Basic Anchoring Procedures

Anchoring procedures are not just about lowering and heaving up the anchor. Prior to this, a number of steps must be followed in order to ensure that the anchor is ready to be lowered or heaved up. The following video explains these steps further.

There is a common belief amongst people and prospective seafarers who have never been on board, that a ship is held in position solely by the anchor. In reality, the weight of the anchor chain is very important when it comes to holding a vessel in position.

The Catenary Ratio

This is the ratio of length of chain on the seabed against that of the chain hanging in the water. In normal weather, the catenary ratio is considered to be 1:5, whilst in heavy weather, the ratio increases to between 1:7 and 1:8. The Master will determine what is required for current and future forecasts.

Dragging Anchor

This is said to occur when a vessel starts to drift without holding power despite being at anchor. This is considered to be extremely dangerous if unnoticed as several accidents such as collision, grounding or stranding have occurred during such circumstances. There are various reasons which might cause a vessel to drag anchor, the main ones include:

• Bad seabed at the anchoring area.
• Heavy weather conditions.

The ship Master needs to keep these in mind before choosing an anchoring position. By checking the type of seabed and looking at the expected weather forecast for the entire duration of the vessel being at anchor, the Master can make a good assessment of how to anchor for the best results.

Here is a link, leading to the Marine Accident Investigation Branch (MAIB) reports. Here you will find various reports of ships dragging anchors resulting in disasters.