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    SES/howden WRV163 oil temp/pressure voes



    So...

    We have an installation with 3 identical compressor units with howden WRV163 compressors on them, watercooled oil coolers and a 3 way mixing valve, NH3.

    they were commissioned a year and a half ago and worked like a charm up until 3 months ago.

    The customer started getting problems, loosing the oil pressure or shut down on high oil temperature.

    I've been on site three times, first time to fix it, second time to find out what was happening and third time trying to find out just what in the H was going on.

    First visit, I changed the oil filters and the 3-way thermostat on 2 of the units, serviced the oil pump on 1 unit that was the problem child, that didn't work, so I switched the oil pump between two units and still one unit remained the problem child.
    Did some adjustments on the oil injection valve (from the oil manifold and into the screws to help cool the discharge), noticed that looking sternly at the valve was the difference between maintaining oil pressure or cutting out on high discharge temp. but managed to get it running at 100% with an oil pressure of 3.2 bar and a discharge temp of 82C (cut out is 2.4 bar and 85C).
    moving the spindle on the oil injection valve about 2mm could take the oil pressure from 3 bar to 6 bar!

    Second visit, I had to adjust the oil injection valve on all three compressors to try and stabilize them, and again managed to keep them running.

    Third visit, at my whits end, noticed that if I opened consumers (platefreezers) to fast (was trying to work like a fisherman operating the plant), the discharge pressure rose so quick that it caught up with the oil pressure from the pump and thereby lost the oil pressure difference. the condenser pump is variable speed, so I made the regulator faster so that the condenser pump could keep up with the "abuse"

    Now I am left with the problem of high discharge temperature. Also the nagging feeling of something not being right with the oil injection valve since looking at it the wrong way makes the difference between low oil pressure or high discharge temp is grinding at the back of my mind.

    Usually, when commissioning a unit like this, you start with the oil injection valve barely open, then you use the bypassvalve on the oil pump to adjust the lubricating pressure, and as you adjust the oil injection valve to add more oil to keep the discharge temp down you follow with the bypassvalve to maintain the oil pressure.

    On these units I had the bypass line closed and I still couldn't maintain oil pressure.

    After much ado, I had three guys from the office on the line while I was running back and forth making adjustments and reading them the values.
    One of them (former service technician and my mentor), kept asking about the suction strainer before the oil pump, It's clean I said, it's clean, I've had it out 2 times already.
    Then he said "unless anyone has any objections, I want you to remove the strainer from one unit and run without it"

    No objections, I sighed and removed the strainer...

    This time, as opposed to the other two-three times I had inspected the strainer and changed the oil filter I noticed that the oil was very dirty, it looked like brown muddy water.

    I didn't really get my hopes up that this would work, but after I started the system without the strainer in the oil pump suction, I could again adjust the oil injection valve 1/2 turn and the change in oil pressure would only change 0.2-0.3 bar and I could again use it to regulate the discharge temp.

    Obviously something has happened to the oil, as far as I know they haven't had an oil change since the system was commissioned a year and a half ago, in my mind, nor should they have had to... Normally on systems like this, they just add some oil every 2-3 months to replenish whatever has been carried over, and they send in oil samples to be analyzed once every 2 months.

    in the end, all I am left with is that the oil has degraded so much that they get cavitation in the oil pump suction when the strainer is in... anyone else seen something similar?


    -Cheers-

    Tycho

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    Re: SES/howden WRV163 oil temp/pressure voes

    Tyco,
    Not sure how fine your strainer is, but if using fine oil pump strainer have found they can look clean but have to be washed & blown out with compressed air, to get rid of the fine stuff.
    If they worked before you should clean & check again.
    Last edited by RANGER1; 16-09-2014 at 08:58 PM.

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    Re: SES/howden WRV163 oil temp/pressure voes

    So the whole oil charge is brown like muddy water?
    So there is a water cooled oil cooler on each compressor, might leak in when servicing compressor,
    or if water pressure higher than package pressure.
    Last edited by RANGER1; 16-09-2014 at 09:03 PM.

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    Re: SES/howden WRV163 oil temp/pressure voes

    Hi Tycho
    Probably a silly question but have you had the oil tested, dirty brown oil doesn't sound too good? Could there be a water leak in the oil cooler?
    What type of oil is it, mineral / synthetic?
    What type of oil pump is used?
    Regards
    Paul
    Born to fish, forced to work

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    Re: SES/howden WRV163 oil temp/pressure voes

    Quote Originally Posted by RANGER1 View Post
    Tyco,
    Not sure how fine your strainer is, but if using fine oil pump strainer have found they can look clean but have to be washed & blown out with compressed air, to get rid of the fine stuff.
    If they worked before you should clean & check again.
    The filter is 250my, it was clean as the day it left the factory however I cleaned it with brake cleaner and compressed air and it didn't change anything.
    -Cheers-

    Tycho

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    Re: SES/howden WRV163 oil temp/pressure voes

    Quote Originally Posted by RANGER1 View Post
    So the whole oil charge is brown like muddy water?
    So there is a water cooled oil cooler on each compressor, might leak in when servicing compressor,
    or if water pressure higher than package pressure.
    The system is around a year old and has not been "opened" in that time.
    water pressure on the oil coolers is 1 bar.

    on our control system we log all pressures and temperatures 6 months, and according to the log the pressure on the discharge, oil separator and oil filter has never been below 4-5 bar.
    -Cheers-

    Tycho

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    Re: SES/howden WRV163 oil temp/pressure voes

    Quote Originally Posted by PaulZ View Post
    Hi Tycho
    Probably a silly question but have you had the oil tested, dirty brown oil doesn't sound too good? Could there be a water leak in the oil cooler?
    What type of oil is it, mineral / synthetic?
    What type of oil pump is used?
    Regards
    Paul
    Not a silly question at all

    the on board engineers are supposed to take oil samples every six months, but for some reason (on all ships), they never take oil samples from the refrigeration compressors.
    Last time I was on board and noticed the dirty oil and managed to get it to run without the suction strainer I told them that they need an oil change and that i had had to remove the filters to make it run.
    I also asked them if they had added any oil and they had added about 20-40 liters on each compressor (they are supposed to enter it in the engine room log when they add oil to the freezing system, but they never do, yay for that).
    The captain was straining on the moorings to get back out fishing while I was there so I didn't get to take a "clean" oil sample for myself, but I'm going to take one next time, before we change the oil so we can find out what has happened.
    I did take a sample of ammonia to check if there was any moisture, and there was nothing.

    The oil is Mineral I believe, Mobil Gargoyle Arctic 300.

    The oil pump is a Maag NP 70/70 pump.

    When this first started going downhill I thought it might be the oil pumps or the internal bypass valve in the pumps or the labyrinth seals in the compressor (Howden WRV compressor breaking down after a year, if I live to see the day), but after seeing the oil and how it works after removing the filter (and that we haven't heard from the ship in 3 weeks (means it works ), I have concluded that "something" has happened to the oil that has deteriorated it to a point where the small pressure drop in the suction filter of the oil pump causes the oil to foam and cause cavitation in the pump suction.


    on a side note, the ship had a R-22 system before and for a while (3-4 months) they still had the oil cans for the R-22 on board. After I saw the dirty oil I checked and saw that the cans were gone, and I asked them if they might have used the old oil by accident.
    The answer was no of course, but when I asked where and when they had moved them off the ship the answer was a bit elusive



    I'm hoping the solution will be a simple oil and filter change (the filter difference has been ok, but we changed them 2 months ago just to be sure).

    posted here to see if anyone might see a mechanical failure somewhere that I had missed

    But it seems we are on the same page
    -Cheers-

    Tycho

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    Re: SES/howden WRV163 oil temp/pressure voes

    Test reopen
    Brian - Newton Abbot, Devon, UK
    Retired March 2015

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    Re: SES/howden WRV163 oil temp/pressure voes

    So, old thread, but I bet Ranger1 would like to know what happened.

    I had stared myself blind and determined there was an issue with the oil pump, or with the design of the pipes on the outlet of oil pump.

    all it took to solve it really was a fresh pair of eyes.

    The oil outlet connection on the oil separator was DN125, it was reduced directly to DN50, and then down to DN40.

    I had mentioned it to our office that the suction line seemed kinda on the narrow side and I were told "nah nah, it's been calculated by the compressor package manufacturer", so I also dismissed it.

    Fast forward 2 years, I had left the company to work for a competitor.

    A service engineer, much younger than me, again pointed out the narrow oil pump suction pipe, he was also dismissed, but he told the engineers to "wake up and smell the coffee" (that sounds better than all the foul words he probably used) and he got the go ahead to rebuild the size of the oil pump suction.

    Also, the customer requested different pumps, because the maag pumps that were originally installed has this earsplitting high pitched whine that could be heard all over the ship.

    So the oil pump suction line was changed from DN40 to DN65 pluss the type of oil pump was changed.

    Increasing size of the pumps suction pipe would probably solve the issue with the oil pressure, and maybe the noise from the Maag oil pumps, but the client wanted a different make and type of oil pumps.

    I've been angry at myself for accepting the "nah nah, it's been calculated by the compressor package manufacturer" and not following my gut feeling, but my hat of to the younger guy that stood his ground.

    any way, that solved all the oil pressure issues on these three compressors
    -Cheers-

    Tycho

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    Re: SES/howden WRV163 oil temp/pressure voes

    Thanks Tycho,
    Haven’t seen you around for ages.
    Last edited by RANGER1; 19-08-2022 at 10:49 PM.

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    Re: SES/howden WRV163 oil temp/pressure voes

    Good to have your own thoughts verified by others even if it did take years and thanks so much for the update.
    Brian - Newton Abbot, Devon, UK
    Retired March 2015

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    Re: SES/howden WRV163 oil temp/pressure voes

    Hi Tycho,

    nice post with good outcome ... lesson learned again ... thanks for the update

    threads like this deserve to be under some kind of sub forum named like ...
    "How NOT to do" ...

    I believe it would be a huge sub forum, because human stupidity is endless ...

    Regarding oil pipe size from oil separator to oil pump inlet I believe all should be Ok if pipe is reduced
    just in front of inlet of oil pump ...

    I saw cavitation on Stal S57 oil pump due to dirty of main oil filter .... main oil filter was huge (and quite expensive to be replaced but rather cleaned ... oil filter should be replaced yearly - stated in service manual ... but that happens maybe once in three years) and oil pressure drop was very small and without oil pressure cut out, but enough to provoke cavitation within oil pump housing during long run ... unfortunately, we discovered the reason much later after many damaged oil pumps ... also complete design of piping was by package manufacturer, but without calculation of a clogged oil filter just a little ...


    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

    Please, don't teach me how to be stupid....
    No job is as important as to jeopardize the safety of you or those that you work with.

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