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Bunker Oil Flow Meter DN15: Fuel Supply Optimization for Marine Boilers
Quick Answer
For marine boilers burning heavy fuel oil (HFO) or low-sulphur fuel oil (LSFO), a DN15 Coriolis mass flow meter delivers direct mass flow measurement of bunker oil without the drift that affects turbine meters when viscosity changes. Silver Instruments supplies a DN15 Coriolis meter with an accuracy of ±0.2% of rate, 4-20 mA HART output, and PED certification for auxiliary boiler fuel lines. Send us your operating temperature (typically 120-150 °C for HFO), pressure (bar), and pipe schedule, and we will recommend the right meter body and transmitter.
The Real Problem with Bunker Oil Measurement on Small Lines
A DN15 fuel line seems simple. Most engineers assume a small positive displacement meter or a turbine meter will work. In practice, bunker oil at 380 cSt or 500 cSt behaves very differently from diesel. When a boiler starts up from cold, the fuel in the line is still thick. A turbine meter will under-register because the rotor does not spin freely. Once the tracing steam or electric heating jacket brings the oil to 130 °C, the viscosity drops to around 10-20 cSt. The same meter now reads high because the clearance leakage changes. You end up with an unaccounted fuel difference between the bunker tank sounding and the boiler log. On a Panamax vessel burning 2-3 tonnes per day in the auxiliary boiler, a 3% error over a 45-day voyage is real money. We have seen this on customer sites many times, especially on vessels that switch between HFO and LSFO in emission control areas.
Positive displacement oval gear meters can handle viscous fluids. But bunker oil often carries small abrasive particles from cat fines or sludge. Over time these particles wear the gears. The meter then needs frequent recalibration or replacement. Worse, a DN15 oval gear meter has small clearances that can clog if the fuel is not perfectly filtered.
Why a DN15 Coriolis Meter Changes the Game
A Coriolis mass flow meter measures mass directly. It does not care if the viscosity is 500 cSt or 5 cSt. It does not care if the fuel temperature shifts from 30 °C to 140 °C. The meter output is in kg/h or tonnes per day, which is exactly what the chief engineer needs for the oil record book and for monitoring specific fuel oil consumption (SFOC).
Silver Instruments supplies a straight-tube DN15 Coriolis meter specifically for small bore fuel lines. The wetted parts are 316L stainless steel. The meter has no moving parts that can wear from abrasive particles. The secondary containment is rated to 100 bar, which covers the typical fuel supply pressure of 20-40 bar after the booster pump. For auxiliary boilers on product tankers or bulk carriers, this meter fits directly into the fuel supply line without requiring flow straighteners or upstream pipe runs. The process connection is usually ½ inch NPT or DN15 PN40 flanged. Because the meter body is compact (about 300 mm face-to-face), it fits into the confined skid space next to the boiler front.
Installation Details from the Field
Last year a Singapore-based ship management company contacted us about retrofitting fuel meters on six auxiliary boilers across their fleet. The boilers were Aalborg OC-TCi units, each with a single burner firing 70-120 kg/h. The existing setup used a small turbine meter that required quarterly cleaning and gave erratic readings when the fuel temperature dropped below 100 °C.
We recommended our DN15 Coriolis meter with integrated PT100 temperature sensor. The transmitter was mounted remotely on the boiler control panel to avoid the high radiant heat. The output was 4-20 mA HART with a pulse output for the fuel consumption counter. The key detail that most engineers skip is the zero calibration at operating temperature. We advised the crew to flush the meter with hot fuel for
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Signal Integration and Boiler Control
The 4-20 mA HART signal from the Coriolis transmitter connects directly to the boiler management system (BMS) or the vessel’s integrated automation system (IAS). The mass flow value feeds into the combustion control loop. For a fixed air-fuel ratio, the burner management system uses the actual fuel mass flow to trim the combustion air damper or fan speed. If the fuel switches from HFO to LSFO, the mass flow reading remains accurate because the meter is immune to density changes. The density output from the Coriolis meter, usually in kg/m³, gives the operator a quick check on the fuel grade in the line. A reading of 980 kg/m³ indicates heavy fuel, while 860 kg/m³ suggests marine gas oil. This secondary information helps prevent fuel mismatches that can damage the boiler refractory.
For vessels targeting Energy Efficiency Existing Ship Index (EEXI) compliance, fuel mass flow data is essential. The data can be logged on a paperless recorder or sent via Modbus RTU to the ship’s performance monitoring system. Silver Instruments offers a compact display unit that shows instantaneous flow rate, totalised mass, and temperature on one screen. The display is IP66 rated and runs on 24 VDC from the ship’s auxiliary supply.
Cost Comparison and Sizing Notes
A DN15 Coriolis meter has a higher upfront cost than a small turbine meter. There is no way around that. But over a five-year period, the total cost of ownership often favours the Coriolis. The absence of mechanical wear means you are not buying replacement internals or paying for off-hire recalibration. On a vessel with dry docking every 2.5 years, the savings in maintenance labour alone can offset the difference.
When you request a quote, give us the minimum, normal, and maximum flow rates. A typical auxiliary boiler on a 50,000 DWT tanker burns about 80 kg/h at normal load and can spike to 150 kg/h during startup. Our DN15 Coriolis meter handles a range of 0 to 200 kg/h for HFO with a pressure drop below 0.1 bar at normal flow. If your load is consistently above 250 kg/h, we would step up to a DN25 meter to keep the pressure drop low.
FAQ
Can a Coriolis meter handle the high viscosity of cold HFO?
Yes, the measurement principle is independent of viscosity. However, you must heat the fuel enough to pump it. The meter body itself does not add significant pressure drop at viscosities up to 1,000 cP.
Is the meter approved for marine use?
Silver Instruments Coriolis meters carry PED certification and can be supplied with classification society certificates from DNV, ABS, or Lloyd’s Register on request. The transmitter housing is available in Ex d IIC T4 for Zone 1 hazardous areas on tankers.
What maintenance does a Coriolis meter require?
There are no moving parts to service. We recommend checking the zero point every 12 months and inspecting the meter tube integrity during dry dock. If the fuel is heavily contaminated, install a Y-strainer upstream to protect the meter from large particulates.
Can I use the same meter for both HFO and diesel oil?
Absolutely. A Coriolis meter measures mass flow regardless of the fluid. No recalibration is needed when switching fuels. The density reading helps confirm which fuel is flowing.
How do we order a DN15 bunker oil flow meter from Silver Instruments?
Send us your fuel type, operating temperature and pressure, process connection type, and required certificates. We will prepare a datasheet and quotation. Address your email to [email protected] or use the inquiry form on flow-meter.com.au. Include the boiler maker and model if available, as this helps us confirm the physical envelope fits your installation.
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