Hydraulic Elevator Systems Flashcards
7 cards from real CET practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Hydraulic Elevator Systems flashcards as text
What is the function of a hydraulic elevator's anti-creep feature?
Answer: Automatically corrects slow unintended car movement due to internal valve leakage
The anti-creep circuit detects slow unintended movement and runs the pump briefly to restore the car to floor level.
Which component in a hydraulic power unit prevents the pump from operating against a closed system when the car reaches the top landing?
Answer: The up-limit switch that de-energizes the pump motor
The up-limit switch de-energizes the pump motor when the car reaches the top terminal, preventing the relief valve from having to handle continuous full-pressure bypass.
Hydraulic oil viscosity MOST directly affects elevator performance by:
Answer: Altering flow rates through valves, which impacts leveling and ride quality
Viscosity determines how easily fluid flows through valves and orifices, directly affecting leveling accuracy, speed, and ride quality.
When performing a pressure test on a hydraulic elevator, the system pressure is typically held at what level above working pressure?
Answer: 50% above working pressure for 24 hours
ASME A17.1 requires a pressure test at 150% of working pressure, held for a specified period to verify cylinder and piping integrity.
What is the purpose of a silencer or muffler installed on a hydraulic elevator pump unit?
Answer: To dampen pressure pulsations and reduce noise from the pump
Hydraulic pump silencers are installed in the pressure line to absorb pulsations that cause noise and vibration in the piping and car.
A submersible hydraulic power unit differs from a surface-mounted unit in that:
Answer: The entire pump-motor assembly is submerged inside the oil reservoir
Submersible units place the motor and pump inside the fluid tank, reducing noise and eliminating the need for a separate machine room.
In a hydraulic elevator system, what is the role of the check valve located between the pump and the cylinder?
Answer: It prevents fluid from returning to the pump when the pump is off, holding the car in position
The check valve allows flow only from pump to cylinder, preventing backflow that would allow the car to descend when the pump stops.