This chapter provides guidance regarding the requirements for the assignment of load lines as well as the closely related topic of maintenance of watertight integrity. Both items are extremely important to vessel safety in that they are designed to prevent conditions of overloading and/or down flooding that could lead to vessel loss.
Since the assignment of a load line to a vessel is almost universally done as part of the original construction or major conversion of a vessel, the material contained in this chapter serves mainly as background information to the operator. However, it is important that vessel operation conforms to load line restrictions and maintains vessel watertight integrity as identified and discussed herein.
The regulations regarding load lines and watertight integrity vary depending on the type and service of the vessel; however, under USCG requirements, the substantial majority of vessels in the UNOLS system will require a load line.
This chapter also provides information on stability and watertight integrity for vessels not required to have load lines because of their service or size. Such information may be of particular use to institutions chartering smaller, uninspected craft to support oceanographic research operations. A list of references is presented in section 2 of this chapter.
The basics of the load lines requirements are effectively addressed and summarized by a publication of the U.S. Coast Guard’s Naval Architecture Division entitled “Load Line Regulations.” Significant sections of this article, which is available on the Coast Guard’s web site at http://www.uscg.mil/hq/g-m/mse/mse2-loadlines.htm have been reproduced below.
LOAD LINES: Load line marks are affixed to vessel side shell plating amidships and indicate the maximum drafts to which the vessel can be lawfully loaded in several different maritime venues. These load line marks are also related to freeboard. The distance at the side of a vessel measured vertically from the edge of its “freeboard deck” to the upper edge of a particular load line mark represents “statutory freeboard”.
LOAD LINE CERTIFICATE: Domestic load line certificates are issued by the American Bureau of Shipping (ABS) on behalf of the Coast Guard.
International load line certificates for U.S. vessels, in accordance with the International Maritime Organization (IMO) International Convention on Load Lines (ICLL), are issued by the American Bureau of Shipping (ABS), or the vessel’s classification society (if approved by the Coast Guard).
The Coast Guard itself does not issue load line certificates other than a “single voyage load line exemption certificate.” This allows a non-load line vessel to make a “positioning voyage” (transit from one port to another) to relocate to a new place of work or go into a shipyard for an overhaul. The local Coast Guard Marine Safety Office (MSO) at the port of departure issues such exemption certificates. “Round trip” exemptions are not issued; the return voyage requires a new exemption certificate issued by the local MSO.
Load line information is given in the vessel’s “Load Lines Certificate.” This document certifies to the correctness of the load line marks and that the vessel is in compliance with all applicable requirements. It also provides a diagram of the assigned load line marks and the freeboard deck line, locating the marks with reference to this line in terms of assigned freeboard, as well as stating any conditions, restrictions and exemptions that the vessel shall observe. The validity of these certificates is reviewed annually in load line inspections and every five years in more thorough load line surveys. During these inspections and surveys, ABS is particularly concerned with the following items:
A load line map showing zones and seasonal areas of the world’s oceans provides the Master with information regarding the maximum draft amidships to which his vessel can be loaded during various segments of a cruise. The vessel must be loaded at the beginning of a cruise so that at no time during the cruise will the applicable seasonal/zone mark be submerged.
Freeboard is vitally important on smaller vessels not subject to load line requirements. Consequently, these vessels should carry information on board regarding maximum drafts amidships to which they can be loaded safely.
ORIGIN OF LOAD LINES: Historically, the concept of a load line evolved during the 1870s in Great Britain to guard against merchant ships being overloaded. Lloyd’s Register established a minimum freeboard requirement for its classed ships, to ensure that a ship had good reserve buoyancy in heavy boarding seas. After considerable persuasive efforts by Samuel Plimsoll, Parliament extended the requirement to all British merchant ships; thus was born the “Plimsoll mark.”
Similar load line requirements were adopted by other maritime nations, until they were internationally standardized in the Load Line Convention of 1930. The present International Convention on Load Lines (ICLL) was drawn up in 1966 (in force since 21 July 1968), and modified by the Load Line Protocol of 1988 (in force since 3 February 2000). The Convention is administered by the IMO, a specialized agency of the United Nations. Vessels of countries signatory to the Convention are required to have an ICLL certificate for international voyages. As of April 2005, 155 countries (representing 98.49% of world tonnage) are signatory to the 1966 ICLL, and 74 countries (representing 66.70% of world tonnage) are signatory to the 1988 Load Line Protocol.
The United States is a signatory nation to both the original 1966 ICLL and the 1988 LL Protocol, and therefore load line requirements for U.S. vessels engaged on international voyages are stipulated in the Convention.
Modern load line requirements also ensure the watertight integrity of a vessel below its waterline (i.e. hull penetrations) and the weathertight integrity above its waterline (i.e. critical openings in the superstructure, deckhouses, cargo hatches, etc). The requirements also provide for crew safety on deck by specifying dimensions and locations of guardrails and walkways.
Load line regulations for U.S. vessels operating solely on domestic routes are developed by the Coast Guard, and reflect the less-severe operating environments of coastwise service. Special load line standards apply to vessels operating on the Great Lakes.
MINIMUM STATUTORY FREEBOARD: The minimum “statutory freeboard” is measured to the uppermost load line mark applicable for a specific maritime venue (for example, there are different marks for normal ocean waters vs. fresh waters) taking into account conditions (as discussed below) of 1) reserve buoyancy (buoyancy which can be supplied by the hull and watertight superstructure above the water line) and height of weather deck above this water line, 2) subdivision, and 3) hull strength. In the United States, ABS is the load line assigning authority on behalf of the U.S. Coast Guard.
Condition 1) - reserve buoyancy -- provides for a minimum statutory freeboard by specifying the maximum draft amidships based on the degree of reserve buoyancy and height of weather deck above the waterline which have been found adequate from past experience in providing for vessel and personnel safety. The basic load line mark thus determined, which passes through the center of the load line disk, fixes the “minimum summer freeboard” in salt water. A series of adjacent load line marks above/below this basic mark provide for decreased/increased minimum statutory freeboard when the vessel is operating during seasons and in ocean areas where less/more severe weather-sea conditions are likely to be encountered than assumed in loading the basic mark. Freshwater marks above the basic mark may be authorized for a vessel in ocean service. If such is the case, care must be taken in loading to these marks as these allowances require the vessel to be in virtually fresh water with a specific gravity of 1.000. If the vessel is in brackish water, proportional use of the fresh water allowances must be based on the actual water specific gravity and standard salt-water specific gravity of 1.025.
Condition 2) - subdivision -- concerns vessels whose hulls are subdivided by transverse watertight bulkheads to limit the extent of damage by flooding due to hull penetration -- such damage causing sinkage, trim and reduction of stability. Subdivision of a vessel is either required or made on a voluntary basis -- it being required for inspected oceanographic vessels per reference 3. In design, the location of these bulkheads along the length of the vessel is based on the vessel floating at a specific water line called the “subdivision load line.” The vessel is said to meet a “one compartment standard of subdivision” if subdivision is such that the flooding of any one main compartment can be sustained without submerging the so-called “margin line” just below the freeboard deck while retaining adequate after-damage, or residual, stability, The validity of this or higher standard of subdivision is dependent on the subdivision load line mark being at or above the waterline of the undamaged vessel. A vessel subject to these requirements cannot be loaded deeper than this mark. Note, however, that the subdivision mark has no meaning and is not affixed to the vessel if it lies above other load line marks. Conversely, any marks above the subdivision mark become meaningless and are not affixed to the vessel. In this case, the minimum statutory freeboard is based on the subdivision load line mark.
Condition 3) - hull strength -- refers to the maximum draft amidships to which a vessel can be loaded from a hull strength point of view -- this draft being called the “scantling draft” (scantling being the cross-section dimensions of plates and shapes comprising the hull girders). The authorizing authority must be satisfied that the hull strength is adequate for the minimum freeboard assigned from consideration (1) or (2). If for any reason the scantling draft mark lies below other marks, these marks are meaningless and not affixed to the vessel. In this instance, the minimum statutory freeboard would be the scantling draft freeboard.
In addition to the above considerations, a vessel’s freeboard has an important affect on its intact stability curve. As freeboard increases, the freeboard deck edge is immersed at greater angles of inclination, which increases the maximum righting arm and angle of occurrence. The result is increased righting energy and resistance to heeling by wind/wave action. This consideration is extremely important for smaller vessels. In general, vessels with higher freeboards have better performance in stormy weather and are less affected by water on deck.
WATERTIGHT INTEGRITY: The basic concept of watertight integrity is to ensure that the entire vessel does not flood with water and sink. The watertight integrity of a vessel is essential to calculations of required freeboard, stability and subdivision characteristics, so it plays an important role in causing the vessel to remain upright in operation through waves and weather.
During the construction of a vessel, appropriate mechanisms must be incorporated to allow for secure and efficient closure of openings in watertight areas of the vessel such as the hull, watertight bulkheads and sections of the superstructure considered watertight. Examples of such openings include hatches, side openings, and internal watertight doorways.
In order to maintain the watertight integrity of vessels, these watertight closures must be utilized as required, properly operated, and be objects of proper maintenance. It should also be remembered that some watertight doors are set to close automatically under certain conditions and that such doors can close with potentially harmful force.
Watertight integrity is vital to vessel safety -- in December 1978, the charter vessel M/V Holoholo, under charter for oceanographic work, was lost with all hands. According to National Transportation Safety Board (NTSB) Report Number: MAR-80-15, the primary reason for this loss was loss of watertight integrity.
The following is a list of the documents that were referenced by this chapter, including the regulations and guidance regarding load lines and watertight integrity for various types of vessels. As these documents may be updated or amended periodically care should be taken that the latest edition is used.
Regulations, Standards and Related Information:
There are no regulations regarding load lines or watertight integrity that apply to all vessels.
The U.S. load line regulations are found in 46 CFR Subchapter E, “Load Lines” (parts 41 thru 47). These regulations were originally derived from the Coastwise Load Line Act and the International Voyage Load Line Act, and also incorporate the requirements of the ICLL. The statutory basis for the regulations comes from chapter 51 of Title 46 of the U.S. Code (46 USC chapter 51).
However, some of the regulations have been superseded by the recodification of 46 USC in 1988, which revamped certain load line requirements (particularly vessel applicability and penalties for overloading). Therefore, until the CFR regulations are revised, 46 USC Chapter 51 must also be consulted.
Similarly, the ICLL is subject to periodic amendment via the LL Protocol (the most recent revisions went into force on 1 January 2005). Therefore, the most current revision of the ICLL is applicable for new vessels.
Also, special load line policies have evolved to meet new vessel designs and configurations that did not exist when the original regulations were developed (for example, liftboats). These special situations are addressed in several Navigation & Vessel Inspection Circulars (NVICs) and Chapter 6 of the USCG Marine Safety Manual. (Note: the Marine Safety Manual has not been recently updated; refer to the discussion below concerning the “Load Line Policy Notes”).
In general, most commercial U.S. vessels more than 79 feet (24 m) in length must have a valid load line certificate when venturing outside the U.S. Boundary Line, whether on a domestic or international voyage (even on “voyages to nowhere” that return to the same domestic port of departure). There are a few limited categories of vessels excluded from needing a load line; refer to 46 USC 5102 for specifics.
The design process for new vessel construction or major modification of a vessel should address all applicable load line and watertight integrity requirements.
Masters of oceanographic vessels subject to load line requirements have the responsibility to maintain load line certificates and current survey reports on board their vessels and to comply with all terms and conditions stated in these documents. Further, they should keep logbook records as prescribed in 46 CFR Subchapter E Section 42.07-20.
Masters of other oceanographic vessels not subject to these requirements should comply with load line, or maximum draft amidships, information supplied to the vessels in lieu of load line certificates.
Masters of all oceanographic vessels have the responsibility for maintaining the watertight integrity of these vessels. This responsibility involves the careful maintenance of all watertight closures and associated systems and the assurance that their functions, operation and status in various normal and emergency conditions are clearly understood by members of the crew and science party.
Inspected vessels that do not represent special exceptions are subject to the load line requirements as set forth in 46 CFR Subchapter E. Also note that in 46 CFR 188.05-35 (from Subchapter U referring to Oceanographic Research Vessels) it indicates that “Certificated vessels shall be subject to the applicable provisions of the Load Line Acts, and regulations in Subchapter E (Load Lines)”.
Some exceptions are:
NOTE: A question often arises as to whether a vessel engaged in oceanographic research upon international waters is on an international voyage if the port of departure, port of return and any intermediate ports are all domestic. Typically, voyages beginning from and terminating at domestic ports are considered domestic voyages, even if international waters are traversed. In certain cases however, the Coast Guard has previously construed voyages to certain ocean dumpsites, offshore weather monitoring stations, etc. to represent arrivals at international destinations, making the voyage an international one. Whether or not some new offshore research area would be considered an international destination should be checked on a case-by-case basis with the Coast Guard office nearest to the departure port.
Inspected vessels are also subject to watertight subdivision requirements, such as those set forth in reference 46 CFR Subchapter S and some watertight requirements which are included in 46 CFR, Subchapter E, Subpart 42.15, “Conditions of Assignment of Freeboard.”
U.S. flag vessels will be classed by ABS and, in addition to all other applicable Regulatory Body requirements, must comply with the applicable set of ABS “Rules for Building and Classing Steel Vessels”. These Rules contain requirements pertaining to load lines, as well as stability, subdivision and watertight integrity.
Regulations from the SOLAS convention (including all current amendments) apply to vessels over 500 GT (international). Vessels less than 500 GT, which do not carry more than 12 passengers, are generally exempt. These Regulations contain requirements pertaining to stability, subdivision and watertight integrity.
There are few specific U.S. regulations applicable to watertight integrity for uninspected oceanographic research vessels that are below 500 GT (international). See requirements under RVSS below.
For vessels less than 65 feet in length, all standards relating to capacity or watertight/weathertight integrity in the “Safety Standards for Small Craft“ published by ABYC should be met. For watertight/weathertight integrity issues see Sections H-3, H-4, and H-27. Also, applicable safety requirements from the Motorboat Act of 1940, including all current amendments, must be followed.
For boats under 26 feet in length the boat load capacity standards outlined by Section H-5 of the “Safety Standards for Small Craft “ published by ABYC should be observed. (See also 33 CFR 183 Subpart C - Safe Loading).
UNOLS vessels will be designed to and maintained in accordance with the applicable load line and watertight integrity requirements as set forth in US regulations, international conventions and accepted marine standards for the size and operating area of the vessel.
While not legally required for uninspected oceanographic research vessels that are below 500 GT (international), 46 CFR, Part 28, Subpart E (Stability) and 46 CFR 179 (Subdivision, Damage Stability and Watertight Integrity) may provide useful guidance. Vessels chartered to do oceanographic research work should meet, as a minimum, the requirements of 46 CFR Subchapter C, Part 28, Subpart E.
Operations managers or Marine Superintendents shall oversee and assist the Master in fulfilling the above listed responsibilities.
Uninspected vessels exempted from load line regulations, including those having state boat registration numbers and not sailing in foreign or international waters, should strive to adhere to load line and related requirements given in 46 CFR Subchapter E to the extent feasible for vessels of their size. These vessels should be surveyed in a manner paralleling the annual and five-year periodic surveys made in reviewing the “Conditions of Assignment of Freeboard” for vessels requiring load line assignments.
Further information is provided in:
“LOAD LINE TECHNICAL MANUAL”: The U.S. Coast Guard commissioned the American Bureau of Shipping (ABS) to prepare a report that integrated U.S. load line regulations & policies, ABS and International Association of Classification Societies (IACS )interpretations, IMO circulars, and the International Convention on Load Lines (ICLL) into a single reference document.
The “Load Line Technical Manual” is the result of that effort. It sets forth the technical procedures for evaluating, calculating and assigning ICLL load lines, using USCG and ABS policies where the Convention leaves certain requirements “to the satisfaction of the Administration” or is open to interpretation.
The Technical Manual applies to U.S. vessels seeking an international ICLL assignment or a domestic U.S. load line assignment for unrestricted voyages by sea; it does not cover U.S. load line regulations for other types of domestic voyages (such as coastwise or Great Lakes).
“LOAD LINE POLICY NOTES”: The “Load Line Policy Notes” supplement Chapter 6.F, “Load Lines,” of the Marine Safety Manual (Vol. IV).
The LL Policy Notes encompass all the current USCG load line policies that have evolved since the previous (1990) revision of Marine Safety Manual (MSM) Chapter 6.F. The LL Policy Notes also include expanded discussions and clarifications for both domestic U.S. and international ICLL load line regimes.