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Oil Pumping and Metering > Section 2 - Centrifugal Pumps > Flashcards

Section 2 - Centrifugal Pumps Flashcards

1
Q

What are the 7 key components of a basic centrifugal pump?

A 
The Casing
The Shaft
The Suction Flange
The Discharge Flange
The Shaft Seal
The Bearing Housing
The impeller.
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2
Q

What is the purpose of a pump casing?

A

The pump casing supports, and contains the rest of the pump components.

Access to the pump is via a vertical split at the back of the casing.

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3
Q

What is the purpose of the suction flange of a pump?

A

The suction flange directs liquid entering the pump casing into the impeller.

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4
Q

What is a pump impeller?

A

A pump impeller imparts the kinetic energy into the liquid.

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5
Q

What is the pump Shaft?

A

The shaft connects the impeller to the primary driver, or motor, through a coupling.

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6
Q

What is the purpose of the bearing housing?

A

The bearing housing serves to support the shaft.

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7
Q

What is the purpose of the shaft seal?

A

The shaft seal prevents liquid escaping from the casing along the shaft.

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8
Q

What are three additionally important, internal components of a basic impeller centrifugal pump?

A

Wear Rings
The Balance Holes
The Packing

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9
Q

What is the purpose of Impeller Wear rings?

A

These act as the seal between the high pressure discharge, and low pressure suction of the impeller. These wear in preference to the impeller, acting as protection, and can be replaced when worn.

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10
Q

What is the purpose of balance holes?

A

The balance holes allow the packing to operate at suction pressure rather than discharge pressure - reducing he DP across the packer and impeller, reducing thrust forces.

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11
Q

What is the purpose of the packing?

A

The packing prevents liquid from escaping the casing.

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12
Q

What are the three main impeller types?

A

Open
Semi Open
Closed

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13
Q

Which is the most expensive impeller design and why?

A

Closed impellers are the most expensive - due to special techniques which are needed to weld the vanes inside the shroud.

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14
Q

What would you expect as impeller design considerations in low pressure, high capacity systems?

A

Large Diameter Impeller

Low Impeller Speed

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15
Q

What design characteristics would you consider with impellers requiring high pressure, high capacity throughout?

A

Small diameter impeller, with high rotating speed.

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16
Q

What shape is a single volume centrifugal pump?

A

This pump takes the shape of an upside down comma, or at operator.

17
Q

How does a single volute pump impart pressure energy?

A

Liquid is thrown into a channel where it is slowed down. The channel has an increasing area of cross section. This is designed to capture maximum energy transfer, and forces the fluid toward the discharge flange.

18
Q

How does a diffuser casing generate pressure?

A

The liquid leaves the tips of the impeller and moves through a set of Angled vanes - diffusers - these guide the fluid into the outer casing, decreasing velocity and increasing pressure energy.

19
Q

What is the purpose of the discharge flange?

A

The discharge flange directs the liquid away from the pump as it exits the casing.

20
Q

What is thrust force?

A

Thrust force is force directed along the axis of the pump shaft - arising because of the differences in pressure between the discharge and suction side of the impeller.

21
Q

How does the thrust bearing operate?

A

It’s mounted between two vertical plates, allowing the shaft to turn with a minimum of friction as it takes up this thrust force.

22
Q

What are slinger rings?

A

The slinger rings are two slender rings, often of brass, which slide up and down the shaft as it rotates. The slinger rings dip into the lubricating oil and centrifugal forces through the lube oil outward and cool the bearing faces and lubricate them.

23
Q

In a packed seal, what are the main components?

A

Packing
Packing follower
Lantern Ring

24
Q

What is the purpose of a lantern ring?

A

A lantern ring is fitted between sections of packing, so that any liquid which has been leaked along the shaft, can be removed.

25
Q

In a mechanical seal, what is the purpose of a seal flush inlet?

A

The seal flush Inlet allows cleaned discharge fluid into the mechanical seal housing for the purpose of cooling the mechanical seal, and lubricating it.

26
Q

What are the main components of a mechanical seal?

A 
Stationary Seal
Rotary Seal
Rotary Seal O-Rings
Shaft Sleeve O-Rings
Seal Flush inlet.
27
Q

How do centrifugal pumps perform in parallel?

A

Centrifugal pumps in parallel result in a maintained head pressure and increased flow rate.

28
Q

How do Centrifugal pumps perform in series?

A

Centrifugal pumps in series result in a maintained flow rate, but increased total discharge head.

29
Q

How does a multi-stage pump work?

A

A multi stage pump works by having multi impellers which serve to increase the total discharge head, much like centrifugal pumps in series.

30
Q

What is the purpose of a centrifugal pump minimum flow system?

A

It’s intent is to ensure that no damage occurs to the pump through generation of heat, as a result of conversion of main driver kinetic energy (such as the motor) to hear energy, as a result of significant turbulence generated against fluid trapped in the pump.

31
Q

What is the dangers of no minimum flow system in a centrifugal pump?

A

Turbulence gives rise to heat energy, which results in a higher risk of cavitation as entrained gases are forced toward their bubble curve causing significant damage.

32
Q

What two common types of minimum flow systems are there?

A

An orifice plate recycle line from Discharge to suction.

A flow meter on the suction side which operates a flow control valve on the recycle line.

33
Q

How does a minimum flow NRV work?

A

As sufficient energy is imparted on the valve it is caused to fully close, allowing full discharge and main flow, if insufficient energy (flow) is present then the flow will travel through the minimum flow system.
If some energy exists then some fluid will flow through the main discharge, where other fluid will follow the minimum flow line.

Oil Pumping and Metering (5 decks)

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