Sludge discharge and poor ignition are but some of the potential headaches that shippers must contend with when burning 0.5% sulfur fuel oil, industry bodies said in an Aug. 19 statement, following a survey on new fuel rules since Jan. 1.

“The industry had widespread experience with how to manage heavy fuel oil, and the survey provides insight into which parameters of the new fuel types are posing the biggest challenges for onboard fuel management,” Christian Baekmark Schiolborg, manager, marine environment at BIMCO, said in a statement.

Ships burning fuel on the high seas cannot emit more than 0.5% sulfur in their exhaust as of Jan. 1 2020, as mandated by the International Maritime Organization. Previously, the limit was 3.5%.

“Since fuel oil properties are fluctuating, it is expected that quality and safety problems will continue to be a challenge for the global shipping industry,” according to the statement.

Industry bodies BIMCO, the International Chamber of Shipping, INTERCARGO and INTERTANKO published the results of the survey, which focuses on the problem properties of IMO 2020-compliant 0.5%S FO. The survey was conducted between Feb. 24 and May 6.

“The survey focuses on potential problems such as increased sludge discharge, clogging of fuel pipes, preheaters, fuel separators and fuel filters, fuel pumps getting stuck, problems with fuel injection and poor ignition of fuel oil,” they said in the statement. “It also focuses on other issues regarding incomplete combustion, wax appearance and increased wear and tear of cylinder liners. These are problems that may lead to loss of propulsion and/or black out.

“The survey indicates global challenges with fuel characteristics and limits being off specifications most frequently when it comes to total sediment, aluminium plus silicon, pour point, ash, flash point, acid number and viscosity."

The most common operations problems are increases in sludge deposits and wax appearance after switching to 0.5%S FO, according to the survey.

The survey showed that sulfur content is the most likely parameter to be breached when tests are run on commercial fuel oil samples.

Variable contents

Very low sulfur fuel oils tend to be a blend between residual and distillate products, and need more consideration on how they are stored, transferred and handled, Steve Bee, group commercial & new business development director at fuel testing company Veritas Petroleum Services, told S&P Global Platts.

"If the fuels are not stored correctly and above the wax appearance temperature, the [paraffinic] wax [from the distillate component] will start to precipitate out of the fuel."

Travel restrictions during the height of the coronavirus pandemic saw demand for road and aviation fuels hit harder than shipping fuels as freight operations remained ongoing.

This increased the variety of choice of blend components within 0.5%S FO.

“We saw overall densities and viscosities becoming lower in VLSFOs from March through to June, which indicates they have been blended with lighter materials,” he said.

Handling question

Chevron Marine Lubricants cautioned that it is the way the fuel is used that is important. "While newer ships do not have a problem using [VLSFO] fuels, engines already closer to an overhaul did struggle sometimes," Luc Verbeeke, Chevron marine lubricants senior engineer, said in a whitepaper by the company published Aug. 17. "Cylinder units that could have run for another six months or a year on HSFO did not survive the tougher conditions with the new fuels."

The reason for difficulties in older engines was the calculated carbon aromaticity index, which measures the ignition qualities of the fuels, according to the report. Most VLSFOs have a lower index than HSFOs.

"In the period leading up to 2020, several operators cleaned their fuel tanks by using fuel additives or diesel oil that flushed high sulfur waste through the fuel system -- effectively using their engines as an incinerator to burn off the waste," according to the report.

"Some of these engines failed pretty quickly and this will potentially also have a longer-term effect," Verbeeke said. "All the cat fines and sludge that were in the tank were put through the engine.

"The fact that reports of scuffing have since declined to usual levels suggests that the industry has now come to terms with the procedures it needs to operate safely and reliably with VLSFO," according to the report.