Laboratory Instruction Manual for Boiler Simulation …pirun.ku.ac.th/~fengwtc/Teaching/208481 Special...Laboratory Instruction Manual for Boiler Simulation Unit 1 208481 Written by

208481 Written by Withit Chatlatanagulchai Revision 1.0, June 2007

Laboratory Instruction Manual for Boiler Simulation Unit

1


Table of Contents

1 Introduction ........................................................................................3 2 Unit Layout..........................................................................................5

2.1 Level Monitoring Sensors ...............................................................6 2.2 Pressure Sensors...........................................................................7 2.3 Burner Unit ...................................................................................8 2.4 Switch Cabinet ..............................................................................9 2.5 Compressed Air Unit ....................................................................16

3 Safety ...............................................................................................16 4 Experiments ......................................................................................17

4.1 Experiment 1: General Knowledge of Boilers..................................17 4.2 Experiment 2: Normal Operation...................................................17 4.3 Experiment 3: Boiler Safety Chain.................................................18 4.4 Experiment 4: Burner Error Simulations.........................................20 4.5 Experiment 5: Level Switches Error Simulations .............................20 4.6 Experiment 6: Pressure Limiter Error Simulations ...........................21 4.7 Experiment 7: Other Error Simulations ..........................................22

5 References ........................................................................................22

2


1 Introduction A boiler is a closed vessel in which water or other fluid is heated under pressure. The fluid or steam is then circulated out of the boiler for use in various processes or heating applications. Boilers can be divided into three types. First, the fire-tube boilers are those with the heat source inside of the tubes, and the water to be heated is outside. Second, the water-tube boilers are those with the heat source outside of the tubes, and the water to be heated is inside. Third, primitive boilers are traditional boilers, the inefficient type where there are no tubes and the fire heats one side of the water container. Figure 1 shows a fire-tube boiler and a water-tube boiler [1]. Boiler construction started in the 17th century. The first water-tube boiler was built in 1804, and the first fire-tube boiler was built in 1811 [2].

(a) (b)

Figure 1: (a) A fire-tube boiler. (b) A water-tube boiler. The boiler simulation unit on which we are doing experiment is a model of a steam boiler that is one type of the fire-tube boiler. The steam boiler outputs hot steam to be used in various applications such as steam turbine. The diagram of the steam boiler is given in Figure 2. The burner unit heats the air inside the flame tube that submerges in the water compartment. A portion of hot gas and exhausted gas are cycled back through the water compartment in small tubes. Some designs use hot and exhausted gas to re-heat the steam. The exhausted gas is finally sent out of the boiler though the exhausted gas outlet. The water in the water compartment is heated and evaporates. The hot steam is sent out via the steam outlet. Since water evaporates, there is a feed water inlet to add water to the water compartment. The level monitoring sensors monitor the level of the water inside. Usually, the water level is maintained within a suitable range since too much water wastes more energy to heat and too little water can cause damage to the boiler. The level monitoring sensors send command to the feed

3


water inlet to add more water when needed. In addition, there is an overflow in case of level monitoring sensors malfunction. There is also a water drain when drainage is required such as when the water compartment is to be cleaned. Pressure monitoring is used to sense the pressure level inside of the steam compartment. More often, there are two sensors to monitor pressure: the pressure switch and the pressure limiter. The pressure switch is used to switch the burner on and off to maintain a pressure set point. The pressure limiter is used to shut down the burner when a set pressure is exceeded. To prevent damage to the compartment in case of the pressure limiter malfunction, a safety valve is used to release the steam to the atmosphere to reduce pressure.

PRESSURE MONITORING

SAFETYVALVE

FEED WATERINLET

LEVELMONITORING

STEAM OUTLET

WATERDRAIN

BURNERUNIT

WATERCOMPARTMENT

STEAMCOMPARTMENT

EXHAUSTEDGAS OUTLET

FLAMETUBE

Figure 2: Diagram of a steam boiler.

Since boilers have high pressure steam inside of the tank, they must be well-maintained by the operators. Boiler explosions are mainly due to too much steam pressure inside of the steam compartment or too little water inside of the water compartment. The former incident can happen from malfunction of the pressure monitoring unit, and the latter incident can happen from malfunction of the water level monitoring sensors. The crack of the boiler enclosure can also cause accidents. In Germany, from 1894 to 1898, on average, there were 23 boiler explosions a year, explosions that caused significant personal injury and damage to property. In the USA from 1879 to 1902, there were 6386 explosions with 7002 killed and 10346 serious injuries [2]. It is therefore important the

4


operators should study how the boilers operate and how to solve problems when they happen. A simulation unit can be used for study in a safe environment.

2 Unit Layout The boiler simulation unit that we use is built by G.U.N.T. company of Germany. The model is ET 860. The unit layout is shown in Figure 3. The plexiglass tank is modeled after the water chamber. The clarity of the tank allows observers to observe water level inside of the tank. The burner unit simulates the actual burner, but there is no actual flame. Since there is no actual flame, compressed air is supplied to simulate steam pressure, and drain water regulatory valve at the bottom of the tank can be opened to drain some water to simulate the water lost due to evaporation. The plexiglass tank is not airtight, so the compressed air is supplied to the pressurized copper chamber to which the manometer, the pressure switch, the pressure limiter, and the safety valve are attached. The switch cabinet contains various alarms, timer, and power switches. With fifteen switches, the error triggering circuit, attaching to the switch cabinet, can trigger fifteen different errors that are used to train the operators to solve problems.

LABORATORYTROLLEY WITHCASTERS

FEED WATER REGULATORYVALVE

FEED WATER PUMP

DRAIN WATER REGULATORYVALVE

FEED WATER TANK

BURNERUNIT

COMPRESSEDAIR CONNECTIONWITH REGULATORYVALVE

OVERFLOWPIPE

PLEXIGLASSTANK (WATERCOMPARTMENT)

ERROR TRIGGERINGCIRCUIT

SWITCHCABINET

MANOMETER,PRESSURE SWITCH,PRESSURE LIMITER,SAFETY VALVE

LEVELMONITORINGSENSORS

Figure 3: Simulation unit layout.

Using the simulation unit, we can demonstrate three scenarios: the normal operation, the safety chain, and the triggering errors.

5


• The first scenario, the normal operation, simulates the boiler in normal working condition. The water level is maintained close to a constant and appropriate level by adjusting the drain water regulatory valve.

• The second scenario, the boiler safety chain, means that the operation of the boiler is controlled and monitored via safety devices that are connected electrically in series. If one of these monitoring or control devices is tripped, the entire system is shut down, an alarm given, or at least the parts of the system at risk shut down. The safety chain generally involves water level monitoring sensors, pressure switch and pressure limiter, and time monitoring that needs acknowledgement from the operator at a set time interval.

• In the third scenario, there are fifteen error triggering circuits. Each error can be activated by pressing each triggering switch. The error can be simulated that gives the operator a chance to learn to solve problem.

2.1 Level Monitoring Sensors Three level sensors are connected to three level switches. The level sensors are inside of the tank, whereas the level switches are on the switch cabinet. Figure 4 shows a picture of all three level sensors.

LEVELSENSORNO. 1-7

LEVELSENSORNO. 1-8

LEVELSENSORNO. 1-5

Figure 4: Level monitoring sensors.

• Regulated level sensor number 1-5 is used to regulate the feed water pump. There are four electrodes, but only the middle two electrodes are used as minimum and maximum level sensors. When the water level reaches the minimum level, the pump is turned on. When the water level reaches the maximum level, the pump is turned off. No alarm is triggered. This level sensor can be activated and deactivated by the level switch

6


number 1-5 on the switch cabinet. During normal operation, the level switch number 1-5 is turned on.

• Low-water level sensor number 1-7 is used as a precaution in case the level sensor number 1-5 malfunctions. If the water level reaches the level sensor number 1-7, the burner is shut down to prevent damage to the chamber. The red “low water” alarm located on the switch cabinet and the “low water” alarm located on the level switch number 1-7 on the switch cabinet are both lighted.

• High-water level sensor number 1-8 is used as a precaution in case the level sensor number 1-5 malfunctions. If the water level reaches the level sensor number 1-8, the pump is shut down to prevent water overflow. The “high water” alarm on the level switch number 1-8 on the switch cabinet is lighted.

2.2 Pressure Sensors

MANOMETER

SAFETYVALVE

PRESSURESWITCH

PRESSURELIMITER

Figure 5: Pressure monitoring sensors. Four components as shown in Figure 5 are used to monitor pressure in the steam compartment.

• A manometer is used to indicate the pressure. • A safety valve is used as a precaution in case the pressure limiter

malfunctions. The safety valve releases steam when the pressure inside of the compartment is too high.

• A pressure switch regulates the steam pressure in the boiler automatically by adjusting the burner unit. On this system, a switching difference of 0.2 bars are set. If, for instance, the boiler is to generate steam with an operating pressure of 2 bars, 2.1 bars are set on the pressure switch. When the boiler is in operation, the pressure switch shuts down the

7


burner when the value set is exceeded. If the pressure in the boiler drops to 1.9 bars (2.1 bars – 1.9 bars = 0.2 bars = switching difference), the burner is switched on again. The pressure in the boiler fluctuates continuously between 1.9 and 2.1 bars.

• A pressure limiter shuts down the burner unit if a permissible operating pressure is exceeded. The “pressure limiter” alarm on the switch cabinet is then triggered. The alarm must be acknowledged (cleared) on the pressure limiter itself by pressing in a red pin. This red pin can only be pressed in when the pressure has dropped below the value set.

2.3 Burner Unit The burner used in this simulation unit is modified from an actual commercially available oil burner used in boilers for domestic hot water. As the operation of the burner is simulated, the operating state of the burner can be recognized from the noise of the burner fan and the display on the burner housing. The display on the burner housing is shown in Figure 6.

Figure 6: Burner housing. When the burner starts, the preheating bulb illuminates first for a couple of seconds, then the operation bulb illuminates indicating that the burner is in steady operation state. The burner flame is mimicked by a light bulb that can be seen when look directly into the burner pipe. The burner flame light bulb is coupled with another light bulb on the burner pipe for convenience. When the burner internally malfunctions, the malfunction light goes up, and the alarm must be acknowledged by pressing in the reset button. However, the button can only be pressed in if the related fault is no longer active.

8


2.4 Switch Cabinet Switch cabinet contains controls and indicators for the system. The switch cabinet layout is given in Figure 7. The following subsections describe each part of the switch cabinet.

2.4.1 Alarm Indicators On the top row, there are six alarms:

• Internal burner malfunction alarm (1) will light if there is any malfunction at the burner unit itself.

• Time control device alarm (2) will light if the time set by the time control device is up. The time is set at the time control device to make sure that the operator comes back to tend to the boiler at every specified time interval.

(1) INTERNALBURNERMALFUNCTIONALARM

(2) TIME CONTROLDEVICEALARM

(3) PRESSURE LIMITERALARM

(4) LOWWATERALARM

(5) BURNER-OFFFAULT RESET

(6) PUMP-OFFFAULT RESET

(8) PUMP OPERATINGINDICATOR

(7) BURNER OPERATINGINDICATOR

(9) BURNERON-OFFSWITCH

(10) PUMPCHANGEOVERSWITCH

(16) THREELEVELSWITCHES

(11) TIMECONTROLDEVICE

(12) MASTERSWITCH

(13) EMERGENCYSTOPSWITCH

(14) NINEMEASURINGSOCKETS

(15) SYSTEMSCHEMATICDIAGRAM

Figure 7: Switch cabinet layout.

9


• Pressure limiter alarm (3) will light if the pressure in the copper chamber is higher than the set pressure and hence the pressure limiter operates.

• Low water alarm (4) will light if the water level in the tank reaches the low point as sensed by the low-water level sensor number 1-7.

• Burner-off fault reset (5) illuminates when the safety chain for the burner is triggered. This alarm must be acknowledged once the source of the problem is cleared by pressing in the button itself.

• Pump-off fault reset (6) illuminates when the safety chain for the pump is triggered. This alarm must be acknowledged once the source of the problem is cleared by pressing in the button itself.

2.4.2 Operating Indicators and On-Off Switches Burner operating indicator (7) illuminates when the pump is working, so does the pump operating indicator (8). The burner on-off switch (9) is used to turn on the burner and the pump changeover switch (10) is used to turn on the pump. There are two states for the pump changeover switch, stage 1 is for normal operation and stage 2 is for test operation. In normal operation, the pump starts and stops according to the water level sensors in the tank, and in the test operation, the pump always works, disregarding the water level sensors. At the bottom right of the switch cabinet, there are a master switch (12) and an emergency stop switch (13). The master switch is used as a main power switch for the whole system and the emergency stop switch will shut the whole system down when pressed.

2.4.3 Level Switches

c d

h i

a b

e f g Figure 8: Level switches on the switch cabinet.

Figure 8 depicts three level switches (16) on the switch cabinet. The middle level switch is numbered 1-5 for the level sensor number 1-5. The level

10


sensor number 1-5 has two switching points. The upper switch point switches off the pump, and the lower switch point switches on the pump. A green LED on the switch (c) provides indication that the pump is in operation. A toggle switch (d) turn on an off the level sensor number 1-5. The up position turns off the level sensor. The down position turns on the level sensor. In case of high water, a red LED (i) illuminates. This alarm can also be simulated by pressing in a pin (h). The left level switch is numbered 1-7 for the level sensor number 1-7. The level switch 1-7 switches off the burner when the water in the boiler is low, so that the boiler is not irreparably damaged by over heating. By switching the rocker switch (b), a functional check can be performed on the level switch. If the level sensor number 1-7 is triggered by the low water, both red LEDs (a and e) illuminate. This alarm can also be simulated by pressing a button (f). A green LED (g) is used as main reference check. The right level switch is numbered 1-8 for the level sensor number 1-8. It is almost identical to the switch 1-7, the difference is that it shuts down the pump when the water level is high.

2.4.4 Time Control Device The time control device (item 11 of Figure 7) is an electromechanical timer relay. The time setting is made on a rotary knob. A black trailing pointer indicates the time set, while a red pointer runs from the time set back to 0. Ten minutes prior to expiration, an acoustic signal is output as a pre-alarm. When the point position 0 is reached, the relay automatically shuts down the system; at the same time the “time out” alarm is signaled on the switch cabinet. Acknowledging the “time out” alarm by pressing it sends the red pointer back to where the black pointer is and the timing restarts. When in operation the boiler must regularly be checked by a boiler attendant. At the latest every 2 hours the boiler attendant must ensure that the system is in correct working order. The boiler attendant must then operate the time control device. If this control device is not operated, the system automatically shuts down.

2.4.5 System Schematic Diagram Figure 9 shows the system schematic diagram. This diagram shows how the boiler safety chain is arranged and is used to assist the faultfinding. Table 1 lists possible malfunctions in the safety chain.

Table 1: Possible malfunctions in the safety chain Type of Malfunction

Cause Consequences Solution

Pressure limiter is triggered.

The operating set pressure is exceeded.

1) Pressure limiter alarm (item 3 of Figure 7) illuminates. 2) Burner-off fault reset button (item 5 of

Follow this sequence. 1) Reduce pressure using the regulatory valve (Figure 11). 2) Press red reset pin

11


Figure 7) illuminates. 3) Pump-off fault reset button (item 6 of Figure 7) illuminates. 4) White burner and pump operating indicators (item 7 and 8 of Figure 7) go out.

located on the pressure limiter(Figure 5). 3) Acknowledge Burner-off and Pump-off fault reset buttons by pressing on them.

Low-water level switch 1-7 shuts down the burner.

Too little water in the boiler.

1) Low water alarm (item 4 of Figure 7) illuminates. 2) Burner-off fault reset button (item 5 of Figure 7) illuminates. 3) White burner operating indicator (item 7 of Figure 7) goes out. 4) Red LED on the level switch 1-7 (item a and e of Figure 8) illuminates.

Follow this sequence. 1) Fill boiler with water until red LED on the level switch goes out. 2) Establish constant water level in the tank using the drain water regulatory valve (Figure 3). 3) Acknowledge the burner-off fault reset button by pressing on it. 4) If necessary, switch burner off and on.

High-water level switch 1-8 switches off pump.

Too much water in the boiler.

1) Pump-off fault reset button (item 6 of Figure 7) illuminates. 2) Red LED on the level switch 1-8 (Figure 8) illuminates. 3) White pump operating indicator (item 8 of Figure 7) goes out.

Follow this sequence. 1) Reduce water level using the drain water regulatory valve Figure 3). 2) Acknowledge the pump-off fault reset button by pressing on it.

System suddenly goes off

Time has expired on the time control device.

1) Time control device alarm (item 2 of Figure 7) illuminates. 2) Burner-off fault reset button (item 5 of Figure 7) illuminates.

Follow this sequence. 1) Move black pointer on the time control device to 120 minutes. 2) Acknowledge Burner-off and Pump-

12


3) Pump-off fault reset button (item 6 of Figure 7) illuminates. 4) White burner and pump operating indicators (item 7 and 8 of Figure 7) go out.

off fault reset buttons by pressing on them. 3) If necessary, switch burner off and on.

Figure 9: System schematic diagram.

2.4.6 Measuring Sockets There are nine measuring sockets (14) on the bottom of the switch cabinet. They are used for voltage measurements to assist in fault finding in the safety chain. A digital multimeter is used to measure the voltage across any two terminals. Figure 10(a) shows how the digital multimeter is connected. During the operation of the system, voltages can be measured at the sockets, with the system switched off, resistances can be measured. The voltages that are measured at the sockets with the system switched on (no error triggering circuit active) are given in the table.

13


X1 X2 X3 X4 X5 X6 X7 X8 X9 X1 - - - - - - 220 V 220 V 220 V X2 - - - - - - 220 V 220 V 220 V X3 - - - - - - 220 V 220 V 220 V X4 - - - - - - 220 V 220 V 220 V X5 - - - - - - 220 V 220 V 220 V X6 - - - - - - 220 V 220 V 220 V X7 220 V 220 V 220 V 220 V 220 V 220 V - - 220 V X8 220 V 220 V 220 V 220 V 220 V 220 V - - 220 V X9 220 V 220 V 220 V 220 V 220 V 220 V 220 V 220 V -

2.4.7 Error Triggering Circuits At the side of the switch cabinet, there are fifteen error-triggering circuits shown in Figure 10(b). These triggering push buttons simulate fifteen different malfunctions to train the operator to solve problem.

(a) (b) Figure 10: (a) Measuring sockets. (b) Error triggering circuits.

The following table lists all triggering errors and their effects.

Simulated Error Effects 1 = Defect in burner’s photocell

• White burner operating state indicator goes out. • Burner tries to light again and goes into the

malfunction condition after 15 s. • Burner alarm illuminates. • Red LED on the burner illuminates.

2 = Defect in burner’s fan motor

• White burner operating state indicator goes out. • Burner fan noise can no longer be heard. • Burner tries to light again and goes into the

malfunction condition after 15 s.

14


• Burner alarm illuminates. • Red LED on the burner illuminates.

3 = Defect in burner’s ignition transformer

• System runs normally after the start. • White burner operating indicator on. • If the burner is switched off, it cannot be

restarted. 4 = Defect in timer switch

• Burner goes out immediately. • Red “Time Out” illuminated pushbutton

illuminates. • Time control device clock continues to operate. • Pump (if on) continues to run.

5 = No fuel for burner

• White burner operating indicator goes out. • Burner tries to light again and goes into the

malfunction condition after 15 s. • Burner alarm illuminates. • Red LED on the burner illuminates.

6 = No power supply for the entire system

• All indicators on the system go out. • System cannot be restarted despite switching on

at master switch and resetting the time control device.

7 = Pressure limiter bridged

• Burner always runs, even if the pressure in the pressure vessel is increased above the set point on the pressure limiter.

8 = Pressure limiter does not work

• Burner goes out after switching the fault. • White burner operating indicator goes out.

9 = Level switch 1-5 switches through continuously

• Pump in operating until level switch 1-8 (high water) trips.

• Burner continues to operate the entire time. • If the pump is shut down via level switch 1-8, the

water level drops until the tank is completely empty.

• Level switch 1-7 (low water) switches off burner. 10 = Defect in pump • Burner operates.

• Pump should be switched on via level switch 1-5 (reducing water level in the boiler), however it does not start.

• White pump operating state indicator illuminates. • On reaching the low water level the burner is

switched off via the level switch 1-7. 11 = Pressure limiter continuously tripped

• Burner switches off. • Pressure alarm illuminates. • Fault reset burner illuminates.

12 = Defect in burner ignition relay

• Burner switches off. • Burner operating state indicator goes out. • All LEDs on the burner go off. • Burner cannot be started again by pressing the

reset button.

15


13 = Level switch 1-7 switches through continuously

• Burner switches off. • Low water alarm on the switch cabinet

illuminates, even though the low water level has not yet been reached.

• Fault reset burner illuminates. 14 = Level switch 1-8 switches through continuously

• Pump goes off, burner continues to operate. • Fault reset pump illuminates, pump can however

not be started by acknowledging this button (Fault reset continues to illuminate).

15 = Defect in level switch 1-7

• Pump goes off, burner continues to operate. • White operating state indicator for pump goes

out. • Fault reset pump does not illuminate.

2.5 Compressed Air Unit As this is a simulation, there is no real flame to generate pressure; all pressures in the system must be supplied by external compressed air. The pressure inside of the system must be set manually using the regulatory valve. Figure 11 shows compressed air connection with service unit.

REGULATORYVALVE

Figure 11: Compressed air connection with service unit.

3 Safety • Be sure there always is water left in the feed water tank. If the pump

operates in the “Test” mode, the pump will always run. If the amount of water is not enough, the pump may run dry and damage.

• Do not overflow the feed water tank. The feed water tank can be overflowed if most of the water in the plexiglass tank (the boiler) is drained out.

• Ensure the electrical parts of the system do not come into contact with water

• Keep the floor dry

16


4 Experiments

4.1 Experiment 1: General Knowledge of Boilers

Objective To understand some boiler topics more deeply through self study.

Instruction Pick two of the following topics to write two essays with minimum of 500 words each.

• Boiler History • Boiler Explosion • Fire-Tube Boiler • Water-Tube Boiler • Superheated Steam Boiler • Cornish Boiler • Steam Engine • Water Level Sensor • Boiler Manufacturers • Manometer

Analysis None

4.2 Experiment 2: Normal Operation

4.2.1 Commissioning

Objective To understand commissioning procedures of the boiler.

Instruction 1) Place system on a flat surface 2) Establish supply of compressed air 3) Fill feed water tank up to approx. 10 cm below the top edge 4) Connect system to main electrical supply 5) Close regulatory valve at the feed pipe 6) Close regulatory valve at the drain pipe 7) Unlock emergency stop switch 8) Set master switch for the system to “on” 9) Switch on pump (position 1) 10) Carefully open regulatory valve at the feed pipe 11) Carefully open regulatory valve at the drain pipe 12) Switch on burner 13) Set pressure in the pressure vessel to around 1.5 bar (can be

checked on the manometer)

17


Analysis None

4.2.2 Normal Operation

Objective To understand normal operation procedures of the boiler.

Instruction 1) Use the level switch 1-5 (Figure 8) to regulate water level in the tank 2) Adjust the regulatory valve at the drain pipe to alter the water level

in the tank

Analysis None

4.2.3 Shutdown

Objective To understand shutdown procedures of the boiler.

Instruction 1) Switch off burner on the switch cabinet 2) Switch off pump on the switch cabinet 3) Set master switch to “off” position 4) Leave water to drain out of the boiler into the feed water tank, but

be careful not to overflow the feed water tank 5) Shut off supply of compressed air 6) Lock emergency stop switch 7) Unplug from the main electrical supply and the compressed air supply

Analysis None

4.3 Experiment 3: Boiler Safety Chain

4.3.1 Pressure Limiter is Triggered

Objective To understand the cause, consequences, and solution when the pressure limiter is triggered.

Instruction 1) Note the set pressures of the pressure switch and the pressure limiter 2) Adjust the air pressure to around the set values of the pressure

switch and the pressure limiter 3) Note the consequences and solve problems 4) Decrease the air pressure to normal 1.5 bar

18


Analysis Discuss the consequences and solution.

4.3.2 Low-Water Level Switch 1-7 Shuts Down the Burner

Objective To understand the cause, consequences, and solution when the low-water level switch 1-7 shuts down the burner.

Instruction 1) Turn off the water level switch 1-5 2) Reduce water level in the tank until the level triggers the level switch

1-7 3) Note the consequences and solve problems 4) Turn on the water level switch 1-5


4.3.3 High-Water Level Switch 1-8 Switches Off Pump

Objective To understand the cause, consequences, and solution when the high-water level switch 1-8 switches off pump.

Instruction 1) Turn off the water level switch 1-5 2) Allow the water level to reach the level sensor 1-8 3) Note the consequences and solve problems 4) Turn on the water level switch 1-5


4.3.4 System Suddenly Goes Off

Objective To understand the cause, consequences, and solution when the system suddenly goes off due to expired time.

Instruction 1) Slowly rotate the black pointer to until it reaches 0 minute. 2) Note the consequences and solve problems


19


4.4 Experiment 4: Burner Error Simulations

Objective To understand the cause, consequences, and solution of a specific error.

Instruction 1) Press the corresponding error trigger switch 2) Note the consequences and solve problems

Analysis 1) Discuss the consequences and solution. 2) Use multimeter to measure the following voltages.

X1 X2 X3 X4 X5 X6 X7 X8 X9 X1 - - - - - - X2 - - - - - - X3 - - - - - - X4 - - - - - - X5 - - - - - - X6 - - - - - - X7 - - X8 - - X9 -

4.4.1 Defect in Burner’s Photocell (Trigger Switch No. 1)

4.4.2 Defect in Burner’s Fan Motor (Trigger Switch No. 2)

4.4.3 Defect in Burner’s Ignition Transformer (Trigger Switch No. 3)

4.4.4 Defect in Burner Ignition Relay (Trigger Switch No. 12)

4.4.5 No Fuel for Burner (Trigger Switch No. 5)

4.5 Experiment 5: Level Switches Error Simulations




20



4.5.1 Level Switch 1-5 Switches through Continuously (Trigger Switch No. 9)


4.5.3 Defect in Level Switch 1-7 (Trigger Switch No. 15)


4.6 Experiment 6: Pressure Limiter Error Simulations





21


4.6.1 Pressure Limiter Bridged (Trigger Switch No. 7)

4.6.2 Pressure Limiter Does Not Work (Trigger Switch No. 8)

4.6.3 Pressure Limiter Continuously Tripped (Trigger Switch No. 11)

4.7 Experiment 7: Other Error Simulations





4.7.1 Defect in Timer Switch (Trigger Switch No. 4)

4.7.2 No Power Supply for the Entire System (Trigger Switch No. 6)

4.7.3 Defect in Pump (Trigger Switch No. 10)

5 References [1] http://en.wikipedia.org/wiki/Boiler [2] G.U.N.T. Instruction Manual, ET860 Boiler Simulation Unit with PC Data

Acquisition

22

Documents

Laboratory Instruction Manual for Boiler Simulation …pirun.ku.ac.th/~fengwtc/Teaching/208481 Special...Laboratory Instruction Manual for Boiler Simulation Unit 1 208481 Written by