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 (ships 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?
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
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
Bunker test cost as proportion of operation cost: 5.5 = 1
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
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:
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 3°C in the same lab (repeatability) while in two different labs, it can vary as much as 6°C (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.
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
Heaters and automatic viscosity controllers
Routine draining of water and particulates from service tanks
Compatibility and stability tests
Shipboard test kit
Blending fuels on board
It is hoped that the above analysis will help generate decisions that make sense; common sense!
Copyright © Viswa
Lab Corporation All rights reserved.