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Heat Exchangers Operation Of Shell And Tube Types Training
WEBVTT Kind: captions Language: en
00:00:04.200 [Music] 00:00:11.95000:00:11.96000:00:18.22000:00:18.23000:00:24.08000:00:24.090 many industrial processes must heater 00:00:27.06000:00:27.070 cool fluids to produce products heating 00:00:30.00000:00:30.010 and cooling are often accomplished by 00:00:31.71000:00:31.720 transferring heat between fluids heat 00:00:34.77000:00:34.780 transfer between fluids occurs in heat 00:00:37.14000:00:37.150 exchangers there are many types of heat 00:00:39.47900:00:39.489 exchangers but one of the most common 00:00:41.70000:00:41.710 types is a shell and tube heat exchanger 00:00:44.00900:00:44.019 shell and tube heat exchangers can be 00:00:46.74000:00:46.750 used for a variety of processes and 00:00:48.81000:00:48.820 operating procedures may vary with each 00:00:51.03000:00:51.040 heat exchanger what you'll see here is 00:00:53.64000:00:53.650 intended to be a guide to the steps that 00:00:55.71000:00:55.720 often have to be taken in the startup of 00:00:58.17000:00:58.180 a shell and tube heat exchanger after it 00:01:00.50900:01:00.519 has been shut down for maintenance but 00:01:02.31000:01:02.320 remember always follow your facility's 00:01:05.25000:01:05.260 operating procedures when you're 00:01:06.81000:01:06.820 starting up any heat exchanger the unit 00:01:09.99000:01:10.000 we'll be using is part of a mixing 00:01:11.85000:01:11.860 process and is used to cool the process 00:01:14.31000:01:14.320 liquid the heat exchanger has cooling 00:01:17.55000:01:17.560 water inlet and outlet lines process 00:01:22.83000:01:22.840 liquid Inlet and outlet lines a series 00:01:28.17000:01:28.180 of isolation valves a vent valve and 00:01:32.94000:01:32.950 drain valves before starting up the heat 00:01:38.01000:01:38.020 exchanger the operator inspects the unit 00:01:40.59000:01:40.600 to see if it's ready he checks the 00:01:42.51000:01:42.520 valves to make sure that all of the 00:01:44.24900:01:44.259 isolation vent and drain valves are shut 00:01:47.51000:01:47.520 after he completes the initial 00:01:49.98000:01:49.990 inspection he establishes the cooling 00:01:52.28900:01:52.299 water supply to the unit he does this by 00:01:55.28900:01:55.299 calling the control room operator and 00:01:57.23900:01:57.249 having him open the shell side vent then 00:02:01.02000:02:01.030 he partially opens the shell side water 00:02:03.41900:02:03.429 inlet valve to slowly fill the shell 00:02:05.76000:02:05.770 side then he calls the control room to 00:02:08.94000:02:08.950 have someone there start the cooling 00:02:10.62000:02:10.630 water pump 00:02:11.52000:02:11.530 when the cooling water pump is started 00:02:13.80000:02:13.810 cooling water will fill the shell side 00:02:15.96000:02:15.970 of the heat exchanger any air that is 00:02:18.45000:02:18.460 trapped on the shell side escapes 00:02:20.22000:02:20.230 through the open vent valve as the shell 00:02:22.95000:02:22.960 side of the heat exchanger fills the 00:02:25.11000:02:25.120 operator listens for air escaping when 00:02:27.63000:02:27.640 the shell side is completely filled he 00:02:29.90000:02:29.910 calls the control room and has them shut 00:02:32.03000:02:32.040 the vent valve then the operator opens 00:02:35.06000:02:35.070 the shell side inlet valve the rest of 00:02:37.22000:02:37.230 the way at that point he informs the 00:02:39.89000:02:39.900 control room that the shell side is 00:02:41.84000:02:41.850 lined up and that they can establish the 00:02:43.88000:02:43.890 proper flow rate through the shell on 00:02:45.91000:02:45.920 the heat exchangers shown in this 00:02:48.23000:02:48.240 example there is no isolation valve on 00:02:51.11000:02:51.120 the outlet of the shell side some shell 00:02:53.78000:02:53.790 and tube heat exchangers have an 00:02:55.40000:02:55.410 isolation valve on this outlet with 00:02:58.22000:02:58.230 those heat exchangers the isolation 00:03:00.53000:03:00.540 valve must be open to complete the flow 00:03:02.84000:03:02.850 path through the unit the next step is 00:03:05.36000:03:05.370 to line up the tube side of the heat 00:03:07.19000:03:07.200 exchanger first the operator opens the 00:03:10.25000:03:10.260 tube side vent valve then he partially 00:03:13.34000:03:13.350 opens the tube side inlet valve to allow 00:03:16.13000:03:16.140 the tube side to fill with process 00:03:18.02000:03:18.030 liquid and to remove any air or other 00:03:20.36000:03:20.370 gases that might be trapped on the tube 00:03:22.31000:03:22.320 side of the unit when the tube side is 00:03:24.71000:03:24.720 filled the operator closes the vent 00:03:27.08000:03:27.090 valve and opens the inlet valve the rest 00:03:30.62000:03:30.630 of the way then he opens the outlet 00:03:33.92000:03:33.930 valve at this point the startup is 00:03:37.22000:03:37.230 complete and the heat exchanger is in 00:03:39.32000:03:39.330 operation after the operator reports to 00:03:42.26000:03:42.270 the control room that the unit is in 00:03:43.85000:03:43.860 operation the control room establishes 00:03:46.43000:03:46.440 flow through the unit shell and tube 00:03:48.71000:03:48.720 heat exchangers are commonly used in a 00:03:50.84000:03:50.850 variety of processes and each may have a 00:03:53.30000:03:53.310 different operating procedure but 00:03:55.49000:03:55.50000:03:57.80000:03:57.810 operating procedures when shutting down 00:03:59.81000:03:59.820 any heat exchanger during shutdown the 00:04:03.17000:04:03.180 side of the heat exchanger with the 00:04:04.88000:04:04.890 hotter fluid is usually shut down first 00:04:07.07000:04:07.080 this helps to prevent the heat exchanger 00:04:09.74000:04:09.750 from being overheated and damaged 00:04:11.78000:04:11.790 let's watch an operator as he takes a 00:04:14.57000:04:14.580 heat exchanger out of service in this 00:04:16.84900:04:16.859 example the heat exchanger which cools a 00:04:19.34000:04:19.350 product from a reactor is being shut 00:04:21.62000:04:21.630 down for maintenance the tube side fluid 00:04:23.93000:04:23.940 is the hotter fluid to shut down the 00:04:27.29000:04:27.300 heat exchanger the operator closes the 00:04:29.65900:04:29.669 tube side inlet valve first and then the 00:04:32.72000:04:32.730 tube side outlet valve when the tube 00:04:35.99000:04:36.000 side has cooled the operator opens the 00:04:38.75000:04:38.760 tube side drain 00:04:40.55000:04:40.560 and vent valves this allows air to enter 00:04:43.40000:04:43.410 the tube side and drains the process 00:04:45.53000:04:45.540 fluid the operator then shuts the shell 00:04:48.86000:04:48.870 side inlet valve on the heat exchanger 00:04:51.20000:04:51.210 shown in this example the shell side has 00:04:54.29000:04:54.300 no isolation valve on its outlet some 00:04:57.35000:04:57.360 shell and tube heat exchangers have an 00:04:59.18000:04:59.19000:05:01.61000:05:01.62000:05:03.92000:05:03.930 valve must be shut to completely isolate 00:05:06.35000:05:06.360 the heat exchanger after the isolation 00:05:09.40900:05:09.419 valve is shut the operator opens the 00:05:12.02000:05:12.030 cooling water drain in vent valves once 00:05:14.99000:05:15.000 all of the fluid is drained from the 00:05:16.73000:05:16.74000:05:19.43000:05:19.440 vent and drain valves to complete the 00:05:21.56000:05:21.570 shutdown now if the heat exchanger 00:05:23.84000:05:23.850 that's being shut down handles flammable 00:05:26.57000:05:26.580 liquids it may have to be purged to 00:05:28.79000:05:28.800 reduce the possibility of a fire or an 00:05:31.19000:05:31.200 explosion caused by flammable vapors 00:05:33.46000:05:33.470 purging means forcing the process fluids 00:05:36.40900:05:36.419 out of the heat exchanger by a substance 00:05:38.90000:05:38.910 that won't react with the process fluid 00:05:40.94000:05:40.950 very often steam or nitrogen is used 00:05:43.46000:05:43.470 when a heat exchanger is in operation 00:05:46.15000:05:46.160 operators must routinely check the unit 00:05:48.92000:05:48.930 to ensure that its operating properly 00:05:50.87000:05:50.880 this may include checking temperature 00:05:53.30000:05:53.310 and pressure instruments to make sure 00:05:54.98000:05:54.990 that their readings are within normal 00:05:56.65900:05:56.669 operating ranges as well as checking the 00:05:59.00000:05:59.010 condition of the heat exchanger itself 00:06:01.81000:06:01.820 by checking a heat exchangers 00:06:04.15900:06:04.169 temperature instruments an operator can 00:06:06.38000:06:06.390 tell how the temperatures of the fluids 00:06:08.24000:06:08.250 change as they pass through the unit 00:06:09.98000:06:09.990 these values can also be used to 00:06:12.32000:06:12.330 determine the difference in temperature 00:06:14.12000:06:14.130 or delta T for each fluid the delta T 00:06:17.81000:06:17.820 can be used to see if the unit is 00:06:19.43000:06:19.440 operating properly for example if the 00:06:22.82000:06:22.830 delta T across the tube side of a heat 00:06:25.01000:06:25.020 exchanger is supposed to be 10 degrees 00:06:27.08000:06:27.090 but it is only 5 degrees it could be an 00:06:30.14000:06:30.150 indication that the tubes in the unit 00:06:31.96900:06:31.979 are becoming fouled or that one or both 00:06:34.40000:06:34.410 of the flow rates are not correct for 00:06:36.52900:06:36.539 proper operation in any event the cause 00:06:39.59000:06:39.600 of the problem should be investigated 00:06:41.48000:06:41.490 and supervisory personnel should be 00:06:43.55000:06:43.560 informed another way the temperatures 00:06:46.07000:06:46.080 can be checked is on a temperature 00:06:47.93000:06:47.940 recorder the recorder plots temperature 00:06:50.63000:06:50.640 values on a chart which allows an 00:06:52.76000:06:52.770 operator to see 00:06:53.80000:06:53.810 the trend is developing additional 00:06:55.96000:06:55.970 information about a heat exchanger can 00:06:58.39000:06:58.400 be obtained by checking the units 00:07:00.12900:07:00.139 pressure instruments by reading the 00:07:02.53000:07:02.540 pressure instruments an operator can 00:07:04.54000:07:04.550 often detect problems with flow through 00:07:06.82000:07:06.830 the unit anytime there's flow through a 00:07:09.58000:07:09.590 heat exchanger there will be a specific 00:07:11.56000:07:11.570 drop in pressure across the unit this 00:07:14.44000:07:14.450 pressure drop is often referred to as 00:07:16.71000:07:16.720 differential pressure or Delta P any 00:07:19.51000:07:19.520 change in differential pressure could be 00:07:22.03000:07:22.040 an indication of a problem as the tubes 00:07:24.76000:07:24.770 become blocked or fouled the 00:07:26.59000:07:26.600 differential pressure will increase 00:07:27.94000:07:27.950 above the normal value once again the 00:07:31.00000:07:31.010 cause of the problem should be 00:07:32.32000:07:32.330 investigated and supervisory personnel 00:07:34.48000:07:34.490 should be informed on many units 00:07:37.42000:07:37.430 temperature and flow are controlled by 00:07:39.34000:07:39.350 automatic systems these systems may 00:07:41.95000:07:41.960 provide indications locally and in a 00:07:44.40900:07:44.419 control room the indications in the 00:07:46.65900:07:46.669 control room can be compared to the 00:07:48.73000:07:48.740 indications on instruments located at 00:07:50.95000:07:50.960 the heat exchanger to verify that the 00:07:53.20000:07:53.210 heat exchanger is operating properly if 00:07:55.99000:07:56.000 a problem is detected it could be the 00:07:58.24000:07:58.250 result of the control valves not 00:08:00.01000:08:00.020 operating properly or valves being out 00:08:03.07000:08:03.080 of position or it could be an indication 00:08:06.13000:08:06.140 that other equipment associated with the 00:08:08.23000:08:08.240 heat exchanger is not operating properly 00:08:10.77900:08:10.789 for example a low Inlet pressure could 00:08:13.99000:08:14.000 indicate a problem with a pump that 00:08:15.70000:08:15.710 supplies the heat exchanger besides 00:08:18.76000:08:18.770 checking instrument readings an operator 00:08:21.15900:08:21.169 should also check for leaks and for 00:08:24.15900:08:24.169 damaged or missing insulation problems 00:08:27.55000:08:27.560 such as these could affect the operation 00:08:29.62000:08:29.630 of the heat exchanger and pose hazards 00:08:31.69000:08:31.700 to personnel working in the area in this 00:08:34.45000:08:34.460 topic we looked at some basic procedures 00:08:36.79000:08:36.800 for the startup and shutdown of a 00:08:38.62000:08:38.630 typical shell and tube heat exchanger we 00:08:41.11000:08:41.120 also looked at some operator 00:08:42.61000:08:42.620 responsibilities associated with 00:08:44.44000:08:44.450 operating a shell and tube heat 00:08:45.88000:08:45.890 exchanger now let's try a few practice 00:08:48.57900:08:48.589 questions when the cooling water pump is 00:08:50.92000:08:50.930 started cooling water will fill the 00:08:53.05000:08:53.060 shell side of the heat exchanger any air 00:08:55.63000:08:55.640 that is trapped on the shell side 00:08:57.16000:08:57.170 escapes through the open vent valve as 00:08:59.41000:08:59.420 the shell side of the heat exchanger 00:09:01.75000:09:01.760 fills the operator listens for air 00:09:04.06000:09:04.070 escaping when the shell side is 00:09:05.94900:09:05.959 completely filled 00:09:07.34000:09:07.350 he calls the control room and has them 00:09:09.35000:09:09.360 shut the vent valve then the operator 00:09:12.20000:09:12.210 opens the shell side inlet valve the 00:09:14.45000:09:14.460 rest of the way at that point he informs 00:09:17.33000:09:17.340 the control room that the shell side is 00:09:19.43000:09:19.44000:09:21.50000:09:21.510 proper flow rate through the shell to 00:09:24.32000:09:24.330 shut down the heat exchanger the 00:09:25.97000:09:25.980 operator closes the tube side inlet 00:09:28.31000:09:28.320 valve first and then the tube side 00:09:30.83000:09:30.840 outlet valve when the tube side has 00:09:34.25000:09:34.260 cooled the operator opens the tube side 00:09:36.92000:09:36.930 drain and vent valves this allows air to 00:09:40.67000:09:40.680 enter the tube side and drains the 00:09:42.62000:09:42.630 process fluid as the tubes become 00:09:45.17000:09:45.180 blocked or fouled the differential 00:09:47.21000:09:47.220 pressure will increase above the normal 00:09:49.19000:09:49.200 value once again the cause of the 00:09:51.59000:09:51.600 problem should be investigated and 00:09:53.27000:09:53.280 supervisory personnel should be informed 00:09:55.75000:09:55.760 fouling is a term that's often used to 00:09:58.22000:09:58.230 describe the build-up of deposits on the 00:10:00.38000:10:00.390 internal surfaces of the heat exchanger 00:10:02.69000:10:02.700 when fouling occurs the result is an 00:10:05.75000:10:05.760 additional layer of material that heat 00:10:07.76000:10:07.770 must pass through this additional layer 00:10:10.19000:10:10.200 reduces the ability of the unit to 00:10:12.35000:10:12.360 transfer heat also if the buildup 00:10:15.11000:10:15.120 becomes excessive the flow of fluids 00:10:17.39000:10:17.400 through the unit may be restricted 00:10:19.15000:10:19.160 fouling can be caused by many things one 00:10:22.25000:10:22.260 common cause is impurities in the fluids 00:10:24.98000:10:24.990 passing through the heat exchanger for 00:10:26.75000:10:26.760 example in a process that uses water 00:10:29.89000:10:29.900 impurities such as calcium can come out 00:10:32.66000:10:32.670 of the water and form an additional 00:10:34.67000:10:34.680 layer of material another source of 00:10:37.22000:10:37.230 fouling is small plants and animals that 00:10:39.38000:10:39.390 enter the heat exchanger many forms of 00:10:42.02000:10:42.030 algae and bacteria can live and grow 00:10:44.42000:10:44.430 inside the unit and form a layer of 00:10:46.73000:10:46.740 slime on the internal surfaces of the 00:10:48.80000:10:48.810 heat exchanger gases dissolved in the 00:10:51.77000:10:51.780 fluids that flow through a heat 00:10:53.09000:10:53.100 exchanger can also cause fouling for 00:10:55.85000:10:55.860 example some gases react with the metal 00:10:58.25000:10:58.260 inside a unit to cause a type of 00:11:00.14000:11:00.150 corrosion the corrosion forms a layer 00:11:02.81000:11:02.820 that acts as an insulator just like 00:11:05.03000:11:05.040 impurities or algae different techniques 00:11:08.39000:11:08.400 can be used to minimize fouling for 00:11:10.61000:11:10.620 example filters and screens can be used 00:11:13.04000:11:13.050 to remove particles from the fluids 00:11:14.99000:11:15.000 before they enter the heat exchanger 00:11:16.70000:11:16.710 fouling can sometimes be minimized by 00:11:19.43000:11:19.440 adding chem 00:11:20.23000:11:20.240 chuckles to the fluids passing through a 00:11:21.82000:11:21.830 heat exchanger for example chemicals 00:11:24.55000:11:24.560 such as chlorine are often added to 00:11:26.56000:11:26.570 cooling water to reduce the amount of 00:11:28.75000:11:28.760 algae or other organisms inside a unit 00:11:31.30000:11:31.310 in some situations 00:11:33.28000:11:33.290 fouling can become bad enough to 00:11:35.01900:11:35.029 restrict the fluid flow this problem may 00:11:37.75000:11:37.760 show up on the heat exchangers 00:11:39.22000:11:39.230 instruments as an increase in the 00:11:41.19900:11:41.209 pressure drop or as a gradual decrease 00:11:43.78000:11:43.790 in the flow through the affected side of 00:11:45.76000:11:45.770 the unit 00:11:46.32900:11:46.339 fouling may also affect the temperature 00:11:48.61000:11:48.620 of both fluids passing through the heat 00:11:50.71000:11:50.720 exchanger when fluid flow is restricted 00:11:53.26000:11:53.270 the heat exchanger must be cleaned one 00:11:56.44000:11:56.450 way that heat exchangers can be cleaned 00:11:58.21000:11:58.220 is by using chemicals when this is done 00:12:00.67000:12:00.680 a chemical solution is passed through 00:12:02.68000:12:02.690 the heat exchanger to dissolve the 00:12:04.72000:12:04.730 fouling on the walls of the tubes 00:12:06.81000:12:06.820 fouling on tube walls can also be 00:12:09.51900:12:09.529 removed by scraping or by spraying with 00:12:12.13000:12:12.140 high-pressure water or steam however 00:12:14.68000:12:14.690 these methods require the heat exchanger 00:12:17.11000:12:17.120 to be shut down and taken apart in some 00:12:20.13900:12:20.149 heat exchangers cleaning can be 00:12:21.91000:12:21.920 accomplished using a technique called 00:12:23.53000:12:23.540 back washing back washing is the 00:12:26.44000:12:26.450 reversing of flow through the heat 00:12:28.24000:12:28.250 exchanger this technique is effective in 00:12:30.81900:12:30.829 temporarily dislodging materials from 00:12:33.01000:12:33.020 the ends of the tubes and the tube 00:12:34.90000:12:34.910 sheets tube leakage is a problem that 00:12:38.26000:12:38.270 can seriously affect the operation of a 00:12:40.38900:12:40.399 heat exchanger it's usually caused by 00:12:42.88000:12:42.890 the failure of a tube as a result of 00:12:45.31000:12:45.320 overheating erosion or corrosion 00:12:48.42000:12:48.430 corrosion is the wearing away of tube 00:12:51.31000:12:51.320 metal caused by the flow of fluids or by 00:12:54.01000:12:54.020 solid impurities in the fluids some 00:12:56.76900:12:56.779 fluids that pass through a heat 00:12:58.06000:12:58.070 exchanger may contain abrasive particles 00:13:00.37000:13:00.380 as these fluids flow through the heat 00:13:02.41000:13:02.420 exchanger the particles come into 00:13:04.32900:13:04.339 contact with the tube metal and erode 00:13:06.46000:13:06.470 the tubes eventually the tube wears away 00:13:09.28000:13:09.290 in a spot and a leak forms corrosion 00:13:12.46000:13:12.470 chemically deteriorates tube metal to 00:13:14.71000:13:14.720 create a leak corrosion is caused by a 00:13:17.38000:13:17.390 chemical reaction between the metal in 00:13:19.48000:13:19.490 the heat exchanger and either the fluid 00:13:21.63900:13:21.649 passing through the unit or impurities 00:13:23.92000:13:23.930 in the fluid the corrosion weakens the 00:13:26.29000:13:26.300 metal until a leak forms the biggest 00:13:29.17000:13:29.180 problem that can result from leaks in a 00:13:31.18000:13:31.190 heat exchanger is 00:13:32.59000:13:32.600 mixing of one fluid with the other fluid 00:13:35.07900:13:35.089 for instance if cooling water mixes with 00:13:37.96000:13:37.970 oil and a lube oil cooler but water 00:13:40.38900:13:40.399 could damage the equipment that the oil 00:13:42.22000:13:42.230 lubricates to prevent this type of 00:13:44.55900:13:44.569 damage from occurring leaks must be 00:13:46.66000:13:46.670 detected one way to check for tube leaks 00:13:49.32900:13:49.339 is to take and analyze a sample of the 00:13:51.81900:13:51.829 lower pressure fluid when a leak occurs 00:13:54.22000:13:54.230 the high-pressure fluid leaks into the 00:13:56.55900:13:56.569 low-pressure fluid in some cases you may 00:13:59.80000:13:59.810 be able to tell there's a leak by just 00:14:01.56900:14:01.579 looking at the sample in other cases a 00:14:03.79000:14:03.800 lab test may be required to prevent 00:14:06.73000:14:06.740 leaks in some applications the process 00:14:09.10000:14:09.110 fluids passed through filters or 00:14:11.35000:14:11.360 strainers to remove impurities that can 00:14:13.66000:14:13.670 erode the tube metal also chemicals may 00:14:16.36000:14:16.370 be added to the fluids to control 00:14:17.98000:14:17.990 corrosion another method of controlling 00:14:20.71000:14:20.720 corrosion involves using a device called 00:14:23.23000:14:23.240 a sacrificial anode when a sacrificial 00:14:26.11000:14:26.120 anode is used impurities in water tend 00:14:29.01900:14:29.029 to react more readily with the anode 00:14:31.12000:14:31.130 than with the metal of the heat 00:14:32.65000:14:32.660 exchanger so the sacrificial anode 00:14:35.05000:14:35.060 corrodes while the heat exchanger is 00:14:37.38900:14:37.399 less affected heat exchangers that are 00:14:39.79000:14:39.800 used with water often have sacrificial 00:14:42.10000:14:42.110 anodes made up of zinc plates mounted 00:14:44.29000:14:44.300 inside when a leak does occur some type 00:14:47.53000:14:47.540 of corrective action must be taken if 00:14:49.90000:14:49.910 only a few tubes in a heat exchanger 00:14:51.42900:14:51.439 have leaks it may be possible to plug 00:14:54.37000:14:54.380 the affected tubes this prevents the 00:14:56.71000:14:56.720 tube side fluid from passing through 00:14:58.54000:14:58.550 those tubes and effectively eliminates 00:15:01.24000:15:01.250 the link however plugging tubes reduces 00:15:04.38900:15:04.399 a heat exchangers heat transfer capacity 00:15:06.68900:15:06.699 if a lot of tubes are leaking the unit 00:15:09.85000:15:09.860 will have to be shut down and the 00:15:11.74000:15:11.750 affected tubes will have to be replaced 00:15:13.82900:15:13.839 when air non-condensable gases or other 00:15:17.62000:15:17.630 vapors are trapped inside a heat 00:15:19.36000:15:19.370 exchanger they can prevent the unit from 00:15:21.75900:15:21.769 operating efficiently this is because 00:15:24.12900:15:24.139 the air or gas can either blanket the 00:15:26.74000:15:26.750 tubes or block the tubes off and prevent 00:15:29.49900:15:29.509 fluid from flowing through them the 00:15:31.54000:15:31.550 effect is the same as the effect created 00:15:33.69900:15:33.709 by fouling less heat can be transferred 00:15:36.04000:15:36.050 across the tubes gas trapped on the tube 00:15:39.22000:15:39.230 side of a heat exchanger can block off 00:15:41.47000:15:41.480 tubes and prevent fluid from passing 00:15:43.54000:15:43.550 through them 00:15:44.39000:15:44.400 gasps trapped on the shell side can 00:15:46.76000:15:46.770 displace the shell side fluid at the top 00:15:48.83000:15:48.840 of the heat exchanger this can reduce 00:15:50.87000:15:50.880 the amount of tube surface area that is 00:15:53.06000:15:53.070 exposed to the shell side fluid and thus 00:15:55.55000:15:55.560 reduce the amount of heat that can be 00:15:57.29000:15:57.300 transferred there are many ways that air 00:15:59.90000:15:59.910 or other gases can get trapped inside a 00:16:01.91000:16:01.920 heat exchanger for example this can 00:16:04.28000:16:04.290 happen during the startup of the unit 00:16:06.07000:16:06.080 during startup the heat exchanger should 00:16:09.05000:16:09.060 be vented to remove unwanted gases if 00:16:11.78000:16:11.790 the vetting is not complete gases will 00:16:14.33000:16:14.340 remain inside the unit another source of 00:16:17.33000:16:17.340 gases as the process itself in some 00:16:19.91000:16:19.920 situations the process can produce vapor 00:16:22.49000:16:22.500 bubbles as the process fluid passes 00:16:25.10000:16:25.110 through the heat exchanger the vapor 00:16:27.05000:16:27.060 collects inside the unit when 00:16:29.48000:16:29.490 maintenance is performed on process 00:16:31.34000:16:31.350 equipment air may be trapped in the 00:16:33.41000:16:33.420 piping or shell as the equipment is put 00:16:35.51000:16:35.520 back together when the equipment is 00:16:37.49000:16:37.500 restarted the air can make its way to 00:16:39.71000:16:39.720 the heat exchanger and become trapped 00:16:41.51000:16:41.520 inside no matter how error other gases 00:16:44.75000:16:44.760 get trapped inside a heat exchanger they 00:16:47.03000:16:47.040 can cause it to become air bound or 00:16:48.98000:16:48.990 vapor bound there are several symptoms 00:16:51.17000:16:51.180 to indicate this for example when 00:16:53.75000:16:53.760 trapped gas blocks flow to some of the 00:16:55.85000:16:55.860 tubes the outlet temperatures of the two 00:16:58.13000:16:58.140 fluids may change this is because the 00:17:00.83000:17:00.840 gas is restricting flow into the tubes 00:17:02.93000:17:02.940 and the restricted flow causes less heat 00:17:05.90000:17:05.910 transfer surface area to be available 00:17:08.19900:17:08.209 the decrease in heat transfer surface 00:17:11.03000:17:11.040 area will cause the outlet temperature 00:17:12.98000:17:12.990 of the process fluid to increase since 00:17:15.68000:17:15.690 less heat will be removed from the fluid 00:17:17.92000:17:17.930 there are also situations where the 00:17:20.36000:17:20.370 pressure inside a heat exchanger may be 00:17:22.37000:17:22.380 affected for example this can occur in 00:17:25.04000:17:25.050 heat exchangers that are used to 00:17:26.63000:17:26.640 condense processed vapors in this 00:17:29.12000:17:29.130 situation non condensable gases 00:17:31.46000:17:31.470 partially fill the unit reducing the 00:17:34.07000:17:34.080 amount of heat transfer area that the 00:17:36.20000:17:36.210 process vapor can come in contact with 00:17:38.12000:17:38.130 in turn this reduces the amount of vapor 00:17:41.27000:17:41.280 that can be condensed the flow of vapor 00:17:43.85000:17:43.860 will start to decrease and the pressure 00:17:46.10000:17:46.110 inside the unit will start to increase 00:17:48.88000:17:48.890 regardless of how gases get into the 00:17:51.32000:17:51.330 heat exchanger the unit must be vented 00:17:53.66000:17:53.670 to allow them to escape 00:17:55.66000:17:55.670 repeated venting may be necessary to 00:17:57.58000:17:57.590 ensure that the heat exchanger remains 00:17:59.68000:17:59.690 free of air and other undesirable gases 00:18:03.21000:18:03.220 however excessive venting can cause its 00:18:06.37000:18:06.380 own problems for example each venting 00:18:08.86000:18:08.870 may allow a small amount of the process 00:18:10.87000:18:10.880 fluid to be lost from the process this 00:18:13.15000:18:13.160 reduces the efficiency of the process 00:18:15.39000:18:15.400 venting may be only a temporary fix if 00:18:18.58000:18:18.590 the source of the gas is the process 00:18:20.65000:18:20.660 there may be a problem with the process 00:18:22.90000:18:22.910 or with one of the components of the 00:18:24.73000:18:24.740 process in this topic we looked at some 00:18:27.37000:18:27.380 of the basic problems that can affect a 00:18:29.26000:18:29.270 typical heat exchanger including fouling 00:18:31.93000:18:31.940 tube leaks and air and vapor binding we 00:18:35.02000:18:35.030 also looked at the causes and effects of 00:18:37.09000:18:37.100 these problems and we saw how they can 00:18:39.04000:18:39.050 be dealt with let's take a moment now 00:18:41.08000:18:41.090 and try some practice questions 00:18:42.85000:18:42.86000:18:45.34000:18:45.350 adding chemicals to the fluids passing 00:18:47.74000:18:47.750 through a heat exchanger for example 00:18:49.84000:18:49.850 chemicals such as chlorine are often 00:18:52.30000:18:52.310 added to cooling water to reduce the 00:18:54.52000:18:54.530 amount of algae or other organisms 00:18:56.50000:18:56.510 inside a unit corrosion chemically 00:18:59.14000:18:59.150 deteriorates tube metal to create a leak 00:19:01.71000:19:01.720 corrosion is caused by a chemical 00:19:04.00000:19:04.010 reaction between the metal and the heat 00:19:05.80000:19:05.810 exchanger and either the fluid passing 00:19:08.17000:19:08.180 through the unit or impurities in the 00:19:10.18000:19:10.190 fluid the corrosion weakens the metal 00:19:12.61000:19:12.620 until a leak forms regardless of how 00:19:15.31000:19:15.320 gases get into the heat exchanger the 00:19:17.53000:19:17.540 unit must be vented to allow them to 00:19:19.45000:19:19.460 escape repeated venting may be necessary 00:19:22.03000:19:22.040 to ensure that the heat exchanger 00:19:24.31000:19:24.320 remains free of air and other 00:19:26.17000:19:26.180 undesirable gases however excessive 00:19:30.10000:19:30.110 venting can cause its own problems for 00:19:32.62000:19:32.630 example each venting may allow a small 00:19:34.90000:19:34.910 amount of the process fluid to be lost 00:19:36.82000:19:36.830 from the process this reduces the 00:19:38.92000:19:38.930 efficiency of the process
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Engineering company LOTUS®
Russia, Ekaterinburg, Lunacharskogo street, 240/12