Emergency Towing Arrangement, Towline Tension, Chock SWL & Tug Bollard Pull Tool | ShipUniverse
SOLAS II-1/3-4 • MSC.35(63) Tanker ETA • MSC.549(108) 2028 Non-Tanker ETA • MSC.1/Circ.1691 • MSC.1/Circ.1255/Rev.1

Emergency Towing Arrangement, Towline Tension, Chock SWL & Tug Bollard Pull Tool

Screen a disabled vessel's towability from environmental resistance through dynamic towline tension, tug bollard-pull requirement, towline and fitting utilization, statutory emergency-towing strength, deployment time and ship-specific emergency-towing readiness. The tool deliberately separates predicted towing force from the approved design load of the emergency towing arrangement.

Currency
Currency selector changes display only. No exchange-rate conversion is performed.

Regulatory & Vessel Basis

The current tanker ETA requirement and the 1 January 2028 new-ship requirement for non-tankers are different. Emergency towing procedures are a separate requirement and apply much more broadly.

tonnes. Tanker ETA strength basis uses DWT.
Use the ship's approved EN. Do not reverse-engineer it from this tool.
MSC.1/Circ.1691 permits the required towing load to be achieved by summing multiple arrangements where applicable.
Planning allowance only. Approved design analysis controls actual load sharing.

Vessel Geometry & Environmental Tow Resistance

Projected-area drag is a screening model for a disabled vessel. If model-test, sea-trial, CFD, salvage-master or approved towing resistance is available, enter it below as a calibrated override.

knots.
m².
m² for beam-current screening.
User-entered screening coefficient, not an IMO constant.
m².
m².
knots true wind relative to vessel heading convention below.
0° head wind, 90° beam, 180° following.
knots.
0° adverse/head current, 90° beam, 180° following.
% applied to steady resultant resistance.
Planning allowance for surge, yaw, wave action and towline dynamics. Not an IMO universal value.
kN. Enter 0 to use projected-area model. If entered, it overrides modeled steady resistance but not DAF.
degrees at ship fairlead/chock.

Advanced Tow Scenario Register

Compare calm harbor connection, coastal tow, deteriorating weather and worst-plausible cases using the same vessel, tug and fitting capacities.

ScenarioSpeed knWind knWind °Current knCurrent °Wave add %DAF

Towline, Chock, Strongpoint & Loose Gear

kN minimum breaking load.
% of MBL. Enter approved / company planning limit. ETA working strength is separately assessed.
kN at the relevant approved tow angles.
kN.
kN.
kN.
degrees from centerline each side.
degrees.
m. Used for ETA pennant minimum length.
m.
m.

Tug Bollard Pull & Available Tow Force

tonnes-force.
% of static bollard pull assumed usable in this emergency tow. User-entered operational factor.
% when more than one tug shares the tow.
% above modeled dynamic towline tension.

Deployment & Emergency Towing Booklet Readiness

minutes for the evaluated end.

Optional ETA Upgrade / Towability Budget

This is a procurement and planning section only. It does not convert a deficient arrangement into an approved ETA.

Engineering limitation: This tool is a screening and planning aid. Emergency towing loads are highly sensitive to vessel heading, yaw, waves, current, tow speed, tug position, towline stiffness/catenary, shock loading, hydrodynamic interaction and damage condition. The projected-area model is not a substitute for a salvage master, towing analysis, class/flag-approved ETA design, certified bollard-pull data, approved shipboard SWLs, manufacturer limits or the ship-specific Emergency Towing Booklet.
Regulatory / guidance basis: SOLAS regulation II-1/3-4; resolution MSC.35(63), Guidelines for emergency towing arrangements on tankers; resolution MSC.549(108), which extends mandatory ETA fitment to new ships other than tankers of at least 20,000 GT constructed on or after 1 January 2028; MSC.1/Circ.1691, Interim guidelines for emergency towing arrangements on ships other than tankers; MSC.1/Circ.1255/Rev.1, Revised guidelines for owners/operators on preparing emergency towing procedures; and MSC.1/Circ.1175/Rev.2 for shipboard towing and mooring equipment from 1 January 2028. For new non-tanker ETAs, MSC.1/Circ.1691 uses required towing loads of 1,000 kN for EN below 3,000; 2,000 kN for EN from 3,000 to below 10,000; and EN × 0.2 kN for EN of 10,000 or more, or a higher value determined by the Administration. Tanker ETA guidance uses 1,000 kN for 20,000 to below 50,000 DWT and 2,000 kN for 50,000 DWT and above. Approved vessel-specific plans, Administration/class requirements and actual certified equipment data always control.
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