Lignum Vitae LLC: Growing Environmentally Safe Water-Lubricated Bearings From Trees
September 7, 2021
It may come as a surprise to learn that some of the best industrial bearings in the world are made not of space-age synthetic materials but of the wood of a tropical tree. Lignum vitae is a hard wood with a distinctive resin that makes excellent water-lubricated bearings. With increasing concerns about the pollution that can be caused by leaks in oil-lubricated bearings, water-lubricated bearings are becoming more popular. Bob Shortridge is the president of Lignum Vitae North America, LLC, which creates water-lubricated bearings for hydro and military applications around the world. In this interview, Mr. Shortridge tells us why he brought lignum vitae wood back into the marketplace, how he started his company, and about his business today.
Hydro Leader: Please tell us about your background and how you came to be in your position.
Bob Shortridge: My background is in construction. For 35 years, I built highly engineered, heavy timber homes, buildings, and ski resorts anywhere heavy wind, snow, and seismic conditions called for structures that could withstand extreme conditions. My passion for engineering the indestructible led me to a lignum vitae auction at the Newport News shipyard. I bought 2½ tons of the wood and started researching its history and uses. I was surprised to learn that lignum vitae wood was used to fashion the first successful stern tube bearing for shipping when sailing vessels gave way to screw vessels. It was patented in hydro in 1882.
I realized that lignum vitae was more than just wood and saw enormous potential in the modern hydroelectric marketplace. After being used extensively in hydro and marine applications for more than a century, it had been largely replaced by modern plastics and engineered composites. These materials, though, come with a number of expensive challenges for today’s hydro plants. Lignum vitae is self and water lubricated and offers decades of uninterrupted performance and improved environmental compliance while reducing ongoing maintenance costs, costly downtime, and fines. I started to promote lignum vitae as the environmentally friendly bearing and got the attention of hydro plants, many of which had been originally equipped with lignum vitae bearings, and some of which were looking for only their third bearing change since 1931. There is literally no other bearing available today that can offer 40–45 years of uninterrupted service before needing to change.
Hydro Leader: How does a lignum vitae bearing compare to a metal or oil-lubricated bearing?
Bob Shortridge: It is difficult to do a direct comparison, because factors such as the machine’s balance and alignment and how the material is used have a big effect. The simplest explanation is that lignum vitae works using what is known as a mixed mode of lubrication. That means that it is both self lubricating and water lubricated. We’ve refurbished about 400–500 hydro plants since 2005 and have found that lignum vitae was used in two different ways: as long strips or tubes and as end-grained blocks. The end-grained blocks were the most effective because they took advantage of the material’s natural hardness and lubricity of its distinctive resin. The material can ride directly under the shaft under a pure load, or it can work hydrodynamically, becoming a wear-free component. When it's working hydrodynamically, there's a thin boundary of water between the shaft and the bearing. That’s why some of these bearings don’t wear for 40–45 years.
Hydro Leader: Where does lignum vitae come from, and how rare is it?
Bob Shortridge: Initially, I was able to find lignum vitae at exotic wood yards around the United States and Europe. From these sources, I was able to launch the business with about 38 tons of material. It is indigenous to what the U.S. Department of Agriculture calls plant hardiness zone 13, which spans from Miami to Costa Rica. Overharvesting during World War II led the Convention on International Trade in Endangered Species (CITES) to set clear guidelines for the sustainable harvest of lignum vitae. Like any valuable commodity, lignum vitae is at risk of exploitation, which is why we are in complete agreement and rigorous compliance with CITES’s harvesting, reforestation, and trade guidelines.
Hydro Leader: What does 38 tons of lignum vitae look like?
Bob Shortridge: Thirty-eight tons is about one small shipping container. To give you a sense of how far that goes, the refurbishment of an 80‑megawatt (MW) unit requires about a quarter ton, or 500 pounds, of material. We have a harvest permit that allows us to remove small quantities of material. Almost any sawmill you’ve ever seen cuts more material before lunch than we harvest in a year. The resources are small, but we harvest them in a sustainable manner.
Hydro Leader: Do other companies use and sell lignum vitae?
Bob Shortridge: We have strategic partnerships all over the world and supply genuine lignum vitae material to them. There are a handful of other companies that claim to offer lignum vitae, but we are the only supplier with a commercially viable and sustainable inventory of genuine lignum vitae.
Hydro Leader: Does lignum vitae wear out or lose its resin?
Bob Shortridge: The resin never washes out; it’s not water soluble. It can only be broken down with acetone, alcohol, or another similar solvent. In fact, even in plants that have been down for 20–25 years, we’ve been able to clean the bearing and reuse it. If the wood dries out, it and the resin are still good. Nothing leaks from it, drains from it, or dries out from it. In fact, lignum vitae can operate both dry and wet.
Hydro Leader: Do you work internationally?
Bob Shortridge: In addition to the United States, we work in Canada, the Czech Republic, England, India, Kenya, Korea, Poland, Sweden, and Vietnam.
Hydro Leader: Would you say that interest in your product is growing in the U.S. market, or is there still a heavy preference for oil bearings?
Bob Shortridge: U.S. Environmental Protection Agency regulations are changing, and so are the politics of renewable energy. Because of that, we’re seeing an uptick of interest in the United States, which is our largest hydro market. We are spinning in more than 10,000 MW in the United States. Canada accounts for about a third of our hydro. We also are engaged in conversations with one of the largest hydropower producers in the world, which is exploring the benefits of changing its fleet from oil-lubricated to water-lubricated bearings.
Hydro Leader: What kind of service does your company provide?
Bob Shortridge: I built this company on finding solutions and bringing a creative problem-solving mindset to every customer we serve. We are proud of our unique ability to fulfill orders correctly and quickly. We know our customers’ names and their pain points. As a point of reference, we have twice delivered aircraft carrier bearings to India within 10 days of a purchase order.
Other examples of our services include machining and installing water-lubricated seals and bearings in new equipment and in older, more challenging turbines; reverse engineering existing bearings; and providing onsite training for bearing installation. We have a 13,000‑square-foot state-of-the-art production facility with full machining capabilities.
Hydro Leader: What are the company’s top concerns?
Bob Shortridge: When I worked in timber framing, we used heavy timbers, a lot of craftsmanship, and specialized equipment, but we found that we weren’t competing against other timber frames—we were competing against two-by-four construction, which was faster, cheaper, and easier. The same phenomenon is happening in the bearing industry: We compete with composites and plastics, which are extruded, cheap, and fast. In 16 years, I’ve only had two people in hydro tell me that longevity didn’t matter and that all they cared about was making the unit run so they could sell it. I seek out customers who take a longer view, and we find that those customers seek us out.
Hydro Leader: What is your company’s vision for the future?
Bob Shortridge: We’re focused on driving sustainability for the environment and for our customers’ businesses. What’s more sustainable than growing our components on a tree? If all are to live in this world, we cannot keep polluting our waterways. We must seek a sustainable path forward; our goal is and will remain zero oil and zero pollution. We were certified by NSF International as the number 1 environmentally safe bearing in the world, and we plan to keep that position.