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Automatic Boiler Controls Flashcards

1
Q

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

A

measure, compare, compute, correct

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2
Q

what does the term manipulated variable mean?

A

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

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3
Q

what does the term controlled variable mean?

A

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

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4
Q

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

A

the feed water control valve

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5
Q

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

A

offset

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6
Q

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

A

set point

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7
Q

the term dead time refers to what?

A

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

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8
Q

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

A

the nozzle and vane assembly; bellows; escapement valves

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9
Q

continuous changing of the controlled variable is called what?

A

cycling

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10
Q

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

A

automatic, remote manual, local manual

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11
Q

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

A

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

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12
Q

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

A

100% Open

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13
Q

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

A

the manufacturer’s technical manual

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14
Q

what does the term supply air pressure refer to?

A

the compressed air that is supplies to each pneumatic unit

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15
Q

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

A

loading pressure

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16
Q

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?

A

600 - 615 psig

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17
Q

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

A

3- 5 psi

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18
Q

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?

A

steam pressure controller

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19
Q

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

A

7 psi

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20
Q

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

A

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

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21
Q

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

A

low limit relay

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22
Q

what is the function of the airflow transmitter?

A

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

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23
Q

the air flow controller serves what function?

A

develops a loading signal to the force draft blower speed control

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24
Q

the airflow controller is what type of controller?

A

proportional plus reset

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25
Q

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

A

steam flow rate relay

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26
Q

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

A

characterizing relay

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27
Q

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

A

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

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28
Q

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

A

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

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29
Q

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

A

boiler drum level, steam flow and feed flow

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30
Q

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

A

drum level transmitter

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31
Q

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

A

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

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32
Q

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?

A

steam flow/ feed flow differential relay

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33
Q

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

A

9 psi

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34
Q

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

A

reverse acting

35
Q

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

A

minimum

36
Q

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

A

maximum

37
Q

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

A

minimum

38
Q

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

A

300 rpms

39
Q

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

A

the air lock system

40
Q

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

A

65 psig

41
Q

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

A

80 psig

42
Q

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

A

40 psig

43
Q

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

A

10 minutes

44
Q

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

A

online verification procedures (OLVs).

45
Q

A boiler flex test shall be conducted in what

A

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
Q

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

A

engineer officer

47
Q

boiler flex testing is conducted at what interval IAW PMS?

A

semi annually

48
Q

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

A

4 minutes

49
Q

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

A

PMS MRC

50
Q

who conducts boiler flex testing?

A

the person assigned as the automatic boiler control tech

51
Q

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

A

NSTM 255

52
Q

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

A

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

53
Q

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

A

the steam pressure controller

54
Q

what are the two inputs to the minimum signal receptor?

A

master demand and airflow

55
Q

what is the function of the fuel air ratio relay?

A

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

56
Q

the term bias refers to what?

A

the act of adding or subtracting from a control system signal

57
Q

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

A

steam pressure, airflow and fuel flow

58
Q

how is biasing accomplished?

A

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

59
Q

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

A

control pressure

60
Q

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

A

steam flow relay

61
Q

who must accomplish adjustment or repair of automatic boiler controls?

A

only authorized and qualified individuals

62
Q

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

A

lag time

63
Q

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

A

feedback

64
Q

output of an escapement valve is determined by?

A

position of the valve seats

65
Q

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

A

flapper

66
Q

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

A

primary elements

67
Q

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

A

rate time

68
Q

an uncontrolled oscillation of a controlled variable is termed?

A

hunting

69
Q

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

A

increase

70
Q

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

A

primary element

71
Q

the automatic control system compares the measure valve with?

A

the desired value

72
Q

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

A

reset

73
Q

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

A

five

74
Q

what boiler flex level is considered optimum for plant operation?

A

level one

75
Q

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

A

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

76
Q

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

A

fuel oil header pressure will decrease to minimum

77
Q

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

A

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

78
Q

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

A

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

79
Q

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

A

fuel and air controls are being manipulated by remove manual means

80
Q

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

A

fuel oil header pressure

81
Q

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

A

reduce the controller sensitivity

82
Q

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

A

mechanical preference

83
Q

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

A

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

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