Materials in Motion

Overhead Cranes for Marine-Duty Locations

For most marine-duty applications, the overhead crane must be equipped to withstand harsh marine conditions in a corrosive salt-water environment. This application calls for specific types of overhead lift systems that are specifically designed for marine and outdoor applications.

If you’re looking for a crane you can use within five miles of salt-water, we do have some suggestions, outlined below.

Freestanding Jib Cranes can be galvanized to resist corrosion when installed near a body of water. It’s important to ensure all components are designed for this specific application. For instance, motorized boom rotation will require a NEMA 4X enclosure to keep the wires safe from salt-water and sea mist found in marine-duty applications. Furthermore, galvanizing the steel will prevent it from corroding in salt-water environments. These are pretty obvious elemnents to keep in mind, but there are many other factors to take into consideration:

  • Stainless steel motors
  • Stainless steel components, such as brackets and chains
  • Powder coated gear boxes 
  • NEMA 4X: comes in two different designs, stainless steel or fiberglass, both of which ensure components will not rust.

Sodium chloride (the chemical term for salt) is extremely aggressive to metals. Stainless Steel must be 316 Stainless Steel for maximum efficiency. You can use 303 or 304 Steel, but they’re not preferred. These types of steel are not stainless and will not resist corrosion as well as 316 Steel. Aluminum must always be avoided, but in rare cases it can be used if it has a marine-duty anodized surface coating to increase corrosion resistance.

What Constitues a Marine-Duty Crane?

Any crane that is installed or used within five miles of a salt-water body or sea mist is considered a marine-duty crane. It’s important to note that marine-duty cranes are not the same as maritime cranes. Maritime cranes are physically bolted to a ship, boat, or on the ground beside a body of water. Any lift system that is to be used on a boat or ship must be gear driven/positively driven in order to hold down components that could flail about at sea. Installing a crane on the shoreline can be very dangerous due to swells, high seas, crashing waves, and water current.

Dockside Applications

In order to maintain worker safety, there are many factors that must be considered. For instance, the wind limit, sea-height limit, water-current speed, and distance from the water itself all play a part in deciding which type of provisions you will need for your overhead crane and applications.

Jib cranes, for example, can be used to pull a boat from the water or lift an engine for replacement or repair. Gantry cranes can also be used to lift heavy equipment from a boat in dock or for a diver training center. Equipment that is operated in salt water must be specifically engineered to meet the requirements of a marine application for safety and durability.

For most manufacturers it’s a good idea to get a written statement from the customer assuring that the marine-duty crane will not be used near waves, there will be no lateral shifting of lifted loads, and there will be no side loading of the boom. This statement should include: “Hoses will not impart any side or lateral load on the boom, and the jib won’t be used to drag or pull hoses laterally.” Jib cranes, for instance, are not designed for any lateral movement at all or to resist lateral loading (pulling or dragging loads).

If you are thinking about providing a dockside or marine-duty crane on any body of water, it is the users responsibility to install the crane safely and protect their workers. For example, a lifting plan should be written to establish safe conditions prior to any lift. But, there are some precautions you can take in the configuration of your material handling system for marine applications. To do so, it’s essential that you let any manufacturer know that your crane needs to be designed to meet marine-grade or maritime standards. Oftentimes, customers will purchase a crane for marine duty, but fail to tell the manufacturer what they will be using it for. Without this knowledge, the manufacturer does not have the necessary information to protect your crane from corrosive and salt-water environments. But if you explain what you will be using the crane to do before it’s designed and sold, the crane manufacturer will most likely implement particular safeguards to protect the crane and workers from injury.

For more information about marine-grade lift systems and applications, check out Lloyd’s of London’s Register code for lifting appliances in a marine environment. Although Lloyds is an insurance company, they released their own standards/code for marine applications to guarantee they’re only insuring systems designed correctly for salt-water environments. This helps them to avoid insuring products that are hazardous, dangerous, or ineffective. And, it can help you to ensure your purchasing the right system for the job with safety and longevity in mind.

If you’re looking to buy an overhead lift system for your dock, boat, ship, or marina, always do your research first and ensure that your system isn’t hazardous, dangerous, or ineffective for your specific application.

Kristina Harman

Technical Writer | Spanco.com

Kristina Harman is the senior technical writer and content manager for Spanco, Inc. Kristina has twelve years of experience in content development, technical communications, and copyediting. She holds a Bachelor of Science Degree in English from Towson University and a Master of Education Certification in English from Johns Hopkins University. She is a member of the Society for Technical Communication and the American Medical Writers Association.

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