00:00:00.949 industrial plants need steam for heating 00:00:03.53000:00:03.540 and other processes boilers are commonly 00:00:06.92000:00:06.930 used to provide this steam you may be 00:00:09.77000:00:09.780 called on to operate the boilers in your 00:00:12.04900:00:12.059 plant the first step towards safe and 00:00:14.69000:00:14.700 productive operation of boilers is a 00:00:16.88000:00:16.890 good working knowledge of boiler 00:00:18.85900:00:18.869 fundamentals the function of boilers is 00:00:21.76900:00:21.779 to produce steam steam is produced by 00:00:24.83000:00:24.840 heating water to its boiling point when 00:00:27.20000:00:27.210 water reaches its boiling point it 00:00:29.17900:00:29.189 changes from a liquid to a vapor it's 00:00:31.64000:00:31.650 this vapour that we call steam so 00:00:34.52000:00:34.530 basically to produce steam you need two 00:00:36.77000:00:36.780 things water and heat to generate the 00:00:40.16000:00:40.170 heat needed for steam production boilers 00:00:42.77000:00:42.780 rely on the process of combustion that 00:00:45.17000:00:45.180 is they burn fuel to provide the heat 00:00:47.93000:00:47.940 required in simple terms there are four 00:00:50.99000:00:51.000 requirements for combustion which will 00:00:53.11900:00:53.129 illustrate on a combustion triangle one 00:00:56.42000:00:56.430 requirement is fuel most boilers burn 00:00:58.81900:00:58.829 oil natural gas or coal the second 00:01:02.36000:01:02.370 requirement is air 00:01:03.68000:01:03.690 more specifically air contains the 00:01:05.99000:01:06.000 oxygen needed for combustion the third 00:01:09.05000:01:09.060 requirement is heat heat is required to 00:01:11.75000:01:11.760 raise the temperature of the fuel air 00:01:13.39900:01:13.409 mixture to a point where a chemical 00:01:15.53000:01:15.540 reaction or ignition takes place the 00:01:18.64900:01:18.659 chemical reaction is the fourth 00:01:20.21000:01:20.220 requirement if any one of the 00:01:23.03000:01:23.040 requirements is missing combustion will 00:01:25.39900:01:25.409 not occur the two requirements for steam 00:01:28.85000:01:28.860 production are water and heat the heats 00:01:31.70000:01:31.710 provided by combustion boilers are 00:01:34.46000:01:34.470 designed to allow the requirements for 00:01:36.71000:01:36.720 steam production and combustion to come 00:01:38.96000:01:38.970 together let's see how by looking at a 00:01:41.56900:01:41.579 boilers basic operating principles we'll 00:01:45.77000:01:45.780 assemble a simplified boiler this is a 00:01:48.77000:01:48.780 container or shell with water in it the 00:01:51.95000:01:51.960 water takes care of one of the 00:01:53.56900:01:53.579 requirements for steam will also add a 00:01:56.69000:01:56.700 pipe to provide a continuous supply of 00:01:59.03000:01:59.040 fuel to the combustion area that is the 00:02:01.85000:02:01.860 area beneath the shell heat from the 00:02:04.63900:02:04.649 flame satisfies the second requirement 00:02:07.19000:02:07.200 for steam production as the shell heats 00:02:10.04000:02:10.050 up heat is transferred from the shell to 00:02:12.86000:02:12.870 the water 00:02:13.52000:02:13.530 and the water boils producing steam but 00:02:17.05900:02:17.069 a boiler modeled on this example won't 00:02:19.16000:02:19.170 work for industrial applications first 00:02:22.19000:02:22.200 of all the shell is open to the 00:02:23.84000:02:23.850 atmosphere so there's no way to collect 00:02:26.33000:02:26.340 the steam in addition as the water boils 00:02:29.12000:02:29.130 to steam there is no way to replenish it 00:02:32.18000:02:32.190 without water the shell could overheat 00:02:35.00000:02:35.010 and be damaged given these factors we'll 00:02:38.54000:02:38.550 have to make some changes first we'll 00:02:41.57000:02:41.580 cover the shell to prevent the steam 00:02:43.34000:02:43.350 from escaping then we'll add a steam 00:02:46.22000:02:46.230 outlet line to collect the steam and 00:02:48.32000:02:48.330 route it to where it can be used we also 00:02:51.05000:02:51.060 need a way to supply water to the shell 00:02:53.57000:02:53.580 so it won't boil dry so we'll add a feed 00:02:57.65000:02:57.660 water line it will provide a continuous 00:03:00.83000:03:00.840 supply of water to replace the water 00:03:02.80900:03:02.819 that's changed to steam now we have a 00:03:05.87000:03:05.880 boiler that can heat water produce steam 00:03:08.36000:03:08.370 and route it out of the shell to where 00:03:10.55000:03:10.560 it's required but this design is still 00:03:13.37000:03:13.380 not as efficient as it could be can you 00:03:15.97900:03:15.989 think of a reason why not with this 00:03:18.17000:03:18.180 design much of the heat in the 00:03:20.06000:03:20.070 combustion area escapes to the 00:03:21.97900:03:21.989 atmosphere this heat is wasted because 00:03:24.65000:03:24.660 it doesn't go toward the production of 00:03:26.81000:03:26.820 steam this boiler can be modified 00:03:29.53900:03:29.549 further to make it more efficient by 00:03:31.85000:03:31.860 adding an insulated casing we can 00:03:34.49000:03:34.500 minimize the heat loss but this creates 00:03:36.83000:03:36.840 another problem the flame goes out 00:03:39.68000:03:39.690 because the casing cuts off the source 00:03:41.93000:03:41.940 of air to correct this we'll add a fan 00:03:45.19900:03:45.209 to supply air to the boiler and an 00:03:48.19900:03:48.209 outlet to remove combustion gases 00:03:50.74000:03:50.750 although this design is still greatly 00:03:53.30000:03:53.310 simplified now we at least have a boiler 00:03:56.27000:03:56.280 that provides a constant supply of steam 00:03:58.67000:03:58.680 efficiently in this topic we saw the 00:04:02.00000:04:02.010 basic requirements for steam production 00:04:04.25000:04:04.260 and combustion we also put together a 00:04:06.94900:04:06.959 simple boiler that operates to meet 00:04:09.41000:04:09.420 these requirements and produce steam 00:04:11.59000:04:11.600 let's take a minute now to try some 00:04:14.15000:04:14.160 practice questions heat transfer is a 00:04:17.42000:04:17.430 natural process that occurs anytime 00:04:19.58000:04:19.590 there's a difference in temperature heat 00:04:22.49000:04:22.500 naturally transfers from a hotter object 00:04:24.86000:04:24.870 to a colder object 00:04:26.26000:04:26.270 basically heat transfer occurs in three 00:04:29.20000:04:29.210 ways radiation convection and conduction 00:04:32.73000:04:32.740 radiation is a process in which heat is 00:04:35.65000:04:35.660 transferred through electromagnetic 00:04:37.39000:04:37.400 waves all matter gives off some radiant 00:04:41.11000:04:41.120 energy in the form of electromagnetic 00:04:42.99900:04:43.009 waves but the best example is probably 00:04:47.35000:04:47.360 the Sun it gives off vast amounts of 00:04:50.35000:04:50.360 radiant energy as the sun's radiant 00:04:52.80900:04:52.819 energy travels through space some of the 00:04:55.39000:04:55.400 electromagnetic waves contact the earth 00:04:57.61000:04:57.620 some of these waves are reflected back 00:05:00.27900:05:00.289 into space but others are absorbed by 00:05:02.74000:05:02.750 the earth only the waves that travel in 00:05:06.07000:05:06.080 a direct line of sight between the Earth 00:05:08.08000:05:08.090 and the Sun come into contact with the 00:05:10.54000:05:10.550 earth the energy contained in the waves 00:05:12.90900:05:12.919 is absorbed by the earth as heat that 00:05:15.33900:05:15.349 warms the earth the amount of heat 00:05:17.77000:05:17.780 transferred depends on the number of 00:05:19.80000:05:19.810 electromagnetic waves absorbed a second 00:05:23.68000:05:23.690 type of heat transfer is convection 00:05:26.04000:05:26.050 convection is the transfer of heat 00:05:28.51000:05:28.520 within a fluid that is a liquid or a gas 00:05:31.62900:05:31.639 it's caused by a mixing action within 00:05:34.99000:05:35.000 the fluid to demonstrate convection we 00:05:38.74000:05:38.750 filled a beaker with water and set it on 00:05:40.77900:05:40.789 a hot plate we'll also add some dye to 00:05:43.54000:05:43.550 show the mixing action as the bottom of 00:05:46.51000:05:46.520 the beaker heats up the temperature of 00:05:48.76000:05:48.770 the water closest to the bottom 00:05:50.23000:05:50.240 increases as the temperature increases 00:05:53.14000:05:53.150 the water becomes lighter or less dense 00:05:56.05000:05:56.060 so it flows upward the warmer water 00:05:59.89000:05:59.900 mixes with the cooler water near the top 00:06:02.20000:06:02.210 of the beaker and heat transfer occurs 00:06:04.77000:06:04.780 this type of heat transfer is known as 00:06:07.57000:06:07.580 free or natural convection because the 00:06:10.65900:06:10.669 movement of the fluid occurs naturally 00:06:13.37900:06:13.389 convection heat transfer that's produced 00:06:15.90900:06:15.919 mechanically is called forced convection 00:06:18.99000:06:19.000 many buildings have forced convection 00:06:21.39900:06:21.409 heating systems these systems use fans 00:06:24.49000:06:24.500 to force warm air into rooms the warm 00:06:28.33000:06:28.340 air then mixes with a cooler air in the 00:06:30.43000:06:30.440 room and convection heat transfer occurs 00:06:33.12900:06:33.139 a third type of heat transfer is 00:06:36.37000:06:36.380 conduction conduction is the transfer of 00:06:39.64000:06:39.650 he 00:06:39.89000:06:39.900 through a solid object or between two 00:06:42.59000:06:42.600 objects as a result of physical contact 00:06:45.65000:06:45.660 for example if we heat the middle of a 00:06:49.90900:06:49.919 steel rod the end will heat up as well 00:06:52.62900:06:52.639 the heat transfer from one end of the 00:06:55.49000:06:55.500 rod to the other is due to conduction 00:06:58.42000:06:58.430 we've now seen the principles behind 00:07:00.98000:07:00.990 radiation convection and conduction the 00:07:04.49000:07:04.500 three main types of heat transfer are 00:07:06.68000:07:06.690 radiation convection and conduction each 00:07:10.43000:07:10.440 of these types is involved in 00:07:12.29000:07:12.300 transferring heat from the burning fuel 00:07:14.45000:07:14.460 to the water in a boiler to see how 00:07:18.35000:07:18.360 we'll use this example this type of 00:07:21.40900:07:21.419 boiler is called a water to boiler but 00:07:24.40900:07:24.419 the heat transfer principles at work 00:07:26.12000:07:26.130 apply to just about all boilers the 00:07:29.99000:07:30.000 boiler has a series of tubes and two 00:07:33.23000:07:33.240 drums which distribute water to the 00:07:35.36000:07:35.370 tubes the tubes form a wall around the 00:07:38.60000:07:38.610 combustion area this is the area where 00:07:41.45000:07:41.460 heat is generated when fuel burns in a 00:07:45.20000:07:45.210 boiler radiate energy in the form of 00:07:47.48000:07:47.490 electromagnetic waves is produced these 00:07:50.65900:07:50.669 waves travel through the combustion area 00:07:52.81000:07:52.820 the waves in a direct line of sight with 00:07:55.82000:07:55.830 the tubes make contact with the outer 00:07:57.86000:07:57.870 tube surfaces and the tubes absorb heat 00:08:01.01000:08:01.020 this is radiant heat transfer the 00:08:04.70000:08:04.710 burning fuel also produces combustion 00:08:07.07000:08:07.080 gases as these hot gases pass through 00:08:10.27900:08:10.289 the boiler they transfer heat to the 00:08:12.80000:08:12.810 tubes as well 00:08:13.82000:08:13.830 this is convection heat transfer as the 00:08:17.75000:08:17.760 outer surfaces of the tubes absorb heat 00:08:20.00000:08:20.010 conduction heat transfer occurs heat is 00:08:23.42000:08:23.430 transferred from the outer surface to 00:08:25.49000:08:25.500 the cooler inner surface then heat is 00:08:28.61000:08:28.620 transferred from the inner surface to 00:08:31.10000:08:31.110 the water flowing through the tube 00:08:34.65900:08:34.669 convection heat transfer also occurs as 00:08:37.69900:08:37.709 the warmer water mixes with cooler water 00:08:40.69000:08:40.700 when enough heat has been transferred to 00:08:43.21900:08:43.229 raise the water temperature to the 00:08:45.01900:08:45.029 boiling point steam is produced when a 00:08:48.11000:08:48.120 boiler is working properly the heat 00:08:50.72000:08:50.730 produced by the burning fuel will be 00:08:52.73000:08:52.740 readily transferred 00:08:53.93000:08:53.940 to the water in the tubes however there 00:08:56.87000:08:56.880 are problems that can interfere with 00:08:58.79000:08:58.800 heat transfer one of these problems is a 00:09:02.00000:09:02.010 condition called scale scale is the 00:09:06.65000:09:06.660 buildup of solid impurities on boiler 00:09:09.20000:09:09.210 components that contain water the 00:09:12.20000:09:12.210 boilers feed water supply may contain 00:09:14.57000:09:14.580 impurities these impurities coat the 00:09:17.87000:09:17.880 surfaces insulate them and restrict 00:09:20.48000:09:20.490 their ability to transfer heat if the 00:09:23.60000:09:23.610 surfaces can't transfer heat to the 00:09:25.61000:09:25.620 water the tube can overheat and rupture 00:09:28.88000:09:28.890 a heat transfer problem can also occur 00:09:32.72000:09:32.730 that feed water supply stops for any 00:09:35.51000:09:35.520 reason without a continuous supply of 00:09:38.15000:09:38.160 feed water the boiler may boil dry with 00:09:42.32000:09:42.330 no water to remove the heat the two 00:09:44.69000:09:44.700 metal rapidly overheats and severe 00:09:47.18000:09:47.190 damage may result in boilers that burn 00:09:50.54000:09:50.550 coal or oil another problem that can 00:09:53.45000:09:53.460 affect heat transfer is the buildup of 00:09:55.67000:09:55.680 suit suits created by ash and unburned 00:09:58.91000:09:58.920 fuel particles in the combustion gases 00:10:00.98000:10:00.990 in this topic we covered heat transfer 00:10:04.46000:10:04.470 we looked at the major types of heat 00:10:06.98000:10:06.990 transfer and we saw how heat transfer 00:10:09.80000:10:09.810 occurs in a boiler we also looked at a 00:10:12.77000:10:12.780 few typical heat transfer problems now 00:10:15.89000:10:15.900 let's try some practice questions 00:10:18.58000:10:18.590 basically fire two boilers route hot 00:10:21.65000:10:21.660 combustion gases through metal tubes the 00:10:24.62000:10:24.630 tubes run through a shell filled with 00:10:26.63000:10:26.640 water fire two boilers vary in design 00:10:30.44000:10:30.450 but most operate under similar 00:10:32.78000:10:32.790 principles the combustion area for this 00:10:36.29000:10:36.300 one is here 00:10:37.25000:10:37.260 a group of horizontal fire tubes routes 00:10:40.79000:10:40.800 combustion gases through the boiler 00:10:43.03000:10:43.040 there's also an outlet for the gases a 00:10:46.01000:10:46.020 feed water line and a steam outlet line 00:10:50.29000:10:50.300 during operation water enters through 00:10:53.32900:10:53.339 the feed water line the water level is 00:10:56.30000:10:56.310 maintained above the fire tubes to 00:10:58.73000:10:58.740 protect the tubes from overheating fuel 00:11:02.09000:11:02.100 and air enter the combustion area the 00:11:04.70000:11:04.710 burning fuel transfers heat to the water 00:11:07.01000:11:07.020 in the show 00:11:08.25900:11:08.269 the hot gases flow through the fire 00:11:11.05900:11:11.069 tubes and additional heat is transferred 00:11:13.85000:11:13.860 to the water surrounding them each time 00:11:17.21000:11:17.220 the gases are routed through the shell 00:11:19.16000:11:19.170 it's called a pass the gases pass 00:11:22.24900:11:22.259 through two times in this example so 00:11:24.82900:11:24.839 it's a two pass boiler the combustion 00:11:28.48900:11:28.499 gases flow out of the boiler here in 00:11:30.91900:11:30.929 this example as the water in the boiler 00:11:34.03900:11:34.049 is heated some of it turns to steam the 00:11:37.36900:11:37.379 steam water mixture is lighter than the 00:11:39.37900:11:39.389 cooler water in the boiler so it tends 00:11:41.96000:11:41.970 to rise steam collects above the water 00:11:45.53000:11:45.540 level then it flows through the outlet 00:11:48.13900:11:48.149 and into the plant the feed water which 00:11:50.86900:11:50.879 is cooler and heavier than the steam 00:11:52.75900:11:52.769 water mixture flows to the bottom of the 00:11:55.18900:11:55.199 boiler it's heated in the combustion 00:11:57.31900:11:57.329 area and the cycle continues 00:11:59.72000:11:59.730 generally speaking water-tube boilers 00:12:02.21000:12:02.220 use tubes to route water and steam 00:12:04.97000:12:04.980 through the boiler the combustion gases 00:12:07.42900:12:07.439 flow past the outside surfaces of the 00:12:10.24900:12:10.259 tubes let's examine this principle in 00:12:13.03900:12:13.049 more detail water-tube boilers may vary 00:12:16.93900:12:16.949 in design but most of them operate in 00:12:19.40000:12:19.410 basically the same way this particular 00:12:22.28000:12:22.290 boiler consists of a series of water 00:12:24.73900:12:24.749 tubes and two drums the drums distribute 00:12:28.81900:12:28.829 water to the tubes the water tubes 00:12:31.40000:12:31.410 connect the drums and form a wall around 00:12:33.82900:12:33.839 the combustion area of the boiler this 00:12:36.61900:12:36.629 is where heat is generated water is fed 00:12:39.98000:12:39.990 into the upper drum through a feed water 00:12:41.98900:12:41.999 inlet line the water tubes and the lower 00:12:45.13900:12:45.149 drum are completely filled with water 00:12:47.55900:12:47.569 the upper drum is only filled to a 00:12:50.15000:12:50.160 certain level this provides space for 00:12:52.63900:12:52.649 steam to collect so the upper drum is 00:12:55.57900:12:55.589 often called the steam drum as fuel is 00:12:59.09000:12:59.100 burned in the combustion area heat is 00:13:01.69900:13:01.709 transferred to the adjacent water tubes 00:13:04.05900:13:04.069 the combustion gases then flow out of 00:13:06.97900:13:06.989 the boiler water circulates from the 00:13:09.82900:13:09.839 upper drum through the water tubes and 00:13:12.01900:13:12.029 into the lower drum the lower drum is 00:13:14.78000:13:14.790 often referred to as the mud drum from 00:13:18.82900:13:18.839 the lower drum the water is distributed 00:13:20.96000:13:20.970 to the water tube surrounding the 00:13:22.73000:13:22.740 combustion area as the water in the 00:13:25.63900:13:25.649 tubes is heated a steam water mixture is 00:13:28.22000:13:28.230 produced the steam water mixture enters 00:13:32.11900:13:32.129 the upper drum the steam is separated 00:13:34.81900:13:34.829 from the water and routed through the 00:13:36.23000:13:36.240 steam outlet and into the plant in this 00:13:39.11000:13:39.120 topic we looked at the two main types of 00:13:41.74900:13:41.759 boilers fire tube boilers and water-tube 00:13:44.66000:13:44.670 boilers we saw basically how they're 00:13:47.11900:13:47.129 designed and how they operate at this 00:13:49.73000:13:49.740 point let's try some practice questions 00:13:52.00900:13:52.019 on fire tube and water-tube boilers
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