Alfa Laval S846 HFO Separator problem

[vkouroub]

Hello dear colleagues,
we are dealing with a rather "crazy" problem with our HFO S846 separator in our power plant.

More specifically, upon discharge and while on timer 66 (Leakage test) it gives an "OIL LEAKING FROM BOWL" alarm and stops. Now the "crazy" part is that this problem occurs i would say randomly or even better in unevenly time periods. It could operate for 24 hours without the slightest alarm and it could work for let's say 2 hours and bring up the problem in a short term permanent way (explaining below).

After every incident we either proceed by disassembling the bowl and checking, cleaning, replacing seals, plugs and rings or we just simply leave it for several hours idle and put in operation afterwards with 100% success (???).

During this leakage test (duration = 20 sec) the feed is cut off, V4 valve is closed and EPC is calculating the time for the PT4 pressure to fall by 1 bar. If it falls more than 1 bar then the alarm hits. So sometimes during the test the PT4 goes extremely high (around 4 bar) and then decreases quite quickly to 1 bar and the alarm is presented. In other occasions, pressure level during the test is normal (around 2.5 bar) but it jumps back and forth from timer 66 to timer 65 (multiple times), to recalculate the pressure range for the test. In the end it usually passes the leakage test successfully.

I think we have tried everything from using the whole intermediate kit replacing seals, plugs and rings to cleaning water & fuel filters, maintaining and replacing SV10, 15 and 16 water valves, cleaning the PT4 sensor, checking feed water & air pressure, cross checking again and again the functionality and the condition of the operation slide, discharge slide, operation water cover, water pump (or ring as mentioned in manual) etc, but we can't seem to solve the problem and we're going nuts!

Any suggestions, guidelines or similar experience would be highly appreciated. Thanks.

PS: I have thought changing the factory values of the duration of the leakage test (Ti 66 = 20 sec) or that of the differential pressure of the test (Fa 46= 1 bar) to let's say somehow cheat the test but.... we all know this is not recommended. What do you think though?

Bill

[Revolver]

Wow no one, nothin....

Check the sensor. Clean it?
Is your V4 valve passing and dropping press too quick, sometimes?
What's timer 65?
Is oil actually leaking from the bowl?

What's on the go?

[sts07]

I know how you feel sir. We are using Alfa 821 on my vessel and they have been dealing same problem.3rd Eng before me said that they have tried everything you have already done. But they didn't check selonodid valves that controls the sv10,sv15 and Sv16. I disconnected sv15 and sv 16 valves from the seperator connection then I started the seperator. I follow up seperator process from the panel when the seperator open the sv 16 I realized that there was not enough water coming from the valve. After that I open sv 16 and found a deformed spring which did not allow the sv 16selonoid open properly. Then I replaced the valve spring and our seperator was started after 4 months.

[Atlantic]

Hi,

Is it belt driven? Check the clutch pads and the surfaces for the pads, belt tension is also important. If it slips the bowl speed drops. Check the manual for number of pads to be used it can differ dependent of what set up you have.

[SanMarino]

Have you tried to change the orifice/flow valve of the operating water?

[vkouroub]

Sorry for the late reply. Found it about 10 days ago.
It was the V5 water drain valve! Apparently during the leakage test this valve (among other things i.e. bowl, V4) should be 100% closed and of course not leaking. If it leaks then the pressure decreases and the system gives an "Oil leaking from bowl" alarm.
How i found it?
Well i simply opened the cap of the discharge sludge pipe during Ti66 (leakage test) timer and while PT4 pressure had a value of about 2.5 bar, i noticed water and then oil coming out from the flexible outlet hose of the V5. I guessed "this shouldn't happen, V5 (Normally Closed) valve opens only upon discharge (Ti73) and on some occasions when water is detected in the outlet and definetly not during Ti66" .
So we overhauled the faulty V5 valve where we found a small piece of some kind of o ring stuck into the piston which obviously was the reason for the abnormal and random behaviour of the valve. We then tested - pressurized (@ 8 bar) the valve with success, placed it back and everything is working fine 10+ days 24/7 without the slightest alarm! Note that in our installation the flexible outlet hose of V5 valve is connected to the discharge sludge pipe which in turn is connected to a sludge tank.

Lesson: "Oil Leaking from Bowl" alarm especially upon discharge process could come from a faulty V5 valve as well. You won't see this written in any Alfa laval manual and you might not hear it from any alfa laval expert either.

Precaution: When removing the cap from the discharge pipe during discharge procedure, make sure that you are in a good distance (2 meters at least) because you can get easily injured from the ejected sludge products upon bowl opening! I had my own unpleasant experience so beware!

@Revolver: Ti65 = Test of water content in oil outlet. V4 was checked no leakages from this valve. Sensors all cleaned no issues.

@Atlantic: Thanks for the suggestion. Although bowl speed was fine we checked the belt and pads and found nothing unusual. Otherwise i guess a "low bowl speed" alarm would have occured at some point.

@SanMarino: Yes one of our earlier actions was to replace SV10 flow valve and also SV15 and 16 valves as well.

@sts07: I "feel" you my man. We have dealt with the same issue many times. That spring in the solenoid valve and the piston in the actual valve could affect opening/closing thus the water flow of SV16 (closing water) and cause problems. Buy some water valve kits and use them accordingly.
Sometimes these valves leak as well causing additional problems. There is a very simple, quick and effective way to check this instead of checking manually the valves 1 by 1:
Place a ball valve and then a 0-6 bar manometer just before water inlet to check SV water valves for leakages. Simply close the ball valve for a few seconds during normal operation (and not during discharge) and observe manometer. If pressure is stable then SV valves are fine. If pressure drops rapidly then some valve is leaking. In our situation SV10 has presented the most leakages. Have your shift guys do this simple check periodically i.e. 3-4 times per shift.

Cheers,
Bill

[SanMarino]

I had the same problem before but i didnt receive any alarms. I just noticed that during seperation, flexible hose going to V5 was too hot and a little bit of fuel flowing in the sludge pipe when i open the cap. Tried to remove this V5 valve and also found this broken oring. Luckily, i have spare valve to replace this one. Do you have any idea why did this happen because it happened 3 times to different purifiers. Maybe it was time to really replace cause of its age.

[vkouroub]

Hello Sanmarino.
In our case the piece we found in the V5 valve didn't belong to the valve itself but probably came from an o-ring of the bowl. This happened either because bowl was not cleaned properly or during assembly some o-ring didn't "sit" well and got cut so the piece led down to the valve. This piece got stuck in such a way that valve couldn't close 100% so when pressurized the valve was leaking. The higher the pressure the more it leaked leading to the Ti66 failure.
To tell you the truth we operate these separators 10 years now and never had any problems with the V5 valves. I think they are very reliable and heavy duty for this cause. If you have frequent problems with these valves one reason could be low quality o-rings of the valve or maybe overheating or as you say simple aging. In any case these valves can be overhauled and the o-rings are replaceable.

Regards,
Bill

[jmbelluga123]

hi sir.

i had also a problem with S846 hfo. alarm indicates oil back pressure pt4 low.. all above rectification is done .speed is ok, air and water pressure ok.
what cause the pt4 suddenly go low.? can u help me with this problem.

[Jameseze24]

Hi, about the leakage alarm, one it could be that your water plug has leakage, low water pressure to close the bowel, sealing is not ok causing bowel leak and pressure drop which results to alarm and trip. Check bowel springs, plug, sealings, and during first 5/10 mins running check from sludge discharge pipe inspection hole or top connection if any leakage. If yes, proper check should be made on sealing water side and feed water pressure should also be checked.

Having said that, the back pressure adjustment should be done in case feed pump has less pressure. Hope this helps you.