Governor & Overspeed Protection Flashcards
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Read the first 7 Governor & Overspeed Protection flashcards as text
On a hydraulic elevator, the overspeed valve (rupture valve) is designed to close when:
Answer: Oil flow rate exceeds a preset limit during descent
The rupture valve closes automatically when downward oil flow exceeds the rated descent speed flow rate, stopping uncontrolled descent.
Where is the overspeed valve (rupture valve) required to be located on a hydraulic elevator?
Answer: On or directly adjacent to the cylinder
ASME A17.1 requires the rupture valve to be located on or immediately adjacent to the hydraulic cylinder to minimize unprotected piping.
Which type of elevator does NOT require a centrifugal governor but uses an alternative overspeed protection method?
Answer: Hydraulic elevator
Hydraulic elevators use a rupture valve or similar device instead of a centrifugal governor because they are driven by fluid pressure, not a rope/drum.
On a roped hydraulic elevator, which overspeed protection device is typically required?
Answer: A governor and safeties in addition to the rupture valve
Roped hydraulic elevators require both a governor/safety system for the ropes and a rupture valve for the hydraulic circuit.
What is the effect of worn or damaged flyweight pivot bearings on a centrifugal governor?
Answer: The governor trips at a higher speed than designed
Worn bearings increase friction, requiring higher centrifugal force (higher speed) before flyweights extend enough to trip the governor.
A progressive safety device is distinguished from an instantaneous safety because it:
Answer: Gradually increases stopping force to limit deceleration rate
Progressive safeties use a wedge or roller system that gradually increases clamping force, limiting car deceleration to protect passengers from injury.
What is the maximum tripping speed for a governor on a traction elevator with a rated speed of 200 ft/min?
Answer: The governor must trip before the car reaches 140% of rated speed
ASME A17.1 requires the governor to trip at no more than 140% of rated speed to ensure safeties engage before excessive speed causes structural damage.