Practical Stability Test: Master’s Guide
Unless you know the plan, stability tests look like choreographed chaos. They completely disrupt the vessel and operations. They frequently require that we adapt to changing conditions. All this adds to a stressful and unpleasant experience. Unless. If you know the plan, things get much better. This article provides a brief guide on stability tests: highlighting the key points for the vessel master.
2.0 Sequence of Events
First, we should lay out the general sequence of events for a stability test. Table 2‑1 summarizes the test events.
Table 2‑1: General Sequence of Events
Action on Your Part
Receive a copy of the approved test procedure.
Skim through this. Much of the procedure contains useful information to explain coordination for the test, including contact information for all the key players.
(Some of the procedure is just boiler plate language required by regulations.)
(About 1 week before test)
Remove deadweight items from the ship and store securely off the ship
(About 1 week before test)
Meet with the Test Coordinator. Ask questions. They will survey your ship and identify any deadweight items that need to come off before the test.
(1-2 days before test)
Ensure the officer on duty has someone ready to open any locked doors on the ship.
Day of the test
Get non-essential people off the ship
– Line handlers
– Tug / small boat
After the test
Arrange to get a temporary stability letter from USCG so you can resume operations.
– Test Coordinator can help with this
3.1 Remove Deadweight
Practically every ship carries too much deadweight for a stability test. Some of it needs to come off and store pier-side, at least temporarily. (This also makes a great opportunity for spring cleaning on the ship). Shipping containers provide great options for secure storage. Specifically focus on cleaning out three types of spaces:
- Bosun’s stores.
- Engine room tools and spares (nuts, bolts, and other small items.)
- Any other storage spaces.
3.2 No Ship Services
During the day of the stability test, all ship services will be offline. No water, no galley, no toilets. Plan for alternative arrangements that day. Portable toilets, pack lunches / order pizza, bring jugs of water. This may be something the Test Coordinator can handle for you.
3.3 Muster Stations During the Test
During the test, people need to stay in the same place. But it seems a little cruel to make someone stand in one spot for the entire day, and unnecessary. During the day of the stability test, we spend the majority of the time organizing and coordinating logistics. Spaced throughout the day, we have brief critical periods, when the naval architects take measurements. These are the only times when people need to be at designated locations. The remainder of the time, everyone is free to move around the ship.
To allow some freedom, we ask that anyone who is on-board during the test pick a location for their muster station at the beginning of the day: someplace that they can stand while we take measurements. Before we start the test, we record the location of every person at every muster station. Generally, we don’t care where they are located; they just need to go back to the same location each time.
3.4 Ship’s Crane
The stability test will require a crane to move weights transversely across the deck. In some cases, the ship has an on-board crane with sufficient capacity to move the weights. The smart vessel owner wants to use that on-board crane and eliminate the cost of renting a pier-side crane. In these cases, yes, we can use the on-board crane. But the on-board crane must be returned to its stowed position each time before we can take measurements.
4.0 Deadweight Survey Access
During the deadweight survey, the Test Coordinator and their staff will need access to every room, storage compartment, and cabin on the vessel. This includes all the locked rooms, and the storage closet that no one opened in six months. Ensure keys are available to open all rooms and make arrangements to address any privacy concerns with crew cabins.
5.0 Mooring Arrangement
During the stability test, the mooring plan needs to let the vessel float free, without the mooring lines affecting the vessel heel in any way. The best arrangement is a set of camels or Yokahama fenders, set at the waterline. (Current waterline of the vessel, not the painted waterline.)
5.2 Mooring Lines
Figure 5‑1 shows a typical mooring arrangement for the stability test.
During the stability test, tension from the mooring lines may heel the vessel just a tiny amount, which biases the test results. The easiest solution is to slack the mooring lines before each measurement. Slack means very slack, with lots of droop, almost touching the water. The sequence for slacking lines will go like this:
- Test Coordinator gets ready to take a measurement and signals that lines need to now be slack.
- When ready, Master commands all lines go dead slack (the vessel usually drifts a slight amount).
- If no fenders were used, the vessel will be pulled away from the pier at this point.
- Coordinator takes measurement. This usually takes 1 – 2 minutes.
- Measurement done. Master commands tension in the lines and stops any vessel motions.
- Re-position vessel and prepare to repeat for next measurement.
Anyone not directly involved in the stability test needs to be off the vessel on the day of the stability test. This includes crew, shipyard workers, and visitors. Once the test starts, the gangway is removed, and no one can get on or off the vessel until the test finishes. People on-board should prepare for a long day. The test typically takes around 8 hours to finish, but in extreme cases may go as long as 16 – 18 hours. All ship services will be offline during the test. No water, no galley, no toilets. Everyone is encouraged to pack some food and water near their station to eat during the day.
Smooth stability tests require planning, and practicality. This guide highlighted some of the more common practical concerns for a stability test. Be sure to talk with your Test Coordinator. Ask questions, clarify division of labor. I wish you a smooth and successful stability test.
ASTM, “Standard Guide for Conducting a Stability Test (Lightweight Survey and Inclining Experiment) to Determine the Light Ship Displacement and Centers of Gravity of a Vessel,” ASTM F1321-92, West Conshohocken, PA, 2004.
Marine Safety Center, “Lightship Change Determination: Weight – Moment Calculations vs. Deadweight Survey vs. Full Stability Test,” in Marine Safety Center Technical Note (MTN) No. 04-95, Ch-2, Washington, DC, United States Coast Guard, Jan 11, 2016.
United States Coast Guard, “Stability Tests (46 CFR 170, Subpart F),” Marine Safety Manual, vol. VI, pp. 6-18 to 6-27, Sep 29, 2004.
United States Coast Guard, “MSC Guidelines for the Submission of Stability Test Procedures,” Procedure Number: GEN-05, Washington D.C., Sep 27, 2012.
A. Kumar, “Ship Stability: Stiff and Tender Ship, Angle of Loll & Inclining Experiment,” Mariner Desk, 11 Dec 2017. [Online]. Available: https://www.marinerdesk.com/stiff-and-tender-ship/. [Accessed 13 Feb 2020].
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Wikipedia Authors, “Pota Potty by David Shankbone,” Wikimedia Commons, 14 May 2007. [Online]. Available: https://commons.wikimedia.org/wiki/File:Porta_Potty_by_David_Shankbone.jpg. [Accessed 13 Feb 2020].
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