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Flashcards in Automatic Boiler Controls Deck (83):
1

what are 4 basic things that any control system must perform?

measure, compare, compute, correct

2

what does the term manipulated variable mean?

any quantity or condition that is varied by a control systems to affect the value of the controlled variable

3

what does the term controlled variable mean?

any quantity or condition that is measure and controlled by a control system

4

an example of a final control element in the three element feed system would be what?

the feed water control valve

5

the steady satte difference between the control point and the value of the controlled variable corresponding to the set point is called what?

offset

6

deviation is the instantaneous difference between the actual valley of the controlled valve and the value of the controlled variable corresponding to what?

set point

7

the term dead time refers to what?

the time required to transport a change from one place to another

8

what are 3 ways that computing and comparison can be accomplished in a pneumatic transmitter?

the nozzle and vane assembly; bellows; escapement valves

9

continuous changing of the controlled variable is called what?

cycling

10

what re the three modes of control in the automatic boiler control system?

automatic, remote manual, local manual

11

what are the three loops associated with the automatic boiler control system?

steam pressure control loop, airflow control loop, fuel flow control loop

12

what will be the position of the feed water control valve if the diaphragm ruptures?

100% Open

13

what is the only authoritative source of information on the boiler control system on any ship?

the manufacturer's technical manual

14

what does the term supply air pressure refer to?

the compressed air that is supplies to each pneumatic unit

15

compressed air that goes from one pneumatic unit to another pneumatic unit is known as?

loading pressure

16

a general regulator automatic combustion control system on a 600 psi steam plant is designed to maintain what set point when measured from the superheater outlet?

600 - 615 psig

17

what is the effective loading pressure range on a General Regulator combustion control system?

3- 5 psi

18

what component within the general regulator combustion control system develops a demand signal to maintain the boiler at a desired standard for any boiler load?

steam pressure controller

19

what is the desired set point on general regulator steam pressure transmitter?

7 psi

20

what is the function of the high limit and low limit relays on a general regulator combustion control system?

to prevent the master demand signal from bleeding out of range on the high end or the low end of the signal range operating pressure

21

the output of the high limit relay is applies to what component

low limit relay

22

what is the function of the airflow transmitter?

measures the pressure difference across the burner opening and develops a loading signal proportional to the rate of airflow per burner

23

the air flow controller serves what function?

develops a loading signal to the force draft blower speed control

24

the airflow controller is what type of controller?

proportional plus reset

25

what component within the general regulator combustion control systems designed to speed up force draft blower response time?

steam flow rate relay

26

what component converts the fuel oil demand signal a nonlinear signal?

characterizing relay

27

how is the minimum fuel oil pressure set on a general regulator FO control valve?

by adjusting the spring fore in the valve with the external spring adjusting screw and locking it in place with jam nut

28

a blown diaphragm within the FO characterizing relay on a general regulator combustion control system will have what effect on fuel oil header pressure?

fuel oil pressure will go to maximum and cause black smoke boiler assembly

29

what three elements are measured within the feed water control system?

boiler drum level, steam flow and feed flow

30

what component within the three element feed water control system develops a pneumatic signal proportional to actual boiler water level?

drum level transmitter

31

what terms are used to describe the three pneumatic signals associated with the feed water control system?

drum level = supervisory signal, steam flow = demand signal, feed flow = response signal

32

what component within the three element feed water control system compares the steam flow signal, feed flow signal and set point signal and develops a pneumatic output signal proportional to the difference between its inputs?

steam flow/ feed flow differential relay

33

what is the set point adjuster set at to maintain a normal water level on the three element feed water control system?

9 psi

34

what type of positioner is always used in conjunction with the feed water control valve?

reverse acting

35

the fuel oil control valve will always fail to what position if control air pressure is lost?

minimum

36

the main feed pump control valve will fail to what pressure if control air pressure is lost?

maximum

37

the force draft blower final control element will fail in what position if control air is lost?

minimum

38

what is the maximum allowable rpm differential on two force draft blowers operating in parallel?

300 rpms

39

what system is designed to hold on final control elements in their last known position upon a loss of control air pressure?

the air lock system

40

what is the master air lock trip valve spring set at?

65 psig

41

a pressure reducing valve is installed upstream of the air lock system and maintains the control air pressure at what?

80 psig

42

individual final control element air lock valves are set to trip at what control air pressure?

40 psig

43

air lock is designed to hold for what minimum time frame IAW PMS?

10 minutes

44

what procedures are used to verify that each automatic boiler control component is functioning properly prior to conducting boiler flex testing?

online verification procedures (OLVs).

45

A boiler flex test shall be conducted in what

an up and down ramp with boiler with a load change at 70 percent in 45 seconds, within a range from 15-95 percent of boiler full power

46

who must witness or designate someone to ensure all boiler flex testing is conducted within PMS requirements?

engineer officer

47

boiler flex testing is conducted at what interval IAW PMS?

semi annually

48

after conducting a boiler flex up ramp or down ramp the boiler parameters must stabilize what time frame?

4 minutes

49

all boiler flex testing is conducted in accordance with what document?

PMS MRC

50

who conducts boiler flex testing?

the person assigned as the automatic boiler control tech

51

what NSTM contains general information on various automatic boiler control systems?

NSTM 255

52

who is tasked with ensuring the boiler flex up ramp or down ramp only lasts 45 seconds?

the person operating the main engine ahead throttle valve (throttle man)

53

the maximum signal selector selects the higher of the steam pressure signals and sends it to what component?

the steam pressure controller

54

what are the two inputs to the minimum signal receptor?

master demand and airflow

55

what is the function of the fuel air ratio relay?

provides the operator with means of adjusting the airflow signal as necessary to provide optimum combustion throughout the firing range of the boiler

56

the term bias refers to what?

the act of adding or subtracting from a control system signal

57

what are three loops associated with the automatic boiler control system?

steam pressure, airflow and fuel flow

58

how is biasing accomplished?

by manually adjusting the hand wheel on the compensating relay (AM station), this can only be accomplished on a 4 way compensating relay

59

the compressed air that goes from a pneumatic unit to a motor operator of a final control element is defined as?

control pressure

60

what component cuts down the lag time casual by forced draft blower inertia?

steam flow relay

61

who must accomplish adjustment or repair of automatic boiler controls?

only authorized and qualified individuals

62

the interval of time between the start of a response and its completion is termed what?

lag time

63

a closed loop system gives a comparison with the desired condition by using?

feedback

64

output of an escapement valve is determined by?

position of the valve seats

65

on a nozzle and flapper assembly, what'd device is used to restrict the flow through the nozzle?

flapper

66

an orifice plate, flow nozzle, thermometer bulb, and air registers are all examples of what?

primary elements

67

the time interval by which rate action advances the effect of proportional position action is?

rate time

68

an uncontrolled oscillation of a controlled variable is termed?

hunting

69

on nozzle and flapper assembly, when the flow through the nozzle is decreased, the output will?

increase

70

a desired restriction in the path of the flow is at?

primary element

71

the automatic control system compares the measure valve with?

the desired value

72

what integral action of a controller will bring it back into balance, after a load change, at set point?

reset

73

boiler flex testing is measure in how many levels IAW PMS?

five

74

what boiler flex level is considered optimum for plant operation?

level one

75

is it allowable to conduct ETT drills on boiler that cannot conduct a satisfactory level three or higher boiler flex test?

never, ETT drills shall only be conducted on boilers that have achieved a level three or higher flex test

76

what effect will a failure of an airflow transmitter have on an operating steam plant?

fuel oil header pressure will decrease to minimum

77

when performing master light off checks what is the reason for conducting the EOP CTRM on the automatic boiler control system?

to verify that the airflow transmitter and minimum signal selector are functioning properly

78

what automatic boiler component must be adjusted prior to conducting boiler soot blow?

the fuel air ratio relay must be adjusted to increase windbag pressure IAW EOSS

79

what is meant by the term two knob centric when dealing with automatic boiler controls?

fuel and air controls are being manipulated by remove manual means

80

during a white smoke condition on an operating boiler, what must never be adjusted?

fuel oil header pressure

81

what action must be taken if a controlled variable oscillates about the set point at high frequency?

reduce the controller sensitivity

82

what is the most common cause of a control valve or actuator not responding to a position input a signal?

mechanical preference

83

the primary function of the automatic feed water control system is to maintain boiler water level within set point ?

normal with a maximum deviation of + - one inch at all boiler loads