Do You Smell That??

Washington Elevator often receives questions about changing hydraulic oil (also referred to as fluid) in hydraulic elevators.  This post is intended to provide some clarity on what causes hydraulic fluid to degrade, symptoms of failed oil and possible solutions. 

If you take nothing else from this post, it is this: DO NOT change your oil without testing it first.   

Why is it important to care about your hydraulic fluid?

It provides many important functions in a hydraulic elevator.  Its primary purpose is to move the elevator up and down using pressure.  In addition to that, it prevents friction of components and transfers heat to keep parts cool.  Hydraulic fluid is not like motor oil, requiring changes after certain intervals.  In the ideal conditions, hydraulic fluid can last for the life of the elevator.  Unfortunately, there are external factors that can cause degradation and can contaminate hydraulic fluid and subsequent equipment damage.  One possible factor is a gel-like, residue called “varnish” which can accumulate in the system, causing mechanical components to wear and/or complete oil failure. 

You may experience one or more of the following symptoms related to hydraulic fluid degradation, which could point to a potential problem, as follows:

• Odor.  Contaminated oil can create unpleasant odors like a skunk (think Pepe Le Pew!), burnt food, rotten eggs, roadkill, almonds and chemical odors.   

• Cavitation.  Cavitation occurs when the volume of fluid demanded exceeds the amount being supplied.  The most common occurrence of this is when there is not enough oil in the system and the pump begins to pump air.  This is presented as a “knocking” or “grinding” noise as the elevator approaches the top floor.  Not only can this cause metal erosion in the hydraulic components (not good), it also introduces air and any contaminants it carries with it into the hydraulic fluid.  This is often solved by returning oil that has leaked from the system back into the tank.  While this resolves the cavitation issue, it can cause long-term damage to the oil.  Your service company should address the source of the leak (often a piston seal).   A clogged screen can also cause cavitation, which vaporizes the fluid and blocks the flow of fluid, which again can cause damage to the equipment and hydraulic fluid.   

• Overheating.  Some buildings just do not have enough elevators to handle the traffic.  They run constantly and the oil heats up as a result.  In some rare situations, the elevator starter gets stuck in the on position, causing the motor to run uncontrollably. As the oil is continually pumped, it can cause the hydraulic fluid to overheat. Overheating degrades the chemical makeup of the fluid.

• Fluctuations in oil temperature.  Imagine an office building that runs consistently during the day and then sits dormant overnight.  The oil warms up during the day and cools off at night.  Some elevator machine rooms are in unconditioned areas of the building, and temperature differences can cause condensation inside the tank (think about your cold beverage on a hot summer day).  This introduces water into the system. Water causes hydrolysis, which degrades not only the base oil’s molecules, but also potential additives. 

• Leveling.  Leveling is the act of moving the elevator platform level with the landing.  Code allows .5” of tolerance between the hall and car sill (this is the threshold you walk over when you walk in and out of an elevator).  However, mechanics are trained to adjust to 0” of tolerance because of the potential tripping hazard that is created.  Do you remember the one possible factor we mentioned above called “varnish”? Well, if that is within your hydraulic system, it can create additional friction on the internal surfaces, causing erratic control which can contribute to mis-leveling.   

• Transition speed.  When the elevator comes to a hard stop, stops between floors, fails to hold its position, stalls with large loads or shows signs of related symptoms, the elevator is experiencing transition problems.  Transition inconsistencies can be due to various oil deficiencies and contaminations.   

Now What? 

If you suspect issues with your hydraulic fluid... Test it!  Although it is very common in the elevator industry to simply replace the oil, each situation can be unique and oil replacement may not (always) be the answer. Testing may be needed to determine a custom solution and can be performed for a minimal cost. 

Why Test? 

1. Oil does not require replacement unless degradation or contamination has occurred.  DO NOT replace your oil just because it is old.  If replacement is recommended by your service provider, they should provide you with a reason why it is needed.   

2. Replacement does not guarantee success.  Varnish is very difficult to remove (or “see”) in the system as it accumulates on hard-to-reach surfaces.  There is the potential that adding new oil may just loosen the varnish, recreating the same issues and creating further problems.   

3. A good oil test checks for five critical health points: viscosity, water, particle count, acidity and membrane patch colorimetry (the MPC checks for varnish levels.) 

Only after you’ve tested your hydraulic fluid can you fully prepare an appropriate plan of action.  Various solutions after a test can include flushing of the system, filtering of particles, water removal and other oil purification processes.  These solutions typically cost far less (and are often more effective) than just replacing the oil alone.  

We hope you found this information helpful and feel free to reach out to our Chief Problem Solver, Sean to discuss your situation in further detail.  

At Washington Elevator, we strive to continuously improve the level of service we provide to our customers and appreciate our partner and lubricant expert, Doug at RelaDyne for his collaboration on this informative post.