Bearings, Seals, and Shaft Couplings Flashcards
7 cards from real CPM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Bearings, Seals, and Shaft Couplings flashcards as text
A mechanical seal in a centrifugal pump creates its primary seal between which two components?
Answer: A rotating seal face and a stationary seat
A mechanical seal prevents leakage through two lapped, highly polished mating faces — one rotating with the shaft and one stationary in the housing.
Compared to compression packing, the primary operational advantage of a mechanical seal is:
Answer: Near-zero leakage during normal operation
Mechanical seals are engineered to produce virtually no leakage, whereas packing requires a controlled drip rate for lubrication and cooling of the packing rings.
A radial lip seal (rotary shaft seal) should be installed with the sealing lip oriented:
Answer: Toward the fluid being retained
The garter spring and lip face the fluid side so that fluid pressure assists the lip in maintaining contact with the shaft, improving the seal.
When replacing compression packing in a pump stuffing box, adjacent packing rings should be staggered by:
Answer: 90° so no two ring joints are aligned
Staggering each ring 90° from the previous ensures no two ring joints align, eliminating a straight leakage path through the packing stack.
What is the purpose of a lantern ring installed within a packed stuffing box?
Answer: To distribute flush fluid or lubricant evenly around the shaft circumference
A lantern ring is a hollow spacer with radial ports that routes seal flush water or lubricant uniformly around the shaft inside the stuffing box.
An O-ring installed in a groove that is too narrow (undersized width) may result in:
Answer: Extrusion of the O-ring material into the clearance gap under pressure
Over-compression in a too-narrow groove forces excess rubber to extrude into any available clearance gap under pressure, causing nibbling and seal failure.
Which type of seal is most commonly used to prevent leakage past a reciprocating piston inside a hydraulic cylinder?
Answer: U-cup piston seal
U-cup seals are designed for reciprocating linear motion; their lips conform to the cylinder bore and seal in both directions of travel.