It pays dividends to consider the most rugged and fault-tolerant material known when looking for a retrofit or newbuild seal option.
Lignum vitae is well known as the hydro industry’s original bearing material. This high-density wood has incredible compressive strength, self-healing properties and innate lubricity from a natural resin embedded in its structure. It is a proven solution for water-lubricated bearings on everything from aircraft carriers to Hydro applications – and now, it can be used for sealing as well.
In partnership with engineering consultancy Hydro Tech, Inc., Lignum Vitae North America (LVNA) has developed a line of seals to solve problems with premature failure of the standard resin-composite materials. The project was initiated for an Upstate New York-based utility, which had a horizontal water turbine that had seen numerous resin-composite seals fail prematurely due to overheating and wear. To solve these problems, LVNA manufactured a drop-in replacement seal of about 33 inches in diameter with a brass backing, designed to fit right into the existing seal housing.
The previous seal material was failing within as little as three days and six stop/start cycles. With the new lignum vitae seal, a break-in period of 1400 hours of operation and 20 stop/start cycles caused very little wear (less than 0.08 inches), and the remaining thickness of the seal did not change after break-in.
“Lignum vitae is an anomaly of nature and is the only known wood with no silica. It has an innate lubricity originating from guaiac resin imbued in every cell and a hardness like aluminum, based on its long-chain tenacious molecular cellulose structure. The mixture of the smooth resin bound up in an extremely dense cellulose structure yields a natural bearing material with a high lubricity and a massive compression strength,” says Bob Shortridge, founder and president of LVNA. “Bearings made from lignum vitae, simply put, are self-lubricating in water and conform by self-healing. The nature of the material is inherently able to adapt to extreme and dynamic operating environments with less than perfect shafts. It is startlingly that simple.”
No synthetic material can outcompete tried and true lignum vitae in real-world bearing performance. LVNA is proud to be leading the way with a sustainable supply of renewable lignum vitae that exceeds every environmental standard and solves EPA compliance requirements. Contact us to see how the Lignum Vitae North America personalized approach can lead to the solution for your needs.
Special thanks to Paul Benecki with Maritime Executive for providing article content.
Thrust bearings are one of the most complex and most expensive components in a hydro-electric plant. So why aren’t plant operators invested in better understanding this important technology?
When Albert Kingsbury patented the oil filmed hydrodynamic thrust bearing around 1910, bearings made from lignum vitae had been in delivering reliable performance for half a century. Kingsbury’s design relied on creating a wedge of oil film between tilting pads and soft Babbitt to give lift to the thrust pads. This system, despite adding complexity to the process, eventually became the industry standard as an extremely reliable and long-lasting solution.
Fast forward 100 years and evolving and increasingly more stringent environmental requirements are demanding cleaner, lower impact materials and processes. For plant operators, this means finding ways to remove oil from the proximity of water. This puts plant operators using Kingsbury’s “modern” oil filmed bearing technology in a challenging position. .
Fortunately, there’s a superior solution that pre-dates and outperforms today’s industry standard: lignum vitae. Quietly and continuously in use for more than 100 years, lignum vitae bearings are the only natural, water-lubricated solution with zero environmental impact.
Water lubricated lignum vitae thrust bearings meet today’s challenges through the unique ability to work on a “mixed mode of lubrication” inherent to the material Mixed mode allows the bearing to operate momentarily on direct contact with no lubrication. When water is restored, equipment can operate hydrodynamically on as little as .001 film of water. Traditional, oil filmed bearings simply can’t compete- wiping out in 1/10th of a second with no lubrication present. Lignum vitae has a natural guaiac resin in every cell that cannot be washed away and creates a glaze that is the perfect operating surface for a rotating shaft. This quality has kept many lignum vitae thrust bearings operating for more than 100 years.
Water lubricated bearings eliminate many of the environmental and performance issues associated with oil filmed thrust bearings. Plant operators can avoid costly maintenance and environmental fines that come from oil contamination, abrasion, thermal expansion, Babbitt/tin metallurgy quality, voltage discharge, high velocity lubricant flows, overheating and misalignment.
Fortunately, there is one provider that can give operators peace of mind when it comes to ensuring a clean, high performance and low maintenance assembly environment. Lignum Vitae North America
Not only was Lignum Vitae N.A. was awarded a US patent for our technology in 2018, we have the largest sustainable supply of lignum vitae material to satisfy the global demand for new and expanding environmental regulations, As oil film becomes obsolete and hydro applications expand, water-lubricated solutions will become the next generation of bearings. Let us show you how lignum vitae is the thrust bearing material that will outperform your expectations. Every application. Every product. Every time.
Lignum Vitae North America introduces a game changing new product, End Grain Water Lubricated Bearings, and how to get maximum life from them.
Since 2005 LVNA has provided water lubricated solutions for over 300 hydro-electric installations worldwide. These solutions were developed at our headquarters in Powhatan Virginia in response to challenges presented by our customers. Previous solutions for wicket bushings, mechanical seals, segmented seals, thrust bearings, shell bearings, and main guide bearings have all been born from this new facility.
In 2020 several customers requested a bearing configuration that could extend the bearing life for non-adjusting machines to address vibration issues and unplanned outages plaguing the plant for years. All the machines studied had lignum vitae installed originally then converted to composites over time. This change required a clearance of 1mil. per inch of shaft for the composite, vs. zero for lignum vitae, effectively adding 30mil additional clearance to a 30” shaft that brought the typical wear down from decades to a “new normal” of months. This new clearance introduced an imbalance in many units that led to a “hammering effect” causing inordinate adjustments and replacements. This challenge was met by our R&D group that immediately began extensive study into the problem and offer solutions.
Many of the machines in question are around 100 years old adding to the challenge of gaining back longevity that they previously experienced with LV. Rough housings with 100 years of rust added yet another layer to the challenge. Lignum vitae is the hardest wood commercially available with a hardness like aluminum and as slippery as Teflon. Lignum vitae holds the distinction as the only known tree with no silica present, instead it has a self-lubricating resin in every cell making it a perfect bearing material and true anomaly of nature.
LVNA had engaged Falex testing laboratory in 2015 to determine various structural parameters such as modulus of elasticity, coefficient of friction, sliding speeds and wear rates. LVNA was also in possession of extensive testing of lignum vitae performed over 100 years ago by the Society of Naval architects and engineers “SNAME” in 1915 and second test done in 1965 for the U.S. Navy that exhibited the EXACT same structural data that Falex documented in 2015. This information guided LVNA to recommend using “End grain” blocks stacked in rows with little to no space and milled as close to zero as possible to help facilitate hydrodynamic action as speeds allow.
When end grain was selected the next step was to determine how to join the ends of blocks for rigidity and stiffness. After some research it was determined end grain blocks may have never been joined in the manner proposed that led to next steps. 1900 era original installation techniques suggested labor intensive methods deemed unnecessary by LVNA that led to end grain joining tests. Multiple joining techniques were undertaken to represent the underwater environment they operate in. Swell tests, tension and compressive loads were applied until they exceeded all criteria without any metallic fasteners or complicated installation. Ultimately a permanent proprietary solution was found that exceeded all the customers’ needs making “end grain staves” available in several widths, thickness, and lengths.
The new staves can be easily installed in square, dovetailed slots, or smooth bores to be bolted, driven into existing dovetail slots, or laid parallel with no need for expensive installation tools. End grain will not shrink away from the shaft and has the unique ability to be milled as close to zero clearance as possible and hold the clearance in a submerged state or when de-watered for months.
Further study by Dr. Chris Ettles of Bearing Sciences demonstrated how lignum vitae can be held at very close clearance due to a phenomena unique to lignum vitae known as a “mixed mode of lubrication” by taking the initial “hard start” directly to the lignum vitae then turns hydrodynamic as speeds allow effectively reducing wear to zero. It was discovered when the lignum vitae contacts the shaft and is warmed a small amount of resin inherent to the wood creates a glazed surface creating an effective hydrodynamic surface that allows a wedge of water between the resin glaze produced and shaft itself. This glazed surface is unique to lignum vitae and is readily available in every cell of the material, is not water soluble and cannot be washed away.
LVNA is available anytime to troubleshoot, educate, supply, and deliver on time on budget every time.
Material training on-line or in person and samples are available on request.
Demand reliability compromise elsewhere.
During 31 years of operation, an upstate New York hydro plant had to replace its mechanical water seal ten times. The original seal had a modest life expectancy of a few years, but replacements failed far too quickly. In January 2018, Hydro Tech was called in to find a solution. Click the link to read the full case study from Hydro Tech.
It’s somewhere that no engineer or maintenance team wants to be – staring down the shaft at a failed bearing. Frustrated that it happened again, and at the worst possible time. Yet it happens, more often than anyone in the maritime industry would like. In recent years, it’s been an unfortunate reality, and all that anyone could hope for was that it was discovered while your asset was in port, where you could seek out a quick fix, or furlough your workers until repairs have been made. Maybe, it happened underway, putting your crew and your customer’s cargo at risk, with no easy or quick way to make repairs. Regardless of the circumstance, you’re faced with costly unplanned downtime, mission readiness is compromised, and you have an urgent problem to address, all because of repeated bearing failure and ongoing challenges keeping your assets operationally on point.
You’re not alone. There’s a simple – old school, even – solution that can solve your bearing problems and reduce your spending on ongoing maintenance and component replacements, all while ensuring that your sea-going assets are ready for any situation. A bearing solution that is unmatched in its longevity, reliability and performance in extreme operating environments.
How is Lignum Vitae N.A. doing it? One piece of wood and one ship at a time, with water-lubricated bearings manufactured using genuine lignum vitae material. The original bearing material used in ships dating back to the 1860s, bearings made with lignum vitae material deliver low wear in abrasive water environments and have a high resistance to shock, loading and vibration. Bearings made with lignum vitae material have been documented in the INS Vikramaditya lasting more than 33 years without a single failure and reducing the need for costly ongoing maintenance. Self-lubricating, ABS and DNV-GL certified, lignum vitae bearings and seals also guarantee no harmful discharge, making them ideal for use in blue and brown water environments.
The proof is in the performance and the maritime industry is taking notice. Last year, representatives working on behalf of the Indian Navy reached out to Lignum Vitae N.A. to help ensure the mission readiness of the country’s naval fleet. Their imperative was clear: design a bearing solution that was capable of ensuring mission-critical reliability while also measurably extending the service life of the fleet to 50 years. Lignum Vitae N.A. engineers were able to respond with a bearing solution that not only replaced all of the existing bearings on the INS Vikramaditya, but restored the ship to her original design specifications with stern tube bearings made with lignum vitae material, helping the Indian Navy ensure another 33 years of uninterrupted service for this important asset.
Click to view this Hydro Review article from May 2013
“When the turbine guide bearings installed at several hydroelectric plants in the U.S. suffered short lives and significant wear, the owners turned to lignum vitae material. Their experience has shown that this material, although more costly, can provide longer service life than composite and plastic bearing materials.”
The addition of the Vacuum Pressure Vessel compliments existing processes designed for total saturation to meet and exceed current Marine and Hydro standards.
Total saturation of a water lubricated bearing guarantees 100% reliability of bearing performance required for everything from large to small hydro.
Installation of this vessel has reduced lead times by reliably saturating material in hours and days vs weeks and months. Proper saturation is critical for water lubricated bearings.
This collapsed timeline was proven critical when LVNA was asked to provide 55 thrust and main guide bearings for the 1912 Historic Blewett Falls Hydro Station operated by Duke Energy. LVNA reverse engineered, produced working drawings, manufactured, and delivered in 30 days from PO. These new lignum vitae bearings will continue to produce clean renewable energy for many more decades.
Lignum Vitae North America provides Longevity, Reliability, and Performance to both the Hydro and Marine Industries. Contact us to see how the Lignum Vitae North America personalized approach can lead to the solution for your needs.
This week on Mythbusters Lori Ann and James debunk the lignum vitae availability myth. While walking through the shop they uncovered 500 tons of premium bearing grade material. If you thought you could no longer obtain genuine lignum vitae, THINK AGAIN! #hydro #lignumvitae #bearing #thrustbearings #material
- It’s The Water Temperature
- It’s The Water Condition/Silty
- It’s The Marine Growth
- It’s The Shaft Quality
- It’s The Air Entrainment
A simple and cost-effective way to address ongoing premature failure, degradation and performance problems in polymers is shifting to lignum vitae bearings and seals.
The no-excuse solution lignum vitae is inherently able to adapt to extreme and dynamic operating environments:
- Zero Clearance
- Run of river water, No Filtering*
- Zero Wiping or Smearing of Material
- High Resistance to Shock, Edge Loading/Vibration issues
- Low Coefficient of Friction
- Oil/Grease-Free Operation
- No Hydrolysis Degradation/perfect memory
- Conforms to Worn Shafts
- Only industrial Renewable Bearing
- Mixed-mode of Lubrication/Dry Start & Hydrodynamic
- First water-lubricated bearing – 1854, the same for centuries
Our team of engineers and specialists collaborates with plant operators to understand their unique challenges to design long-term solutions made with lignum vitae. Contact us to see how the Lignum Vitae North America personalized approach can lead to the superior solution for your needs.