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    Oil pressure issue Howden WRV255, stumped again



    Here's a good one

    I have two "identical" Howden WRV 255 units, running side by side on the same plant.

    one has a maag NP 70/70 oilpump and the other has a Viking oil pump.

    One has a Danfoss ORV oil mixing valve I suspect has a 48C thermostat, the other has a aamot mixing valve and I think the mixing thermostat is 42C

    the one with the maag pump is running with an oil temperature of 52C, discharge of 98,7C.

    The one with the viking is running with an oil temperature of 43C and a discharge of 84C.

    The problem was that the one with the maag pump would slowly loose oil pressure while it was running in 100% load, and as the pressure dropped, the discharge temp would rise.

    I have tightened the spring on the internal safety valve on the maag oil pump but no luck, I closed the external pressure relief, still no change.

    The howden WRV has oil injection valves used to regulate the oil flow into the rotors, used to cool the discharge gas, I fine tuned these, by closing them until the discharge temp started rising more and then opening them again until the discharge temp stabilized, then fine tuning by opening a 1/4 turn and watched as the discharge temp dropped, hen opened another 1/4 turn and so on until the oil pressure started dropping, figuring I had reached equilibrium and could not adjust more

    The last thing I did was to close the economizer, and the oil pressure rose .6 bar from 1,4 to 2.1 bar in 3 minutes or so.

    I have noticed in similar plants that a 1 Kelvin rise in OT would result in a 2-3 Kelvin rise in discharge temp, so I have ordered a new 42C thermostat for the ORV.

    My thinking is that lowering the OT 10 kelvin will give me a 15-20 kelvin drop in the discharge temp.

    What has me stumped is why closing the economizer gave me a better oil pressure?
    the economizer pressure was -30C (0,2 bar), and if anything, it should help cool the discharge, or am I wrong?


    --------------------------

    Also, on googling the subject, my boss came up with a thread from RE about LRI injection vs economizer, where I was heavily involved (baiting ), and he showed it to me and said, "see, it says right here" I didn't have the heart to tell him I had written the text he showed me


    -Cheers-

    Tycho

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    Re: Oil pressure issue Howden WRV255, stumped again

    Hi Tyco.
    Would the system with the Maag pump which is running hotter. Be the one that has the Danfoss ORV valve?
    I ask this because occasionally we get issues with Danfoss ORV's Failing and the relevant machine will have higher Oil Temps.
    Since Danfoss changed the ORV design several years ago their failure rate has dramatically reduced.
    Please keep us informed as yours is a intriguing problem.
    Grizzly
    Despite the High Cost of Living it still remains Popular!

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    Re: Oil pressure issue Howden WRV255, stumped again

    Tycho,
    Obvious questions apart from changing Danfoss ORV which if bypassing you would be able to feel bypass line around oil cooler.
    Even at 52 C oil thought it would still be ok, but discharge temp may derate pump a fair bit with viscosity.
    I would say oil injection not open enough, but realize you are tring to keep it going in the meantime.

    - Oil filters cleaned or changed.
    - Assume it has worked before.
    - oil cooling, water, has it been cleaned, is divider plate in end cap in good condition.
    - oil pump condition, can you see gears & faces if OK.
    - Compressor condition, thrust check, when last checked out.
    - metal in filters

    Maximum discharge temp is 100 deg C, so you are operating at trip point.
    Even other one discharge temp seems a little hot with low oil temp.

    Anything else changed recently like operating pressures, could there be air in system, or condenser not working 100%.
    Once had a similar problem, found oil pump pre-filter to fine starving pump.
    Oil pump motor speed, is it correct, as someone could have changed motor.
    Last edited by RANGER1; 26-09-2017 at 12:22 AM.

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    Re: Oil pressure issue Howden WRV255, stumped again

    Hi Tycho,

    check both capacity of oil pumps (l/tr), could be different. When running conditions change, if nominal oil flow is to low, oil pressure decrease suddenly.
    I have monitored the oil flow on a compressor for such a trouble; when pressure ratio increased, oil pressure dropped in a few seconds. oil pump KF3 had been replaced but wrong gear length used so nominal oil flow was reduced.
    your oil pump can also be worn.

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    Re: Oil pressure issue Howden WRV255, stumped again

    Sometimes oil pressure drop if sleeve bearings are worn out. It that case too much oil going to the bearings and pressure drop. This issue becomes worse at higher discharge pressure.

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    Re: Oil pressure issue Howden WRV255, stumped again

    Plant running conditions & pump details/speeds would be helpful.
    Can compare pump capacities.
    Pump motor amps as well.

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    Re: Oil pressure issue Howden WRV255, stumped again

    Quote Originally Posted by Grizzly View Post
    Hi Tyco.
    Would the system with the Maag pump which is running hotter. Be the one that has the Danfoss ORV valve?
    I ask this because occasionally we get issues with Danfoss ORV's Failing and the relevant machine will have higher Oil Temps.
    Since Danfoss changed the ORV design several years ago their failure rate has dramatically reduced.
    Please keep us informed as yours is a intriguing problem.
    Grizzly
    Yes, the maag one has the ORV, I've checked this.

    The oil coming out of the cold side on the oil cooler is 38c, and the mixed temp is pretty stable on 51-52c

    I remember the problems with the older types of ORV, but this one is the new model.

    also it ticks me off a little bit that when you order a new ORV insert you have to order the glide strip separately.

    Because when the oil has been to hot because of a failed ORV thermostat, the glide strip gets harder and doesn't give an adequate seal around the moving part of the ORV
    -Cheers-

    Tycho

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    Re: Oil pressure issue Howden WRV255, stumped again

    Quote Originally Posted by RANGER1 View Post
    Tycho,
    Obvious questions apart from changing Danfoss ORV which if bypassing you would be able to feel bypass line around oil cooler.
    Even at 52 C oil thought it would still be ok, but discharge temp may derate pump a fair bit with viscosity.
    I would say oil injection not open enough, but realize you are tring to keep it going in the meantime.

    - Oil filters cleaned or changed.
    - Assume it has worked before.
    - oil cooling, water, has it been cleaned, is divider plate in end cap in good condition.
    - oil pump condition, can you see gears & faces if OK.
    - Compressor condition, thrust check, when last checked out.
    - metal in filters

    Maximum discharge temp is 100 deg C, so you are operating at trip point.
    Even other one discharge temp seems a little hot with low oil temp.

    Anything else changed recently like operating pressures, could there be air in system, or condenser not working 100%.
    Once had a similar problem, found oil pump pre-filter to fine starving pump.
    Oil pump motor speed, is it correct, as someone could have changed motor.

    There are two oil injection valves, danfoss REG 15 if I remember correctly.
    When I came on site, one was full open and one was half open, so I started adjusting the full open one until I found the equilibrium between loosing oil pressure and rising discharge temp.
    They are so fine tuned now that if you tighten the cap to hard, the discharge temp will start rising


    Oil filter is new, it has worked before, but it has always been running warmer than the other unit.

    Oil cooling is thermosyphon on both and I have checked both for oil, and there was not even a speck of it.

    the problem unit is 3 years old and has 4800 hours running time, I haven't been able to open the pump because we don't have gaskets and o-rings yet.
    I did take out the internal overflow valve and checked if something had made it past the suction strainer and it looked brand new and no debris.

    The other unit is 15 years old and is purring like a kitten, I would have liked to have the discharge temp on that one down to around 70-75C, but it's mackerel season and I dare not touch it out of fear of jinxing it
    -Cheers-

    Tycho

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    Re: Oil pressure issue Howden WRV255, stumped again

    Tycho,
    You are not giving us anything to work on!
    Suspect you will change ORV & problem solved.
    I suspect oil pump is borderline, that's why oil injection is so finely tuned.

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    Re: Oil pressure issue Howden WRV255, stumped again

    Quote Originally Posted by RANGER1 View Post
    Tycho,
    You are not giving us anything to work on!
    Suspect you will change ORV & problem solved.
    I suspect oil pump is borderline, that's why oil injection is so finely tuned.
    Looks like I spoke to soon again!
    Any idea on Viking oil pump size & speed?

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    Re: Oil pressure issue Howden WRV255, stumped again

    Quote Originally Posted by cricri View Post
    Hi Tycho,

    check both capacity of oil pumps (l/tr), could be different. When running conditions change, if nominal oil flow is to low, oil pressure decrease suddenly.
    I have monitored the oil flow on a compressor for such a trouble; when pressure ratio increased, oil pressure dropped in a few seconds. oil pump KF3 had been replaced but wrong gear length used so nominal oil flow was reduced.
    your oil pump can also be worn.
    I've spoken to the supplier and confirmed the capacity of oil flow on both pumps should be the same, and adequate for the compressor.

    at startup, the oil pressure is 6.4 bar, and as the slidevalve increases capacity it drops steadily down to 3 bar as the slide valve closes. with the slide closed, the oil pressure keeps dropping slow and steady until it reaches 1.7 - 2 bar
    -Cheers-

    Tycho

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    Re: Oil pressure issue Howden WRV255, stumped again

    Quote Originally Posted by RANGER1 View Post
    Plant running conditions & pump details/speeds would be helpful.
    Can compare pump capacities.
    Pump motor amps as well.
    Suction pressure -38.5 C
    Discharge pressure: 27.1 C
    Same for both


    Maag pump runs at 1450rpm capacity is 264 l/min (theoretical at dP 0 bar)
    Viking pump runs at 1750 rpm capacity is 240 l/min (theoretical at dP 0 bar)

    I didn't think to check the amps, but they are running full production today until 2am, and the machinist is going to keep me updated on the running conditions via sms, so I'll ask if he can check if he has time
    -Cheers-

    Tycho

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    Re: Oil pressure issue Howden WRV255, stumped again

    Quote Originally Posted by Tycho View Post
    Suction pressure -38.5 C
    Discharge pressure: 27.1 C
    Same for both


    Maag pump runs at 1450rpm capacity is 264 l/min (theoretical at dP 0 bar)
    Viking pump runs at 1750 rpm capacity is 240 l/min (theoretical at dP 0 bar)

    I didn't think to check the amps, but they are running full production today until 2am, and the machinist is going to keep me updated on the running conditions via sms, so I'll ask if he can check if he has time
    Tycho,
    Model number of pump handy as well.
    Example AK4195

    Oil pump suction strainer size ,type, mesh size even at a guess like coarse , fine, very fine.

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    Re: Oil pressure issue Howden WRV255, stumped again

    I might drop by the factory tomorrow, just out of my own curiosity to figure this out.

    also, the reason I had "stumped again" in the title is because of this thread:
    http://www.refrigeration-engineer.co...-pressure-voes

    on that ship, they are still running with high discharge temp and low oil pressure, but they manage without tripping the system because the compressors never run at 100% capacity for too long because of varying amounts of fish being frozen in the plate freezers.

    The one I am having an issue with now is running on two blast freezers where they are freezing over 200 metric tons/24 hr if I remember correctly

    I'll keep you informed on the progress
    -Cheers-

    Tycho

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    Re: Oil pressure issue Howden WRV255, stumped again

    Quote Originally Posted by RANGER1 View Post
    Tycho,
    Model number of pump handy as well.
    Example AK4195

    Oil pump suction strainer size ,type, mesh size even at a guess like coarse , fine, very fine.
    No luck on the model of the pumps, the compressor package builder has removed the manufacturers plates and replaced them with their own with just the bare minimum of information :/

    Pump suction strainer is a danfoss FIA 50 filter (DN50) mesh is 250 or 500 μ, I know I looked at it when I had the filter out, but I've been in Denmark supervising the installation of a NH3 plant on a trawler (the pipe installation is a week behind schedule) and my focus has been there, so I just don't remember
    -Cheers-

    Tycho

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    Re: Oil pressure issue Howden WRV255, stumped again

    Quote Originally Posted by Tycho View Post
    No luck on the model of the pumps, the compressor package builder has removed the manufacturers plates and replaced them with their own with just the bare minimum of information :/

    Pump suction strainer is a danfoss FIA 50 filter (DN50) mesh is 250 or 500 μ, I know I looked at it when I had the filter out, but I've been in Denmark supervising the installation of a NH3 plant on a trawler (the pipe installation is a week behind schedule) and my focus has been there, so I just don't remember
    Tycho,
    Motor size in kw & amps might narrow it down.
    How is it running at 1750rpm & other at 1450 rpm VSD ?

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    Re: Oil pressure issue Howden WRV255, stumped again

    Quote Originally Posted by Tycho View Post
    I might drop by the factory tomorrow, just out of my own curiosity to figure this out.

    also, the reason I had "stumped again" in the title is because of this thread:
    http://www.refrigeration-engineer.co...-pressure-voes


    on that ship, they are still running with high discharge temp and low oil pressure, but they manage without tripping the system because the compressors never run at 100% capacity for too long because of varying amounts of fish being frozen in the plate freezers.

    The one I am having an issue with now is running on two blast freezers where they are freezing over 200 metric tons/24 hr if I remember correctly

    I'll keep you informed on the progress
    Tycho,
    In this post you indicate maag ng 70/70 pump on Howden 163 & is same pump on Howden 255, is that correct?
    I guess speeds could be different, but they must like this model!

    maag data sheet pretty vague & with 0 pressure across it & no viscosity of medium does not mean to much.

    http://www.pumpfundamentals.com/pump...p-hydrolub.pdf

    Viking pump selector not much equates to maag, except bigger or higher oil flows, so mystery.

    http://tools.vikingpump.com/pumpsele...ectvalues.aspx

    What does pump look like
    http://www.spec-net.com.au/press/0509/kpa_130509.htm
    http://generalpumpandmachinery.com/p...viking-al4195/
    Last edited by RANGER1; 29-09-2017 at 11:53 PM.

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    Re: Oil pressure issue Howden WRV255, stumped again

    Quote Originally Posted by RANGER1 View Post
    Tycho,
    In this post you indicate maag ng 70/70 pump on Howden 163 & is same pump on Howden 255, is that correct?
    I guess speeds could be different, but they must like this model!

    maag data sheet pretty vague & with 0 pressure across it & no viscosity of medium does not mean to much.

    http://www.pumpfundamentals.com/pump...p-hydrolub.pdf

    Viking pump selector not much equates to maag, except bigger or higher oil flows, so mystery.

    http://tools.vikingpump.com/pumpsele...ectvalues.aspx

    What does pump look like
    http://www.spec-net.com.au/press/0509/kpa_130509.htm
    http://generalpumpandmachinery.com/p...viking-al4195/
    My hat of to you Ranger!!
    f1f54d557cea8230d89ab11a47bad369.jpg

    You really have attention to detail good sir!

    I had a double take myself when I went back to my old post and saw that it was a maag NP70/70 pump on the WRV163 as well... because they are two different pumps completely

    On the WRV 163 unit the pump looks like this:
    maag7070.jpg
    The system has three compressors, and during commissioning, two of the pumps seized within 4 hours of running. the third survived for two days.
    The compressor package manufacturer sent us 2 new pumps to begin with, they also seized within a few hours.
    They then sent us new bearings and rotors for the pumps, so we had to overhaul them on site, but after the overhaul, with a different kind of bearings they have been running for 10 years.
    Personally I don't like them, first because of the breakdowns, second because they are noisy.
    on this ship, the compressors are in the bow of the ship, and if we draw a straight line from the maneuvering bridge to the compressors, it's two decks down and the distance is perhaps 30 meters.
    when I remote started the system from the bridge I could hear the oil pump going "NJEEEEEEEEEEEEE" and that's not the way it should be.

    I've been all over google to find a maag pump that looks like the one installed on the WRV255 unit and haven't found anything in pictures or service manuals that looks anything remotely like it, on the plaque it says NP 70/70, that's all.
    I have a printout of a user manual for all maag pumps, but it's very general and it doesn't show the model that is on the WRV 255 unit, so it's a lot of guesswork

    The Viking pump on the old unit is indeed this type:
    vikingpump.jpg

    I serviced this one 2 years ago or so because the oil pressure was fluctuating slightly, it had dug slightly into the wall, but a lot of elbow grease and some fine tuning on the adjustment ring and it was back in action



    Also, the compressor unit manufacturer has been bought by a US company, so not it's close to impossible to find out who to contact, and all inquiries has to go through "inquiries@....."
    Last edited by Tycho; 30-09-2017 at 01:27 AM.
    -Cheers-

    Tycho

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    Re: Oil pressure issue Howden WRV255, stumped again

    When I first started out in Kvaerner, we used the Kral MFUG-55 screw pump, it would run for twice the hours of the compressors without needing any service, only the vertical ones needed shaft seals replaces every now and then, because the operators didn't drain the gas that collected on top with the shaft seal after a long stand still (they even had a purge screw )
    -Cheers-

    Tycho

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    Re: Oil pressure issue Howden WRV255, stumped again

    Quote Originally Posted by Tycho View Post
    When I first started out in Kvaerner, we used the Kral MFUG-55 screw pump, it would run for twice the hours of the compressors without needing any service, only the vertical ones needed shaft seals replaces every now and then, because the operators didn't drain the gas that collected on top with the shaft seal after a long stand still (they even had a purge screw )
    Tycho,
    Viking is a good pump with all the information for sizing etc on link I posted.
    It can plot pump output with different differential pressures, oil viscosity, speed etc.
    If you had motor amps & motor size we could pinpoint model.
    Could be AS or AK4195.
    If you change differential pressures or viscosity, it shows pump output changes to see what's going on.
    Maag pump probably cheap & sized borderline.
    I do not have Howden programme at the moment, but Mycom 250S M or L requires 200l/min under your conditions.
    I know Howden require probably 20% more than Mycom due to monster clearances & agricultural design
    I bet Viking pump is bigger.
    My guess is compressor oil pump should be 5 l/second to be good for all situations, even if shipped to Australia.
    That does not help you much, but sometimes it helps to know if pump was sized correctly, as if compressor wears a bit & certain conditions like maximum load & differential pressure across machine mean unreliable.
    You could pull out suction filter to pump & see like you have previously, as not much to lose.
    Made gauges of transducers reading accurately.
    Last edited by RANGER1; 30-09-2017 at 10:23 PM.

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    Re: Oil pressure issue Howden WRV255, stumped again

    So...

    Something we have all missed... Oil level.

    On the MAAG pump unit:
    I checked the oil level, and according to the level glass, the oil level was approximately 15 cm over the oil pump suction during standstill, when the compressor started, the oil level rose to approximately 20 cm above the oil pump suction. So I didn't think anything of the Oil level.
    Friday night, the machinist added 70 Liters of oil, and the oil pressure has been steady at 5 bars ever since, discharge temp is around 94C, so with the added oil it might be possible to get it down further by opening the oil injection valves.

    I didn't think to add oil at all, because the level was well above the oil pump suction.

    Also, the levels on the unit with the Viking pump is exactly the same, and from experience on the Viking pump unit, if you add 5 liters too much, it will throw out the 5 liters pluss another 20 liters, so even the machinists have asked us not to add oil to the viking pump unit...

    whaaaaaaat?
    -Cheers-

    Tycho

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    Re: Oil pressure issue Howden WRV255, stumped again

    Tycho,
    Operator needs a big mark on glass for correct level & future reference.

    What type of oil separator, vertical or horizontal?
    Normally a sight glass would not show this much level indication.
    As you say makes no sense unless sucking gas, cavitation.

    Is pump a bit quieter now?

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    Re: Oil pressure issue Howden WRV255, stumped again

    Quote Originally Posted by RANGER1 View Post
    Tycho,
    Operator needs a big mark on glass for correct level & future reference.

    What type of oil separator, vertical or horizontal?
    Normally a sight glass would not show this much level indication.
    As you say makes no sense unless sucking gas, cavitation.

    Is pump a bit quieter now?
    It's a vertical oil separator, the sightglass is a vertical glass approx 40 cm long.

    I know the internal design of the oil separator, the suction for the oil pump goes in below the level glass and it has an elbow going down once inside the separator, so the oil pump suction is another 15/20Cm below where the suction pipe enters the oil separator.

    This unit is still running 15C hotter than the twin, so we are still going to try to replace the thermo element of the ORV to see if we can get it down to running conditions I am more happy with.

    They recently expanded with 3 more WRV255 units on a separate system that are running equally high discharge temperature, so if we can get it down by replacing the ORV element, they will request the contractor for the other plant to do the same.
    -Cheers-

    Tycho

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    Re: Oil pressure issue Howden WRV255, stumped again

    Tycho,
    With 45 deg C oil discharge temp should be 73 deg C.
    I sent something to you on your gmail address, if it works.
    If not let me know new email.

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    Re: Oil pressure issue Howden WRV255, stumped again

    Hi, Tycho

    Quote Originally Posted by Tycho View Post
    It's a vertical oil separator, the sightglass is a vertical glass approx 40 cm long.

    I know the internal design of the oil separator, the suction for the oil pump goes in below the level glass and it has an elbow going down once inside the separator, so the oil pump suction is another 15/20Cm below where the suction pipe enters the oil separator.

    This unit is still running 15C hotter than the twin, so we are still going to try to replace the thermo element of the ORV to see if we can get it down to running conditions I am more happy with.

    They recently expanded with 3 more WRV255 units on a separate system that are running equally high discharge temperature, so if we can get it down by replacing the ORV element, they will request the contractor for the other plant to do the same.

    ORV is Amot or Danfoss ... thermostatic element can be different so does the oil temperature ... it is possible to replace element, but the main question is if the oil cooler is capable to cool the oil then the ORV will do the rest ...


    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....
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    Re: Oil pressure issue Howden WRV255, stumped again

    I received the new thermostat insert, 43C a few weeks ago, but I have been commissioning a new freezing plant on a trawler, so I only had time to change the ORV thermostat today.

    Lo and behold, the one I removed was a 43C one, just like the new one... and Danfoss failed to send the teflon "glide strip" I ordered, so I didn't get to change that one.

    and I have had the teflon "guide strip" become hard because of excessive high oil temp and then make the thermostat leak internally...

    it costs the owner a lot to start these machines, so they only start them when they have fish coming in, so I will know tomorrow afternoon when they have vessels lined up

    I hope I don't have to go into hiding
    -Cheers-

    Tycho

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    Re: Oil pressure issue Howden WRV255, stumped again

    Tycho,
    Have you got an email address these days?

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    Re: Oil pressure issue Howden WRV255, stumped again

    Quote Originally Posted by RANGER1 View Post
    Tycho,
    Have you got an email address these days?
    I've got my gmail back
    -Cheers-

    Tycho

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    Re: Oil pressure issue Howden WRV255, stumped again


  30. #30
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    Re: Oil pressure issue Howden WRV255, stumped again

    Quote Originally Posted by RANGER1 View Post
    Haven't been there, I have sailed past it tho

    This is a video I made as we were entering the port of Svolvaer (Svolvær) some year ago
    It's very beautiful up there
    -Cheers-

    Tycho

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    Re: Oil pressure issue Howden WRV255, stumped again

    -Cheers-

    Tycho

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    Re: Oil pressure issue Howden WRV255, stumped again

    25 years ago I worked on LPG gas carrier and we loaded propane in Norway. It was really beautiful there.

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    Re: Oil pressure issue Howden WRV255, stumped again

    Quote Originally Posted by Tycho View Post
    I received the new thermostat insert, 43C a few weeks ago, but I have been commissioning a new freezing plant on a trawler, so I only had time to change the ORV thermostat today.

    Lo and behold, the one I removed was a 43C one, just like the new one... and Danfoss failed to send the teflon "glide strip" I ordered, so I didn't get to change that one.

    and I have had the teflon "guide strip" become hard because of excessive high oil temp and then make the thermostat leak internally...

    it costs the owner a lot to start these machines, so they only start them when they have fish coming in, so I will know tomorrow afternoon when they have vessels lined up

    I hope I don't have to go into hiding
    So I got word back, as I said earlier, they have maintained dOP after he filled oil, and there was no change in oil temp or discharge temp after I replaced the thermostat in the mixing valve.

    Luck would have it that he kept the old thermostat, because earlier this week it failed on another machine and we were able to reuse the old one
    -Cheers-

    Tycho

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