I haven't been on the site for a while so I haven't joined in this thread before.
I hope you have now solved your problem.
A couple of points though, where did all this water come from in the oil? Is it Fresh or Salt? With that level of water content you must have had a major leak into the engine or the purifier was assembled wrongly, or with damaged "O" Rings, and was putting water in, rather than taking it out. First problem is to stop the water ingress.
Many years ago I joined a Panamax OBO, the Acina, with a slow speed MAN engine, the Chrome plating on piston telescopic pipes had broken up and the rough edges had chewed up the telescopic glands and the water had somehow leaked into the crankcase, before I joined the L.O. had been changed and the old emulsified oil had been put into the renovating tank. A sample was taken and sent for analysis, and came back as 35% water.
It was a stable emulsion and before I joined the Engineers had been draining a few gallons a watch out of the tank hoping to get the water out, but it was a stable emulsion. When I joined I put the steam heating on the tank, brought it up to 100Celsius for a day, broke the emulsion, and clean water just poured out of the drain cock. After a couple of days all the water had all gone and we sent off another sample for testing and the results came back that it was fit for use. I had been a bit concerned that the additives might have been washed out of the oil by all that water but it was fine.
One another ship, there was a separate L.O. Purifier Sludge Tank and the Chief Engineer wanted to minimise L.O. consumption so he had the engineers drain the water from this and then purify the rest back into the engine sump, unfortunately a new Engineer joined and he failed to drain the water out just tried to purify the entire sludge tank straight into the Sump, the purifier just pumped all the water and dirt straight into the engine, and emulsified all the oil, fortunately we discovered this just before we sailed and had to cancel sailing, Renovate all the oil and manually clean the L.O. Drain Tank, it was a big Sulzer so it was a Hell of a job. Stupidity on the part of the Chief Engineer really, if the purifier is operating correctly, no oil is discharged into the Sludge Tank, if he thought we were losing L.O. into the Sludge Tank the solution was to overhaul and thoroughly check the operation of the L.O. purifier, not pump all the **** the purifier had taken out, back into the Sump!
One another ship, a Car carrier, the crankcase air vent was inside a Box at the ship's side, this Box filled with Salt water and rusted through the Vent pipe dumping loads of Saltwater into the Sump.
I wouldn't want to be circulating oil with that water content through the engine, there is a danger that the water, in the absence of air, could react with the Tin in the Bearings to form Tin Hydroxide, which is not a problem in itself, BUT in the presence of air the Tin Hydroxide oxidises into Black Tin Oxide which is much harder than the engine shafts in the bearings and can rip them to scrap.
I wouldn't be concerned about trying to get all the water out in one pass through the purifier, by far the best way, if you have a Renovating tank, is to purify the oil from the sump to the Reno Tank, at the highest temperature and slowest flow rate that you can, keep the Reno Tank heated to 100C and purify from the Reno tank back to the Reno tank, draining any water from the Reno tank drain cock every hour or two until the oil looks O.K.
Then purify the oil back to the sump and continue purifying Sump to Sump. If you succeed in removing the 35% of mixture which is water you will have to replace at least some of that with Fresh Oil.
For at least 30 years, to my certain Knowledge, all Purifier makers, in agreement with all the oil Companies say that L.O. Purifiers should be run at 95 Celsius for engines where there is no Physical barrier between the cylinders and the crankcase and 90 Celsius where there is (i.e. Slow speed 2 stroke engines with a scavenge space between the crankcase and the pistons to stop any blow past from the pistons.
Batch purification is by far the most effective, i.e with fuel from the Settling Tank to the Service Tank, with L.O. from Sump to Reno Tank or Reno Tank to Sump, for the simple reason that the clean output from the purifier is not contaminated by being dumped back into the dirty oil system it came from.
The slower the throughput through the purifier, the cleaner the oil coming out, so when batch purifying the flow rate should be reduced to a minimum, so that all the oil is cleaned to the highest standard.
When purifying Sump to Sump however, the clean oil is mixed with the contaminated oil back in the Sump, so the aim is to remove the maximum quantity of water/ dirt from the oil per hour. In order to do this, the flow through the purifier should be at the top of the Purifiers designed flow rate, the oil coming out of the purifier will not be so clean, but because there is a larger flow rate, more water and dirt are removed from the system in any given time.
Ref your original, Post: -
If the SG of the oil is 0.86 and that is mixed with water in a ratio of 2:1, the SG of the emulsion will be over 0.9
The Mousse you describe as discharging from the heavy phase outlet, is emulsified oil, so you are dumping potentially good L.O. into the Sludge Tank.
In order to for the purifier to separate the oil from the water you have to break the emulsion first, to do this you have to heat it up to at least 100C and hold it at that temperature for as long as possible, as other posters have said you need to get the L.O. temperature as Hot as you can and the flow rate as slow as possible so that it has as long a time to separate out in the heater and pipe work to the purifier. If you are purifying from the Sump, put the steam heating coils on to get the sump as hot as possible (if you have them). Do not worry about the Flash Point you will not reach it. The oil Temperature in the Engine will often be well over a 100 C, locally for a short period, I very much doubt that you will be able to get the oil hot enough to damage it. At present the "oil" is useless as a lubricant, if you can not get the water out, you will have to pay someone to take it away as waste.
Initially, you were running the purifier far too cold, at 80C you might as well leave it shut down for all the good it will do.
Regarding the size of the Gravity Disc, water temperatures, back pressures etc this is all laid down in the maker's Instruction manual.
The main reason to maintain a back pressure is so that if the water seal is lost the flow of the light phase out of the purifier reduces, therefore the pressure drop across the discharge throttling valve drops, triggering the loss of seal alrm (which is operated by a pressure switch before the throttling valve). Before Loss of seal alarms the discharge from the purifier had no back pressure as the oil just fell by gravity down to the sump and there could actually be a partial vacuum at the purifier outlet. However, the back pressure can effect the water seal so it has to be adjusted in accordance with the maker's manual. Obviously the pressure will change with oil temperature/viscosity and flow rate so when any of these change the throttling valve has to be adjusted. Obviously you need a pressure gauge to monitor this, unless you have a very old purifier that predates Loss of Seal Alarms!
Regarding choosing the correct Gravity disc the details of exactly how this is done varies from maker to maker. Firstly you start with the SG at 15C which is the International Standard Temperature for measuring SG and is given in the Oil Companies Specification for that Oil, always check this if the grade of oil used in the engine changes, you may have to change the Gravity Discs in the L.O. Purifiers, the same as you would in the HFO Purifiers after Bunkering.
The SG at 15 C is then corrected to the SG at the Temperature that you will be purifying it at(this done on a graph in the manual) , obviously as the oil is heated it expands and the SG becomes less. This new SG is then used to find the size of the Gravity Disc from another Graph in manual.
With Laval Purifiers, if I remember correctly, these 2 stages are combined in a single Nongram where you follow the lines for SG at 15C and the actual purifying temperature to find the correct Disc size.
Regarding the difficulty in cleaning the purifier discs when running at high temperatures I don't believe that this will be a problem so long as you have this water content.
However, many purifiers are not set up to de sludge often enough. The first generation of automatic purifiers, back in the 1960's were designed to de -sludge every 4 hours, and many Engineers assume that the more modern purifiers should be set to de-sludge at this frequency. However, since then the size of purifiers has been greatly reduced and the sludge storage capacity with it, modern purifiers are generally designed to be de- sludged every 30 minutes or so, otherwise heavy sludge deposits will build up inside the Disc stack. As always, read the instruction manual!!!!
I have found In service Cleaning to be very effective, must of the Purifier Manufacturers supply kits for this that pump powerful chemicals through the Purifier and Or the heater and clean them without having to dismantle them, it obviously saves a lot of dirty work and the purifiers then only have to be dismantled for Bearing changes and other overhauls, and Chemically cleaning them first makes this much easier.
However, a word of warning, these are very powerfull Chemicals and are not in the slightest bit OWS friendly, so make sure none of them end up in the Bilge system!!
Another interesting point is that it has been demonstrated that "packaged" purifier units in a module are less effective at removing water and dirt from Oil than the Traditional system installed by the shipyard as separate components. After much research it was concluded that this was because the length of pipework from the Heater to the Purifier was less, so the oil was not heated for such a long time before going through the purifier, so if you want to increase the efficiency of your purifiers, increase the length of the pipework, to increase the "Dwell Time" at high temperatures, which particularly in your case, gives the oil and water time to separate before going into the purifier.
The Purifier can not and will not break the emulsion, it will only separate the light phase from the heavy phase and in your case the heavy phase appears to have been emulsified oil. Breaking the emulsion can only be done by a combination of heat and time.
I hope this helps you or someone else out there.
It is always better to ask a stupid question than to do a stupid thing.