Practical Compliance With Latest USCG and IMCO REGULATIONS
The introduction of IMCO regulations, last amended in 1978, and the publication of USCG regulations, September 1979, require that all ships calling on U.S. and IMCO nations' ports will be required to comply with these regulations by the specified dates.
In the U.S. this date is June 1, 1981. IMCO will be implemented two years after ratification, however, several member nations have already required implementation. For new ship construction, the regulations are specific and compliance offers no particular problem since initial ship designs will integrate the required changes. However, for existing ships, compliance requires complex modifications. The regulations allow several options for compliance, which gives the operator some leeway. For example, for tankers over 70,000 dwt, the owner has the option of converting the ship to a segregated or clean ballast tanker or installing a crude oil washing system in the cargo tanks. Obviously, economics will direct the approach. The most difficult portion of this will be to predict accurately the future utilization of the ship, i.e.: trade routes, charters, guaranteed pumping rates, fuel costs and fuel availability. However, in order for timely compliance with regulations decisions must be made based upon best estimates. This paper outlines some of the methods which can be utilized, which factors are important and how to best comply with the regulations.
The regulations apply to all ships in the applicable tonnage categories. However, ships other than tankers can usually comply with minor additions of equipment and modifications.
The Intergovernmental Maritime Consultative Organization (IMCO) has published standards and regulations which form the basis of the U.S. as well as each member nation's regulatory policy. The U.S. regulations are nearly identical to those of IMCO and are published in the Code of Federal Regulations and are administered by the U.S. Coast Guard.
Alternatives Existing tankers over 40,000 dwt must have either Crude Oil Washing (COW) or Segregated Ballast Tanks (SBT). Clean Ballast Tanker (CBT) is allowed until June 1, 1985 for 40,000 to 70,000-dwt crude carriers or until June 1, 1983 for 70,000-dwt crude carriers. This allows an operator to plan future modifications for the newer ships or a planned phase-out of older ships.
For existing VLCCs or ULCCs, there usually is an obvious choice of only COW. Most of the more modern ships already have a COW system installed even though it probably does not meet IMCO or USCG requirements. To upgrade an existing COW system is usually the best alternative.
Those ships with no COW system are more difficult to convert to COW, especially tankers with deepwell pumping systems. Additionally, ships with COW systems must have an Inert Gas System (IGS). Should an existing ship not have IGS, the additional cost of an IGS installation may direct a different approach. It is imperative that before a decision is made for each vessel, a complete economic analysis be performed which includes the trade routes, cargo revenue and operating costs as well as conversion options. In each case, the life expectancy of the ship and the guaranteed pumping rate of the charter are additional factors to consider.
System Selection Owners of vessels in the charter business (and fleet operators) are interested in modifications which will not affect the charter rate of the vessel and which will allow the vessel to operate in a variety of trade routes and have the capability to carry different types of cargo on different voyages. The time frame in which these modifications can be carried out is also very important. The USCG date may affect the vessel's operation in an existing charter. The law allows no provisions for granting extensions to these dates for compliance with the regulations. Recent amendments to the regulations, from the November 1980 IMCO meeting, allow owners to switch the trade of the vessel, i.e., from a product carrier to a crude carrier, without recertification. This allows an owner to operate a vessel in the crude trade on one voyage and in the product trade on the return leg of the voyage without recertification. Under these conditions, a ship must comply with the ballast system regulations for each trade.
Ballast Systems A permanent ballast system is an alternative to meet the regulations. The ballast system consists of designated tanks and associated piping systems to carry ballast only, and all other remaining tanks are used for cargo.
The selection and arrangement of tanks for ballast use is primarily based on the amount of ballast needed to meet the draft and trim requirements of the regulations and the size and the number of tanks on the vessel. These requirements, along with the vessel's bending and shear limitations, determine the possible ballast tank arrangement. It is apparent that a vessel with a large number of tank divisions will have more possible tank arrangements available.
The final arrangement of tanks can be based upon the alternatives of pumping and piping arrangements and the trade in which the vessel will operate in the future. This arrangement must be submitted to regulatory bodies for approval.
There are basically two types of ballast systems, clean ballast tanker and segregated ballast tanker. It should be noted, however, that a CBT system is a means of compliance for a temporary period of time.
In a clean ballast system, it is possible to isolate one of the existing cargo-oil pumps and suction lines such that it may be used for ballast. This may require small piping modifications both in the cargo tanks and in the pump room. The modifications will consist of connecting and breaking pipe connections and installing valves for the double valve isolation. The disadvantage of this system is that the cargo pumping capacity will be reduced with one pump used for ballast. This arrangement will, however, accommodate cargo pumping and ballasting operations simultaneously. A segregated ballast system will require the installation of an additional pump specifically designated for ballast service. Placement of the new pump is dependent on available space in the pump room and/or machinery space. With a pump located in the pump room and its driver in the machinery space, a new ballast main is installed through the cargo tanks. This new ballast main services the designated ballast tanks. Any existing cargo lines servicing the designated ballast tanks will be removed or blanked.
The owner also has the option of installing a pump and driver in the machinery space. With the pump in this location, a main line can be run to the upper deck servicing the ballast tanks. It should be noted that the use of line blinds for segregation of ballast from oil is not acceptable. A positive break in the system is required with stored spool pieces which would be used for specific emergencies.
Crude-Oil Washing Crude-oil washing is another alternative for compliance with the regulations.
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structure of the cargo tanks to remove the waxy asphaltic deposits that build up from the voyage. The tank-cleaning machines used in these operations either have a programmed pattern or have a selective program option to the pattern. The tank-cleaning machines are supplied by a main line that is connected to the discharge side of the cargo pumps, either in the pump room or on the upper deck (sometimes supplied from the cargo manifolds).
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So if you want a ship put in shape, come to Sun Ship. We've got what it takes to get the job The number and placement of the COW tank-cleaning machines is determined by the computation of shadowed areas in the tanks. Shadows are those which do not receive a direct impingement from the tank-cleaning machines. The amount of shadowed areas allowed, as stated in the Regulations, is 10 percent for horizontal surfaces and 15 percent for vertical surfaces.
As essential to the satisfactory placement of COW tank-cleaning machines is the design and installation of a tank stripping system which is capable of maintaining the tank bottom free of standing oil during the tank cleaning operation. It has been the practice of many owners to increase the tank stripping capability of the vessel. An increased capability in the tank stripping system will allow for the simultaneous operation of a greater number of tank-cleaning machines, thereby reducing total tank cleaning cleaning and terminal time.
One application utilizes a constant- pressure regulating valve to reduce any pressure surges that may be caused by stopping the tank-cleaning machines. Also, the use of this valve may decrease the terminal time of the vessel due to additional shore discharge of cargo which is not needed for COW operations.
On the ballast leg of the voyage, the clean-ballast-designated tanks are crude washed and water rinsed prior to receiving clean ballast. Dirty ballast (departure and/or emergency) is discharged in accordance with the regulations without regard to tank washings.
Inert Gas Systems The Inert Gas System require- ments of the regulations requires modifications to the system. An inert gas system directs flue gas from existing boilers (or from an inert gas generator) through a scrubber unit, blower, and pressure regulating valve to suitable distribution piping located on the upper deck. A deck water seal is also included in the system. The IGS system must maintain an oxygen content of less than 5 percent in gas.
One major area of importance in the design of the system is the consideration of what type of materials should be used for the components in the system. This is due to the corrosive nature of the gas. Some owners have opted to use reinforced thermosetting resin type piping in the distribution system. It should be noted that the use of this piping has not yet been approved by all regulatory bodies.
Another major concern is that the system is designed to maintain a positive pressure in the cargo tanks, e s p e c i a l l y during cargo pumping and COW operations. The venting arrangement is extremely important.
Costs and Conclusions The following costs for modifications of existing ships can be used as a guide in estimating future modifications. Each ship will be different due to its particular configuration.
Inert gas installations, for existing tankers, are in the vicinity of $1,000,000 per ship for a 100,- 000-dwt crude carrier.
Crude oil wash system installation for a 280,000-dwt crude carrier should cost $600,000 to $1,000,000. However, most recently constructed VLCC and ULCC vessels have an existing COW system which probably does not meet regulatory body requirements. A typical modification requiring additional fixed deck machines, some submerged machines, new piping and a modified s t r i p p i n g system would cost $300,000 to $400,000.
For a deepwell-pump-type tanker, the cost will increase due to the necessity of providing improved stripping capability.
For existing tankers, 150,000- dwt, installation of a segregated ballast tank system with new piping, a new pump and electrical modifications might cost $500,000 to $600,000. For an 80,000-dwt tanker, the modification of an existing system to a dedicated clean ballast tank system, including isolation of one of the existing cargo pumping systems for use in the CBT, will cost approximately $150,000.
It is then obvious that the costs are considerable and are an important factor in the decision of which approach to take. However, it is imperative to evaluate the entire regulatory requirement and operational profile as well as the expected life and utilization of each ship before undertaking the modernization of the ship.