Page 7: of Maritime Reporter Magazine (October 1971)

The Application Of Super Barges

For Distributing Petroleum Products

Super Barges Are Becoming An Important Part Of The Distribution

System For Petroleum On The East And Gulf Coasts. They Can Compete

Economically With Handy-Size Tankers On All But The Longest Runs.

Adrian S. Hooper*

Generally speaking, those of us engaged in offshore barging spend a great deal of time, effort and money on research and develop- ment of hull forms for barges and tugs.

In towing a large barge it is nec- essary to be sure that the barge will follow the tugboat on a true course under all weather condi- tions, light and loaded. Since tlhe writer's company prefers not to ballast the barge on the ballast voyage, it is extremely important that in this light condition the barge remains on a stable course in high winds and avoids structural damage in heavy seas.

Although much has been done in this field, we find experts disagree- ing on fundamentals. The writer's company assisted in the funding of a study for the determination of an optimum seagoing barge design at the University of Michigan. The paper, "Design Considerations and the Resistance of Large, Towed,

Seagoing Barges" by J.L. Moss and Corning Townsend III, was submitted to The Society of Naval

Architects and Marine Engineers in September, 1967. However, since that time hull designs for seagoing barges that have been built would not be recognizable in the study.

For our 31,000-ton barges, seven separate stern models were con- structed and tested prior to final determination.

Hull form is important since barges are inherently slow. An in- crease of half a knot is a mucih higher percentage increase than with a ship making IS knots.

The seagoing tugs required to handle these barges are deep draft with high horsepowers, watertight bulkheads, monitoring systems for engine-room equipment, back-up electrical systems, twin screw and are constructed under American

Bureau of Shipping rules. The tugs have radio-signal systems with anchoring devices on the barges that automatically drop the barge's anchor. There are back-up systems for towline pick-up and back-up systems for anchor con- *Mr. Hooper, president, Interstate Oil

Transport Company, presented the pa- per condensed here before the 16th

Annual Tanker Conference of the Cen- tral Committee on Transportation by

Water of the Division of Transportation of the American Petroleum Institute held in Ponte Vedra Beach, Fla. trol. In short, these vessels are seaworthy, safe and practical and they are a product of research and development for the use intended —towing large barges at sea at designed hull speed.

Growth Of Barging

For the purpose of this discus- sion, we have set an arbitrary minimum size of around 80,000 barrels or about 10,000 dwt for the barges. Also, the barging consider- ed is coastwise and ocean barging and bears little relationship to river barging.

Our prime interest should be how present day and future barges will affect petroleum distribution as it now relates to tankers. As to the maximum size of barges, there is no known physical limitation.

There are reasons why we would not rush out and build a 300,000- ton barge, but there is no reason why it could not be built.

The writer feels that sheer size in itself is not what we are striv- ing for but rather an optimum, economically feasible vehicle to serve the industry on a particu- lar path of tlhe product's journey to the ultimate consumer.

Pushing at sea using the so- called conventional method with cables where there is no "mechani- cal connection" has been successful in moderate seas. There is little question about the advantages of pushing.

So far the Coast Guard has ap- proved only one mechanical push- ing system for operation on the 'high seas. This is the Breit-Ingram

System. The system was approved acknowledging the cargo-carrying unit as an unmanned seagoing barge and the tug as a self-propel- led motor vessel over 300 gt and subject to inspection, certification and appropriate manning require- ments.

In recent months additional re- search into mechanical methods of pushing at sea has been somewhat restricted. The writer's company has had to completely re-evaluate the extensive and costly testing done in the Netherlands Sihip Mod- el Basin due to the uncertainty of the regulations pertaining to me- chanical linkage systems. As the interpretation of regulations are put into workable perimeters, much more will be accomplished to improve the technology of tug- barge linkage.

Economics

Perhaps the least thought of cost advantage and yet one that should have a significant place in a ship- per's determination of transport methods is the probable increase in escalating costs. This becomes an important input for projecting one's future position in a market.

Many ships operating in coastwise trade today are operating on costs determined by depreciated values and their ratio of operating costs to fixed cost should be a barometer in considering future needs.

The barge industry is working from a high base. Super barges are all relatively new with a high book value so that the ratio of fixed cost to total is presently high, in- dicating that rate increases due to unpredictables would not neces- sarily be shockers.

The moment you make compari- sons on a new for new basis, the cost of capital or fixed-capital in- vestment comparison is changed.

However, on a new for new basis capital required per deadweight ton is over twice as much for ship construction as for combination barge-tug, unless the barge system is designed for the potential of ob- taining ship speed, then construc- tion costs are comparable with ships and the major saving be- comes one of crew costs only.

In order to quantify the advan- tages of large barges in this trade, an analysis was made of four new hypothetical vessels, namely, a 31,- 000-dwt barge and tug unit and a 30,000-dwt tanker, and a 20,000-dwt 3.0 2.5 2.0 1.5

COST OF CAPITAL 1.0

AOMIN.& GEN.

INSURANCE

HULL, P&l CARGO 0.5

M&R STORES & SUPPLIES

CREW barge unit and a tanker of equal deadweight, operating between

Houston and various East Coast ports.

A simple deterministic model was made to generate the Required

Freight Rates starting with a typi- cal cross-"Gulf trip (Houston to

Tampa) and then for a series of greater distances in increments of 100 nautical miles up to maximum of 2,500 miles between ports. The latter distance covers the entire range of ports from Texas to Port- land, Me.

Tug and barge performance cri- teria is based on our average ex- perience with equipment of this size as are capital and operating costs. Ship costs and criteria were harder to obtain and, consequently, the data used is a compromise of information dbtained from ship- owners, shipyards and various ref- erence sources. It should be noted that we have not attempted to de- velop actual freight rates. We have tried to objectively compare the relative economic advantages of barges versus self-propelled tankers of equivalent deadweight.

Fixed operating costs are shown in Chart 1. Freight rates assume unlimited demand and are based on cargo on one leg only and 100- percent vessel utilization. A weath- er factor was applied to the design speeds, which in the case of the two barges ranged from five to seven percent, depending on dis- tance and, in the case of the tank- (Continued on page 11)

Chart 1—Fixed operating expense (annual average). 30000 DWT

TANKER 31000 DWT

BARGE & TUG 20000 DWT

TANKER

October 1, 1971 9