over the weekend I had a vacuum system fail on me.
In a nutshell, from high to low vac:

vac chamber turbo pump electronic safety valve foreline trap
rotary pump oil mist filter exhaust hose


There were no power surges.

It looks to me like the safety valve overheated and failed.
This introduces a small air leak so the system can slowly vent.

The rotary pump spewed out all it's oil through the exhaust. The
filter was full, dripping and there's a puddle on the floor. The RVP
is almost completely empty.
I can't fathom what sort of failure could cause this.

I checked the exhaust filter for little bits of material (to see if
something crumbled inside the pump) but it was clean except for the
oil.

Is there a problem is these pumps are not perfectly level? I can't see
how that would cause this... but that's all I've got right now... it's
not that far off level...

Any ideas? Thanks everybody!

Matthew Karam writes:

over the weekend I had a vacuum system fail on me.
In a nutshell, from high to low vac:

vac chamber turbo pump electronic safety valve foreline trap
rotary pump oil mist filter exhaust hose


There were no power surges.

It looks to me like the safety valve overheated and failed.
This introduces a small air leak so the system can slowly vent.

The rotary pump spewed out all it's oil through the exhaust. The
filter was full, dripping and there's a puddle on the floor. The RVP
is almost completely empty.
I can't fathom what sort of failure could cause this.

I checked the exhaust filter for little bits of material (to see if
something crumbled inside the pump) but it was clean except for the
oil.

Is there a problem is these pumps are not perfectly level? I can't see
how that would cause this... but that's all I've got right now... it's
not that far off level...

Any ideas? Thanks everybody!

The only thought I have is that if the safety valve failed and the rotary
pump was running near 1 atm for many hours, it could have dumped nearly
all its oil out the exhaust. No problem with pump (or at least there
wasn't). Running with low oil probably didn't do it any good.

--
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Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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On Aug 18, 4:35 pm, (Samuel M. Goldwasser) wrote:

The only thought I have is that if the safety valve failed and the rotary
pump was running near 1 atm for many hours, it could have dumped nearly
all its oil out the exhaust. No problem with pump (or at least there
wasn't). Running with low oil probably didn't do it any good.



Hi Sam,

Thanks for the input. For all I know, the valve failed 5-minutes after
I left on Friday. The solenoid overheated and all the DC wires melted.
This opens a slow leak... not sure how long that "slow leak" takes to
reach 1 atm... but then the RVP ran like that for up to two days until
I noticed the puddle today.

Seems strange to me that this leak would take it even close to 1 atm
considering the RVP should take the system to 10^ -1 quickly and
easily.
I'll run it again and hopefully that fixes it.
The RVP wasn't making bad sounds today... so I presume it's ok. It
spit out a lot of oil mist when I first turned it on but that's to be
expected.

Bah, another $500 valve

Thanks,
-Matthew

Matthew Karam wrote:

On Aug 18, 4:35 pm, (Samuel M. Goldwasser) wrote:

The only thought I have is that if the safety valve failed and the rotary
pump was running near 1 atm for many hours, it could have dumped nearly
all its oil out the exhaust. No problem with pump (or at least there
wasn't). Running with low oil probably didn't do it any good.



Hi Sam,

Thanks for the input. For all I know, the valve failed 5-minutes after
I left on Friday. The solenoid overheated and all the DC wires melted.
This opens a slow leak... not sure how long that "slow leak" takes to
reach 1 atm... but then the RVP ran like that for up to two days until
I noticed the puddle today.

Seems strange to me that this leak would take it even close to 1 atm
considering the RVP should take the system to 10^ -1 quickly and
easily.
I'll run it again and hopefully that fixes it.
The RVP wasn't making bad sounds today... so I presume it's ok. It
spit out a lot of oil mist when I first turned it on but that's to be
expected.

Bah, another $500 valve

Thanks,
-Matthew

Ah, I remember spending hours one Monday cleaning vacuum pump oil off of
EVERYTHING (e.g.: dielectric coated laser mirrors). Guano happens.

How about some sort of watchdog against future disaster? Perhaps a vacuum
sensor to initiate a delayed shut down of the rotary pump and some way to
gracefully leak the system up to atmosphere?

On Aug 18, 5:48 pm, Bryce wrote:

Ah, I remember spending hours one Monday cleaning vacuum pump oil off of
EVERYTHING (e.g.: dielectric coated laser mirrors). Guano happens.

How about some sort of watchdog against future disaster? Perhaps a vacuum
sensor to initiate a delayed shut down of the rotary pump and some way to
gracefully leak the system up to atmosphere?


Luckily this was an easy cleanup. A little bit of that kitty-litter
stuff they use on oil spills and it was done.

I'd need a sensor that would signal if the pressure stayed above a
certain level and then power down the rotary pump.

Problem with a sensor like that is I would need to keep the "trigger
pressure" really high otherwise I'd have to clean my foreline trap all
the time.
The system leaks to atmosphere fine... seems like the problem is going
to be powering off the rotary pump if the safety valve fails...


I suppose I just hope my next safety valve doesn't melt on me.

On Mon, 18 Aug 2008 15:25:51 -0700 (PDT) Matthew Karam
wrote:

It looks to me like the safety valve overheated and failed.
This introduces a small air leak so the system can slowly vent.

It wouldn't have to come up to 1 atm; it just has to be enough
liters/sec to get the rotary pump misting.

It's pretty unusual for those relief valves to fail. Who made this
one?

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

Matthew Karam wrote:
over the weekend I had a vacuum system fail on me.
In a nutshell, from high to low vac:

vac chamber turbo pump electronic safety valve foreline trap
rotary pump oil mist filter exhaust hose


There were no power surges.

It looks to me like the safety valve overheated and failed.
This introduces a small air leak so the system can slowly vent.

The rotary pump spewed out all it's oil through the exhaust. The
filter was full, dripping and there's a puddle on the floor. The RVP
is almost completely empty.
I can't fathom what sort of failure could cause this.

I checked the exhaust filter for little bits of material (to see if
something crumbled inside the pump) but it was clean except for the
oil.

Is there a problem is these pumps are not perfectly level? I can't see
how that would cause this... but that's all I've got right now... it's
not that far off level...

Any ideas? Thanks everybody!


I've run Ultra High Vacuum systems for 40 years with no serious problems
!, Electron Microscopes !

My son was supervising the operation of a Mass-Spectrometer with a
Turbo-Molecular pump, RVP system when a Carbon-Fiber Vacuum coupling
failed on the high Vacuum side.
I don't know what it cost the manufacturers for repairs , but I know
the TMV pump tried to go into Full-afterburner mode and filled the
Ultra-high Vacuum system with pulverized metal dust when the TMV-pump
swallowed atmospheric air ! Which is why the inclusion of the
"electronic safety valve" This probably saved your TMVP!

I would suspect the diaphram in the "electronic safety valve" ruptured
on the roughing pump side and protected the TMVP and shut it down safely

It is ironic but a 2 stage rotary vacuum pump is not really designed to
handle large volumes of air. 99% of its operating cycle is pumping at ~
10u pressure. The exhaust port is part of a reed valve set-up sealed by
the flat spring-like reed which is made gas-tight by the oilbath
reservoir. Normal operation has only a trickle of bubbles flowing out
from under the spring, usually from bypass operation to flush moisture
(condense-able vapors ) from the pump. It is only during the initial
roughing cycle that a significant amount of air flows though the pump
and carries a small amount of atomized Vacuum pump oil with it, hence
the oil mist filter. The RVP is designed to pump down a Closed system.
not an open to the atmosphere system, so it is no surprise that it
flushed out its charge of oil when it was opened to the atmosphere.

BTW Philips/Ewards High Vac. now recommend using "AMSOIL" Compressor
oil ISO-46 (PCI) SAE 20 for their Vacuum Pumps. Much better pump life !

Yukio YANO

On Aug 18, 6:49 pm, Jim Adney wrote:
On Mon, 18 Aug 2008 15:25:51 -0700 (PDT) Matthew Karam


It wouldn't have to come up to 1 atm; it just has to be enough
liters/sec to get the rotary pump misting.

It's pretty unusual for those relief valves to fail. Who made this
one?

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

I've discovered why it failed.
This was a valve that I pulled from our "random extra parts" closet
HPS model 145-0040K-24V

I should have pulled the spec sheet on it long ago... it required
24VAC and we were feeding it 24V DC
I'm surprised it worked fine for the first week.....

On Aug 18, 9:56 pm, Yukio YANO wrote:

I've run Ultra High Vacuum systems for 40 years with no serious problems
!, Electron Microscopes !

My son was supervising the operation of a Mass-Spectrometer with a
Turbo-Molecular pump, RVP system when a Carbon-Fiber Vacuum coupling
failed on the high Vacuum side.
I don't know what it cost the manufacturers for repairs , but I know
the TMV pump tried to go into Full-afterburner mode and filled the
Ultra-high Vacuum system with pulverized metal dust when the TMV-pump
swallowed atmospheric air ! Which is why the inclusion of the
"electronic safety valve" This probably saved your TMVP!

I would suspect the diaphram in the "electronic safety valve" ruptured
on the roughing pump side and protected the TMVP and shut it down safely

It is ironic but a 2 stage rotary vacuum pump is not really designed to
handle large volumes of air. 99% of its operating cycle is pumping at ~
10u pressure. The exhaust port is part of a reed valve set-up sealed by
the flat spring-like reed which is made gas-tight by the oilbath
reservoir. Normal operation has only a trickle of bubbles flowing out
from under the spring, usually from bypass operation to flush moisture
(condense-able vapors ) from the pump. It is only during the initial
roughing cycle that a significant amount of air flows though the pump
and carries a small amount of atomized Vacuum pump oil with it, hence
the oil mist filter. The RVP is designed to pump down a Closed system.
not an open to the atmosphere system, so it is no surprise that it
flushed out its charge of oil when it was opened to the atmosphere.

BTW Philips/Ewards High Vac. now recommend using "AMSOIL" Compressor
oil ISO-46 (PCI) SAE 20 for their Vacuum Pumps. Much better pump life !

Yukio YANO



As a matter of fact, most of the UHV parts I used to build this
(including the turbo) were from an electron microscope that we got
donated in surplus.
The diaphragm didn't rupture. The solenoid that opens the valve
melted. And yes, as you pointed out, failures in these valves are
designed to close off the UHV from the roughing side to keep from
destroying our expensive stuff.

Thanks for the info on roughing pumps though. Interesting stuff...

-Matthew

Matthew Karam writes:

On Aug 18, 6:49 pm, Jim Adney wrote:
On Mon, 18 Aug 2008 15:25:51 -0700 (PDT) Matthew Karam


It wouldn't have to come up to 1 atm; it just has to be enough
liters/sec to get the rotary pump misting.

It's pretty unusual for those relief valves to fail. Who made this
one?

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

I've discovered why it failed.
This was a valve that I pulled from our "random extra parts" closet
HPS model 145-0040K-24V

I should have pulled the spec sheet on it long ago... it required
24VAC and we were feeding it 24V DC
I'm surprised it worked fine for the first week.....

Geez, major meltdown. I'm also surprised it didn't smoke in the
first few minutes.

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

On Tue, 19 Aug 2008 10:17:38 -0700 (PDT) Matthew Karam
wrote:

I've discovered why it failed.
This was a valve that I pulled from our "random extra parts" closet
HPS model 145-0040K-24V

I should have pulled the spec sheet on it long ago... it required
24VAC and we were feeding it 24V DC
I'm surprised it worked fine for the first week.....

Well, that certainly explains it.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------