5 Important Things You Need to Know About Marine Anchor Chain

Edward Wang
Edward Wang

General Manager

Marine anchor chains play a crucial role in the shipping industry by ensuring secure and dependable mooring for ships and vessels. At Zava Marine, we have compiled a set of five essential questions about anchor chains. Our comprehensive guide aims to help you gain a thorough understanding of the boat anchor chain. To empower you to make informed decisions regarding the selection of appropriate anchor chains and their maintenance. Delve into the following sections to acquire valuable insights into this vital component of the maritime industry.

anchor chain

What is a chain of anchor?

A marine anchor chain refers to a heavy-duty chain specifically designed for use with ship anchors. It serves as a critical component of the anchoring system, providing strength, stability, and weight to keep the anchor securely in place.

The marine anchor chain connects the anchor to the vessel and acts as a link between the anchor and the ship’s structure. It plays a crucial role in holding the vessel in position, preventing drifting or movement caused by wind, currents, or waves.

Manufacturers typically produce marine anchor chains from high-strength steel, offering various sizes and grades. The selection of chain size and grade depends on factors such as vessel size, anchor weight, and intended usage.

What are the different chain grades?

In the context of boat chains, marine applications commonly utilize specific grades known as “marine-grade” or “boat-grade” chains. While a standardized grading system for boat chains does not exist exclusively, the marine industry often associates the following grades with marine use due to their corrosion resistance and durability:

Grade 30: This grade represents a general-purpose, low-strength chain suitable for light-duty marine applications. Grade 30 chains find utility in tasks such as anchoring small boats or securing non-critical loads on board.

Grade 40: Marine-grade chains often start at Grade 40, which provides higher strength compared to Grade 30 chains. Boaters commonly use Grade 40 chains for anchor lines, mooring lines, and other moderate-duty marine applications.

Grade 50: This grade offers a higher strength level and increased corrosion resistance compared to Grade 40 chains. Boaters often utilize Grade 50 chains for anchor chains on smaller vessels or for other critical marine applications that require enhanced strength.

Grade 70: Marine-grade chains can also encompass Grade 70 chains, specifically designed for transportation and tie-down purposes. While not exclusive to boats, Grade 70 chains with appropriate corrosion-resistant coatings can be suitable for certain marine applications.

Stainless Steel Chains: Stainless steel chains are highly corrosion-resistant and are often preferred for marine environments. They are available in various grades, such as 304 and 316 stainless steel, which offer excellent resistance to saltwater corrosion. 

Chain GradeStrengthCommon Applications
Grade 30LowAnchoring small boats, securing non-critical loads
Grade 40MediumAnchor lines, mooring lines, moderate-duty applications
Grade 50HighAnchor chains on smaller vessels, critical marine applications
Grade 70HighTransportation, tie-down purposes
Stainless Steel ChainsVaries depending on grade (e.g., 304, 316)Anchor chains, mooring lines, critical marine applications

How is anchor chain length calculated?

To achieve optimal mooring of a marine vessel, experts generally recommend using specific ratios for chain length or anchor line length relative to the water depth.

A chain length of approximately 5 to 8 times the water depth is typically considered sufficient for anchoring. This guideline ensures proper scope and allows the anchor to hold securely.

When using an anchor line instead of an anchor chain, a general rule of thumb is to ensure that the line length is at least ten times the water depth. This increased length compensates for the lower weight and reduced holding power of anchor lines compared to ship anchor chains.

Adhering to these recommended ratios helps to maximize the effectiveness of the anchoring system, providing the necessary scope for the anchor to set and hold the vessel securely in place.

anchor chain blog

How is boat anchor chain size determined?

Determining the appropriate anchor chain size involves considering several factors related to the vessel, anchor type, and anchoring conditions.

1. Vessel Size and Weight: The size and weight of the vessel play a significant role in determining the anchor chain size. Larger and heavier vessels require thicker and stronger ship anchor chains to provide sufficient holding power.

2. Anchor Type and Weight: Different anchor types have varying holding capacities and recommended chain sizes. It is crucial to match the anchor type with the appropriate chain size for optimal performance. The anchor manufacturer usually provides recommendations for the compatible chain size.

3. Water Depth: The depth of the water where the vessel will be anchored is an important consideration. The general rule of thumb is to have a scope ratio of 5:1 – the length of the anchor chain should be five times the water depth. This ratio allows for proper anchoring and provides enough horizontal distance for the anchor to hold securely.

4. Holding Requirements: Consider the expected weather conditions, currents, and seabed composition at the anchoring location. Stronger currents or softer seabeds may require a larger anchor chain size to ensure secure mooring.

Regulatory Guidelines: Some maritime regulations or classification societies may have specific guidelines or requirements for anchor chain size based on vessel type or size. It is essential to consult these regulations to ensure compliance and safety.

anchor chain size

Images and data from suncorstainless.com

How often should ship anchor chains be inspected?

The frequency of inspections may vary depending on factors such as vessel usage, operating conditions, and the chain’s age and condition. 

1. Pre-Departure Inspection: It is advisable to visually inspect the anchor chain before each departure. Check for any visible signs of damage or wear, such as rust, corrosion, bent links, or excessive wear on the links. Make sure to secure the chain properly and ensure that it is free from any entanglements or obstructions.

2. Regular Maintenance Inspections: Conduct more comprehensive inspections at regular intervals, such as monthly or quarterly. It depends on the frequency of vessel use. These inspections should include a thorough examination of the entire length of the chain. You need to pay close attention to areas near the anchor and connections to the vessel. Look for signs of wear, elongation, distortion, or any other indications of damage or weakness.

anchor chains inspect

3. Professional Inspections: Periodically schedule inspections by qualified marine surveyors or chain experts to ensure anchor chain integrity and expertise. These inspections should occur at longer intervals, such as annually or biennially. You can evaluate the structural integrity of the chain, measure wear, and detect any potential issues.

4. Post-Extreme Weather Inspections: After experiencing severe weather conditions, storms, or rough seas.It is crucial to inspect the anchor chain thoroughly. These events can subject the chain to significant loads and stresses, potentially causing damage or weakening its structural integrity.

Remember, if you detect any signs of damage or significant wear during inspections, it is crucial to address them promptly. You should promptly undertake necessary repairs or replacements to maintain the reliability of the anchor chain and ensure safe anchoring operations.

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