Most hydraulic elevator jacks installed in the past only have a single bottom and were placed directly in the ground. These in-ground cylinders are prone to corrosion and electrolysis which can lead to small leaks or catastrophic failure of the entire hydraulic system. Updates in the safety codes require that replacement cylinders have double bottoms, which minimizes serious safety and environmental risks.
When a replacement hydraulic cylinder is necessary, Northern Elevator Company can replace your single bottom cylinder with a double bottom cylinder which is tape coated and installed in a PVC liner. The thick PVC liner surrounds the sides and bottom of the cylinder and protects the cylinder from groundwater electrolysis. We also install a thick rubberized tape coating as an extra measure of protection. Taken together, these measures almost entirely eliminate the risk of catastrophic hydraulic cylinder failure.
Whether your hydraulic cylinder is currently leaking or you are taking proactive preventative measures to ensure against a catastrophic hydraulic failure, Northern Elevator has a solution that will increase the safety of your passengers and protect the environment.
Replacement Hydraulic Cylinder / Safety Code Mandated Design Changes
For years, the standard industry cylinder design was a cylinder with a single plate welded to the bottom. If the weld at the bottom of this cylinder fails, the elevator system can experience an immediate loss of oil pressure, resulting in an uncontrolled descent of the elevator car and a potential high-speed stop in the pit.
In 1971, United States elevator safety codes began requiring that a “safety bulkhead” or double bottom cylinder be used. The double bottom referred to is an additional plate which contains an orifice which allows a controlled evacuation of oil in the event of a failure of the cylinder. In 1989 the United States elevator safety codes began requiring various forms of corrosion protection for hydraulic cylinders. Depending upon the exact location and date of the particular installation, a tape coating, cathode protection or PVC protection may have been required by applicable code.
Many of these code changes are not retroactive, so many hydraulic elevators with single bottom cylinders, as well as hydraulic elevators with no protection from corrosion, are still in service. Several proposals addressing this issue have recently been acted on by the A.S.M.E. hydraulic elevator code committee, including specific maintenance procedures, and making mandatory certain upgrades or hydraulic cylinder replacements.
Regular and systematic elevator maintenance, together with periodic testing of the equipment, is no guarantee against catastrophic failure of the cylinder, particularly with respect to the older single bottom elevators. For example, the bottom plate of the cylinder may suddenly give way, resulting in a potentially severe accident, without the system experiencing any previous underground loss of hydraulic oil. Therefore, an ongoing program of preventive maintenance alone does not provide absolute assurance against a catastrophic failure of the cylinder.