Hydraulic Jack Failure Alert
There is a noticeable increase in hydraulic jack failures that we want to share with you. Specifically, this safety concern is with Dover DMC’s. As a reminder, Dover DMC’s were installed from approximately 1985 to 2001 and thousands are still in operation. While these systems can run for years, parts are getting harder to find, and failures can happen without warning, which would cause major disruption. Dover equipment is easily identified by the unique Dover “Impulse” fixtures.
WHAT MAY BE CAUSING HYDRAULIC JACK FAILURES?
We have recently been involved in multiple repair & modernization hydraulic projects involving failed Dover hydraulic jacks and we have received similar feedback, from a local drilling company, where most of their work is done on elevators from the 1960s to mid-80s / early-90s. For these reasons, the following email notification was recently sent to Washington Elevator service customers:
As your service partner, we want to alert you to a growing trend we’ve observed: an increase in catastrophic jack failures in hydraulic Dover DMC elevators, specifically those equipped with in-ground jacks.
Upon failure, our inspections have consistently revealed leaks at the assembly joints — the connection points where individual jack sections are screwed together. In-ground jacks are buried below the elevator pit floor, making them difficult to inspect or access, which often delays detection of critical issues.
While your elevator system may not fall into this category, we believe it’s important to share important and relevant industry developments to help you stay informed and proactive.
HOW DO YOU KNOW IF YOUR HYDRAULIC JACK HAS FAILED OR IS AT RISK?
Because of safety concerns, code has very strict guidelines for hydraulic systems.
Any compliant State of Washington Maintenance Control Program (MCP) will have an oil loss log. Elevator companies must log any time oil is added to the system. In many cases, oil leaks from the jack packing, which is collected in a bucket and returned to the reservoir, which is common.
If there is ever unexplained oil loss that cannot be identified, it must be logged in the MCP and further tests are required.
Failing jacks typically present in one of two ways:
(1) There is a slow leak that causes the elevator to slowly descend. The elevator will relevel frequently or “cavitate” (struggles) at the top floor.
(2) Failure can occur during a Category 1 test (completed once a year) - which checks the pressure inside the system to make sure it’s safe. Or during a Category 5 test (completed every 5 years) - which makes sure an elevator can still carry the heaviest weight it’s supposed to — and do it at the right speed going up and down. For example, in Washington State we load the elevator to 125% of its rated capacity by loading 2,500 lbs into a 2,000 lb‑capacity elevator.
If a hydraulic elevator fails a Category 1 or Category 5 test, the elevator must be taken out of service immediately.
This is a picture of a jack that failed. During original installation it was wrapped with tape. After decades of use, it developed a small leak at one of the joints. This was installed underground, so there is no way to inspect it.
IMMEDIATE NEXT STEPS.
Don’t hesitate to contact your service provider or your favorite Chief Problem Solver with Washington Elevator Sean, who would be happy to help you build a plan that fits your building’s needs. You know your building best. The urgency depends on your risk tolerance. To read more about hydraulic jacks click here or to learn more about a DOVER DMC’s click here.
**Disclaimer: The information shared here is meant to be helpful and informative about recent safety events. While we do our best to make sure it’s accurate, we can’t guarantee it’s complete or perfect for every situation. Please use your own judgment and check other sources if needed.