Practical Stability Test: Chief Engineer’s Guide

by | Sep 7, 2020

1.0 Introduction

As Chief Engineer, you always have an ongoing list of maintenance jobs.  And that list gets even worse when the ship prepares for a stability test.  Of course, it would help if someone actually told you what to expect from the test.  The test procedure provided extensive details about the test and theory about the math.  But that doesn’t answer the important question:  What do you need to do for preparation?  This guide provides practical advice on preparing the ship for a stability test.

2.0 Check the Tank Configuration

The stability test procedure will come with a planned tank configuration.  The tanks need to very closely match that configuration on the day of the test.  Small deviations in tanks levels are fine, but any tanks expected as empty or pressed full should match the procedure.  Tell the Test Coordinator in advance if your tanks will not match the listed configuration.  In most cases, the procedure can be quickly updated and US Coast Guard (USCG) will accept the update.  But we do not want to make last minute updates on the day of the test.  Especially warn the Coordinator if the fuel tanks will not match the configuration.

2.1 Strip and Gas Free All Empty Tanks

Any tanks listed as empty in the procedure must be gas free and stripped completely dry.  There can be moisture on the walls, but no pools of liquid.  The Test Coordinator and USCG Inspector will crawl inside these tanks to check them.  We will go to the lowest point in the tank and search for pools of liquid.  Make sure we don’t find any.

3.0 Finish All Work During Deadweight Survey

The day before the incline experiment, the Test Coordinator will perform a deadweight survey (Day 1).  Ideally, all work on the vessel should be done by then (repairs, installs, shipyard work).  If any equipment is not installed by the day of the test (Day 2), at least ensure the equipment is placed near its final installed location.  No matter what, installation work can not continue into the day of the test (Day 2).  Not even just the morning.  All contractors and shipyard personnel need to have their tools off the vessel by the end of Day 1. 

Work may still continue while the Test Coordinator and their staff conduct the deadweight survey (Day 1).  Contractors can finish up and clear out tools.  But the Test Coordinator and staff need to know which items to include in their deadweight survey.  Do a quick walkthrough with the Test Coordinator on the morning of Day 1.  Point out which items will be taken off the vessel. 

4.0 Save Time for The Test Coordinator

During Day 1 and Day 2, the Test Coordinator will have questions on tank locations, system configurations, spares, and several other things.  Make sure you save time during the day to answer those questions.  Better yet, carry a walkie-talkie so the Test Coordinator can call you up with a quick question.

5.0 Remove Deadweight

Practically every ship needs to store their equipment and deadweight on the pier-side during the test.  At least some of it to ensure we remain under required limits.  Shipping containers provide great options for secure storage.  Specifically focus on cleaning out three types spaces:

  1. Boson’s stores.
  2. Engine room tools and spares (nuts, bolts, and other small items.)
  3. Any other storage spaces.

One thing that does stay on the vessel:  any required lifesaving or fire protection equipment. 

  1. EEBD’s
  2. Fire fighting gear
  3. Life rings
  4. Life jackets / Immersion suits

6.0 Tank Soundings and Inspection

The morning of the incline experiment (Day 2), all tanks will need to be sounded.  That means all the tanks.  Even the empty voids.  Have someone ready to go with the Test Coordinator for sounding each tank.  The USCG Inspector will also need to climb into each empty tank and verify they are dry.  Have the manholes loose and the tanks certified gas free (only the empty tanks.  Tanks with liquid in them can stay sealed).

6.1 Press Full Tanks

Any tanks listed as full will need to be pressed full.  The USCG inspector will need this demonstrated on the day of the stability test.  This normally means pumping into the tank until liquid comes out the vent pipe.

6.2 Check Cross Connects

During the stability test, every single cross connect valve must be closed.  All tank valves need to be closed.  We can’t have any liquid moving from one tank to another during the test.

7.0 Ship’s Crane

The stability test will require a crane to move weights 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.  And we will need ship’s crew on-board to operate the crane:

  1. Crane operator
  2. Ground crew to land the weights on deck

8.0 Conclusion

Work lists do best when planned ahead.  A stability test requires extensive work to prepare the vessel, and this guide should give you some advanced warning of what to expect.  I wish you a smooth and successful stability test.

9.0 References

[1]Code of Federal Regulations, “Determination of Lightweight Displacement and Centers of Gravity,” in Code of Federal Regulations, Washington, D.C., U.S. Government, 2020, pp. 46 CFR 170, Subpart F.
[2]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.
[3]United States Coast Guard, “MSC Guidelines for the Submission of Stability Test Procedures,” Procedure Number: GEN-05, Washington D.C., Sep 27, 2012.
[4]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.
[5]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].
[6]Wikimedia Authors, “Liquid Natural Gas Membrane Tank,” Wikimedia Commons, 05 mar 2011. [Online]. Available: https://commons.wikimedia.org/wiki/File:Liquid_natural_gas_membrane_tank.jpg. [Accessed 13 Feb 2020].
[7]Wikipedia Authors, “Garage Workbench Clutter,” Wikimedia Commons, 05 Dec 2019. [Online]. Available: https://commons.wikimedia.org/wiki/File:Garage_Workbench_Clutter.jpg. [Accessed 13 Feb 2020].
[8]Wikipedia Authors, “2016 Port de Barcelona,” Wikimedia Commons, 28 Jul 2016. [Online]. Available: https://commons.wikimedia.org/wiki/File:2016_Port_de_Barcelona_-_70.jpg. [Accessed 13 Feb 2020].

 

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