Diesel generator biodiesel blend changes three things: the filter life, the cold flow and the oil change interval. Read how far the blend may go before the order, and Tesla Power will return a quotation with the approved fuel written into the handover file.
- Ask which blend the engine maker approves, because the cold flow figure on the fuel decides the winter start.
- Check the filter interval, since a blend loosens deposits that the first tanks carry to the filter.
- Watch the oil, because a blend that reaches the sump thins it without any alarm.
- Keep the fuel certificate, because a claim about a failed pump starts with the batch.
What does a diesel generator biodiesel blend change?
The blend changes the fuel rather than the engine, and the engine meets it through three systems. The filter catches what the blend loosens, the injection pump seals meet a solvent that mineral diesel does not contain, and the lubricating oil absorbs whatever passes the rings. Each of the three has a limit, and the limit is set by the blend share rather than by the fuel brand.
The most visible change is the filter, and it is the first thing most diesel generator manufacturers warn about. Fatty acid methyl ester, the part of the blend that comes from oil rather than from crude, dissolves deposits that mineral diesel leaves on the tank wall over years. The first few tanks of a blend therefore carry that material to the filter, and a site that changes the filter on the usual interval blocks it instead. The first month is the filter month, and the schedule should say so.
Which blends are approved for an export set?
Three bands cover most orders, and the engine maker states the band rather than the fuel name. Up to 7% is the standard European road blend and needs no change to the set. Up to 20% is approved by most makers with a shorter oil interval and a watch on the filter. Above 20% needs a fuel system built for it, and most export frames are not.
The ISO 8528-1 rating classes say nothing about fuel, so the approval comes from the engine maker's sheet rather than from the set standard. That is why the band belongs in the order rather than in the commissioning note, and why a site that changes supplier mid-year can move outside its approval without any hardware change. The fuel grades behind the bands follow the ISO fuel classification rather than a national road standard. Tesla Power writes the approved band on the handover sheet.
| Blend share | Approval on an export set | What changes |
|---|---|---|
| up to 7% | Standard, no change | Nothing beyond the normal schedule |
| up to 20% | Approved with conditions | Oil interval halved, filter watched |
| 20% to 100% | Needs a built fuel system | Seals, lines and a heater |
| any blend, stored over 6 months | Not advised | Water pickup and microbial growth |
Worked example: 500kW on a B20 blend
Take a 625kVA frame at 500kW, which is 0.8 power factor, burning a 20% blend. The calorific value of the blend sits about 5% below mineral diesel, so the engine burns more of it for the same output. A frame that uses 100 L/h on diesel uses about 105 L/h on the blend, and 105 × 8 = 840 L covers an eight hour shift.
The tank then needs a margin it did not need before. A day tank sized for 900 L holds one shift on diesel with 60 L to spare, and holds the same shift on the blend only if the figure is read at the blend rather than at the diesel. Tesla Power Equipment states the consumption at the fuel the site names, so the tank and the delivery plan are sized on the right number.
Why does FAME attack the fuel system?
Because it is a solvent rather than a lubricant, and the pump relies on the fuel to lubricate its own internals. Mineral diesel leaves a film on the plungers and the distributor. A blend carries that film away and, at a high share, delivers less lubrication than the pump was built for. The wear appears as a falling delivery pressure rather than as a leak.
The seals are the second point. Natural rubber and some older elastomers swell in the presence of ester, and a pump built for mineral diesel can weep at the shaft after a season on a high blend. Most makers changed the seal material years ago, and a frame built for export carries the compatible set. Ask which material the pump uses rather than which blend it takes, because the two answers belong together, and Tesla Power states both on the offer.
- Filter interval halved for the first three months on a blend.
- Oil analysed at the first service rather than at the book interval.
- Pump seal material named in the order.
What does cold flow do to a blend?
It raises the point at which the fuel stops flowing, and it does so differently from mineral diesel. A blend cloud point sits higher than the diesel it replaced, and the paraffin that forms is finer and blocks a filter faster. A site that ran through winter on diesel can block a filter on the same blend at the same temperature.
The answer is a winter grade rather than a heater in most cases, because the fuel is easier to change than the system. A diesel generator in a cold store needs the cold filter plugging point stated on the delivery note, and the figure belongs beside the ambient on the site sheet. A blend bought on price alone carries whatever cold flow the batch happened to have.
How does storage change with a blend?
A blend absorbs water and holds it, where mineral diesel lets it settle to the bottom of the tank. The water then sits in suspension, and the boundary between fuel and water becomes a place where microbes grow. That growth forms a mat that blocks filters and, in a bad case, corrodes the tank from the inside.
The practical limit is about six months in a bulk tank and less in a warm climate. A standby site that fills the tank once a year is the worst case, because the fuel sits long enough for the water to accumulate. A diesel generator for a standby set belongs with a rotation plan and a water drain at each inspection, and the fuel storage notes set out the rotation interval.
Which records belong in the fuel file?
Four records turn a fuel decision into something a warranty can be read against. The delivery certificate with the blend share, the cold flow figure for the batch, the filter change dates and the oil analysis results are the four. A site that keeps the certificate and nothing else has kept the one document that proves the fuel rather than the one that proves the maintenance.
The oil analysis is the record that catches a problem early, because it shows dilution before the level on the dipstick moves. Most diesel generator manufacturers will provide a certificate of analysis on request, and Chinese diesel generator suppliers often provide a batch number without the analysis. Tesla Power asks for the certificate before the frame is released, because a fuel claim without one is read as a maintenance claim.
What goes wrong on a B20 site?
The first failure is a filter blocked in the first month, which is the deposit the blend loosened rather than a fault in the set. That change belongs on the handover schedule. The second is oil that thins past the grade, which shows as low pressure at idle after a long run. Both are cheap to fix and both are read as engine faults when they appear without a record.
The third is a tank that grows a microbial mat over a year of standing. That one is expensive, because the tank has to be cleaned rather than the filter changed. A site that runs the set every week moves the fuel and keeps the water dispersed, and a site that runs it twice a year does not. The water separator notes cover the hardware, and the range of frames we build lists the fuel system each size carries.
How is the fuel written into the order?
Diesel generator biodiesel blend for a site visit goes on the order as a band rather than as a brand, and the band is repeated on the handover sheet. The engine maker's limit, the cold flow figure and the oil interval belong beside it, so a site that changes supplier can check the new fuel against the same three lines. A band written as a brand name cannot be checked at all, and Tesla Power states the band on the order confirmation.
A frame ordered for a high blend also carries a different filter and, in some sizes, a fuel heater, Those items are cheaper at the factory than at the site, and they are the ones a buyer forgets when the fuel decision is made after the order. The fuel band belongs on the enquiry, and the answer changes the specification rather than only the note.
Frequently asked questions about biodiesel blend
Only with a fuel system built for it. Pure ester attacks the pump and the seals of a frame designed for mineral diesel, and it gels at a higher temperature. Most export frames are approved to 20% and no further, and the engine maker's sheet states the band.
It reduces the energy in each litre rather than the rated output. The engine delivers its plate figure and burns more fuel to do it, so the tank and the delivery plan change rather than the rating. A site budgeting from diesel consumption should add about 5% for a 20% blend.
At half the usual interval for the first three months, then at the normal interval once the tank is clean. The first change is the one that matters, because it catches the deposit the blend loosened from the tank wall. Keep the old element until the new one runs clean.
It does when the blend sits outside the approved band or the fuel has no certificate. A claim read without a fuel record is read as a maintenance claim, and the maker decides on the evidence rather than on the fuel. Keep the certificate with the service file, and Tesla Power asks for it before a claim is opened.
They mix, and the resulting share is somewhere between the two, which means nobody knows the figure. A site that receives a 7% delivery into a tank holding 20% has an unknown blend rather than an average one. Empty the tank or accept the uncertainty in writing.
It changes the cold flow requirement rather than the blend share. A warm site can burn a higher share in summer and the same site needs a winter grade in January. State the lowest ambient the site sees, not the average.
Write the blend band, the lowest ambient and the storage period on one page, and send it to our export desk. Yangzhou Tesla Power returns the fuel specification and the filter schedule with the quotation. The diesel generator biodiesel blend CE marking requirements sit in the technical file rather than on the plate, and conformity assessment for the assembly follows the same route as for a mineral diesel frame, so one file covers either fuel.