We hope you find this information valuable and insightful. When it comes to critical life safety decisions, Lonestar Jack & Drill is dedicated to equipping you with the knowledge you need to make informed choices throughout this process.
We encourage you to explore all the pages on this site to gain a better understanding of the different jack assembly construction and installation methods, as well as the various safety and cost options available to you.
Direct-acting hydraulic elevators function by forcing pressurized oil through a valve into an underground steel cylinder. This cylinder extends to a depth equal to the elevator’s travel distance. The hydraulic pressure pushes a piston upward, lifting the elevator platform and car enclosure. To lower the car, the system releases oil from the cylinder in a controlled manner, using the car’s weight to regulate descent, braking, and stopping. Hydraulic systems do not require load-bearing guide rails, as the elevator is fully supported by the piston and jack cylinder. However, due to their design, hydraulic elevators cannot be fitted with traditional safety mechanisms without significant modifications to both the elevator system and the building structure.
For many years, the standard industry design for hydraulic elevator cylinders featured a single plate welded to the bottom. If this weld were to fail catastrophically, the system could suffer an immediate loss of oil pressure, leading to an uncontrolled descent of the elevator car and a potentially dangerous high-speed stop in the pit.
To address this risk, U.S. elevator safety codes were updated in 1971, requiring the use of a “safety bulkhead” or double-bottom cylinder. This design includes an additional bottom plate with an orifice that allows for a controlled release of oil in the event of a bottom failure, significantly reducing the risk of injury to passengers.
By 1989, further updates to elevator safety codes mandated the use of corrosion protection for hydraulic cylinders. Depending on the installation date and location, protective measures such as tape coatings, cathodic protection, or PVC encasements were required. However, many of these safety improvements were not made retroactive, meaning numerous older hydraulic elevators still operate with single-bottom cylinders or without corrosion protection.
Despite regular maintenance and periodic testing, older single-bottom cylinders remain at risk of catastrophic failure. In some cases, the bottom plate may suddenly collapse, causing a severe accident—even without any prior signs of underground hydraulic oil leakage.
To enhance safety, the A.S.M.E. hydraulic elevator code committee has proposed updates, including specific maintenance procedures and mandatory upgrades. However, relying on preventive maintenance alone does not provide absolute assurance against cylinder failure, particularly for aging elevator systems.
The underground environment poses several challenges for hydraulic cylinders. Factors such as alkalinity, sulfur, salt, electric currents, and other chemical agents in the surrounding soil and groundwater can lead to cylinder corrosion.
As the risks of underground cylinder corrosion became evident, elevator cylinder manufacturers introduced various protective measures. Some cylinders have been coated with tapes and specialized coatings, while others utilize cathodic protection through an anode or impressed current. Additionally, some cylinders are enclosed within PVC encasements to further minimize corrosion.
While these methods help extend the lifespan of hydraulic cylinders, they do not provide the same level of protection against overspeeding or free fall as traditional safety mechanisms. Despite these advancements, accurately determining the current condition or remaining lifespan of an underground hydraulic cylinder remains a significant challenge.
The jack is the core component of an in-ground hydraulic elevator, responsible for raising and lowering the load. Modernizing your hydraulic jack enhances the safety of your elevator for passengers while also helping to reduce environmental impact by protecting the assembly from corrosion and leaks underground.
Many older hydraulic elevators may lack the safety devices and environmental protection features that are standard in newer installations.
Before 1971, the national elevator code (ASME A17.1) required underground hydraulic cylinders to have a single welded bottom. Many of these single-bottom cylinders remain in service today. However, the welded joint that connects the bottom plate to the cylinder wall is vulnerable to corrosion and leaks over time.
This deterioration can lead to a sudden loss of oil, causing the elevator to descend at an unsafe speed, posing a serious risk of injury to passengers and potential environmental hazards to the property.
In response to these risks, recent code updates in Maine and Rhode Island now mandate the replacement of single-bottom cylinders. In Massachusetts, regulations require that these cylinders either be fitted with a safety device or replaced with a cylinder featuring a safety bulkhead. Additionally, in 2002, the State of New Hampshire issued a safety advisory notice, recommending the replacement of all single-bottom cylinders to enhance passenger safety and system reliability.
Before 1966, many of our installations featured cylinders with a double-bottom flat plate and a safety bulkhead plate.
This cylinder design remains code-compliant today, as it helps reduce the safety risks associated with a single-bottom weld failure. However, most of these cylinders have been underground and unprotected for over 40 years, making them susceptible to corrosion and leaks.
To ensure long-term safety and reliability, we highly recommend replacing these aging cylinders.
The safety bulkhead design includes an orifice that restricts the elevator’s descent speed to 15 feet (4.5 meters) per minute in the event of a cylinder bottom failure.
In 1971, the ASME A17.1 code mandated that all new installations incorporate this double-bottom plate with a dished safety bulkhead. This design shifts the bottom welds to a less vulnerable area of the cylinder, enhancing safety and durability.
“If you rely on an elevator, you can rely on Lonestar Jack & Drill!”
In 1989, the ASME A17.1 elevator code was revised to introduce corrosion protection requirements for underground cylinders. New installations were required to include tape coating, cathodic protection, or PVC protection to prevent deterioration.
Since then, Lonestar Jack & Drill has recommended PVC protection for all new elevator installations. This protective barrier encases the walls and bottom of the in-ground cylinder, shielding it from soil and environmental elements. Made from durable, non-corrosive material, PVC protection enhances the longevity and reliability of hydraulic elevator systems.
“If you rely on an elevator, you can rely on Lonestar Jack & Drill!”
Today, Lonestar Jack & Drill installs sealed High-Density Polypropylene (HDPE) protection wherever possible. This protective barrier fully surrounds the walls and bottom of the in-ground cylinder and is sealed at the cylinder head. Made from durable, non-corrosive material, HDPE protection exceeds current code requirements, providing enhanced long-term safety and reliability.
Sealed HDPE protection offers a reliable way to monitor the space between the cylinder wall and the protective barrier. It includes an evacuation port that allows for the removal of water or other liquids that might otherwise come into contact with the cylinder and cause corrosion. While HDPE protection is primarily used for new installations, it can also be implemented in replacement projects where access conditions allow.
“If you rely on an elevator, you can rely on Lonestar Jack & Drill!”
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