Understanding Dunnage: Essential Cargo Protection Techniques.
Introduction
Ever wondered what keeps cargo safe and secure during rough seas or long voyages? Whether you’re a seasoned deck officer or a budding cadet, one term you’ll often hear on board is dunnage. It might sound simple, but it’s one of the most crucial aspects of cargo handling and stowage.
In this blog, we’ll dive deep into the world of dunnage—unpacking what it is, why it matters, what materials are used, and how it’s applied on merchant ships. As a fellow seafarer, I’ve seen how proper use of dunnage can mean the difference between a safe passage and serious cargo damage.
So, grab your cup of tea or coffee and let’s set sail through this essential part of cargo operations.
What is Dunnage?
Dunnage refers to the materials used to protect, support, and secure cargo during transportation—especially inside the cargo holds of ships.
In simple terms, it’s the stuff that goes between, under, or around cargo to stop it from moving, absorbing shock, or getting damaged. Think of it as a cushion or barrier placed strategically to prevent friction, water damage, or crushing during loading, unloading, and transit.
Who Uses Dunnage?
Dunnage is extensively used by:
- Deck officers and cargo supervisors aboard merchant ships
- Stevedores and terminal operators at ports
- Logistics planners and cargo engineers
In short, anyone involved in the safe handling and shipping of cargo appreciates the value of well-used dunnage.
Why is Dunnage Important in Shipping?
Onboard a moving vessel, cargo shifts are risky—often dangerous. Adjusting weight or sudden rolling of the ship can cause unsecured items to shift, crash, or break.
Here’s why dunnage is critical:
- Prevents cargo damage: It acts as a buffer to minimize rubbing, vibration, and impact, especially with delicate items.
- Avoids contamination: Keeps the cargo clean and free from moisture or contaminants from the hold.
- Improves ventilation: Facilitates air circulation around cargo, which is vital for perishables.
- Ensures even load distribution: Helps spread the weight evenly to prevent excess load on certain parts of the ship.
Trust me, eliminating dunnage from cargo planning is like omitting lifejackets from a lifeboat—you just don’t.
Types of Dunnage Materials Used on Ships
Now the big question—what materials are used as dunnage?
Different types of dunnage suit different cargo and vessel types. Here are the common materials used by us seafarers:
1. Wooden Dunnage
This is the most traditional and commonly used type on board general cargo ships.
- Usually made of rough timber or planks (untreated or lightly treated)
- Placed under and between cargo for support
- Resistant to compression and shock
- Ideal for heavy cargo and pallets
Note: It’s essential to use pest-free wood in compliance with international regulations like ISPM 15, especially for cargo bound for ports with strict quarantine laws.
2. Plastic Dunnage
Plastic mats, sheets, or spacers are often used when moisture resistance is a priority.
- Common in reefer containers and ships carrying food items
- Helps in quick cleanup and reusable
- Lighter than wooden alternatives
Tip: When carrying food or pharmaceutical products in reefer containers, I always prefer polypropylene dunnage to avoid contamination.
3. Paper-Based Dunnage
Environmentally friendly and often used where chemical purity is crucial.
- Includes corrugated paper, kraft paper rolls, or honeycomb boards
- Lightweight and recyclable
- Ideal for separating delicate items like electronics
4. Air Bags (Inflatable Dunnage)
Airbags or inflatable bags are used to fill gaps between cargo in containers or inside ship holds.
- Quickly adjustable to any size
- Great for reducing lateral movement
- Useful in container ships and general bulk carriers
5. Foam Dunnage
Foam comes handy when you’re dealing with sensitive and fragile cargo like electronics or high-value items.
- Good shock absorption
- Customizable and cut to fit any shape
- Often used in Ro-Ro vessels or car carriers
6. Metallic or Synthetic Dunnage
- Used where additional strength is needed
- Typically found in transporting steel coils or large cylinders
Where is Dunnage Applied?
The use of dunnage is seen:
- In the cargo hold of multipurpose vessels
- Inside containers (container stuffing)
- On deck when securing heavy cargo
- In port terminals during temporary storage
Proper placement is critical—especially below the cargo (to keep it off the wet bilge), between items (to prevent rubbing), and sometimes on the top (as shock absorber or separator).
How to Use Dunnage Effectively?
Using dunnage is more than just tossing timber beneath the boxes. It’s a skill—probably something you’ll perfect over time and multiple voyages. Here’s what I’ve learned from my years at sea:
- Inspect your dunnage: Make sure it’s clean, dry, and free from pests.
- Keep it dry: Damp dunnage can ruin cargo quickly—especially paper-based items.
- Choose the right type: You don’t use air bags for steel coils or timber for frozen food.
- Follow ship’s cargo plan and stability requirements.
- Secure even the dunnage itself: Loose dunnage becomes a hazard during rolling or pitching.
When is Dunnage Especially Necessary?
There are certain cargo operations where you can’t skip dunnage at all:
- When the cargo isn’t palletized (like loose cartons or boxes)
- For breakbulk and out-of-gauge cargo
- During heavy weather transits
- Transporting cargo with high moisture sensitivity
Trust me, dunnage is your invisible superhero during monsoon season across the Bay of Bengal or while sailing through the unpredictable North Atlantic.
Regulations and Best Practices
As global trade becomes more efficient, there are international standards you must follow regarding dunnage use. The International Maritime Organization (IMO) and SOLAS provide regulations for safe cargo handling, including dunnage.
For wooden dunnage used for international shipping, regulations from the International Plant Protection Convention (IPPC) under ISPM 15 ensure it’s properly treated to prevent pest transmission.
Make sure:
- Wood dunnage is heat-treated and marked appropriately
- All types of dunnage are disposed of per port and environmental regulations
- Cargo securing and dunnage follow the ship’s Cargo Securing Manual (CSM) as per SOLAS Chapter VI
Conclusion: Dunnage—Small Material, Big Impact
To sum it up, dunnage might be something simple like a wooden plank or an inflatable bag, but it plays a giant role in maritime cargo safety.
As a seafarer, I’ve seen first-hand what happens when proper dunnage isn’t used—broken cargo, rework, claims, and long hours spent fixing preventable mistakes. On the flip side, smart use of dunnage can save time, protect cargo, and ensure safe voyages across international waters.
So next time you’re on board, preparing for cargo loading, pay special attention to this humble, yet vital element of shipping. Your ship, your cargo, and your chief officer will thank you.
Useful Resources
For more in-depth information, you can reference:
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