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COMMON SENSE IN BUNKER FUEL SELECTION AND TESTING

by Dr. R. (Vis) Visweswaran

Analytical Services & Materials, Inc.

Hampton, Virginia U.S.A.

"The crown of all faculties is common sense. It is not enough to do the right thing;

it must be done at the right time and place. Talent knows what to do;

tact knows when and how to do it."

- William Mathews

 

Common sense is not such a commonly available commodity!

Every day in ship operations, one is required to make decisions. Though a lot of data is made available to make those decisions, mere numbers cannot dictate decisions. An undercurrent of common sense, previous experience, and general feel for the situation are the factors that will dictate the decisions. Some of the items on which decisions have to be made are listed below. Common sense solutions are provided for the guidance of the ship manager. These are based on the many years of experience of the author on all three aspects of the bunker-user (ship’s engineer), impartial observer (surveyor), and analyst (lab in charge). It is hoped that this common sense approach will be useful for practical situations that arise in ship operations. These are only suggestions, not recommendations. Obviously, decisions have to be based on actual situations.

 

COMMON SENSE CONCERNS IN

BUNKER FUEL SELECTION AND TESTING:

1. Choose 180 Grade or 380 Grade? Are there real benefits in 180 Grade that warrant paying $5/ton additional price?

2. Should the user go with oil majors and pay $3 - $5/ton more, or is it better to go to smaller players - bunker brokers?

3. If bunker fuel does not meet specs, what to do -- reject/throw out -- How far out of spec can be tolerated?

4. Costs of testing and not testing.

5. How reliable are lab results? Why do different labs put out different results?

6. What on-board treatment can solve bunker fuel problems?

The above concerns are discussed below.

GRADE 180 OR GRADE 380?

Difference:

Grade 180 - 7-15% distillate content

Grade 380 - 2-5% distillate content

Price of grade 180 is at least $3 - $5 more than grade 380

Why Choose 180?

Engine Maker recommendation

Perception that 180 is better than 380

 

AS&M Experience:

Sulphur More of the 180 grade samples (0.7%) had more sulphur than 380 grade

Si + Al More samples (0.5%) of grade 180 had more Al + Si than samples of grade 380

Na + V More (1.5%) samples of grade 180 were nearer to the undesirable 1:3 ratio of sodium and vanadium than these of grade 380.

EFN EFN or Engine Friendliness Number is a computer-generated index, developed by AS&M, that provides a unique method of assessing quality of individual bunker supply, and gives fuel users better insight into how fuels will perform in service. Based on a scale of 1-100, the lower numbers represent less engine-friendly fuels which are nearer to the upper end of specification limits, and the higher numbers approaching 100 indicate more engine-friendly fuels which are nearer to the lower end of the specification limit.

Based on hundreds of samples received at the AS&M lab, it is clear that grade 380 is more engine-friendly than grade 180.

But the perception of many ship managers is that grade 180 is a better fuel and they are therefore willing to pay a higher price to get an inferior fuel. (This argument assumes that the engine manufacturer permits the use of both grades of fuel in the engine.)

 

ECONOMICS OF TESTING:

 

Say a vessel bunkers 8 times per year.

Annual cost per ship - AS&M Program: 8 x $250 = $2000

Say you bunker 1000 tons each time: @ $100 per ton

Total bunker cost is 8 x 1000 x 100 = $800,000

Testing cost as a proportion of bunker cost = 1/400

Testing cost as additional cost on a ton of bunkers = $100.25, i.e. 25 cents more per ton

 

 

Say ship operation cost is $8,000 per day --

Bunker test cost per day = 2000 = $5.5

365

Bunker test cost as proportion of operation cost: 5.5 = 1

8000 1500

 

CONCLUSION: TESTING COST IS A PITTANCE, AND THE QUESTION IS

NOT IF YOU CAN AFFORD TO TEST, BUT CAN YOU AFFORD NOT TO TEST!

COMPARISON: OIL MAJORS VS. BUNKER BROKERS

ITEM

OIL MAJOR

BUNKER BROKER

Share of the market for bunker supply in 1982

Oil majors, 54.2%

Bunker brokers, 45.8%

Share of the market for

bunker supply in 1993

Oil majors, 27.8%

Bunker brokers, 72.2%

Price for bunker

$4 - $5 more than bunker

broker price

(competitive price)

Supply services

Better (where available)

Varies, but available everywhere

Testing

Tested in their own lab

Tested in any lab of convenience

Warranties on quality of fuel

More customer-friendly

Likely to be stringent

Disputes

Less likely

More likely

Dispute resolution

Can be more protracted

Compromise more likely

Fuel quality

Knows exactly what he is supplying

Broker himself may not know and this may result in some undesirable fuel supply

 

 

COMMON SENSE IN BUNKER PURCHASE

1. Buy 380 grade if engine manufacturer permits use of this grade

2. Do test, it costs only 25 per ton of fuel

3. Try out only a reputed bunker broker and also test the fuel; you may save a few dollars per ton compared to what you pay to an oil major.

LIMITS BASED ON COMMON SENSE:

How Much Out of Spec Can Be Tolerated?

The table below lists the various parameters and their values, as specified by the various grades of bunker fuel. The question is, how much out of specification can be tolerated? Here are some suggestions:

 

Problem

Limit

Suggestion

Remarks

High Density

Limit 991

Extend to 996 if water <0.5%

Operate as clarifier

heat and settle and drain

High Viscosity

180 at 50C

380 at 50C

225 at 50C

475 at 50C

Tank heating, fuel heating should be effective. At injection temp. viscosity difference is very low.

High Water

1%

Extend to 3%-5%

Related to density and whether it is salt water or fresh water

Carbon Residue

15%

Increase by 20%, i.e. 18% carbon residue

Do this for only one voyage. Inspect exhaust passages.

Ash

0.1%

25% higher, i.e. 0.13

Purify continuously. Oil soluble elements V, Zn, Mg cannot be reduced. Al, Si, Fe can be. Salt water in fuel increases ash.

Aluminum & Silicon

80 ppm

100-120 ppm

Further purification can reduce it.

Vanadium

300 ppm

Increase 20%, up to 360 ppm

Do this for only one voyage -- watch for Na:V ratio of 1:3.

Total Sediment

0.1%

0.2%

Limits of precision of the test method allow this

Sulphur

5%

--

Limit rarely crossed

CCAI

850

870

Usually a problem with high density -- low viscosity fuels.

Used lube oil contamination

 

 

 

 

Expect emulsions if water is present in fuel. Expect transfer of metallic particles into engine.

STANDARD SPECIFICATIONS:

HOW MUCH OUT OF SPEC CAN BE TOLERATED?

The standards give ranges for "out of specification" under two categories:

Repeatability - defined as the variance in results when the same sample is tested in the same lab, using the same method, by two different analysts.

Reproducability - defined as the variance in results when the same sample is tested in two different labs, by two different analysts, using the same method.

A single-lab system is preferable, where the quality can be maintained within much tighter limits. ASTM has criteria for repeatability, and is 2-3 times more stringent than reproducability. In other words, for example, pour point can vary only within 3C in the same lab (repeatability) while in two different labs, it can vary as much as 6C (reproducability). Density in the same lab can vary .0006 kg/m3 (repeatability) whereas in two different labs it can vary by .0015 kg/m3 (reproducability). If you want the highest quality, you must test the fuel in only one lab.

 

FACTOR

REPEATABILITY

REPRODUCABILITY

Density

0.0006

0.0015

Viscosity:

ASTM

1.3% of mean + 8 cSt

4% of mean + 8 cSt

 

 

ISO

0.35% of mean

0.7% of mean

Water

0.1 or 2%, whichever is greater

0.2 or 10%, whichever is greater

Carbon residue

(%C)2/3 X 0.077

(%C)2/3 X 0.245

Pour Point

3C

6C

Sulphur

0.017 (X + 0.8)

0.055 (X + 0.8)

Ash

0.001 to 0.0079

0.080 to 0.0180

 

0.003

0.007

 

0.005

0.024

Aluminum

Silicon IP-377

0.066x

0.0643x

0.337x

0.332x

Sediment:

 

for residual

for distillate

0.123 times square root of x

0.048 times square root of x

0.341 times square root of x

0.174 times square root of x

x = average value

SHIPBOARD FUEL TREATMENT SYSTEMS:

Bunker fuel as received at custody point is the bunker fuel that gets into the engine. What can shipboard treatment do? Every ship has considerable capability for fuel treatment onboard, and these well-known facilities are listed below, along with suggestions for imaginatively combining the facilities to obtain the desired fuel treatment:

• Heat the fuel, settle it, drain the water

• Purify it, remove water and heavier particles

• Clarify it and remove solid particles

• Two purifiers in series (remove excess water)

• Two clarifiers in parallel

• Various filters

• Heaters and automatic viscosity controllers

• Routine draining of water and particulates from service tanks

• Compatibility and stability tests

• Shipboard test kit

• Fuel additives

• Blending fuels on board

 

It is hoped that the above analysis will help generate decisions that make sense; common sense!

mailto:#customerhelp@viswalab.com

 


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