A genset water separator removes free water and coarse solids before the fuel reaches the fine filter, and the grade of that first stage decides how long the injection pump lasts. Tesla Power specifies a 30 micron coalescer ahead of a 10 micron final filter. This guide shows how to pick both grades before you request a quotation.
- Water reaches a tank as condensation, so a half-empty tank collects more of it than a full one.
- A 30 micron coalescer drops free water out; a 10 micron final filter protects the pump but cannot separate water.
- Drain the bowl before every start on a standby set, and weekly on a prime set.
- State the tank and the fuel source on the enquiry, and the frames in the export frame range come with the right filter head.
What does a genset water separator remove from the fuel?
It removes free water and particles above its rating, and it does nothing about dissolved water or water held in emulsion. Free water is the drop that collects at the bottom of the bowl, and it is the fraction that damages a pump, because water has no lubricity and the plungers score within hours. Particles above 30 micron are the ones that block the final filter early. Tesla Power writes the figure into the offer line so the basis travels with it.
The separator also acts as a settling chamber. A coalescer element forces small droplets to merge into large ones, and the large ones fall out of the flow into the bowl. A centrifugal head does the same job with a spinner and no element, which suits dirty fuel and a site that cannot buy elements. Both are called a water separator, and the two behave differently in service. Most genset manufacturers ship a coalescer head as standard, and Chinese genset suppliers often fit it after the lift pump instead of before.
How much water does a tank collect in a year?
A tank breathes as the fuel level moves, and each breath brings in air with its humidity. A 1,000 L tank that cycles between half and full twice a week moves about 40 m³ of air a year, and at 30°C and 70% relative humidity that air carries roughly 0.9 kg of water. Most of it leaves with the next breath, and the part that condenses settles at the bottom.
Work the case at 1,000 L and 60 L/h, against the fuel specification in the ISO 3046-1 consumption basis. A 320kW set burns 67 L/h, so the tank turns over about once every 15 hours of running, and a standby site running 50 hours a year turns it over three times. A prime site running 4,000 hours turns it over 270 times, and the water that settles each cycle accumulates faster than the drain interval on most maintenance sheets assumes. At 0.8 power factor that 320kW figure is a 400kVA frame, which is the size most of these tanks serve.
| Duty | Tank turnovers a year | Water expected at the bowl | Drain interval |
|---|---|---|---|
| Standby, 50 h/year | 3 | Under 20 mL | Before each start |
| Prime, 2,000 h/year | 130 | 150-300 mL | Weekly |
| Prime, 4,000 h/year | 270 | 300-600 mL | Twice weekly |
| Bulk tank, 20,000 L | 13 | 200-400 mL | Weekly, plus polishing |
Which filter grade belongs at each stage?
Put a 30 micron coalescer first and a 10 micron final filter second. The first stage takes the water and the coarse dirt, and the second protects the pump clearance. Reversing the order blocks the fine element with water and dirt, and a fine element that has absorbed water stops passing fuel altogether. Yangzhou Tesla Power states the ambient and the altitude beside the rating.
Some builds use a 10 micron first stage and a 5 micron second, which protects a common rail pump better and costs more to run. The choice follows the pump rather than the engine size: a common rail system with tight clearances needs the finer first stage, and a mechanical pump is happy with 30 micron. Ask which pump the engine carries before fixing the grade.
Coalescer or centrifugal: which suits a site?
The coalescer removes water down to a lower level and needs an element change, while the centrifugal head removes free water and dirt without an element and leaves the fine filter to do the rest. A site with clean delivered fuel and a sealed tank does well with a coalescer. A site that fuels from drums, or from a bowser that has carried other products, does better with a centrifugal head that cannot be defeated by a saturated element.
The cost difference sits in the consumables. A coalescer element is changed once or twice a year and the bowl is drained often. A centrifugal head has a rotor to clean at the same interval and no element, so a remote site with no supply chain is easier to keep running. A genset for a drum-fed site therefore does better with the centrifugal type, whatever the fuel cleanliness claims. Neither removes dissolved water, and neither replaces a settled tank.
How often should the bowl be drained?
Drain before every start on a standby set, because a standby set sits for weeks and the water has time to settle into the bowl. Drain weekly on a prime set, and twice weekly where the tank cycles more than once a day. The bowl has a drain screw at the bottom and the water sits below the fuel, so a few seconds of flow shows the change from water to fuel. Tesla Power reads that figure on the site sheet before the plate is printed.
Drain into a clear container rather than onto the floor, because the volume tells you something. A bowl that yields 200 mL a week has a tank problem, and a bowl that yields nothing for a month on a prime set has a separator that is not working. Record the volume on the service sheet, and the trend is more useful than any single reading. A genset for standby duty needs the drain at the start rather than at the end of a run, because the water has settled by then.
What happens when water reaches the injection pump?
The plungers and the delivery valves score, and the pump loses delivery pressure at low speed first. The engine then idles roughly and starts hard when cold, and the fault reads as a governor problem until someone drains the filter. A common rail pump is less tolerant again, because the clearances are tighter and the pump runs at a higher pressure.
The repair is a pump overhaul rather than a filter change, and the cost is a large multiple of the separator. That arithmetic is why the first stage matters more than the second, and why a site that fuels from drums should fit the best separator it can rather than the cheapest. The 500kVA silent set with the ATS option carries the sensor as standard for that reason. A genset water separator on a drum-fed site earns its price in one avoided pump.
Where does the separator belong on the circuit?
Fit it after the tank and before the lift pump, on the suction side, so the pump draws through the element rather than pushing into it. A separator on the pressure side works but cannot be drained while the set runs, and the bowl has to hold the full pump pressure. Most engine makers put the first stage on the suction side for that reason. A genset water separator on the pressure side also cannot be drained while the set runs, which is the practical argument against it.
Leave 200mm below the bowl for the drain and a container, which sounds trivial until a separator is fitted at floor level and nobody can get a cup under it. Fit isolation valves on both sides so the element can be changed without draining the line, and mount the head so the bowl is visible from the service door. A bowl that needs a torch and a mirror is a bowl that gets skipped.
What does the factory check before shipment?
The test bay runs the set for two hours at load with a separator fitted and records the vacuum at the filter head, because a separator that is too small shows as a rising vacuum before it shows as a fault. A clean assembly reads under 0.05 bar, and a reading above 0.15 bar means the head or the element is restricting the flow.
Our bay also checks the bowl for leaks under vibration, since a bowl that weeps at the drain screw is the most common complaint on the first service. Tesla Power Equipment fits the drain screw with a sealing washer rather than an O-ring on export sets, because a washer survives a site that overtightens. The test sheet records the vacuum and the leak check together, and the factory and the test bay keep it with the order file.
How should the enquiry state the fuel supply?
State four items: the tank size, whether fuel arrives by pipeline, tanker or drum, the expected running hours a year, and whether the site can buy filter elements locally. The four decide the separator type and the spares kit, and the spares question is the one that decides whether a remote site keeps running.
Send the four with the load list to the export desk, and the reply carries the separator model, the element part numbers and the drain interval written into the service schedule. The site planning notes carry the same four items as a form, and Tesla Power sends a spare element with every set so the first change does not wait on a purchase order.
What does a water-in-fuel sensor add?
It turns the drain from a habit into an alarm, and a habit fails when the crew changes. The sensor sits in the bowl and closes a contact when water reaches the electrode, and the controller then displays a warning or shuts the set down depending on the setting. On an unmanned standby site the shutdown is the safer setting, because the alternative is a pump running on water. The monthly test in the NFPA 110 routine is where the sensor is proved, and a sensor nobody has tripped is a sensor nobody trusts.
Fit the sensor on any set above 200kVA and on every set that runs unattended. The cost is small against the pump, and the wiring is one pair back to the controller. A site that keeps the sensor but ignores the alarm has the same fault as a site with no sensor, which is why the alarm belongs in the monthly test rather than only in the manual. Tesla Power keeps the reading beside the load record rather than in a covering letter. The same frame appears in the 400kW frame on the Weichai WP13 platform, where the plate states the same basis.
Frequently asked questions about genset water separator
It can where the two share a day tank and a common suction header, and each engine then needs its own final filter. Size the separator for the combined spill flow rather than the combined burn, because the spill is what actually passes through it.
It removes free water and not the water that a blend absorbs, because a biodiesel blend holds more dissolved water than diesel. That water drops out when the fuel cools, so a blend needs a separator and a settling tank rather than a separator alone.
The water sits at the bottom and looks darker and clearer than the fuel above it. A drain into a clear container shows the boundary at once. Some bowls have a level line moulded into the side, and the line is the figure to watch.
Usually because the tank is shedding mill scale or the fuel is carrying wax at low temperature. A new tank blocks the first element within weeks and then settles. Wax blocking happens below the cloud point, and the answer is a heater rather than a coarser element. A genset in a cold store sees wax before it sees water, so the heater is the first purchase.
Not in every case. A pre-filter strains dirt and may have no water bowl at all. A separator has a bowl and a drain, and the bowl is what makes it a separator. Check the head before assuming the two are the same.
It can, and it then has to hold the pump pressure and cannot be drained while running. The suction side is the better position and the one most engine makers specify. Fit it there unless the engine drawing says otherwise.
Any water that reaches the element is too much, so drain before the bowl fills to the element base. A bowl that fills within a week points at the tank rather than the separator, and the tank then needs draining and polishing.
The genset CE marking requirements cover the assembly, and the fuel circuit including the separator sits in the technical file. Conformity assessment for the assembly checks that the fitted separator matches the drawing. Tesla Power lists the element part number in the file so a replacement can be traced.