Pumps, Bearings, and Turbines_DOT 3 Flashcards
In radial piston pumps, displacement depends on?
The amount of offset distance between the center of the ring in the center of the rotating element.
In what position would the cam ring be in for fluid to flow in reverse direction through the pump?
A position under the center position.
What type of pump can pump into a shut valve or system without the threat of damaging the piping system, although eventually pump damage may occur?
Centrifugal pumps.
What type of pump is a machine that adds energy to a liquid by increasing its velocity (kinetic energy) or it’s pressure (potential energy). The liquid being pumped is accelerated by the vanes of the impeller?
Centrifugal pumps
Centrifugal pumps can be classified as?
- single stage
- multi-stage
- suction position
- impeller design
- volute design
- shaft position
Define direct coupled or frame mounted?
When the impeller shaft is connected to the prime mover with a coupling device.
What are the four classifications of center fuel pump impellers?
- Radial vane impeller
- Francis vane impeller
- Propeller or axial flow impeller
- Mix flow impeller
Common types of wear rings include?
- Flat type
- L shaped type
- Labyrinth type
- Floating rings
What is the purpose a flat wear ring?
They maintain impeller clearance on either the outside diameter or axially. L-shaped rings seal on both, the outside diameter an axially.
What will occur if a continuous flow of cooling water or lubricating liquid is not maintained through the stuffing box?
The friction between the sleeve and the packing generates heat and the packing can easily overheat.
What component is placed between the rings of packing in a stuffing box when an external source of cooling fluid is used?
A spacer or Lantern ring.
What component provides critical support to the impeller and shaft assembly and maintains the position of the impeller both radially and axially?
Bearings
What are critical procedures that must occur during pump start-up?
Open the section valve and casing vent to remove entrapped air.
If a pump has been operating satisfactorily and loses suction what could be the issue?
Air may be entering the system through the suction line or the packing gland.
What are the most common mechanical reasons for excessive vibration within a pump?
- Misalignment of the unit
- A distorted foundation or base plate
- Worn impeller wear rings
- Worn bearings
- A bent shaft
- An improperly balanced impeller
- A partially clogged or broken impeller.
The general procedures for shutting down or securing a centrifugal pump are?
Close the discharge valve, stop the motor, close the suction valve
Define hydraulic turbines?
A mechanical device developed for the purpose of converting water power potential into usable mechanical energy
What type of hydraulic turbine is used for heads of 850 feet or more, including specifically, the Pelton-type runner?
Impulse wheels
The principle factor involved in the selection of a wheel for a specific power installation is?
The connection with the impulse runner and the operating head involved. With the head of 1500 or 2000 feet or more an impulse or Pelton-type runner would be used
What are the hydraulic turbines with the greatest capacity?
The Frances unit
What type of turbine may also be designed for large capacity, but are limited as to head?
Propeller type turbines, they are the largest type…most impulse turbines are comparatively small to propeller type turbines
What controls the size of the jet and the amount of water discharged within an impulse turbine?
Needle valves
What components are used to control runaway speeds in case of load rejection?
Jets are deflected from the buckets by deflector veins or plates, deflectors are operated by the governors
Instead of deflector vanes to protect against runaway speeds or load rejections older models use what?
A tilting nozzles
What component of a reaction turbine forms a water passage completely around (100%) the turbine and allows a water to enter the turbine uniformly from all sides?
The scroll cases
In what direction does a spiral or squirrel of a turbine case arranged?
It’s always arranged so that the direction of the flow of water around the spiral is in the same direction as a rotation of the turbine runner
What is the purpose of draft tubes?
Is a portion of the water passage of a reaction turbine which conducts the water discharged from the turbine runner to the tailrace in the draft tube
