First thing with separators, have you checked that the bowl is turning at the correct RPM?
Possible causes are that the clutch/ drive belt is slipping or somebody has mistakenly ordered and fitted the wrong ratio of gears or pulleys, also it is possible that a motor of the wrong speed has been fitted at some time.
There are always 2 sets in the spare parts list, one for 50 Hz electrical supply and one for 60 Hz. The 60 Hz motor will run 20% faster than the 50 Hz motor, and to keep the Purifier bowl speed the same the Velocity Ratio for the drive from a 60Hz Motor will have to be 20% less.
If you are running on a 50 Hz supply and use parts from a 60Hz drive chain, the purifier will run too slowly to work, if you have a 60Hz supply and use a drive chain designed for 50Hz the bowl will over speed by 20% and will be liable to explode due to excessive centrifugal force.
Second question, did you use every single seal and "O" ring in the intermediate kit? The only one left over should be the one for operating as a Clarifier bowl, rather than as a purifier.
Third question, what temperature are you purifying the oil at? It should be 95 Celsius for a 4 stroke engine or 90 C for a slow speed 2 stroke. (98 C for HFO). The oil should be recirculated, through the heater, until it reaches this temperature, before admitting it to the purifier.
(Also, when shutting down the purifier the oil should be recirculated through the heater until it goes cold, to prevent the oil overheating and carbonising in the heater.)
Fourth question have you checked that all the water supply filters are clean and flow is unrestricted and that the operating water pressure is correct according to the makers manual, are any orifices fitted "Original Equipment Maker's parts" and the correct flow rate? Many modern separators have precisely controlled water pressure and precision flow control orifices to deliver a precise amount of water in a certain time, so that all the quantities of water delivered can be controlled by a computerised timing system.
Because the bowl sealing water tends to evaporate at the temperatures Lubricating Oil and HFO are purified at, there is usually a timer that will automatically add a small quantity of "top up" sealing water at short intervals, again see your maker's Manual for full details.
Fifth question have you thoroughly cleaned all the water spaces including the drilled passages through the bowl?
Sixth question have you checked the oil flow rate is that recommended by the Makers Manual? Too high a flow rate can cause loss of seal and also means that less dirt is removed from the oil, because the "Dwell Time" in the bowl is less.
If all the mechanical points above are correct, then start to compare the programming of the values in the operating system against the values in the makers Manual, in case some idiot has changed these.
Please let us know how you get on, and good luck.
It is always better to ask a stupid question than to do a stupid thing.