Subchapter M Equipment and Construction

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EDT TPO Services 

EDT is a Third Party Organization (TPO) to conduct audits, approve and issue Towing Vessel Safety Management (TSMS) certificates, conduct annual and drydocking surveys, and issue survey reports. EDT consultants who attend your towing vessel for annual and periodic surveys as required in 46 CFR 137 will provide fair and impartial inspections of your towing vessels. Each surveyor from EDT is a registered professional engineer and/or a seasoned ship surveyor.

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Towing Vessel Equipment Requirements

Parts 141 through 144 of Subchapter M describe in detail requirements for lifesaving equipment, fire protection equipment, machinery and electrical systems and equipment, and construction which need to be part of a towing vessel issued a COI under Subchapter M. For a new towing vessel, compliance with these Parts of Subchapter M should be automatic – the shipyard contacted by the operator for the towing vessel should be completely aware of these requirements and include all noted aspects into the proposed design and contract.

Towing vessels transferring from Subchapter C, Part 26, into Subchapter M will need to review Parts 141 through 144 more closely. Many towing vessels may be fitted with equipment similar to, but not properly approved, equipment required in Parts 141 through 144.  It is important to make sure the equipment meets the approval standards within the applicable Parts – the surveyor/inspector will write a deficiency against unapproved equipment.

Also, the requirements for documenting stability under Subpart C of Part 144 are tricky and may require use of a consultant to validate compliance. Below is a summary of the content of Parts 141 through 144 and a link to a page with greater detail.

Lifesaving Equipment – Part 141

The lifesaving requirements in Part 141 cover equipment to assist the crew should the towing vessel need to be abandoned – for instance, after a collision or loss of stability – and means for the crew to call for help. Personal life saving equipment such as lifejackets and lifering requirements are covered, as is requirements for the entire crew. Distress signaling equipment such as EPIRBs, rockets, flares or other attention getting devices are specified.  What your towing vessel will need depends on size and area of operation.

Survival Craft Requirements Table
The requirements for survival craft are given in the table below.

liferaft requirements for subchapter m


Lifejackets are required for all persons onboard a towing vessel.  If berthing spaces are provided for the crew, additional lifejackets need to be provided at watch stations.  If the towing vessel operates above 32° North Latitude (all of the Pacific and the Atlantic north of Savanah, Georgia) and not on rivers, then survival suits need to be provided for the crew, in the same amounts, as well.

Two (2) liferings are required on towing vessels longer than 26 feet but less than 79 feet, one on each side of the vessel.  For towing vessels 79 feet in length or greater, four (4) liferings are required, two (2) each on opposite sides of the vessel.
Distress Hailing
Distress hailing include Emergency Position Indicating Radio Beacons (EPIRBs), flares and/or smoke, and line throwing apparatus.  The requirements for distress hailing are given in the table below.


Hand held red flares or rocket parachute flares are dual purpose day/night signals.  Hand held smoke or floating orange smoke signals are day signals only.  Line throwing appliances need to be readily available and have a second set of rocket and line.

As forensic engineers, our consultants have deep understanding of towing vessel construction and safe operation. Learn more about our Subchapter M Services

Fire Protection – Part 142

The fire protection requirements of Part 142 address requirements to identify and fight fires onboard a towing vessel.  The fire identification and warning requirements are expanded from the requirements in Subchapter C, Part 27.  The requirements for fire suppression and fire fighting vary depending on vessel characteristics such as date of construction, length, engine size, area of operation, and tonnage.

For towing vessels contracted before November 19, 1952

These towing vessels must meet the requirements set forth in Part 142.  Existing unapproved systems may continue to be used, if properly maintained.  If they cannot be maintained, then they must be replaced with approved systems.

For towing vessels operating on the Great Lakes less than 3 miles from shore or more than 3 miles contracted before August 27, 2003

These towing vessels shall meet the requirements for all towing vessels below and be fitted with either one (1) B-V semi-portable fire extinguisher or a fixed fire extinguishing system in the machinery space.

For towing vessels operating limited coastwise, coastwise, ocean, or more than 3 miles on the Great Lakes and contracted after August 27, 2003

These towing vessels shall meet the requirements for all towing vessels below and be fitted with both one (1) B-V semi-portable fire extinguisher and a fixed fire extinguishing system in the machinery space.

For new towing vessels contracted after July 20, 2018

These towing vessels shall meet the requirements for all towing vessels below and be fitted with both one (1) B-V semi-portable fire extinguisher and a fixed fire extinguishing system in the machinery space.  In addition, if fitted with a galley, a heat detection system shall be installed and tie into a fire alarm system on the bridge.

For all towing vessels

Compartments for stowing paints and other flammable liquids shall be enclosed in steel and provided with an additional B-II portable fire extinguisher.

Each towing vessel over 79 feet in length and not fitted with a fixed fire extinguishing system shall have two (2) complete fireman’s outfits with self-contained breathing apparatus having 30 minutes air.

Each towing vessel shall have at least one (1) fire axe accessible from the exterior.

Towing vessels shall be equipped with portable fire extinguishers per the following tables.  The first table defines the classes of fire extinguishers; the next two (2) tables define application.

Subchapter M Fire Protection Table for Towing Vessels


Fire Extinguishers
In addition to the number of B-II portable fire extinguishers above, one (1) additional B-II fire extinguisher shall be carried in the machinery space for every 1000 horsepower or fraction of the main engine, up to a maximum of six (6) additional B-II extinguishers.
Fire Pumps

Each towing vessel shall have a fixed or portable fire pump.  Fixed fire pumps shall have automatic or remotely controlled with suction valve controls at the remote station, enough hydrants to access any point in the machinery space, and a section of 50 foot, 1-1/2” hose with dual purpose nozzle at each hydrant.  Portable fire pumps shall be self-priming, have a 50 foot, 1-1/2” hose with dual purpose nozzle, and be stored outside the machinery space.

Fire Detection Systems

Each towing vessel shall have a fire detection system monitoring the machinery space and alarming on the navigating bridge.  Fire detection systems shall be self monitoring; indicate power, faults, and alarms visually and audibly; and have two sources of power. Towing vessels built prior to January 18, 2000 may use an existing engine room monitoring system.

Each towing vessel shall have smoke detection in cabins and public spaces.

Mechanical/Electrical Systems – Part 143

The machinery and electrical requirements of Part 143 are intended to enhance the safe operation of the machinery and electrical installations on a towing vessel.  Like the fire protection requirements of Part 142, the requirements for machinery and electrical installations varies by age, length, and service.

For towing vessels built prior to January 18, 2000

These towing vessels shall meet the requirements set forth in Part 143 except as noted below. Existing unapproved systems may continue to be used, if properly maintained. If they cannot be maintained, then they must be replaced with approved systems. Any new system, not previously fitted, shall be approved in accordance with this Part.

For towing vessels built after January 18, 2000

These towing vessels shall comply with the requirements of Part 143 except those applicable to new vessels and the following:

  1. Portable fuel systems complying with American Boat and Yacht Council (ABYC) H-25 are only allowed for outboard engines and portable fire pumps.
  2. Vent pipes for integral tanks shall be fit at the highest point of the tank, discharge to the weather deck through a gooseneck, and have a 30 x 30 mesh stainless steel screen.
  3. Fuel lines shall be seamless pipe, except for non-metallic hose less than 30 inches of reinforced rubber with compression fittings (or double clamped). Piping complying with ABYC H-33, Chapter 5 of NFPA 302, or 33 CFR, Subchapter S are alternatives.

Existing unapproved systems may continue to be used, if properly maintained. If they cannot be maintained, then they must be replaced with approved systems. Any new system, not previously fitted, shall be approved in accordance with this Part.

For new towing vessels (built or undergone major conversion after July 20, 2017)

Generally, new towing vessels are to be constructed in accordance with the American Bureau of Shipping (ABS)Rules for Vessels under 90 Meters or Rules for Service on Rivers and Intercoastal Waterways, or, for major conversions, the following ABYC Standards:

a. E-11, AC & DC Electrical Systems on Boats

b. H-2, Ventilation of Boats Using Gasoline

c. H-22, Electric Bilge Pump Systems

d. H-25, Portable Gasoline Fuel Systems

e. H-32, Ventilation of Boats Using Diesel Fuel

f. H-33, Diesel Fuel Systems

g. P-1, Installation of Exhaust Systems for Propulsion and Auxiliary Engines

h. P-4, Marine Inboard Engines and Transmissions

There must be a source of electrical power sufficient for all essential systems, minimum habitability, and all other installed and/or portable equipment. Back-up or secondary power shall be fitted adequate to power alarms, lighting, radios, navigation equipment, and essential systems. A generator driven off the propeller may be a secondary source or batteries with 3 hour’s reserve.

The following systems shall be served by two independent, identical sources of electricity:

a. High bilge level alarm

b. Emergency egress lighting

c. Navigation lights

d. Pilothouse lighting

e. Engine room lighting

f. Radios and navigation equipment indicated in Part 140

g. Distress equipment indicated in Part 140

h. Fire detection system

i. Other essential systems

Power and lighting circuits shall have overcurrent protection. Essential and non-essential systems shall have separate overcurrent protections. Ungrounded distribution systems must have a ground fault detector; grounded distribution systems shall have a grounded neutral at the main switchboard. Electrical conductors and connections shall have capacity for the full available load and be protected from immersion, weather, crushing, and be suitable for the installation environment.

For towing vessels over 65 feet in length

Navigation lights shall meet UL 1104. If fitted with overnight accommodations and multiple shifts, have a ‘deadman’ alert system unless the vessel uses two watchkeepers per watch location.

For towing vessels intended to move oil tank barges of hazardous materials in bulk

These towing vessels for towing oil or hazardous material in bulk shall have alternate means to control propulsion and steering separate from the primary controls located near the equipment with independent communication and means to monitor the power and direction and rudder angle. The propulsion shall maintain speed and direction after a single failure or bring the vessel to a stop.

Audible and visual alarms at each operating station shall warn of propulsion or rudder control failure. Two power sources must be provided for steering and propulsion capable of operating for a minimum of 3 hours and the second source shall start automatically on failure of the primary source. All propulsion support shall be duplicated.

For all towing vessels

Equipment shall be maintained for safe operation of the towing vessel. The crew shall be able to demonstrate ability to operate primary machinery and electrical systems, including alarm response and restoration of power after loss.

Piping shall be insulated over 220° C and means used to prevent leaking flammable fluid. Combustibles shall not be stored in machinery spaces unless in a suitable container.

Means shall exist to monitor and control thrust, rudder angle, and direction of thrust at each control station. Each towing vessel shall have the following essential alarms, audible at each control station:

a. Main engine low lube oil pressure

b. Main engine high cooling water temp

c. Auxiliary engine low lube oil pressure

d. Auxiliary engine high cooling water temp

e. High bilge level(s)

f. Low level, hydraulic steering fluid (if applicable)

g. Low fuel level in day tank

The following equipment shall have gauges at the machinery location:

a. Main engine lube oil pressure

b. Main engine RPM

c. Main engine cooling water temp

d. Auxiliary engine lube oil pressure

e. Auxiliary engine RPM

f. Auxiliary engine cooling water temp

g. Hydraulic steering system pressure, if equipped

Each towing vessel shall have a general alarm, audible, with a supplemental flashing red light in high noise areas; public address systems may be used if otherwise meeting this requirement. Two-way communication between the bridge(s) and machinery room shall be provided with a back-up. Towing vessels with redundant propulsion and direct control from the bridge are exempt, as are towing vessels with less than 10 feet between the engine room and bridge.

Electrical equipment and piping for flammable liquids, cooling, and fire fighting must have isolation devices and be marked with all information needed for safe operation and identification. A continuous supply of clean fuel shall be available to main and auxiliary engines. Remote shutoff valves shall be fitted to each day-tank supplying an engine.

Construction and Arrangement (Part 144) Details

Part 144 addresses the physical construction of a towing vessel and gives guidance on arrangement to enhance personnel safety and vessel integrity. For the most part, structural modifications to meet this Part for an existing towing vessel will be unnecessary. Towing vessels registered with a recognized classification society, issued a Load Line Certificate, or constructed to comply with SOLAS 1974 will meet Part 144.

Existing towing vessels shall be provided with closures for all deckhouse and hull penetrations which could let water in, suitable for the intended route, and have freeing ports in bulwarks on the main deck sufficient to release entrained water starting July 20, 2016. Existing towing vessels shall comply with all other requirements below by July 20, 2018.

The hull shall be marked with the name and hailing port, have draft marks if stability documentation is required, have load line marks permanently scribe if assigned a load line, have all watertight doors and hatches marked to be kept closed, and have all emergency exits marked to be kept clear.

Proof of stability will be required of all existing towing vessels. The operator must be able to convince the OCMI or his TPO of sufficient stability or have a stability assessment completed.

Exhaust ducts shall be insulated with non-combustible materials. Exhausts shall be protected against crew burns. Any pipe containing fluid, gas, or vapor over 150° F shall be insulated.

Crew spaces shall have at least two widely separated escape routes; a single escape route is allowed if the space is less than 322 square feet, has no source of flame or heat, the escape is away from a machinery space or fuel tank, and is not a deck scuttle or ladder from an accommodation space. Windows may be used as escape on vessels below 65 feet in length. Accommodation spaces shall be ventilated. Machinery spaces shall have been to close and shut off ventilation outside of the machinery space. The deck above crew accommodations must be above the deepest load waterline.

Cabins shall be provided for vessel operating for more than 12 hours of every 24. Rails or lifelines shall be provided on open decks. For towing vessels on ocean or coastwise service, rails or grabs in passageways. Exposed rotating machinery shall have guards.

Windows and openings at the navigating bridge shall provide clear field of vision for safe operation in all anticipated modes. A view astern shall be provided for vessels towing astern or with azimuth drives. Each window or portlight shall be capable of withstanding the wind and wave loads of the towing vessels anticipated route(s). Deadlights or covers over windows designed as escape shall be removable from within the space.

Verification of compliance of a towing vessel to this part must be performed if the vessel is new, is undergoing a major conversion or alteration, or a new installation that is not ‘replacement in kind’ prior to the action or issuance of the COI. Verification can be done by a Professional Engineer, working within his scope of registration, or an authorized classification society (see Subchapter M Plan Approval)”