Govenors

Question 1

What are the 3 main things governors control?

Answer 1

1. Maintain the selected speed
2. Limit the slow and fast speed
3. Shut down the prime mover if it overspeeds

Question 2

What are the order of events of a governor?

Answer 2

Detection
(A speed sensing element detects a change in speed)

Transmission
(Signal is transmitted mechanically, hydraulically, pneumatically or electrically to the throttle control mechanism)

Correction
(The throttle is then corrected to keep the equipment running at its required speed)

Question 3

What are the events in a basic diesel governor system?

Answer 3

1. Governor reacts
2. Control rod moves
3. Fuel flow adjusts
4. Engine varies speed

Question 4

What is a isochronous control?

Answer 4

A governor that maintains a uniform and constant speed without fluctuation

Question 5

What is a variable speed control?

Answer 5

It holds the driver at a steady speed just like a isochronous governor, the difference is that the variable speed governor can be adjusted by the operator to maintain any selected speed

Question 6

What is a speed limiting control?

Answer 6

They are used to prevent overspending of the driver. This governor does not shut down the driver if it over-speeds, but instead it limits the speed to a maximum

Question 7

What is a pressure regulating control?

Answer 7

Mainly used on pipeline pumps to ensure a constant pumping pressure.

It can sense pressure from a piston, diaphragm or bellows.

Question 8

What is an electric load sensing control?

Answer 8

They are used when stable frequency must be maintained, regardless of wide and often rapid changes in load.

Question 9

What is an electric speed sensing control?

Answer 9

They react to engine speed by measuring the frequency of the electric current produced by the generator

Question 10

When talking about governors, what is Hunting?

Answer 10

When the governor responds to quickly and swaps back and forth between too fast and too slow repeatedly

Question 11

When talking about governors, what is Speed droop?

Answer 11

The certain changes in speed required before the governor produces a change in throttle.

It’s useful for preventing Hunting by the governor when the load changes.

Question 12

How does a flyweight governor work?

Answer 12

They work off the concept of when the flyweights move in and out from centrifugal force, they translate the motion to an ax axial movement.
Radial force to axial force

Question 13

What is a mechanical-hydraulic governor?

Answer 13

A mechanical governor like a flyweight governor that includes the addition of a separate hydraulic system to supply the extra force needed to operate larger valves and linkages.

Question 14

What is another name for a mechanical flyweight governor?

Answer 14

A ballhead

Question 15

What does the mechanical flyweight adjust on a mechanical-hydraulic governor?

Answer 15

The mechanical flyweight controls a pilot valve

This valve controls the flow of oil from a separate hydraulic system into a simple reciprocating piston.

Question 16

What is a speed droop attachment?

Answer 16

It is a mechanical linkage that is connected between the servo piston (which controls the throttle) and the governor speed setting in such a way that as fuel flow increases, the speed setting decreases.

The lever now ties the operation of these 2 parts together.

Question 17

What is a pure hydraulic governor and how does it operate?

Answer 17

It uses the change in pressure of a fluid discharged from a shaft mounted pump.

If the pump speed increases so does the pump output cause a rising in pressure which operates a bellow. The variable speed in controlled by a needle valve, as the valve is opened, there is a pressure drop causing the governor to to open fuel control and raise the speed.

Question 18

What is an electro-hydraulic governor and how does it work?

Answer 18

It’s a hydraulic governor that uses electrical controls to actuate the actuator.

It reacts quicker
Keeps constant speed for proper frequency

Question 19

What are the 3 basic components of an electro hydraulic governor?

Answer 19

The sensor to detect the speed and/or load

The system controller (computer) transmits the processes sensor inputs and generates an output signal for the actuator.

The actuator, to move the fuel metering control and change the fuel delivery.

Question 20

How does a solenoid work?

Answer 20

It is a soft iron core with seres of wire coils formed around it. The current flowing through the coils caused the coil to act like a magnet.

The greater the current to the coil, the greater the magnetic attraction causing the iron core to move further into the controller. If the current is decreases the spring within has enough force to move the iron core out of the coil.

Question 21

How does the system controller work?

Answer 21

It counts the number of signals it has received from the speed sensor and calculates the machines speed. It then compares this speed with the desired speed and sends an output signal to the actuator.

Question 22

What is the normally range to set the overspeed trip too?

Answer 22

10-15% of the maximum operating speed under normal operating conditions.

Question 23

How does the pin operate on an overspeed mechanism?

Answer 23

It is a pin that is held inside a hole on the shaft by the use of a compressed spring, as the machine over-speeds the pin overcomes the spring compression by centrifugal force and is thrown out of the hole.

Question 24

What are the 3 main types of over speed trips?

Answer 24

Mechanical

Hydraulic

Electric

Question 25

At what speed do mechanical governors become unreliable?

Answer 25

Above 10,000 RPM

Question 26

In a Diesel engine, what does the governor do to meter more or less fuel?

Answer 26

It adjusts the fuel rack