Yachting Monthly - April 2016

technical

84 http://www.yachtingmonthly.com APRIL 2016

Reasons to be paranoid about fuel

(2,000 bar) on HPCR engines,

with some as high as 40,000 psi

(2,700 bar). Predictions are that

pressures may go as high as a

staggering 60,000 psi (4,000

bar). These kinds of pressures

require orifice sizes, clearances

and machining tolerances to

within 1-3 microns, where a

micron is a millionth of a meter.

To put this in perspective, a

European standard, ISO 4406.

But even if fuel supplies from a

refinery meet the ISO standard,

typical contamination levels in

fuel tanks and at primary filters

have been found to be ten times

higher than the ISO target. In

point of fact, HPCR engines

require a fuel cleanliness at the

injection pump and injectors

that is up to one hundred times

lower than the ISO target and

one thousand times lower than

common tank contamination

levels in the real world. This

represents a major challenge for

the fuel filtration industry.

Traditional fuel filter elements

are not adequate for HPCR

systems. What is more, the

filtration industry does not

currently have particle counters

(or laboratory test dust) suitable

for calibrating instruments below

4 microns – in other words, the

smallest particle detection and

counting level is above the size

of the most damaging particles

for HPCR systems! Discussions

are under way to, among other

things, revise international

standards to account for

‘Changes to emissions rules are having

profound consequences for boat owners’

human hair is around 80 microns

thick; the human eye can detect

objects down to about 40 microns.

Fluids at these pressures are

capable of acting like water jet

cutters, especially if there is

even microscopic hard particle

contamination in the fuel. The

result is scoring and abrading

of critical injection pump and

injector components. For

conventional (low pressure) fuel

injection systems the critical

particle size to initiate abrasive

wear is about 6-7 microns. With

HPCR injection, the critical particle

size is approximately 2-3 microns.

Absolute fuel cleanliness is

essential to engine life.

Inadequate standards

As long ago as 1998, engine

manufacturers developed the

Worldwide Fuel Charter (WWFC)

to define minimum diesel fuel

cleanliness levels based on a

PHOTO: Nigel Calder

PHOTOS: Nigel Calder

Nigel’s fuel sampling

pump, used to take a

sample from the base of his

fuel tank after refuelling

This fouling in Nigel’s own fuel system was caused by the solvent properties of biodiesel, which dissolved

‘gunk’ out of a fuel-supplier’s tank and completely plugged the suction line and primary filter