I don't put grease on the diff pump KF flange because I fear it would somehow get down in the diff pump. But that flange is usually slippery with diffusion pump oil anyway. Question, maybe its not supposed to be?

[LALman]

You both like Apezion L better than Dow Corning high vacuum grease? I have some Apezion M but not L.

Well, I did some reading up on Apezion's website. No more silicon based greases for my systems.

[benhutcherson]

I started using Alpezion L because that's what the manually for the 5975 specifically says to use on the door O-ring. Of course with any of these, if you can see it, it's too much.

My predecessor had put the standard green tube Dow Corning hi-vac grease(that at U of L we bought 10 tubes at a time) on the door previously, and I managed to get somewhat better vac readings with the silicon stuff cleaned off and the Alpezion applied.

The 5975 manual also says to apply it, again lightly, to the O-ring that seals the vent valve.

I assume(as I'm getting a 5973 up and going) that the same procedure should apply to it as at least the door on the vac manifold isn't appreciably different than the 5975, and even though the vent valve is different I'd think the same general procedure would apply.

There again, with the 71 ring, I'm going based on what Brenda told me. James knows Brenda(probably much better than I do) and would probably agree that you can pretty much take what she says about any of this stuff as gospel.

When I've pulled diff pumps, I've usually wiped up the worst of the oil on seal but didn't worry about getting them spotless, again going back to the fact that Santovac 5P is a good vac "grease" in its own right.

BTW, for application of any of this stuff, I usually put a dab on my gloved fingertip and run it over the seal. I then follow with a dry Kimwipe to spread it out/pick up any globs.

[James_Ball]

The tube of Apezion L I have either came from Brenda or Jim who used to work with her. I have been using it for at least 25 years now. So for such a small tube to last that long, it doesn't take but a very little each time.

[LALman]

I have a 50g tube coming next week. Just in time for getting the RV-3 pump running as foreline backing.