Using Sensors on a Floating Dry Dock

A dry dock is a narrow land-based basin or vessel which may be flooded to permit a load to be floated in, then drained to allow that load to come to rest on a dry platform. Dry docks are utilized for the maintenance, construction, and repair of boats, ships, and other types of watercraft.

Mainly used to carry ships that need repair or maintenance, a floating dry dock is in the form of “U” structure. Numerous regular sea-going, small and mid-size vessels also dry dock in a floating dock. The ship is brought close to the channel where the floating dry dock will submerge itself partially, the ship is then slid into the dock.

The floating dock is de-ballasted once the ship is in position, this is to drain the water from its hollow floors and walls to support the vessel for maintenance or repair. The entire process takes about eight hours, during which the drydock is submerged.

Floating dock side view. It is 220 yards long and 18 yards height from upper deck to bottom.

Floating dock side view. It is 220 yards long and 18 yards height from upper deck to bottom. Image Credit: Senix Corporation

Floating Dry Docks have advantages over regular dry docks:

  • By extensive retrofitting/rebuilding, the floating dry dock can be modified and increased in size in all dimensions.
  • By ballasting the dock, the complete floating dry dock can be aft or forward trim, which further assists the ship or the damaged vessel, which cannot be given a trim.
  • They may be installed close or far from the shore inside the harbor, making them a space-saving, portable structure without taking space of the shore facility.

A high quality and a sensitive level sensor was required by Asistechio Ltd. of Uruguay in order to monitor all aspects of floating drydock operation, including submersion, leveling, and strain control. Senix ToughSonic Ultrasonic sensors were chosen, as they are designed to be tough.

With its potted and protected electronics, 316 stainless steel housings, and IP68 rating, Senix sensors can be employed in tough environments, like marine applications with exposure to seawater.

Front views. Ships being repaired resting on the dock’s working surface.

Front views. Ships being repaired resting on the dock’s working surface. Image Credit: Senix Corporation

To measure liquid level, Asistechio was utilizing bubbler type sensor technology previously, one sensor in each ballast tube. A tougher sensor technology was needed for the application. Expected operating temperature range of 28 °F to 122 °F and humidity range of 50 - 100 %.

After doing rigorous testing, Horachio Venturino of Asistechio Ltd. Said, “Our Floating dry dock project is advancing, and we haven’t had any problem with Senix sensors. In fact, I would say it is a pleasure to work with these superb quality sensors.”

Asistechio’s project started in Oct 2017 with 24 tanks, which needed liquid level measure for their floating dry dock for either river or ocean use. Their dock is submerged then a ship is floated over it, and air pressure is applied to tanks in the dock to raise it and the ship.

In order to measure the level in vertical tanks used to sink and raise the dock, multiple sensors are utilized. Other sensors were used to measure overall dock freeboard and tilt management to control tilt and height.

The ToughSonic 50 sensors were mounted in the top of 37 feet long, 8 inches diameter stilling tubes.

The ToughSonic 50 sensors were mounted in the top of 37 feet long, 8 inches diameter stilling tubes. Image Credit: Senix Corporation

Each ballast tube had a Senix ToughSonic 30 sensor mounted in the top of a closed "air pouch or bell" (a tube of 8 inches diameter and 32 inches long).

The sensor/tube array was mounted to the tank's ceiling. The tube’s length was calculated so that at the maximum depth, the trapped air compressed but the water level stopped at around 32 cm below the sensors' surface to maintain the minimum working range required by the sensors.

The numerous ToughSonic 30 sensors were employed to measure both the tide and the dock’s inner ballast tanks water levels. The multiple ToughSonic 50 sensors were utilized to measure the dry dock’s outer ballast tanks water levels and also the whole dock freeboard and draft. These were mounted high on each of the dock’s corners in addition to the middle of the sides.

We have successfully completed the floating dry dock project for which we bought Tough Sonic sensors. We owe that to Senix sensors superb quality added to the versatility of their configuration. Totally satisfied!

Horacio Venturino, Asistechio Ltd.

The ToughSonic 30 sensors were mounted in the top of a closed "air pouch or bell" (a tube of 32 inches long and 8 inches diameter)

The ToughSonic 30 sensors were mounted in the top of a closed "air pouch or bell" (a tube of 32 inches long and 8 inches diameter). Image Credit: Senix Corporation

This information has been sourced, reviewed and adapted from materials provided by Senix Corporation.

For more information on this source, please visit Senix Corporation.

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