Question 1

In a direct-acting hydraulic elevator, the jack is located:

Accepted Answer

A direct-acting (holeless or in-ground) hydraulic elevator uses a single-acting cylinder (jack) installed directly beneath the car. The pressurized hydraulic fluid extends the plunger upward, lifting the car. Descent is controlled by releasing fluid back into the reservoir through the control valve. Holeless hydraulic systems use a telescoping jack that doesn't require an underground casing.

Question 2

A hydraulic elevator car slowly lowers (drifts) by itself when stopped at a floor. The MOST likely cause is:

Accepted Answer

Slow drift (downward creep) in a stopped hydraulic elevator is typically caused by a leaking down (lowering) valve that doesn't fully close, allowing fluid to slowly return to the reservoir. It can also be caused by an internal cylinder seal leak or a leaking check valve. This is a maintenance concern — excessive drift can cause a re-leveling issue or floor sill height non-compliance.

Question 3

The pressure relief valve on a hydraulic elevator power unit is set to:

Accepted Answer

The pressure relief valve (PRV) is a safety device that opens if system pressure exceeds a set point — typically 125–150% of the normal working pressure. This prevents damage to the cylinder, fittings, and pump unit from over-pressurization. The PRV must be checked and verified as part of periodic maintenance. It must not be used as a flow control device.

Question 4

A single-acting hydraulic elevator can only be driven:

Accepted Answer

Single-acting hydraulic elevators use the pump to push oil under pressure to raise the car. Lowering is accomplished by opening a control valve allowing oil to return to the tank by gravity, with the car's weight providing the force.

Question 5

The lowering valve (dump valve) in a hydraulic elevator controls:

Accepted Answer

The lowering valve (often an electrically operated proportional valve) controls how quickly oil can return from the cylinder to the reservoir tank. Regulating this flow controls car descent speed, acceleration, and deceleration.

Question 6

ASME A17.1 requires a hydraulic elevator to have a rupture valve (velocity fuse) that activates when:

Accepted Answer

The rupture valve (velocity fuse) is installed in the hydraulic line and automatically closes if the oil flow rate exceeds a preset limit, which would indicate a failed pipe or hose. It prevents an uncontrolled descent in the event of a hydraulic line failure.

Question 7

Environmental protection for underground hydraulic cylinders is typically addressed by:

Accepted Answer

Modern codes require underground cylinders to have secondary containment (a sleeve around the cylinder) with leak detection to prevent hydraulic oil from contaminating soil and groundwater. Many older single-bottom cylinders are being replaced for this reason.

Question 8

A hydraulic elevator car that levels above the floor (stops above the landing) is likely caused by:

Accepted Answer

If the car settles above the floor level over time, it typically indicates oil leaking past the control valve or check valve, reducing pressure and allowing the car to rise slightly. Seals and valves should be inspected and replaced.

Question 9

The purpose of the muffler (silencer) in the hydraulic power unit is to:

Accepted Answer

The muffler/silencer is installed in the hydraulic supply line to dampen pressure pulses produced by the pump, reducing vibration and noise transmitted through the hydraulic line and into the building structure.

Question 10

An in-ground (direct-plunger) hydraulic elevator is limited in travel compared to holeless hydraulic designs primarily because:

Accepted Answer

In-ground hydraulic elevators require a cylinder buried below the pit floor equal to the total rise. For taller rises, this requires drilling deep into the ground, which is costly and may hit the water table or rock. This limits practical travel typically to 4–6 floors.

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