Hydraulic Jack RAM: Direct Holeless Telescopic or Indirect Roped 2:1, Stainless Piston 40-200 bar, Relief Valve, EN 81-2 Buckling Factor 4

The hydraulic jack (also called ram, plunger, or cylinder-piston assembly) is the primary actuator in a hydraulic elevator. Types: (1) Direct-acting (holeless or telescopic): the jack is positioned directly beneath the car; a holeless jack is a telescopic multi-stage cylinder that does not require a borehole in the ground, instead fitting within the hoistway height; a single-stage direct jack requires a borehole at least as deep as the travel; (2) Indirect-acting (roped hydraulic): the jack is positioned horizontally or in the pit and connected to the car via a roping system (typically 2:1) — this allows the jack stroke to be half the car travel and eliminates the need for a borehole; (3) Jack construction: a stainless steel piston rod (ram) reciprocates within a steel or composite cylinder; seals prevent oil leakage; a stop ring or mechanical safety device at the top of the cylinder prevents the piston from being ejected; (4) Nominal operating pressure: typically 40–200 bar depending on car weight and cylinder bore; (5) Overpressure protection: a pressure relief valve set above the maximum working pressure prevents structural overload; (6) Failure modes: oil seal failure (slow leak, gradual car descent) — detected by re-levelling frequency or pressure loss monitoring; cylinder corrosion; piston buckling in overlong single-stage jacks. EN 81-2 (hydraulic lifts standard) specifies jack design, testing, safety valve requirements, and the required factor of safety against buckling (≥4).

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