When I ask mechanics what type of oil they are using in their hydraulic elevators, the typical answer is AW32, which is usually correct, but this answer does not necessarily mean what it once did.  The additive packages of AW32 have changes to meet specific needs of different machines and industries.

An AW32 picked up at an auto parts or farm store may have different additives than the bulk AW32 that the service company purchases for a mod.  Zinc, Phosphorus and Calcium were typically the only additives used in hydraulic elevators.

A new trend I am seeing, while analyzing oil from hydraulic elevators, is the presence of emulsifiers and detergents like Barium and Boron.  Boron is commonly used in the automotive industry as a detergent to scrub and emulsify particles in hydraulic system.  The emulsified particles are suspended in the oil and do not settle out to form sludge.

In the automotive industry, inline filters can hold these contaminants until the next oil change, however, this is not the case for hydraulic elevators.

Hydraulic elevators do not have inline filters and the oil is rarely replaced.  Boron in a hydraulic elevator, emulsifies the contaminates, constantly sending them through the valve.  Contaminates can foul the valve and wear out other hydraulic components.

Cloudy oil that will not settle out, even after the oil is removed from the reservoir is an indication of an emulsification problem.  Because the MSDS typically lists the additive package as proprietary, an oil analysis is the only way to know for sure what is in the oil

These additional additives do not have to be detrimental to the function of the elevator; however, they do change how we approach hydraulic oil maintenance and troubleshooting.

In the past, without the emulsifiers, the solvent refined oils would dissolve water and particles until they became saturated, at which point the solids would drop out of the oil as sludge.  Most elevator pistons were in-ground, so the sludge would drop to the bottom of the casing and not be seen until new oil was added to the system.  The new oil would dissolve the sludge and the oil would appear cloudy after a few weeks.

To protect the valve and other hydraulic components from being damaged by the suspended particles, offline filtration with a “depth” filter should be employed.  The advantage of the offline filtration system is that it does not interfere with the operation of the elevator.  The oil line does not have to be broken and the oil can be filtered below 5 microns.

Continuous fine filtration allows the water and particles to be removed from the oil, which will extend the life of the oil and hydraulic components.  Offline filtration takes advantage of the detergent additives, so they are beneficial instead of detrimental.

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