Heavy Fuel Conference Report: Bergen, B&W, Krupp MaK, B&W Alpha, Pielstick, Sulzer, ACBL, Operators' Viewpoint And Modern Diesel Power

[continued] that time some shipowners found it advantageous to use intermediate fuels (IFO) on their auxiliary engines.

Since then the number of engines equipped for IFO operation has increased every year, and at the present time about 80 percent of Bergen's annual engine production is sold for IFO operation. There are today approximately 320 Bergen Diesel engines, totaling 2,700 cylinder units, commissioned for IFO operation.

The majority of the 210 generating engines and a fairly large number of the propulsion engines which are in operation worldwide have to accept the wide variety of fuel qualities available.

Experience has shown that, provided Bergen's recommendations for fuel treatment, engine temperatures and load levels are met, overhaul times and wear figures generally did not alter significantly compared to marine diesel fuel operation.

Representatives of B&W Diesel, Inc. presented a paper on "The Low-Speed Diesel and the Future Energy Scenario." The authors spoke of the current B&W Diesel engine program which is based on the all-fabricated design which was introduced with their K-GF engines in 1973. Because of the oil crisis in 1973 and the subsequent demand for increased propulsion efficiency, B&W decided to develop a slower running version of this series.

Due to the uniflow scavenging system of the B&W engine, the slower turning of the propeller could be obtained for the same output by increasing the stroke of the engine.

With the introduction of constant-pressure turbocharging in 1978 and the improved turbocharging efficiency, the exhaust-valve timing was modified such that, at the same maximum cylinder pressure and at the same mean indicated pressure, a more favorable cylinder process was obtained. An increase in thermal efficiency and a lower thermal load was obtained.

This led B&W to the next logical step, which was that of further utilizing the built-in power reserve by increasing the mean effective pressure by 12 percent and the speed by three percent. At the same time, the maximum cylinder pressure was increased by about five percent.

B&W two-stroke engines have in principle been designed to burn all commercial grades of heavy fuel, limited by only a few guiding parameters, mainly related to the handling of the fuel oils.

B&W has systematically investigated for the past three years the effect of such so-called future fuels on a test engine, a two-stroke crosshead uniflow-scavenged engine and in fact, found indication that such fuels will not cause appreciable difficulties.

Hugo Fiedler, Krupp MaK Maschinenbau GmbH, spoke on the "Prospects of Medium Speed Four-Stroke Diesel Engines in View of Future Fuel Problems." This paper reports on investigations by Krupp MaK in the low-quality fuel field. Prospects for lowering of fuel consumption and possibilities of maintaining low maintenance costs in spite of increasing difficulties are discussed.

The general feeling has been that high engine speed might result in difficulties in burning heavier and less combustible fuel components on account of less time for combustion. Consequently, Krupp MaK looked for various fuels representing future parameters as close as possible and investigated the influences on combustion and thermodynamics, deposits on the combustion chamber and neighboring area as well as on the general engine performance and lubricating oil contamination.

The tests proved that even engines running at speeds as high as 1,000 rpm provide enough time for complete combustion. This means that a diesel engine will be able to run on any kind of liquid fuel if designed according to requirements.

Extensive lubricating-oil contamination tests have shown that there is of course an increase of lube-oil contamination when changing from gas oil to lighter intermediate fuels but even bunker fuel of 700 cST viscosity has not given any additional contamination in the upper load range.

If designed and developed according to requirements and equipped with modern fuel processing, medium-speed four-stroke engines are capable of coping with all liquid fuels to be on the market for shipping in the future.

A paper on "Alpha Propulsion Systems Intermediate Fuel Oil Recommendations" was presented by representatives of B&W Alpha Diesel Engines. This paper pointed out that during the past few years the number of B&W Alpha Diesel medium-speed engines operating on intermediate fuels have increased considerably. An earlier paper of B&W Alpha predicted that fuel qualities would deteriorate, resulting in increased demands on diesel engines and on the fuel handling systems, and that fuel prices would continue to rise, making intermediate fuel more attractive. Both of these predictions have come true.

These developments have affected the design of diesel engines, and the safe operation on intermediate fuels is today a main design feature of B&W Alpha Diesel engines.

Also, since that earlier paper, quite a few changes have taken place. The specification of the recommended fuels has been altered, the main idea being not to specify viscosity as this parameter only defines the necessary preheating and has nothing to do with quality. On the other hand, commercially available fuels are identified by their viscosity.

The main problem today with regard to intermediate fuel operation is no longer to make the engine burn the fuel, but to clean the oil before it is injected so as to avoid excessive wear of the engine.

J.F. Chapuy of S.E.M.T. Pielstick spoke on "Heavy Fuels and PA.6 Ship Propulsion Engines." As early as 1953, S.E.M.T., using the alkaline reserves of detergent oils, showed that in spite of having no positive separation between the combustion chamber and the crankcase, medium-speed engines could burn heavy fuel. Thus, the use of lubricating oils with a high total base number has made heavy fuel almost traditional for Pielstick PC type engines since 1960.

However, high-speed engines running at 1,000 to 1,500 rpm generally remained out of the heavy-fuel-burning area, mainly because of fears of difficulties with the injection system and combustion process, and the consequences on engine operation. The PA.6 model, with its rating of 400 bhp per cylinder, was investigated from the beginning to burn high-viscosity residual fuel.

From the start, good results were obtained with a four-cylinder PA.6 test engine running at 1,000 rpm which had aggregated over 10,000 hours by November 1979 on several fuels of 3,500 sec. Redwood No. 1, viscosity of 380 cST at 50°C.

At the present time, over 300 engines of the PA.6 type have been ordered with more than half of them already in service. Sixty-six engines are running in continuous service on heavy fuel (out of 44 as main propulsion units) and have accumulated roughly one million operating hours.

G.A. Lustgarten, Sulzer Brothers Limited, described "Recent Developments on the Sulzer AS25-Engine." He stated that heavy-fuel operation is economical for a high-speed four-cycle engine like the Sulzer AS25 engine only if certain requirements concerning maintenance and fuel quality as well as its treatment are taken into consideration.

The author also stated that heavy fuel oils with low impurity level (roughly equivalent to intermediate fuel IF 30) allow operation close to the economic optimum, taking into account fuel and maintenance costs, plant availability, etc. Poorer fuel grades can be used economically only under very favorable operating conditions. In general, higher total maintenance costs have to be accepted when burning poor quality heavy fuels.

Further, the fuel treatment and lube-oil filtration are exceptionally important to heavy-fuel operation. Correct layout of the installation is just as decisive as the engine design.

If the specified requirements are met, heavy-fuel operation is an economically attractive solution.

R.P. Spock and J.E. Nivin of American Commercial Barge Line Company, gave an overview of "The ACBL Blended Fuel Program."

In early 1980, the rapidly increasing price of fuel was approaching 50 percent of the operating costs for the ACBL fleet of over 60 vessels. At this point, management decided that it should look seriously at various methods to reduce fuel consumption. As a result of preliminary discussions concerning blended fuels, it was decided to call a meeting to thoroughly discuss the subject with an oil company, engine supplier and shipyard representatives. This meeting was held in June 1980 and included Shell Oil Company, Alco Engine, ACBL and Jeffboat representatives.

The philosophy of ACBL and Jeffboat was to develop a fuel-handling system which could be adapted to the standard 145-foot boat with a minimum of change and make the system flexible enough so that the main fuel tanks could hold 2-D later if the blended fuel was unavailable or the price difference made it uneconomical to use blended fuel.

The final scheme selected basically was: when the vessel is operating on blended fuel, the fuel is drawn from the unheated main bunker and preheated in a sump external to the main tank. From there, the fuel goes directly to the fuel heating package or "HOPS" unit as ACBL refers to it. In the HOPS unit, the fuel is strained and then pumped into the loop by a positive displacement pump. From there it passes through a heat exchanger which utilizes engine jacket water as a heating medium. Following further filtration, the fuel goes through a regulating valve and on to a three-way valve system that is used to select the correct routing of the fuel. Controls built into the system also evolved from this meeting and are designed to provide an automated system.

ACBL is enthusiastic about the benefits to be gained from using blended fuels. They anticipate being able to recover the additional cost per vessel within a year, so thereafter, they will have flexibility to make use of that fuel which provides the most economical operation.

John G. Lynch, Mayank Jain and Deepak Varshney spoke on "Selecting Heavy Fuel Engines—The Operators' Viewpoint." This article is an informal summary on some advantages and disadvantages of heavy-fuel engines. Specifically, the investigation involves tugboats/towboats and the comparison between non-U.S. built medium-speed (500 to 900 rpm) diesel engines of 2,400 hp, operating on heavy fuels, and U.S.-built engines in the same range presently on the market, operating on 2-D oil.

While most engine manufacturers claim to be able to operate on bunkers equivalent to No. 6 oil or Bunker "C", in reality there is very little, if any, long-term operating experience involving medium-speed diesels in the lower horsepower range burning bunkers with a viscosity greater than 180 centistokes at 50°C (1,500 sec. RW1 at 100°F). The state-of-the-art for smaller engines seems to be in the intermediate fuel level, IF 60 to IF 80. This is the fuel oil most manufacturers would recommend for continuous duty in towboats or tugs; it also seems to be the economic break-even point between higher capital costs and reduced operating costs.

Whether the dilemma of rising operating costs can be solved totally or partially by utilizing heavy fuel oil can only be answered by each individual owner or operator. An important consideration is that, while heavier fuel oil may be the economic answer to a vessel owner's problem, it will also be the cause of maintenance and engineering problems. It is, however, apparent that increasingly volatile fuel costs will play a more prominent role in the future selection of tugboat and towboat engines.

William Smith, vice-president of Modern Diesel Power, Inc. of New Orleans, La., presented an interesting account of a retrofit performed at Bender Ship Repair Inc., Mobile, Ala., on the towboat Great America, owned by the Great America Boat Company.

The vessel was fitted with two S.E.M.T. Pielstick engines, model 12VPA6 280, that develop 3,600 bhp each and which were supplied by Modern Diesel Power. Basing his remarks on his experience with the engines and the repowering of the vessel, Mr. Smith explained the reasons for vessel design changes and described benefits expected from the first use of the French-built engines on the Mississippi River. Both Modern Diesel Power and the Great America Boat Company are owned by the Smith family.

Mr. Smith explained the decision to retrofit was made for several reasons. It is faster than constructing a new vessel and provides a practical demonstration of engine performance in actual river operations in a vessel with an existing record of previous performance for comparison.

The engines burn heavy diesel fuel No. 5 — approximately 600 Redwood Sec. I—which, Mr. Smith contended, along with engine efficiency, will achieve significant savings for the operator, Bunge Towing. The Great America once held the record for barge towing on the Mississippi — moving 62 barges from New Orleans to Cairo, Ill.

The new Pielstick engines will drive 117-inch-diameter stainless-steel propellers in new Kort nozzles through Falk model 3548 reverse/reduction gears at 900 rpm.

In addition to the engine retrofit, other work was done on the towboat. Thought to have a draft problem, it was discovered by Bender Ship Repair officials that the Great America actually had a trim problem that could not be solved with existing tank arrangements. To solve the problem, Bender changed the tanks around completely. In addition, the center of gravity of the vessel was changed with the new machinery, producing an acceptable draft on the Mississippi River. The towboat has also been fitted with sophisticated monitoring equipment to measure fuel use, engine wear, and vessel efficiency, Mr. Smith noted.

For further information and copies of the above presentations, write the appropriate number on the Reader Service Card:

ACBL ("The ACBL Blended Fuel Program") — write 50; Alfa-Laval, Inc. ("Recommendations for Pretreatment and Cleaning of Heavy Fuel Oil") — write 51; B&W Alpha Diesel ("Alpha Propulsion Systems Intermediate Fuel Oil Recommendations") — write 52; B&W Diesel ("The Low Speed Diesel and the Future Energy Scenario") — write 53; Bergen Diesel ("Bergen Diesel Engines Operating on Intermediate Fuels") — write 55; Krupp MaK Maschinenbau GmbH ("Prospects of Medium Speed Four-stroke Diesel Engines in View of Future Fuel Problems") — write 56; Mobil Oil Corporation ("Trends in Marine Fuel Quality and Economics That Will Affect U.S. Medium-Speed Diesel Operators") — write 57; Modern Diesel Power (Repowering the Great America) — write 58; S.E.M.T. Pielstick ("Heavy Fuels and PA.6 Ship Propulsion Engines") — write 59; Sulzer Brothers, Ltd. ("Recent Developments on the Sulzer AS25-Engine") — write 60; "Selecting Heavy Fuel Engines — The Operators' Viewpoint" by Messrs Lynch, Jain and Varshney — write 61.