Everything you need to know about under keel clearance

  • 18/01/2022
  • 10 minutes

When a charterer understands some routine concepts in ports, navigation can be done in a much safer and faster way! That’s because, in a team where everyone is able to understand the safety needs to adjust the capacities of each vessel, it is possible to optimize processes and costs.

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An example of this is the Under Keel Clearance, or UKC, which is part of the terms of maritime chartering and must always be taken into account. We invited the expert Antonio Paulo Bastos, from Nautis Consultores Ltda., to further explain the concept and how this simple measure impacts several logistical decisions in a port terminal. Check it out!

What is Under Keel Clearance (UKC)?

Under Keel Clearance, also known in Brazil as “pilot’s foot”, is a simple measure, but very important for the routine of ports and ships. This indicator determines the smallest water depth between the bottom of the boat and the seabed. In other words, the space between the keel and the seabed.

The UKC usually needs to be determined in shallower regions such as rivers, deltas, canals and especially when approaching and maneuvering within port terminals.

The objective, of course, is to provide safety for maritime transport, preventing the vessel from running aground or breaking when it finds its berth. Therefore, it is the type of concept that influences various practical, marketing and logistical planning decisions in cargo handling and transportation.

How is measurement determined at ports?

The UKC is determined on the basis of ship size and port cargo volume capacity. And for that, two measures are defined: the pilot’s foot for the ship being loaded/unloaded (stationary) and during entry and exit maneuvers (in motion).

This is because the stationary ship allows for a smaller UKC. “When the ship is stationary, it may have a smaller safety margin below the keel. The ports themselves dig as little as possible for operational depth. It has to be enough for the boat not to touch the bottom”, comments Bastos.

When the vessel is in motion, the pilot’s foot needs to be more generous because of an important phenomenon called SQAT or SQUAT.

When the ship accelerates and water starts to flow faster through it, the pressure dynamics tends to cause it to sink a little deeper than when it is stationary. Therefore, the speed and nature of the movement influence this measure.

Other factors also determine the optimal Under Keel Clearance. One of them is the soil itself where it is being measured. Silting speed, type of bottom and quality of dredging carried out can impact the decision — even in the long term.

Another example that Antônio Bastos gives is the size of the canal: “the ship normally enters and leaves at high tide, with the UKC of the berth always considered at low tide. But, in São Luís, the ship cannot travel the entire channel at high tide, because there is no time. This had to be considered in the measure defined for the location”.

How important is the UKC in cargo transport?

Despite being a simple measure in concept, Under Keel Clearance is vital for the maritime operation and greatly influences trade logistics in the region. See how this importance is given to fundamental aspects of pilotage in ports and vessel movement.

General logistical planning

The entire operation of ships entering and leaving port terminals depends on the UKC. It will determine compatible ship types, maximum cargo movement on each of them and even movement times depending on the tide.

In other words, the measure impacts operating hours, the volume of cargo in the port, the type of adequate cargo and the order of entry of vessels for loading and unloading. Based on these needs, operators are able to optimize logistics with a planning that ensures maximum movement with as much load as possible at all times.

Operational Safety

Surely the productivity in ports is optimized to the maximum, but only to the point where safety is guaranteed. And a mistaken pilot’s foot calculation can lead to serious risks.

Antônio tells us that running aground can result in tears in the ship’s hull, in breaking the rudder or even in propeller blades. These are unusual events today precisely because of the seriousness with which the UKC is treated in the sector.

Bearing in mind that this type of incident is not just a safety issue for the professionals involved, it is also a source of damage: for the companies that own the ship and cargo and for the entire port, which may need to pause the operation.

Investment in new ports

Under Keel Clearance is not a primary factor in choosing suitable locations for building ports, but it can be an advantage in some ways.

When the bed in the chosen region is less prone to silting and already has a naturally greater depth, the terminal administration needs to spend less on dredging and other maintenance processes.

Cost optimization and cargo negotiation

An issue directly related to the UKC is the commercial side of operating a port. After all, the account impacts the cargo capacity on ships.

Ideally, all professionals and companies in the sector would like them to operate at all times at their maximum capacity, but each port terminal has its specific features and its pilot foot.

This means, for example, that even if the port where the vessel will be loaded allows for more volume, it is also necessary to think about the size of the destination terminal. A miscalculation can cause the ship to be prevented from docking.

It is a complicated matter of negotiation as it impacts the shipping quote, operating costs and the final price of the product. But whenever this dispute happens, the UKC has to be taken into account. Antonio details better:

“The charterer has to trust the carrier. If the first one says that he chartered the ship to load a number of tons in 11 meters of draft when entering the north bar, the maximum draft varies, but let us assume that it is 11.5. A ship that could enter with 12 must enter or leave with a reduced load in order to comply with the maximum draft.”

In other words, Under Keel Clearance is a simple and technically straightforward measure, but it needs to be well checked and respected for operational safety and cost optimization. With intelligence and planning, you can work efficiently taking the indicator into account.

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