Alfa Laval S936 Bowl leakage

[apples12345]

Currently having trouble with Alafa laval S936 bowl leaking. Would really appreciate some advice as we are a little stuck with this one. Initially purifier was giving us discharge feedback error and pt5 was showing 0, purifier was opened and found very dirty so full cleaning was carried out. Upon putting purifier back in service during calibration of water flow bowl was leaking and not building any pt4,pt5 pressure.
It was decided to carry out intermediate service as it was almost due, all o-rings etc changed. During start up again during calibration of water bowl was leaking and no pt4/pt5 pressure, water coming through sludge port. We tried manually closing the bowl, as per operating instructions. Opening sv15 for 5 seconds (p244), waiting 15 seconds and opening sv16 for 15 seconds. During this quite a lot of water was leaking from the sludge port. We attempted to supply displacement water which immediately could be seen in the sludge port.
Nothing can be seen coming from v5 valve drain line to sludge port.

since then purifier has been opened a few times and the following carried out with no luck:

• Water block changed with new one: orifices blown with air and checked for size with other purifier.

• Water hoses blown with air and found ok testing in to bucket. Water supply to bottom of shaft verified all ok.

• Drain valve on displacement water (pneumatic vale on water block) found not passing.

• Paring tube opened and all passageways clear. Non return valve operating. Arm moving freely under spring.

• Valve plugs orientation correct and firmly in place.

• Water pump at bottom of bowl and discharge slide orientation correct.

• Discharge slide moving freely. Gn paste applied to all sealing surfaces.

• All rectangular rings in place and condition “looks” ok.

• Teflon ring in the hood found depressed and groove forming suggesting bowl has been at least partially closing.

• Axial wobble found ok.

• Belt changed due to stretching of old one.

• Water drain line pt5 and v5 valve removed, cleaned and v5 swapped with known working valve.

• Clean oil outlet line pt4 removed, cleaned, pressure sensors cleaned and gauge verified. V4 valve operating ok. Even closing manual discharge valve after water transducer fully builds no pressure.

• Parameters checked against default valves and other purifiers. All set to default.

After putting purifier back and testing it is now tripping on a57 oil leaking from bowl immediately when it tries to make first discharge to start separation. It doesn’t even reach the calibration stage now.

Once oil is supplied form bowl you can hear rpm drop and leakage start, oil visible in sludge port. Again no pt4/pt5.

currently bowl is open and i will try to polish all faces with some polishing paper, any suggestions appreciated.

[Atlantic]

Hi,

What about bowl speed? Did you check the clutch? Also is to run with frequency converter? If so check that. If you figure out what’s wrong please let us know.

[popeye62]

Hello apples 12345, nice report. As Atlantic says, check the speed (is speed sensor installed and enabled?). It seems an issue with closing water but there is evidence that the bowl has been closing. Is the 1.5 mm nozzle (part no. 545869 in the operating slide in my 946 manual) in place and not blocked? Opening SV16 for 15 seconds should close the bowl and you will see this water overflowing in the sludge chute. Did you shut SV16 before opening SV10 for displacement? I would check all the parameters in the control system (EPC50?). Check the volume of water with the manual. Still seems like low speed.

[apples12345]

Thanks for the fast replies!

So to confirm speed wasn't the issue I changed the clutch pads today, bowl speed is staying at 10,400rpm and only dropping slightly during opening / closing - always staying above 10,000. speed sensor is enabled and rpm reporting ok. Motor is constant speed belt driven.

I re confirmed all passageways were clear and blew everything through with air, the1.5mm nozzle on the discharge side is not blocked. I used some polishing paper on all the major surfaces and tested again today. Tripping the same.

so when closing the bowl with sv16 for 15 seconds you hear a positive clang sound (louder now than before or maybe I'm going crazy) after a few seconds and see water overflowing. closing / releasing sv16 and then supplying opening sv10/water seal the water is then visible after a few seconds again through the sludge port.

Same is true when letting the purifier try to start. Answering yes to the bowl opened and cleaned questions, then starting separation gives the following sequence. SV15(opening) 5 seconds, 15 second wait, SV16 (closing) for 15 seconds, then oil feed on. which you can hear immediately leaking, pt1 drops to 0.2/3 and a57 comes.

I compared all the parameters on the control panel (epc60) everything is default. I noticed "'p233 filling time conditioning water (calculated during calibration)xxx(120 initially)'' was set to 8 seconds, the same as our other purifiers no not sure why that hasn't gone to 120 default as the calibration hasnt been carried out. I tried setting it to 120 no change. p243 SV16 opening time is set to defualt 15 seconds.

Thanks in advance!

[popeye62]

I am not familiar with hearing the bowl close with a clang which may be the operating slide as the bowl closes on the polyamide seal (genuine parts?). I am not sure how far open the bowl is during stopped as it is a 'Flex' and uses the Centrishoot system and there is no sliding bowl bottom. Are there impressions on the valve plugs? What happens if you leave SV16 open (apart from it filling the sludge tank) while filling the bowl, do you get any pressure? If it is not calibrated it will use the last setting but 8s seems very quick to fill the bowl and register a pressure at PT4. Did you try disabling PT4 (P153 = 0)? It seems that a lot of stuff is looking at PT4. Having said that, it still looks like a closing water issue and a lack of hydraulic pressure but not from a lack of speed. Could the bowl height be an issue?

[GamerDiver]

Hi,

We had a similar problem with the S937 purifier on my ship when I join a few weeks ago.

At first it seems the purifier was sized (we have a problem with the sludge tank getting pressurized when the p/v breaker run out of water anyway). Then the bowl won't close.

My coworker tried just about anything, checked all water and air lines, checked all the gasket, Teflon ring and guide ring has been change plus couple of O-ring and he couldn't find the problem. The purifier was dismantled a few times. No success.

When I joined, I dismantled it, change 1 O-ring and the 3 valve plugs, inspected every parts and put it back together. Now the bowl was closing but I had a low back pressure alarm. I adjusted RV4.

Now the purifier runs like it never happened.

Have you changed the valve plugs? They may look good but are the one causing the issue possibly.

Good luck.