Dangerous Liquids

A dangerous liquid is classified by the Coast Guard as hazardous when transported in bulk.

Regulations

The Coast Guard has detailed hazardous materials in Table 30.25-1 and Table 151.05, Title 46 of the CFR (Code of Federal Regulations).

CFR Role

The CFR implements laws set by Congress, allowing enforcement agencies, like the Coast Guard, to create and enforce regulations.

Unit of Measurement

• Barrel: Standard measurement in the industry. 1 barrel = 42 US gallons at 60°F.

• Kirby's Barge Identification System: The first two digits denote approximate barrel capacity in thousands. The last three digits provide further identification, with the letter "b" indicating a box-shaped barge.

Design of Inland Tank Barges

• Overall Shapes: Inland tank barges come in 3 basic shapes for efficient multi-barge towing.

• Bow Barges: Positioned at the front to reduce resistance (rake facing forward).

• Box Barges: Located in the center of the tow for easier makeup.

• Stern Barges: Positioned at the back where the towboat pushes.

• Integrated Tow: Efficient configuration combines box barges between the bow and stern.

• Goosenecks: Attached to the upper part of the cargo tank, goosenecks facilitate the connection of cargo lines and help in the handling of liquid transfer during loading and unloading. They are designed to ensure a smooth flow without sharp bends that could impede the movement of liquids. Goosenecks also often include equipment attachments for hoses or pipes that must be able to withstand pressures from tank contents and environmental conditions.

Hull Structure

• Main Body: The hull provides flotation and consists of six structural components:

  • Bottom Plate: Runs underneath the barge to provide stability and support.

  • Sides: Extend along the length from bow to stern, contributing to the strength and integrity of the hull.

  • Transom: Crosses the stern side-to-side to form a watertight seal at the back of the barge.

  • Bow Rake Compartment: Empty space forward of cargo tanks to enhance buoyancy.

  • Headlock: Connects the rake bottom to the bow rake deck, allowing for drainage and fluid management.

  • Knuckle: Curved steel plating where surfaces meet, providing structural reinforcement.

  • Decks: Flat surfaces forming the top of tanks, serving as working surfaces for equipment and crew.

  • Bulkheads: Upright partitions separating compartments for improved stability and safety.

  • Frames: Provide strength to support plating, bulkheads, and decks with additional support where needed.

  • Wing Tanks: Auxiliary tanks located on the sides of a vessel's hull, used to increase stability and buoyancy. They can also serve as additional storage for liquids, such as ballast water or fuel, thereby enhancing the distribution of weight and improving the handling and performance of the vessel.

Cargo Tank Details

• Cargo Tank: A barge compartment for liquid cargo, designed to handle specific liquid types and pressures.

• Expansion Trunk: Raised portion of the tank above the deck that allows for the expansion of liquids due to temperature changes.

• Tank Dome: Extension for monitoring and accessing cargo levels during loading and operations. The tank dome usually contains hatches for inspections and sampling.

• Framing Types: Internal framing results in smooth decks ideal for operational efficiency; external ribs support walkways and safety measures over the cargo tanks.

• Construction Materials: Primarily mild carbon steel is used, but other materials may be required based on the specific properties of the cargo being carried, such as corrosion resistance.

Principles of Cargo Containment

• Primary Containment: Includes bulk liquid cargo tanks and piping systems designed to hold liquid cargo securely, also managing vapor containment related to the cargo.

• Secondary Containment: Aimed at enclosing liquid that escapes primary containment, incorporating features like drip pans, spill rails, and containment dikes to prevent environmental contamination.

Hold Types and Regulations

• Hull Type 1: Maximum preventive measures for very dangerous cargoes (e.g., phenl, acetone).

• Hull Type 2: Significant preventive measures for dangerous liquids and gases (e.g., acrylonitrile).

• Hull Type 3: Moderate control for less hazardous products, typically single skin constructions.

Cargo Tank Types

• Integral Tanks: Part of the vessel's hull, ensuring structural integrity and reducing potential flexing during transit.

• Independent Tanks: Installed separately from the hull, minimizing flexing and allowing for cleaning or repairs without affecting the hull structure.

• Gravity Tanks: Designed for liquid cargoes carried without pressure (up to 10 psi) which depend on gravity to move the liquid cargo.

• Pressure Tanks: Designed for transporting liquids under pressure, with robust materials and structural reinforcements that ensure the integrity of the cargo is maintained during transit and handling, suitable for materials needing higher containment measures to prevent vapor release.

Special Design Features

• Coffer Dam: Void space to prevent inter-tank contamination during bulkhead failure; must be gas-free.

• Drip Pans: Required for tank barges carrying oil or hazardous material, with a minimum capacity based on hose diameters to collect spills or leaks.

• Venting Systems: Tanks must be equipped with vents for pressure regulation (minimum diameter: 2.5 inches) to allow gases to escape during loading and unloading.

• Emergency Pressure Vacuum Relief Valves: Open automatically to relieve pressure and balance vacuum conditions; essential for maintaining tank integrity and preventing potential ruptures. For grade A B and C cargo.

• Gooseneck: A vent; curved pipe or fitting that comes out of the top of the tank, stops rain and seawater from entering the tank.

• Flame Screens: Devices fitted to vent openings of tanks that prevent potential ignition sources from entering, significantly reducing the risk of explosion or fire during transport. To be placed on P/V valves, goosenecks and when venting cargo tanks through an open hatch

Ballasting and Deballasting

• Definition: Process of taking in/out seawater for stability, critical for maintaining the proper trim and balance of the barge during transit.

• Types of Tanks:

  • Clean Ballast Tanks (CBT): Former oil tanks cleaned for ballast use.

  • Segregated Ballast Tanks (SBT): Dedicated tanks for carrying ballast water that do not mingle with cargo tanks to prevent contamination.

• Ballast Pumps: Separate from cargo pumps, necessary for ballast operations to control the inflow and outflow of ballast water efficiently.

• Stability Considerations: Inland barges typically manage stability through careful loading and cargo distribution, ensuring a safe transport environment to avoid capsizing or excessive rocking due to uneven weight distribution.