Customer application 21 September 2017

Heeling Compensation

The stability of mobile cranes on land is comparatively easy to ensure; a suitable counterweight is set based on the load, and a few minutes later, hydraulic supports extend several meters outwards for balance. However, it is commonplace for bulky and especially heavy loads to be transported to their destinations primarily via water. This raises the question as to how stability is ensured for onboard cranes – water is known as an unstable surface. Systems made of pumps, valves and ballast tanks hold cargo and commercial ships upright. Often called “heeling pumps,” these systems prevent listing of the ship’s body in the case of unevenly distributed loads. To control them, the specialists at BESI rely on WAGO's PFC200 Controllers in combination with the WAGO-I/O-SYSTEM 750 for Ex and non-Ex areas.

Vessels which can be identified from afar are called “MPV Heavy Lifters,” as they have at least two large cranes on deck. These multi-purpose vessels are designed specifically for handling bulky and heavy cargo. According the Michael Borchers, Chief Technical Officer at BESI, their cargo has included rocket parts, turbines and even entire trains. In a current new construction project, the two cranes of one “MPV Heavy Lifter” can exceed 1500 metric tons of lifting capacity. The heeling compensation systems on such ships have to be designed with corresponding abilities.

Tank Ballast and Cargo Management – Here’s How WAGO Supports You:

  • Automation and communication technology from WAGO has all of the necessary approvals for maritime use, so it meets international standards.

  • The modularity of the WAGO-I/O-SYSTEM guarantees flexibility and allows custom adaptation and expansion of the automation.

  • The WAGO-I/O-System offers a high degree of functionality in a compact design.

Balancing Act with Ballast Water

“The ship has compensation tanks distributed across the entire stern, which our system can quickly and precisely empty or fill with ballast water,” explains Borchers. This is the only way for the ship to maintain its balance during loading and unloading. Lifting the cargo and compensation by the pumps is performed in parallel. Consequently, the loading process can only move as fast as the heeling pumps are able to create weight compensation using ballast water – nevertheless, this should function as fast as possible to maintain short logistics times, according to Borchers. However, the heeling compensation system must function reliably, above all, regardless of the time demands. “If one pump suddenly fails, then an entire ship can turn extremely fast,” says Borchers. By this, he means that the boat will capsize, or “turn turtle,” as it is colloquially known. “If the heeling system is interrupted, then the crane operator cannot react fast enough to lower the load at the correct time when arranging heavy loads onto the deck.” Dropping the load from the hook in an emergency is still possible from the quay, because the ship can use the quay itself as a counter weight; however, this is impossible from the sea side, because the load would crash onto the ship.

Redundant Industry Standard

This is a scenario that explains why BESI relies on high-availability technology and equips its systems with sufficient redundancies. To control the “flow management” process, the company from Bremen uses WAGO's PFC200 Controllers – and in a redundant and spatially distributed function network configuration. BESI groups the heeling system, as well as the measurement, control and monitoring of tank contents, under flow management. Due to the high fuel consumption in large commercial and container ships, fuel and ballast water must be regularly transferred during travel so that the ship retains a stable trim that’s optimized for energy efficiency.

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Omitting Zener barriers enables a space-saving control cabinet design.