2Nd Class Fireman, High Pressure Boilers, Chapter 9, Exam

Front 1

A burner must be started in a particular sequence to ensure ____

Back 1

Safe startup

Front 2

A ____ cycle is a predetermined period of time during which air is blown through the furnace to remove any combustible vapors

Back 2

Purge

Front 3

A ____ is used to sense the pilot and main flame in the burner

Back 3

Flame sensor

Front 4

Proving the main flame is sighting the main flame through a flame scanner to verify that the ____

Back 4

Main flame is lit

Front 5

____ is a purge that occurs after burner shutdown

Back 5

Postpurge

Front 6

If steam is being used faster than it is being generated, the steam pressure _____

Back 6

Decreases

Front 7

_____ can be used in plants where the steam load is steady and allows the burner to be started and stopped

Back 7

ON/OFF control

Front 8

A(n) _____ is a combination control system that is used to adjust the firing rate to a degree that is proportional to the steam load

Back 8

Modulating control system

Front 9

A(n) _____ is a combustion control system in which the flow of fuel and air are measured and adjusted in correct proportions based on steam pressure

Back 9

Metering control system

Front 10

Combustion controls use signals sent from measuring instruments to the controller and from the controller to a(n) ____ that changes flow

Back 10

Final element

Front 11

The primary function of a combustion control system is to regulate the _____ in a boiler

Back 11

Fuel supply, air supply, draft

Front 12

ON/OFF control is used to start and stop a burner without doing what? _____

Back 12

Without modulating the flame to match steam load

Front 13

A siphon is used to protect an operating pressure control from ____

Back 13

Live steam

Front 14

An operating pressure control must be connected to the _____

Back 14

Highest part of the steam side of the boiler

Front 15

The two settings found on the boiler operating pressure control are used to _____

Back 15

Set the operating steam pressure range of the boiler

Front 16

The combustion blower continues to run after fuel is shut off to the burner during ____

Back 16

Postpurging

Front 17

To eliminate the danger of a furnace explosion during startup, the programmer must allow _____

Back 17

A prepurge period

Front 18

The purpose of the flame sensor in a flame scanner is to prove _____

Back 18

Both the pilot and the main flame

Front 19

A flame sensor is sensitive to ____

Back 19

Infrared, visible, or ultraviolet light

Front 20

In the event of a flame failure, the programmer _____

Back 20

Shuts the burner down

Front 21

A modulating control system is sensitive to changes in the ____

Back 21

Steam pressure

Front 22

A(n) _____ is a controller that distributes steam production requirements across several boilers to maintain the steam pressure at the setpoint

Back 22

Plant master

Front 23

A preignition check includes _____

Back 23

Verifying that the fuel pressure proving switch is closed

Front 24

After a programmer proves the main flame what happens to it _____

Back 24

Releases to automatic control

Front 25

If steam is being used faster than it is being generated, the _____

Back 25

Steam pressure decreases

Front 26

What does a high-limit pressure control have? ____

Back 26

a manual reset

Front 27

The flow of fuel through valves and air through dampers is usually linear or nonlinear?_____

Back 27

Nonlinear

Front 28

Single-point positioning uses the ____ as the controller input and has only one output

Back 28

Steam pressure

Front 29

A low firing rate needs _____ than at a high firing rate

Back 29

More excess air

Front 30

Parallel positioning uses steam pressure as the controller input and uses how many output signals and what are they? _____

Back 30

Uses two output signals

1: fuel valve fuel flow

2: air damper air flow

Front 31

A modulating control system adjusts the firing rate proportional to the _____

Back 31

Steam load

Front 32

Nonlinear flow means that the percent a valve or damper is open does not necessarily correspond to _____

Back 32

Percent of flow

Front 33

The final preignition step is to ___.

Back 33

Pre-purge the furnace.

Front 34

A(n) ___ detects the presence of a flame and signals to the burner management system whether it is safe to operate the boiler.

Back 34

Flame scanner.

Front 35

A(n) ___ failure is a situation where a pilot or main flame fails to light properly or goes out unintentionally during normal operation.

Back 35

Flame.

Front 36

A(n) ___ is a sensing device in a flame scanner that generates a small electric current when one end of the sensor is placed directly in a flame.

Back 36

Flame rod.

Front 37

If there is a flame failure while a burner is firing, the signal stops and the burner management system shuts down the burner and ___.

Back 37

Purges the furnace.

Front 38

A burner should normally fire for ___.

Back 38

Longer periods than it is idle.

Front 39

The fuel flow rate is controlled by a ___.

Back 39

Valve.

Front 40

A(n) ___ pressure control is an ON/OFF control with a manual reset that sends a signal to the combustion control system to shut down the burner in the event of a high pressure condition that exceeds the operating pressure control cut-out setting.

Back 40

High-limit.

Front 41

___ positioning is a modulating control strategy that uses steam pressure as the input signal and outputs a signal to a modulating motor that turns a jackshaft to modulate the air and fuel flow.

Back 41

Single-point.

Front 42

The most common instrument used to measure the flow of steam is a(n) ___.

Back 42

Orifice installed in the steam line.

Front 43

___ is a control strategy in which increases in airflow lead increases in fuel flow, and decreases in airflow lag behind decreases in fuel flow.

Back 43

Cross-limited control.

Front 44

Typical blower motors operate at a constant speed at ___ Hz.

Back 44

60.

Front 45

Digital signals consist of ___ signals in the form of low-voltage DC pulses sent over a network, or fieldbus.

Back 45

Binary (ON/OFF).

Front 46

What are safety interlocks that affect the burner firing sequence?

Back 46

Preignition checks, purge cycles, lighting the pilot, lighting the main flame, and postpurge during shutdown.

Front 47

What are some preignition checks?

Back 47

Burner management system, operating and high-limit controls, fuel pressure proving switch, air dampers, gas pressure proving switch.

Front 48

Why is there an interlock during preignition?

Back 48

To prove airflow during the firing cycle.

Front 49

What determines how long a purge cycle will last?

Back 49

The furnace size, standard procedures, and insurance company requirements.

Front 50

What happens if the burner management system cannot prove that the pilot has been lit?

Back 50

The burner management system shuts down the system, purges the furnace, and initiates a flame failure alarm.

Front 51

Why is the flame scanner tested?

Back 51

To prevent the possibility of furnace explosion.

Front 52

What are the most common flame sensor types?

Back 52

photocell flame sensors, infrared flame sensors, ultraviolet flame sensors, flame rod sensors.

Front 53

In regards to the burner management system, what is "releasing to automatic control?"

Back 53

- After the burner management system proves the main flame it goes into "automatic control." The system continues to monitor the signal from the flame scanner. If there is a flame failure while the burner is firing, the signal stops. The burner gets shut down by the system and the furnace gets purged.

Front 54

How should the fire be when it's turned on and off?

Back 54

You always want to start the boiler at a low fire (flame) and shut it down with a low fire (flame).

Front 55

Why is steam pressure measured?

Back 55

The most common measurement used to determine the balance between steam generation and steam use.

Front 56

How is the control system related to steam pressure?

Back 56

The control system maintains the proper ratio of fuel and air in the burner.

Front 57

What is operating pressure cut-in and cut-out pressure?

Back 57

Start at a certain pressure and stop at a certain pressure.

Front 58

What should a boiler operator always assume when a boiler shutdown occurs?

Back 58

Assume that a safety device has functioned correctly. It is always best to assume that an unsafe condition exists than to assume a safety device is faulty.

Front 59

What is a purge cycle based on?

Back 59

Size of the furnace volume.