Atlas Copco Dumped Oil

[Amber Gold]

I have a Atlas Copco GVS25 vacuum pump w/ 3-phase motor that's on its 5th season. Oil is changed every year and have had zero issues with it until now. Below is everything that happened, in the hopes that someone knows what happened, so I can keep it from happening again and/or help someone else out. Thanks in advance for any help.

Tuesday, watching my security camera, I notice vac levels drop over the course of the day, but then no vac. Pump shut off. I'm thinking there's leaks and the moisture trap filled up, shutting the pump off...no big deal. Nope, vac. pump off and moisture trap empty. Look around some more and find all the vac. pump oil on the pump shed floor. Check the pump site gage no oil...not good. My guess is the pump lost all oil, pump siezed, overloaded the motor, VFD shut things down to protect the motor. Take the pump home, check it over, and can't find anything wrong with it. No cracks in the pump casing, no oil on the motor (like if the mechanical seal blew), nothing. Refill with oil, turn it over a bunch by hand (seems OK??), and bring it back to the woods. Hook it back up, start it up, and after a rough start, clears up and runs. However, every once in a while, you can hear the motor load up, pump stops turning, motor tries harder, and pump starts spinning again. It'll do this 3-4 times then run fine again for a while, and then repeat. Vac levels are 29"+ with the woods valves closed, 28" ish with the woods open (things are froze), so it appears the pump can still make good vac. At this point, not sure if I can trust it all night, so I shut it off to revisit in the morning.

Wednesday morning, start the pump up again and same thing: runs fine for a while, motor goes under heavier load, pump stops, motor overcomes it, starts spinning again, repeats 3-4 times, and then runs fine for a while. I babysit it for a couple hours, and then for that last hour, the pump doesn't bind up at all...just runs smooth, so I leave it running. I go back that night, and still running, it pulled 25" ish vac all day, and oil level is still good. I leave it running.

Today, I bring a multimeter and test it. 121V each leg going into the VFD with motor leg readings of 131V, 133V and 138V. I have no baseline to know if the motor voltages are good or bad. Do those numbers mean anything to anyone?

So, my questions:

How/why did the pump dump all the oil out? The exhaust vents outside, so it didn't come from there.
Not sure if there's damage to the pump head, but it seems to pull the same vac levels as it did before...29"+ on just the releaser. Although, I'm not sure if the pump's CFM capacity has been reduced.
My guess for the reason why the pump was binding up has something to do with it siezing, but I'm guessing what happened internally has resolved itself from it being continuously operated.
Anything I should do differently? Additional maintenance?

[BAP]

Did you buy it from MES? If so Clayton is really good helping with vacuum pump problems. Give him a call.

[eagle lake sugar]

Do you have a check valve between the pump and releaser? It's possible that the pump shut off for overload, etc. and the vacuum remaining in the releaser sucked the oil out of the pump if there's no check valve.

[red maples]

I just picked up a check valve to install on mine because I got a little back flow the other day when I shut it down.

But that is weird. did the oil valve vibrate open? even just cracked warm oil will come out. and the valve seems a little cheap to me for what the pump costs. I was thinking about another valve in addition to the one thats there.

what temp is the pump when you start it up? I find that load happens when the pump is colder and the lines are frozen and the vac pressure comes up quick the motor will load up like that so I keep the pump shed about 60* so when I turn it on it closer to room temp. and the motor doesn't load. I also have valves built in so I can open them when it starts and let it run free for a minute or 2 to warm things up a bit then then shut them.

[Shaun]

Just out of curiosity how often are you changing the exhaust cartridge?

[Amber Gold]

Thanks for the replies

There's no external check valve. I understand there's an internal check valve in the pump itself, so I didn't install one. It may be something I add as a backup measure.

In shutting down the pump personally, I have not noticed the pump spinning backwards. I thought of that too.

I checked the exhaust filter and it looks clean. Still nice and white. It has not been changed before.

I talked to MES when it happened, and the exhaust filter was one idea, pulling high CFM and no vac, and clogged vac port.

[Amber Gold]

The pump is checked daily when I collect sap and has been running fine since the first episode; however, on Monday, the pump dumped the oil out again. Fortunately, I caught it while it still had oil in it and refilled.

Something I noticed yesterday, and Red Maples got me thinking about it, is the pump is filling up with sap. My guess is as it's running, it's collecting moisture inside the pump. The reservoir fills up, oil gets dumped (somehow), water evaporates off, and pump runs dry. Interestingly, when it dumps the oil, it happens over the course of a single day. Yesterday, I noticed the pump was overfull and the oil was cloudy, so I drained and refilled. If this keeps up, I'm going to need to do an oil change every few days.

For 3-4 seasons, I've had this pump and the setup is unchanged, and this is the first season I've had this problem. It's an electric vertical releaser, into MES's moisture trap (a bit higher than the releaser if it matters), and down into the vac. pump. There's maybe 4' of piping in total. I'm not getting any moisture in the moisture trap. Any ideas on what's going on or that I need to change? I tried uploading a pic of the setup, but it repeatedly failed.

[Shaun]

A quick look at the manual says to change the exhaust filter every 500 hours under severe use. I would consider use for maple as severe times 10 if any leaks are present for a long duration. I'm no expert but these types of pumps are designed to typically run at high vacuum as roughing pumps for turbo pumps and such. If they do evacuate chambers and what not CFM level is probably only high for a very short period of time. This is at least what I have seen in industrial applications.

I have a similar pump and there is a warning label on the oil reservoir to avoid pressure. This pump also has a pressure gauge built into the oil fill cap that helps monitor pressure. I change my exhaust cartridge once a year and if my vac falls below 27" I'm in the woods right away.

That said I have a hard time changing the filter because it doesn't "look" dirty and have saved every filter I have taken out for 6 seasons. It may be worth starting with that and at least rule out one thing at a time?

Good luck, I know how important our vac pumps are especially on a year like this.

[corrowbasin]

Did you ever figure out the root cause? Sounds to me the internal gas ballast valve or internal bypass valve. During running, the vapour will condense and if the internal gas ballast valve isn't opening could be condensing. Is your oil cloudy?

[Amber Gold]

I thought about the exhaust filter, but there's still mist coming out of the exhaust pipe, so I figured it was OK?? It couldn't hurt to replace it. Where do you get your filters? I didn't have much luck finding them online. I too agree this is extreme use to be conservative. I run the woods at 27"+.

I have not figured out the root cause. What is the gas ballast valve? I can't find any info on it. From what I can tell, it's this rubber ring that spins around the nipple that sticks up...it doesn't seem to be attached to anything. Should it be doing more than that?Should it be open or closed? I have it closed.

The oil is milky white. I gave it another oil change yesterday.

Thanks for the help with this issue. Frustrating to say the least.

[Shaun]

I am not familiar with that pump exactly. Some pumps have a gas ballast and some do not. The gas ballast valve is used to rid oil of contaminants, (water for us). A google search can probably describe it a lot better than I can. I run the pump with the gas ballast open all the time. I'm not sure if this is correct but the oil remains looking good for an entire season, this will reduce ultimate vacuum pressure but not by much. My gas ballast valve is just a slotted screw you open and close a quarter turn with a screw driver.

[Amber Gold]

Shaun, that makes sense, and I'll move it to open and see what happens. Before, I searched online to find out what it does, and what position to have it in, and the Atlas Copco literature just says it has gas ballast, but that's it.

This is the first year that I've had this issue, but I don't remember what position I had the gas ballast in before. Maybe by chance I had it open and didn't realize it.

[1arch]

Interesting thread. Although my equipment is from a different manufacturer I experienced a similar scenario this year. What I found was my releaser was momentarily wo hanging up and the vacuum pump would take in a large gulp of sap before the moisture trap would react. Oil every where and sap in the oil tank.