ASI Group

Performing a Liner Runout Underwater

image of top of shipping vessel

The first step in making a repair is identifying the problem. A thorough inspection requires gathering the right data needed to make an informed decision. Recently, ASI received a call about a vessel leaking oil from a newly installed stern seal. The ship had returned from dry-dock and the client suspected the liner was misaligned, causing the seals to leak when underway. They needed to confirm the cause of the leak before committing to a maintenance schedule. The tool used to test the alignment of a liner is called a dial indicator. The dial indicator is used to perform a ‘runout’ which will confirm how much the alignment has deviated. However, this tool is not usually used underwater.

The first step was to test the indicator in ASI’s test tank located in-house to see how the tool performed underwater. Once a liner runout was thoroughly tested, ASI confirmed with the client that although some water entered the gauge, the readings were accurate enough to make a reliable reading. The dial indicator could be used to successfully perform the liner runout underwater.  

commercial diver testing a dial indicator in a test tank
A commercial diver testing the dial indicator in ASI’s test tank, located in Stoney Creek, Ontario.

ASI’s team of divers were mobilized to the docked vessel, entered the water and proceeded to attach the dial indicator to the ship’s liner. While in-water, the dive team directed the ship’s crew to rotate the shaft and observed the gauge for any abnormalities. If the liner was misaligned (depending on the amount of the deviation), the dive crew would be able to realign it without returning the vessel to dry-dock.  

underwater image of a dial indicator attached to the ship liner of a large vessel
The dial indicator affixed to the ship’s liner.

The initial readings were just under the tolerance of the liner and appeared to be within the normal range for specifications. However, ASI’s divers noticed oil coming up from the aft cover ring (see the image below). This meant the leak was originating from a broken seal (or seals) and not from a misaligned liner. The oil was not only leaking when underway, as originally reported, but was also happening while the vessel was static. A realignment of the liner would not fix the problem.

image of underwater leak from ship liner
The red arrow indicates the location of the leak.

ASI’s diving crew was able to troubleshoot, test and apply a new method of inspection using an existing device. The data collected helped to identify the leak, providing the client with the information they needed to plan the appropriate maintenance and avoid making an unnecessary repair.

Sometimes a tactile approach is needed and ASI’s experienced commercial divers are ready to mobilize when our clients need them. From the West Coast of BC to the Great Lakes and beyond, ASI’s commercial dive crews provide a variety of reliable underwater maintenance and ship services.

Click here to learn more about these services.