Tips for Cutting and Grinding in Shipbuilding Applications

By Tony Hufford, Category Manager, Metal Fabrication, and David Jescovitch, Abrasive Specialist Manager, Weiler Abrasives Group

 

Shipbuilding applications bring to mind massive external structures fabricated from large pieces of metal, possibly using an automated process for long seam welds. But what may not come immediately to mind are the many parts inside a ship that need to be fabricated — including all of the tubes and pipes used for the vessel’s electrical and plumbing systems or even handrails and stairs.

These smaller components typically require cutting and grinding as part of proper weld preparation and post-weld finishing. Operations try to fabricate as many of these components as possible under roof in a job shop environment and may assemble them in the shipyard before installing them inside the vessel as the last step in the process. But that isn’t always possible. Sometimes the cutting, grinding and finishing needs to take place in the more difficult-to-reach confined spaces of the ship itself.

Learn how to choose the right cutting and grinding products for shipbuilding applications and some key best practices to gain optimal results.

 

Common Challenges in Shipbuilding

Because final assembly of many parts takes place inside the ship, work is often completed in hard-to-reach, confined spaces — often under tight contract deadlines.

The operator may have to walk or crawl through the ship ballast with tools and equipment to get to the point where the work is done — which can be hundreds of feet from the power source. When the power source is a long distance from where the work is performed, it can affect which cutting and grinding tools are best suited for the job.

Many operators prefer air (pneumatic) tools over electrical tools, but when the compressed air hose is stretched over a long distance, it can result in pressure that is too low to properly run the tool and abrasive being used. Air tools will bog down more than electric right-angle grinders when trying to maintain surface speed if they are underpowered. In both cases of an air or electric tool being underpowered, using a grinding or cutting wheel with a softer bond can help optimize performance.

 

Cutting and Grinding Needs  

Handheld tools such as air and electric right-angle grinders and die grinders are most often used in the line fabrication, finishing or painting areas of a shipyard operation for tasks like weld prep, cleaning in between weld passes, and post-weld cleaning and finishing.

There are numerous handheld tools and product options available. While operators sometimes use the tool and accessory that are most convenient, it pays off in greater productivity and labor savings to choose the right product for the job. Determining the best solution requires considering several key factors.

• Customer requirements. Will the end product be used in a military fleet or as a commercial vessel? This has a big impact on the final specifications and any regulations or requirements, including the type of coatings that may be added to the ship. Understanding the final specifications is the first step toward selecting the proper tool and accessories.
• Material type. Aluminum and carbon steel are two common materials used for components in shipbuilding, but operators may encounter other metal types as well. Be sure to know what type of material is being worked on and use an abrasive product designed for use with that metal. To avoid cross-contamination, do not use products designed specifically for steel on aluminum or stainless steel. Also, if a product specifically designed for aluminum or stainless applications has been used on steel, do not use it on aluminum or stainless.
• Work environment and conditions. It’s important to consider whether speed of completion or product longevity is more critical when cutting and grinding in these confined space applications. If it takes the operator 30 minutes to get to the point of the work — and he or she is limited in how many tools they can carry to the site — it’s not very efficient to use a fast cutting or grinding product that only lasts 15 minutes before it needs replacing. In this situation, it can save time and money to use a more durable product, such as a ceramic disc. While battery-powered tools are becoming more popular in these applications, they often don’t have the battery life to perform in all-day production environments. Using a super thin cutting or grinding wheel, such as a 1-millimeter-thick wheel, on cordless tools helps reduce tool strain to prolong battery life.

 

Abrasive Product Options

The wide variety of abrasives used in shipbuilding applications can range from coated and bonded abrasives to wire brushes to nonwoven abrasives. For example, wire brushes are frequently used to remove the discoloring that forms on aluminum during welding, while resin fiber discs may be used to remove excess material and get to bare metal so the operator can reapply necessary coatings. Each product category has pros and cons depending on the specific task.

Bonded abrasives, such as grinding wheels, can be used to remove thicker mill scale in preparation for welding or for grinding parts down to ensure they’re all uniform. Cutting wheels can be used for plunge cuts, such as cutting out a window in a larger piece of metal. They are also commonly used to edge into the tops and bottom of welds to ensure complete penetration and aid in inspection.

Coated abrasives include flap discs and resin fiber discs, which are common accessories for shipbuilding applications. These can be used for blending, oxidation removal, grinding and finishing welds. Coated abrasives provide a fast cut rate without the potential for slowing down or loading up like a bonded abrasive might.

Power wire brushes come in many sizes and configurations, including wheel brushes, cup brushes, and end brushes. These products are often used to remove spatter between weld passes or for post-weld cleaning. Choosing a specific type of power brush depends on the work being performed. End brushes, for example, are good for cleaning fillet welds and hard-to-reach small spaces. 

Operators who use air tools sometimes choose a needle scaler instead of a wire brush, especially for thick rust or dirt. While needle scalers have a long life and can work well to remove very heavy material, they are also much slower to get the job done compared to wire brushes. An operation using needle scalers should consider the significant productivity gains that could be achieved by using wire brushes for those tasks. 

 

3 Best Practices for Success

Once the proper product for the application is selected, following some basic best practices can help prolong accessory life and deliver better performance.

1. Avoid using extra-long air hoses or power cables for hand-held electric or air tools on the jobsite, since this can cause a drop in performance and power. If using a long power cord or air hose is the only option, be aware that certain abrasive accessories work better and more efficiently than others when there is less power or air pressure.  Understand the psi at a particular work station to make informed decisions.
2. While it’s tempting — especially in hard-to-reach, confined spaces — don’t settle for using the same accessory for every job. Operators may also turn to the same product they’ve always used without considering how different products can provide greater success. Matching the abrasive to the job can help improve performance, productivity, and operator safety.
3. Always follow proper techniques for safe usage of abrasive products. This includes using the tool guard and any necessary safety gear. Proper operator training can also help reduce the labor time spent on cutting and grinding since products typically deliver better performance when they are used at the intended angle, speed, pressure and orientation to the material.

 

Optimize Cutting and Grinding Results in Shipbuilding

The specific challenges of cutting, grinding and finishing in shipbuilding applications make it especially critical to choose the proper abrasive accessory for the job. The right product can help save time and money — and reduce hassles for operators working in difficult environments.