Centrifuge filters: when the separator is due for attention
The centrifugal separator is a mature, class-approved technology, and on many ships it is mandatory. But it is costly to run, and it does not catch everything. If your separator is due for an overhaul or replacement, that is a natural moment to work out what it should be complemented or replaced with. Here is an honest overview.
What the centrifuge does well
A purifier separates free water continuously and without an upper limit, and it removes the heavy, coarse particles. For fuel treatment of residual fuel (HFO) and for system oil on HFO-fuelled engines, the engine manufacturers prescribe separator operation. There, the centrifuge is not up for discussion.
What it costs to run
Separation requires heat and rotation. When treating heavy fuel, the oil typically has to be heated to around 98 °C, and the bowl is driven by an electric motor in continuous operation. On top of that comes fixed, manual maintenance: industry sources state manual bowl cleaning roughly every 500 operating hours, plus scheduled overhauls beyond that.
The separator also produces sludge, which has to be stored on board and discharged ashore. With HFO operation, the industry reckons that 1 to 3% of the fuel quantity ends up as sludge.
What it physically cannot catch
A centrifuge separates by density. Contaminants close to the oil's own density therefore stay in the oil: soot, oxidation residues and the precursors that over time turn into varnish. The finest solid particles also pass through. That is exactly the range depth filtration is built for.
Complement: a fine filter alongside the separator
The separator stays in place and handles bulk water and the coarse particles. An offline depth filter runs in a kidney loop alongside it and removes fine particles, soot and varnish. The combination is well documented in the industry, and it requires no changes to the existing installation.
Replacement: possible in some systems
For lube oil on auxiliary engines and on engines running on distillate (MGO/MDO), established suppliers in the category now document that a fine filter can take over from the separator. The same applies to smaller vessels without heavy fuel, where the separator is often oversized for the task.
And in the systems where centrifuges have never been standard (stern tube, thrusters, gearboxes, steering gear and hydraulics), offline filtration is already the normal choice.
Where offline filtration cannot replace the centrifuge
- Fuel treatment of HFO: the flow rates and sludge quantities are far beyond what cartridge-based systems are built for.
- System oil on HFO-fuelled engines: the engine manufacturers' requirements call for separator operation, and departing from them is a warranty and insurance matter.
- Constant, heavy water ingress: a cartridge has a finite water capacity and cannot match continuous water separation.
If one of these points applies to your installation, we will tell you before we go any further with the numbers.
An established market, and where we stand in it
Offline fine filtration for ships is an established market, and the category has been documented over decades. Our contribution is Delta Xero: compact systems with filtration down to 0.1 µm, where the cartridge is the only wear part. Whether it is the right choice for your installation depends on the numbers, and we are glad to work through them with you.
Have a technical conversation
If service or replacement is coming up, call76 20 80 10. Please have the system volume, operating hours and service costs to hand, and we will work out complement and alternative together.