Lerch Bates Inc. Building Insight

Global Leaders in Technical Consulting for the Building Industry

Hydraulic Jack Leaks

Has your elevator maintenance contractor told you that you have a leak in a hydraulic jack and that it must be replaced?  Have they told you that it will cost you anywhere from $25,000, (on the low end), to over $100,000?  Have they told you that this price is not firm and if they encounter unexpected underground condition the cost could go significantly higher?  Have they told you that this added cost is on an hourly, time and material basis, and that the rate is over $350/hour?

The cost to replace a below ground hydraulic jack is huge!  And leaks are always unexpected.  So unless these kinds of dollars don’t mean much to you, you may want to make sure that the leak is REAL!   If the jack moves a foot or more, and there is no visible signs of the displaced oil, chances are you have a leaker.  But if the movement is several inches or less, more testing is still a lot cheaper than that complete jack replacement job.

Elevator codes require no-load hydraulic jack tests annually and full-load tests every five years.  But it is impossible to know for sure what is going on under the surface, so there is no way to be sure if there is a leak.  An elevator may pass the testing one day, and start leaking the next.

Prior to 1972, in ground hydraulic jacks were made with flat, single bottoms.  The stationary part of the jack, the part that is burried in the ground and subject to corrosion and electrolysis, is the cylinder.  Early cylinders were nothing more than standard pipe with a welded cap at the bottom.  Starting in 1972, the elevator code required that cylinders have a safety bulkhead, commonly referred to as a double bottom.  The double bottom jack provides protection against catastrophic failure from the whole bottom of the jack giving way, typically at the welded cap, due to deterioration of the weld and the pressure in the hydraulic system.  But a double bottom doesn’t protect against the effects of electrolysis along the entire length of the burried jack.  Most leaks these days occur somewhere along the length of the jack where is has been exposed to water or other unknown and unpredictible below ground conditions.

In California, Code requires that an elevator be shut down if there is any unexplained loss of hydraulic oil.  But there are many possible explainations for a loss of oil.  Oil can leak through the various valves in the system and back into the tank.  The volume of oil decreases as the temperature of the jack decreases.  Over the years small amounts of oil can leak around the jack head and into the ground. Drip cans and buckets often fill up and overflow, or the drain lines may clog, causing the oil to leak around the top of the jack down to the pit floor.   Most jacks over 20 ft. in length are made from multiple sections.  The piston, the moving part of the jack that is attached to the bottom of the elevator car, is a machined piece of hollow pipe and multiple sections are threaded together.  A rubber ‘O’ ring seals the joint.  If that ‘O’ ring fails, the oil can even leak into the jack itself.

The surface area of an elevator tank is large enough that, even on smaller tanks, a single gallon of oil, more or less, is unnoticable.  So if the oil leaks back through the valve and into the tank, there is no way of knowing for sure.

We recently encountered a 15 inch diameter jack that the elevator company claimed was leaking.  They tested the elevator with a full load of almost 20,000 lbs. and in one hour the elevator dropped less than one half inch.  This they claimed was a leaker.  But this owner was not about to authorize spending over $100,000 on this evidence.  So we did another test.  The oil in the ground was allowed to cool to ground temperature to eliminate thermal effects.  Next, the elevator was loaded to full capacity.  Then the oil line in the pit was disconnected as the cylinder so there was no chance of any oil leaking back into the tank or anywhere along the oil line.  The location of the car was marked, and the elevator was left for over 24 hours.

Low and behold, the elevator did not move.  No leak!  This test cost the owner less than $5,000.  Pretty good savings compared to replacing a jack that might not even be leaking.

There are 50 year old single bottom jacks installed in areas with high ground water that continue to work without leaking.  And there are jacks less than five years old, installed with protective tape coating and installed within sealed PVC liners, that leak.  There are many variables in the installation process that can render the PVC and other protections ineffective.

A leaking jack is a serious and costly problem, not to mention that the EPA frowns on hydraulic oil contaminating the ground.  This is not a problem to be taken lightly.  But considering the costs, it is best to make double sure that the leak is genuine and not imagined.

Should you inspect and test your exterior building maintenance system?

Worker safety should always be a number one priority when working with exterior building maintenance equipment. Due to wear and tear and in some instances faulty installation, OSHA requires annual inspection and testing of exterior building maintenance equipment.

Testing should include a visual inspection of all system components, including eye bolts, davit pedestals, davit sockets, davit arms and hoisting cables. The inspection should also include safety tie backs and horizontal lifelines.  All deficiencies should be noted and corrected before use.

Frequently, areas in which the components are connected to building structures are not visible, due to roofing materials etc.. In these circumstances, a visual inspection of the attachment to building structure is not possible.  In this instance a load test is required in order to ensure that the equipment is in safe workable order.  At a minimum, regardless of accessibility, the equipment should be load tested at least once every ten years.

The test results including deficiencies should be presented in a report format so that the building maintenance company may clearly understand the noted deficiencies and correct them before the equipment is utilized.

Earthquakes and Elevators

In March 2010, I had the unique opportunity to review earthquake damage on 11 traction elevators located in two hotels in Santiago, Chile.  On Sunday, February 27, 2010 at approximately 3:30AM, and lasting for nearly four minutes, an 8.2 Richter earthquake struck near Santiago Chile. Damage was extensive to many buildings and a loss of life was experienced in and around the epicenter, which was about 130 miles from Santiago.

The two hotels, while in close proximity to each other were very different; one was older and low rise while the other was newer and higher rise. The first, an 8-story low-rise hotel included six traction elevators; three passenger and three service.  All elevators were installed in 1965. The second, a 24 story high-rise hotel included five traction elevators; three passenger and three service.  All elevators were installed in 1998.

After the quake, in the 8-story hotel, each of the six traction elevators had the counterweight assemblies come out of the rails.  Fortunately, the hotel had a seismic monitoring device that automatically stopped the elevators at the next floor when seismic activity was first detected.  This feature, which worked just as designed, prevented more damage to the elevator cars like counterweight frames crashing into the car tops.

In the 24-story hotel no counterweights came out of the guide rails.  These elevators were also equipped with a seismic detection instrument that immediately placed the cars out of service when seismic activity was detected. One of the passenger cars had its hoist cables come out of the 2:1 car top sheave grooves while the car was in motion.  The hoist cables had to be replaced.    Other than that, no damage occurred to the cars with bracket spacing at 1.8 meters.

The biggest cause of damage to the elevators occurred with a 6 inch waterline on the top floor of the 8 floor hotel ruptured allowing water to flow across the floor for two hours running down the passenger elevator shaft.  This caused failure of the microprocessor boards on top of the car (Mitsubishi locates their car controller on the car top).  It also damaged door operators and caused flooded pits.

The lessons I learned from this experience were:

  • Lesson 1: in earthquake zones, always equip the elevators with seismic detection instruments to immediately stop the car.
  • Lesson 2:  Guide rail brackets should be spaced more closely together.  All of the counterweights derailed in the hotel with bracket spacing of 4.0 meters but none of the counterweights derailed with bracket spacing of 2.0 meters.
  • Lesson 3:  All sheaves should be equipped with rope restraints eliminating the ability of the ropes to jump grooves.
  • Lesson 4:  Always know where the shut off valves are located for major water pipes in the building.  While this is not an elevator related piece of equipment, it would have prevented the significant damage to the electrical boards.