A Bunch of Failures

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Bruce Meagher
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Re: A Bunch of Failures

Post by Bruce Meagher » Sat Jan 13, 2018 9:33 pm

When you ballast the pump you only crack open the cap a turn or so. You don’t actually physically remove the cap. You appear the have 7 connections between the pump and your gauge that are possible leak sources. Is the male 1/4” NTP just above your KF-25 adapter wrapped with teflon tape (it doesn’t look it from the pic)?

To blank off the pump remove your gauge and put a KF-25 blank on your KF-25 fitting. Then there is only 3 possible leak sources. The pump should be relatively quiet when the ballast is closed and the inlet is blanked off. Does it sound different when blanked off? If so, that's a sure sign of a leak above. Post a short video with the ballast open and closed and what you think is a weird noise.

Also, it's not great to have the gauge directly line of sight to the inlet port. You should at least have a 90 degree elbow.

Tom McCarthy
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Re: A Bunch of Failures

Post by Tom McCarthy » Sat Jan 13, 2018 9:39 pm

Keep it running for an hour or so, should be hot to the touch, not just warm.

My pump kept improving noticeably after each such run for the first 3 I remember, note that I was starting off at about 40 microns and got to 10, somewhat different to your situation.

Jackson Oswalt
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Re: A Bunch of Failures

Post by Jackson Oswalt » Sat Jan 13, 2018 10:01 pm

All npt threads have Teflon tape on them. Also, I ballasted my pump with the cap completely off for 15 minutes. I then ran it for an hour and was borderline painful to touch. I have an extra 90" elbow that I plan to use, but I fear that will increase the volume of air that heads to be pumped out by quite a bit. When the ballast is closed, the pump is quite as can be. Just a light humming noise. With the ballast completely open it makes a loud gurgling noise as described by John. Currently I'm letting the pump cool off before I run it for an hour with the ballast closed. I will do this with a 90 degree elbow. Thanks for all the help so far!

Jackson Oswalt
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Re: A Bunch of Failures

Post by Jackson Oswalt » Sat Jan 13, 2018 11:41 pm

I tested it once again and only got to 430 microns with the added volume of the elbow.

Bruce Meagher
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Re: A Bunch of Failures

Post by Bruce Meagher » Sun Jan 14, 2018 7:32 pm

The small added volume doesn’t matter. In fact, an excellent exercise is to calculate approximately how long it should take to pump down to 100 mtorr (assuming no leaks and no outgassing). (hint: for your test system with the E2M5 the number should be less than 15 second).

You’re not reaching this level of vacuum, and you've run the pump for an extended period of time with the ballast open and closed. Therefore, imo, the most probable causes are (in what I think is the most probable order):

1) a leak.
2) contaminated vacuum gauge (e.g. oil inside)
3) contamination in the parts you installed from the inlet to the gauge
4) broken or uncalibrated gauge
5) contamination in the pump
6) pump needs rebuilding

Assuming you cleaned the parts before you assembled everything here’s a quick test to run.

Fully close the ballast port. Start the pump and record how long it takes to reach 500 mtorr. Then turn off the pump and record the pressure every 20 seconds for 10 minutes. Plot the results and report your findings.

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Dennis P Brown
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Re: A Bunch of Failures

Post by Dennis P Brown » Tue Jan 16, 2018 1:51 pm

In a previous post you said:
Note: I had filled the pump up to the max marking. I lost this much oil after 1hr 10mins of combined run time (two 20 minute runs and one 30 minute run). Is this normal?
No, that is not normal! No way that much oil should be lost even if the ballast is open. I have used my pumps over five years and the oil level is about the same as when I started five years ago - also, I have purged via the ballast twice in the period. Again, no significant oil lost. Unless a seal is leaking (and oil is on the table) the only other method to lose oil is via vapor out the exhaust port or minor inflow into your vacuum system. If this was a one time only, maybe a mistake. If it has continued, that issue will cause major problems and indicate something is very, very wrong.

I am suspicious of the connection you are using for the vacuum gauge detector. Those are really for refrigerator service and may or may not be useful for low micron range. Also, you have a lot of couplings any/all could have leaks.

A major air leak will cause large oil loss from the pump out the exhaust port via a oil mist - is that occurring out your exhaust port when the pump is running?

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Richard Hull
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Re: A Bunch of Failures

Post by Richard Hull » Tue Jan 16, 2018 4:58 pm

I feel that a general comment is due here. You have had more problems than one might imagine related to just arriving at even a very crude and worthless vacuum level. This is virtually unheard of in these forums. Can you trust your gauge? We do not know. Do you have a good pump, at last? We do not know. If you have a leak, it is one of the most gross one might imagine in the world of vacuum. This, we also do not know.

Do you have a friend, a teacher, a professor or anyone with a vacuum system in your area that might be able to determine what component you have that is either working or defective? If you can't think of any, search them out.

This thread is one of the best and most completely documented abject failures to obtain even a gross technical vacuum level via repeated failures of gear or technique. I commend the effort by yourself to obtain good gear in good faith and all here who have assisted you in your effort.

It is time to take the bull by the horns and either get someone on site with you or have you take your gauge and pump to someone competent and capable of testing your pump and your gauge, separately. Treat each item as a separate entity. A good , helpful refrigeration shop might be an option. Yes, their stuff is crap by our standards, but is far better at hitting a known vacuum level than you seem to be able to achieve. If they find your pump is terrible, make sure to get them to test you gauge on their gear. No one will ever get anything done in vacuum technology without a reliable and accurate gauge.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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