The hydraulic fluid used in oil-filled elevator buffers to absorb and dissipate the kinetic energy of a descending car or counterweight in an emergency stop.
Full Definition
Oil buffers used in elevators rated above a certain speed use a controlled orifice through which hydraulic fluid is displaced as the plunger strokes under impact, converting kinetic energy to heat. The oil specification — viscosity grade, pour point, and oxidation stability — is critical to ensure consistent buffer stroke characteristics across the operating temperature range. Using incorrect oil can result in too-fast or too-slow buffer stroke and failure to meet EN 81-20 deceleration limits. Oil level must be checked at each periodic inspection and topped up with the grade specified on the buffer data plate. Oil must be replaced at the intervals specified by the manufacturer, as degradation affects viscosity and buffer performance.
