Air bubbles in the oil........

Discussion in 'Compressors, Boosters and Blending Systems' started by widget, Oct 6, 2008.

  1. widget

    widget Manta Ray

    # of Dives:
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    ............One of our Bauer compressors (K14) has started showing air bubbles in the oil sight glass, above the oil pressure regulator adjuster.

    I am assuming this is an indication that the final stage suction valve is finished, but before I go take it off line for repair, could there be any other fault (reason for this) I could check first?

    Oil pressure is still fine, but I have noticed a slight increase in oil usage, which leads me to think the floating piston and sleeve may need replacement as well.

    The unit has done roughly 900 hours since its last valve change, so its not bad going, but I was hoping for a bit more hours, Bauer recons a 1000 hours is usual for the final stage valves and I got a bit more on the previous set, maybe 1300 hours before it started popping the 3rd stage safety valve.

    We use the unit constantly, so I would rather make sure before I have to schlep it off for repairs, any ideas would be welcome.
     
  2. pescador775

    pescador775 Loggerhead Turtle

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    What type of oil and when was it changed? Sometimes, the Bauer oil pump needs to be deaireated after an oil change.
     
  3. widget

    widget Manta Ray

    # of Dives:
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    Locally we use the SHELL CORENA P 150 oil which is approved by Bauer for use in their machines - it may have another trade name elsewhere, but unfortunately I am not aware of it.

    Pescador, the oil was changed about 200 hours back, I cant think the technician did any kind of deairation of the oil pump at the time, basically just changed the oil and reset the pressure into spec. I didnt see any bubbles before Saturday (three days ago) when I checked the unit, - there may have been, I just didnt see them, - but now its very obvious, and the oil looks slightly "frothy" in the sight glass after a few hours from start up.
     
  4. pescador775

    pescador775 Loggerhead Turtle

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    Check a small sample and observe whether the oil is milky. If blowby is aerating the oil then maybe water in present also. Has the output (cfm) and final psi been measured? That, along with blowby would be the definitive tests. Blowby should be about 8%-12% of output @ 3000 psi but I don't have the factory spec for your machine.

    Corena is a good oil.
     
  5. captain

    captain Orca

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    Is it possible it was overfilled and the oil is being aerated by being churned up by the crankshaft.
     
  6. CraigAClark

    CraigAClark Scuba Instructor

    # of Dives: I'm a Fish!
    Location: Pembroke Pines, FL
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    I assume you are talking about during operation. Does the sight glass empty after shut down? What is the final shut off pressure and the oil pressure? Does the oil pressure fluctuate when running?

    There are several reasons why "blow-back" in the sight glass happens. Sometimes the final discharge valve is bad, or the oil pressure is too low for the final pressure. These are the simplest causes. The oil regulator could have a bad seat, the oil pump may be bad or the final piston and sleeve could be worn out. Indications from the oil pressure gauge and sight glass can direct you to the problem.

    I have seen this problem several times and it has turned out to be one or a combination of the above.

    Craig
     
  7. widget

    widget Manta Ray

    # of Dives:
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    Thanks Craig, I will try and answer as best I can, maybe it will assist you to get a clearer picture.

    All the affirmatives first..........:D

    Yes, sure I was referring to "during operation" and on the sight glass issue, I have noticed it is emptying out on shut down quite quickly (which I thought a bit odd)............... and then, "Yup" there is a bit of fluctuation in oil pressure during operation which is also new, before, it was rock steady.

    Craig I am not quite sure what you mean by "final shut down pressure" could you maybe just help me out a bit there.?

    As I said, I am also experiencing a bit of extra oil usage, which lead me to think the floating piston and sleeve was "kaput"??

    How would I check on the oil pump seat Craig? Thats something I was not aware of before?

    The oil gets quite frothy in the sight glass whilst running, but I checked the oil in the sump and it dosnt appear to have moisture in it, at least I cant see any signs of it.

    Pescador...... Is there any way of checking "blow by" without that little gauge - (short of removing the head and sucking on the valve to see if it allows air through :D) ...........a kind of quick test??

    I really do appreciate all the assistance guys, I hope between us we can sort of nail it down to one or two causes I can tackle with the shortest downtime, besides, not only am I learning a bit more, but I find it very comforting to know there is a wealth of information willing to be shared amongst the members here.
     
  8. pescador775

    pescador775 Loggerhead Turtle

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    Final pressure refers to the set pressure for shut down. What pressure is it topping out, specifically, and moreover, what is the oil pressure doing at that point. Craig is possibly concerned about back flow of air from the fourth stage into the oil. The regulator is pretty simple. One should be able to unscrew the cap and inspect the innards. Mind the spring. You did say "fluctuation". Not much to go on but is a clue. He'll have to take it from here but the regulator could be at fault.
     
    Last edited: Oct 7, 2008
  9. CraigAClark

    CraigAClark Scuba Instructor

    # of Dives: I'm a Fish!
    Location: Pembroke Pines, FL
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    Hey Widget,

    The fact that you are seeing the sight glass empty after shut-down is indicating to me that air is being "forced back" from the 4th stage. You say there is fluctuation in the oil pressure while running. Is it several hundred PSI or just a little?

    If your final pressure (shut-down) is 3500 psi, you can usually get away with 750 psi oil pressure. If your final is at 4500 psi you should set the oil pressure around 850-900 psi.

    Pesky will probably correct me on this as I don't know the specific terminology, but with the final piston and sleeve not having rings, the oil pressure acts as a seal, during compression, that prevents the air from "blowing Back". Normally, if the oil pressure is too low, the bubbles will not appear until your final pressure is in the range(s) I mentioned above.

    Now if the oil pressure fluctuation is several hundred PSI, then it is pretty certain that the oil pressure regulator is not holding adjustment. The oil pump is basically a diesel injector that only knows how to pump oil. The regulator is what controls the oil pressure. In my experience, I have never seen an oil pump fail, including machines that have been rebuilt after 5000 hours and are well into their second 5000 hours.

    Pesky, you mentioned about the oil pump needing to have the air relieved. The only time I have ever needed to do this is when the pressure doesn't come up immediately. The pump (injector) has basically lost prime. Most often this step, priming the injector, isn't necessary.

    Craig
     
  10. widget

    widget Manta Ray

    # of Dives:
    Location: South Africa
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    Okay, please correct me here if I am wrong, but if the air is been forced back from the 4th stage (as it appears because the sight glass definately empties) then its pretty sure the suction valve has gone?

    Our final pressure is at 4500 but I saw our oil pressure is a little less than 800psi - I will up it tomorrow and see if it helps.

    Oil pressure isnt fluctuating by that much Craig, maybe 50 Psi?? at the most, but before it was rock steady, no fluctuation at all.

    I agree on the final piston though Craig, and your comment makes sense because bubbles only appear at pressure, so its likely the sleeve is worn and allowing air back - its done roughly 1900 hours I saw on the log, so I think its pretty much at its limit anyway, dont you think?.

    I think your pointers are confirming my initial suspicion that the valves and floating piston are at their limit, and one if not both are failing, I am going to raise the oil presure tomorrow to 900 psi and see what happens.

    Just a last question, do you guys think its okay to run the unit like this? It runs on average, roughly 5-6 hours a day or more in tandem with another K14 as we are heavy users of air, I could shut it down if it will do damage, but then I fear the other one will have to run 10 -12 hours to keep up, which is also not that great I guess - my aim was to keep it running until Friday, when I can have it repaired over the weekend, but if you think it will just cause extra issues, I will just have to stop it.

    Thanks again for the help.
     
  11. pescador775

    pescador775 Loggerhead Turtle

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    Check the dip stick to see if the oil is frothy. If not, and oil press is above 50 bar, my feeling is that is OK to run it for a few days. I don't see how the 4th stg could be failing without anyone noticing decline in output, excess blowby or decrease in output press. A bad intake or discharge valve should be causing an OPV to blow or at least cause clicking sounds or similar. However, the increase in oil consumption could cast suspicion on the fourth stage piston regardless.
     
  12. CraigAClark

    CraigAClark Scuba Instructor

    # of Dives: I'm a Fish!
    Location: Pembroke Pines, FL
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    If you increase the oil pressure and notice the fluctuation changes, becomes radical, then I would suspect the piston and sleeve. I'm assuming you know how to adjust the oil pressure.

    Has the machine always run at the 4500 PSI shut-off pressure?

    The oil pressure regulator has a "seat" which is a ball-bearing captured in a housing. Similar to a bullet crimped into a casing, but with the ability to rotate in the housing. Wear grooves can form on the bearing, which when contacting the sealing surface of the orifice, can actually leak by. This causes a fluctuation in the oil pressure if the "worn" grooves over-lap. Usually shows up as a 200-300 PSI pressure fluctuation.

    I'm leaning to the final piston and sleeve as the culprit. Remove the final stage head and use a magnet to pull the piston from the sleeve. If you notice "scortch marks on the piston or it is not concentric and shiney, I would replace it. You will have to remove the upper cylinder to do a "drop" test, but if you see vertical wear (scortch) marks on the piston, you can pretty much consider it bad. If you do remove the upper cylinder, check the guide piston for fractures.

    Craig
     
  13. widget

    widget Manta Ray

    # of Dives:
    Location: South Africa
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    Craig, Pescador - you had it right, increasing oil pressure causes a bigger increase in the oil pressure fluctuation, over 200 PSI movement!!

    Gotta be the piston and sleeve.

    Took a "stiff whiskey on the rocks" :D in anticipation of the price shock before calling Bauer to order the parts, - $638.00 (Equivalent in our currancy) for the piston and sleeve,- so I took a few more deep breaths, and thought, while the head is off I will just as well change the final stage valves, another $160.00 - they will deliver friday.!!

    They told me for an extra $390.00 (so $390 + $160.00 = $550.00 odd) I can have a complete overhaul kit, (ie) valves for all the cylinders and a few other odds I cant remember - must have been caused by shock.!

    Is it worth doing all the cylinders guys, or should I just repair as it fails - of course Bauer claims if one part gos the rest wont be far behind, but they have a vested interest in getting my money.:D

    We have only ever done the final stage valve overhaul, I cant see the piston change been difficult, but is there anything I should look out for, if we go the whole overhaul, is it possible to do ourselves effeciently?

    Bauer here dos NO maintainance, they just authorise private workshops in the main cities and as we are very remote, the closest one is about 500 kilometers (300 miles) from us - there is no question I am going to lug the unit there, so its a "do it yourself business" here.

    We have the Bauer workshop manuals etc.
     
  14. pescador775

    pescador775 Loggerhead Turtle

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    Some folks say, "if it ain't broke don't fix it". However, doing replacement engineering at this time makes sense. If it were me I would undertake the work during a slow period if possible. Get the kit with the "few other odds". Otherwise, in a year or two we'll be going through the diagnostic cycle again.

    We are lucky to have Craig, an experienced technician, to provide some insights and neither of us are getting any younger. If you prefer someone to "sit in" or audit (from 10,000 miles away) the top cylinder overhaul, sooner, rather than later, would be a good time.
     
  15. CraigAClark

    CraigAClark Scuba Instructor

    # of Dives: I'm a Fish!
    Location: Pembroke Pines, FL
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    Widget, did you actually look at the piston and sleeve? Remember what I said about the oil pressure regulator. Before I would have ordered the parts, I would have looked at the piston and sleeve as well as doing a "drop test" on it. I would hate for you to replace it and find out it is the oil pressure regulator that is the problem. The fact that when you adjusted the oil pressure the fluctuation became that significant, is telling me further investigation (requiring some disassembly) is needed.

    Craig
     
  16. pescador775

    pescador775 Loggerhead Turtle

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    Words to the wise from Craig. Come to think of it, I'm still not hearing confirmation of a fourth stage problem based on performance of the machine, just bubbles and fluctuation. I would get the kit and tuck it away but that's just me. LOL, I tend to squirrel parts and stuff away like with my MIL surplus compressors. In anticipation of the day when NO parts or spares would be available I stocked up on enough of everything to last 50 years. My kids will auction a lot of stuff on EBay someday. No need to go that route with Bauer but stuff will never be cheaper. On the other hand, it requires a long term commitment to a particular brand and model.

    Where are you, Namibia? Wait, that can't be right-- strong current and no divers. Are you in or near Mozambique?
     
  17. widget

    widget Manta Ray

    # of Dives:
    Location: South Africa
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    Yeah, spot on, about 200 kms up the coast at a small place called XAI-XAI (Pronounced Shai - Shai) we are laying a pipe line and telecommunication cables, about 9 months into a 2 year contract.

    I actually live in Johannesburg South Africa, but work two weeks here and two weeks back at the company in Johannesburg, so Yup, no chance in heck of getting the unit to a workshop.
    The guys here subscribe to the idea that if it cant be fixed with some barbed wire, spit and a lot of hope - we dont want it.:D - just kidding, but it has its challenges out here for sure.

    Well, the parts are a-coming :D - soooo, ............!!.

    Craig, good point, I am stopping the unit and I will check the piston tomorrow, I think output is down though (although its difficult to judge as the two units work in tandem) and there appears to be excessive oil in the discharge.

    Will heat have a lot to do with it ?, its around 40 degrees centigrade out here with no breeze, the compressor room has exhaust fans but inside it gets super hot.

    I would really be most appreciative of assistance from 10,000 miles away Pescador and Craig, I dont profess to be anywhere near as knowledgeable on compressors as you guys, and here its a case of sort it out yourself.
     
  18. pescador775

    pescador775 Loggerhead Turtle

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    At that temp, it is a good thing that the compressors are four stage. Heated cylinders and oil can affect air purity. Just maintain them regularly and so long as there is air flow throught the fan things should be OK. With the DIY filter I assume that hopcalite is not being used. That is a catalyst for carbon monoxide which is normally included in a triplex cartridge. The Corena 150, a 40 weight synthetic oil, is the right juice for the machines. It has been shown that under certain conditions, break down of oil can produce toxic gas which is adsorbed by the charcoal. If the charcoal breaks down the bad stuff can be tasted by the diver. However, rarely, without catalyst, the CO can be "cleaned" but not detoxified by the filter and could present a silent threat. There have been documented cases, the most recent in the Maldives, or one of those other Indian Ocean Islands. Also, believe it or not, there was a case in Canada (fire dept) and in Georgia, USA.
     
  19. widget

    widget Manta Ray

    # of Dives:
    Location: South Africa
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    Yes, I have dived recreationally on some of those Indian Ocean Islands,- atrocious maintainance of everything is the norm.!!

    I am not even sure its due to lack of cash, as these little islands bustle with tourists from Europe, I think its a lot to do with lack of experienced and capable people, not to mention its just such a logistical, expensive and buerocratical nightmare to get anything into and out of the Island.

    ........but yes, I read about the Maldives issue, - but I have to say it sounded like a severe lack of maintainance there - theres no excuse for that.

    ..............anyway, off to go start stripping the machine - already 35 degrees and its only 7.30 am.!!

    Let you know later.
     
  20. windyairman

    windyairman Nassau Grouper

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    a quick easy way to check your final piston is
    Remove final cylinder head
    clean top of piston with a rag.
    then run compressor with head removed.
    if you can see oil leaking past the piston / liner
    then its worn out.
    other posts on this forum,oil reg valve/ suction&delivery valves etc are also correct.
    its a quick easy field test that can be done to save strip down time & a lot of -about
     

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