Heat Exchangers Operations of shell and Tube types

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Kind: captions
Language: en

00:00:11.550
many industrial processes must heat or
00:00:14.640 00:00:14.650 cool fluids to produce products heating
00:00:17.460 00:00:17.470 and cooling are often accomplished by
00:00:19.170 00:00:19.180 transferring heat between fluids heat
00:00:22.230 00:00:22.240 transfer between fluids occurs in heat
00:00:24.600 00:00:24.610 exchangers there are many types of heat
00:00:26.939 00:00:26.949 exchangers but one of the most common
00:00:29.160 00:00:29.170 types is a shell and tube heat exchanger
00:00:31.470 00:00:31.480 shell and tube heat exchangers can be
00:00:34.049 00:00:34.059 used for a variety of processes and
00:00:36.060 00:00:36.070 operating procedures may vary with each
00:00:38.340 00:00:38.350 heat exchanger what you'll see here is
00:00:40.920 00:00:40.930 intended to be a guide to the steps that
00:00:43.020 00:00:43.030 often have to be taken in the startup of
00:00:45.479 00:00:45.489 a shell and tube heat exchanger after it
00:00:47.789 00:00:47.799 has been shut down for maintenance but
00:00:50.070 00:00:50.080 remember always follow your facility's
00:00:52.530 00:00:52.540 operating procedures when you're
00:00:54.119 00:00:54.129 starting up any heat exchanger the unit
00:00:57.299 00:00:57.309 we'll be using is part of a mixing
00:00:59.189 00:00:59.199 process and is used to cool the process
00:01:01.619 00:01:01.629 liquid the heat exchanger has cooling
00:01:04.859 00:01:04.869 water inlet and outlet lines process
00:01:10.140 00:01:10.150 liquid Inlet and outlet lines a series
00:01:15.480 00:01:15.490 of isolation valves a vent valve and
00:01:20.310 00:01:20.320 drain valves before starting up the heat
00:01:25.319 00:01:25.329 exchanger the operator inspects the unit
00:01:27.899 00:01:27.909 to see if it's ready he checks the
00:01:29.789 00:01:29.799 valves to make sure that all of the
00:01:31.560 00:01:31.570 isolation vent and drain valves are shut
00:01:34.760 00:01:34.770 after he completes the initial
00:01:37.289 00:01:37.299 inspection he establishes the cooling
00:01:39.599 00:01:39.609 water supply to the unit he does this by
00:01:42.569 00:01:42.579 calling the control room operator and
00:01:44.550 00:01:44.560 having him open the shell side vent then
00:01:48.330 00:01:48.340 he partially opens the shell side water
00:01:50.730 00:01:50.740 inlet valve to slowly fill the shell
00:01:53.069 00:01:53.079 side then he calls the control room to
00:01:56.249 00:01:56.259 have someone there start the cooling
00:01:57.899 00:01:57.909 water pump when the cooling water pump
00:02:00.330 00:02:00.340 is started cooling water will fill the
00:02:02.609 00:02:02.619 shell side of the heat exchanger any air
00:02:05.219 00:02:05.229 that is trapped on the shell side
00:02:06.719 00:02:06.729 escapes through the open vent valve as
00:02:08.940 00:02:08.950 the shell side of the heat exchanger
00:02:11.309 00:02:11.319 fills the operator listens for air
00:02:13.620 00:02:13.630 escaping when the shell side is
00:02:15.510 00:02:15.520 completely filled he calls the control
00:02:17.820 00:02:17.830 room and has them shut the vent valve
00:02:20.149 00:02:20.159 then the operator opens the shell side
00:02:22.979 00:02:22.989 in
00:02:23.460 00:02:23.470 valve the rest of the way at that point
00:02:25.740 00:02:25.750 he informs the control room that the
00:02:28.260 00:02:28.270 shell side is lined up and that they can
00:02:30.330 00:02:30.340 establish the proper flow rate through
00:02:32.220 00:02:32.230 the shell on the heat exchanger shown in
00:02:35.280 00:02:35.290 this example there is no isolation valve
00:02:38.010 00:02:38.020 on the outlet of the shell side some
00:02:40.590 00:02:40.600 shell and tube heat exchangers have an
00:02:42.540 00:02:42.550 isolation valve on this outlet with
00:02:45.390 00:02:45.400 those heat exchangers the isolation
00:02:47.670 00:02:47.680 valve must be open to complete the flow
00:02:50.010 00:02:50.020 path through the unit the next step is
00:02:52.530 00:02:52.540 to line up the tube side of the heat
00:02:54.360 00:02:54.370 exchanger first the operator opens the
00:02:57.420 00:02:57.430 tube side vent valve then he partially
00:03:00.510 00:03:00.520 opens the tube side inlet valve to allow
00:03:03.270 00:03:03.280 the tube side to fill with process
00:03:05.160 00:03:05.170 liquid and to remove any air or other
00:03:07.380 00:03:07.390 gases that might be trapped on the tube
00:03:09.480 00:03:09.490 side of the unit when the tube side is
00:03:11.850 00:03:11.860 filled the operator closes the vent
00:03:14.250 00:03:14.260 valve and opens the inlet valve the rest
00:03:17.790 00:03:17.800 of the way then he opens the outlet
00:03:21.090 00:03:21.100 valve at this point the startup is
00:03:24.390 00:03:24.400 complete and the heat exchanger is in
00:03:26.490 00:03:26.500 operation after the operator reports to
00:03:29.400 00:03:29.410 the control room that the unit is in
00:03:31.020 00:03:31.030 operation the control room establishes
00:03:33.600 00:03:33.610 flow through the unit shell and tube
00:03:35.699 00:03:35.709 heat exchangers are commonly used in a
00:03:37.830 00:03:37.840 variety of processes and each may have a
00:03:40.290 00:03:40.300 different operating procedure but
00:03:42.479 00:03:42.489 00:03:44.790 00:03:44.800 operating procedures when shutting down
00:03:46.800 00:03:46.810 any heat exchanger during shutdown the
00:03:50.160 00:03:50.170 side of the heat exchanger with the
00:03:51.870 00:03:51.880 hotter fluid is usually shut down first
00:03:54.060 00:03:54.070 this helps to prevent the heat exchanger
00:03:56.729 00:03:56.739 from being overheated and damaged let's
00:03:59.729 00:03:59.739 watch an operator as he takes a heat
00:04:01.770 00:04:01.780 exchanger out of service in this example
00:04:04.259 00:04:04.269 the heat exchanger which cools a product
00:04:06.780 00:04:06.790 from a reactor is being shut down for
00:04:09.090 00:04:09.100 maintenance the tube side fluid is the
00:04:11.430 00:04:11.440 hotter fluid to shut down the heat
00:04:14.430 00:04:14.440 exchanger the operator closes the tube
00:04:16.890 00:04:16.900 side inlet valve first and then the tube
00:04:19.920 00:04:19.930 side outlet valve when the tube side has
00:04:23.610 00:04:23.620 cooled the operator opens the tube side
00:04:26.250 00:04:26.260 drain and vent valves this allows air to
00:04:30.030 00:04:30.040 enter the tube side and drains the
00:04:31.980 00:04:31.990 process fluid the operator then shuts
00:04:35.370 00:04:35.380 the shell side inlet valve
00:04:37.380 00:04:37.390 on the heat exchanger shown in this
00:04:39.210 00:04:39.220 example the shell side has no isolation
00:04:42.030 00:04:42.040 valve on its outlet some shell and tube
00:04:45.030 00:04:45.040 heat exchangers have an isolation valve
00:04:47.040 00:04:47.050 on this outlet with those heat
00:04:49.110 00:04:49.120 exchangers the isolation valve must be
00:04:51.600 00:04:51.610 shut to completely isolate the heat
00:04:53.670 00:04:53.680 exchanger after the isolation valve is
00:04:56.850 00:04:56.860 shut the operator opens the cooling
00:04:59.430 00:04:59.440 water drain in vent valves once all of
00:05:02.520 00:05:02.530 the fluid is drained from the heat
00:05:03.990 00:05:04.000 exchanger the operator closes the vent
00:05:06.660 00:05:06.670 and drain valves to complete the
00:05:08.550 00:05:08.560 shutdown now if the heat exchanger
00:05:10.830 00:05:10.840 that's being shut down handles flammable
00:05:13.560 00:05:13.570 liquids it may have to be purged to
00:05:15.780 00:05:15.790 reduce the possibility of a fire or an
00:05:18.180 00:05:18.190 explosion caused by flammable vapors
00:05:20.450 00:05:20.460 purging means forcing the process fluids
00:05:23.400 00:05:23.410 out of the heat exchanger by a substance
00:05:25.890 00:05:25.900 that won't react with the process fluid
00:05:28.080 00:05:28.090 very often steam or nitrogen is used
00:05:30.690 00:05:30.700 when a heat exchanger is in operation
00:05:33.050 00:05:33.060 operators must routinely check the unit
00:05:35.820 00:05:35.830 to ensure that its operating properly
00:05:37.890 00:05:37.900 this may include checking temperature
00:05:40.200 00:05:40.210 and pressure instruments to make sure
00:05:41.880 00:05:41.890 that their readings are within normal
00:05:43.560 00:05:43.570 operating ranges as well as checking the
00:05:45.900 00:05:45.910 condition of the heat exchanger itself
00:05:48.710 00:05:48.720 by checking a heat exchangers
00:05:51.060 00:05:51.070 temperature instruments an operator can
00:05:53.310 00:05:53.320 tell how the temperatures of the fluids
00:05:55.140 00:05:55.150 change as they pass through the unit
00:05:56.910 00:05:56.920 these values can also be used to
00:05:59.220 00:05:59.230 determine the difference in temperature
00:06:01.020 00:06:01.030 or delta T for each fluid the delta T
00:06:04.710 00:06:04.720 can be used to see if the unit is
00:06:06.330 00:06:06.340 operating properly for example if the
00:06:09.720 00:06:09.730 delta T across the tube side of a heat
00:06:11.910 00:06:11.920 exchanger is supposed to be 10 degrees
00:06:13.980 00:06:13.990 but it is only 5 degrees it could be an
00:06:17.040 00:06:17.050 indication that the tubes in the unit
00:06:18.870 00:06:18.880 are becoming fouled or that one or both
00:06:21.180 00:06:21.190 of the flow rates are not correct for
00:06:23.310 00:06:23.320 proper operation in any event the cause
00:06:26.460 00:06:26.470 of the problem should be investigated
00:06:28.380 00:06:28.390 and supervisory personnel should be
00:06:30.450 00:06:30.460 informed another way that temperatures
00:06:32.970 00:06:32.980 can be checked is on a temperature
00:06:34.830 00:06:34.840 recorder the recorder plots temperature
00:06:37.560 00:06:37.570 values on a chart which allows an
00:06:39.660 00:06:39.670 operator to see if a trend is developing
00:06:42.140 00:06:42.150 additional information about a heat
00:06:44.250 00:06:44.260 exchanger can be obtained by checking
00:06:46.470 00:06:46.480 the units pressure instruments by
00:06:48.900 00:06:48.910 reading the pressure instruments and
00:06:50.810 00:06:50.820 operator can often detect problems with
00:06:53.120 00:06:53.130 flow through the unit anytime there's
00:06:55.790 00:06:55.800 flow through a heat exchanger there will
00:06:57.950 00:06:57.960 be a specific drop in pressure across
00:07:00.020 00:07:00.030 the unit this pressure drop is often
00:07:02.750 00:07:02.760 referred to as differential pressure or
00:07:05.210 00:07:05.220 Delta P any change in differential
00:07:08.120 00:07:08.130 pressure could be an indication of a
00:07:09.920 00:07:09.930 problem as the tubes become blocked or
00:07:12.500 00:07:12.510 fouled the differential pressure will
00:07:14.570 00:07:14.580 increase above the normal value once
00:07:17.030 00:07:17.040 again the cause of the problem should be
00:07:19.100 00:07:19.110 investigated and supervisory personnel
00:07:21.230 00:07:21.240 should be informed on many units
00:07:24.170 00:07:24.180 temperature and flow are controlled by
00:07:26.120 00:07:26.130 automatic systems these systems may
00:07:28.730 00:07:28.740 provide indications locally and in a
00:07:31.190 00:07:31.200 control room the indications in the
00:07:33.410 00:07:33.420 control room can be compared to the
00:07:35.510 00:07:35.520 indications on instruments located at
00:07:37.730 00:07:37.740 the heat exchanger to verify that the
00:07:39.980 00:07:39.990 heat exchanger is operating properly if
00:07:42.710 00:07:42.720 a problem is detected it could be the
00:07:44.990 00:07:45.000 result of the control valves not
00:07:46.790 00:07:46.800 operating properly or valves being out
00:07:49.850 00:07:49.860 of position or it could be an indication
00:07:52.910 00:07:52.920 that other equipment associated with the
00:07:54.980 00:07:54.990 heat exchanger is not operating properly
00:07:57.370 00:07:57.380 for example a low Inlet pressure could
00:08:00.770 00:08:00.780 indicate a problem with a pump that
00:08:02.630 00:08:02.640 supplies the heat exchanger besides
00:08:05.510 00:08:05.520 checking instrument readings an operator
00:08:07.940 00:08:07.950 should also check for leaks and for
00:08:10.910 00:08:10.920 damaged or missing insulation problems
00:08:14.300 00:08:14.310 such as these could affect the operation
00:08:16.400 00:08:16.410 of the heat exchanger and pose hazards
00:08:18.470 00:08:18.480 to personnel working in the area in this
00:08:21.140 00:08:21.150 topic we looked at some basic procedures
00:08:23.480 00:08:23.490 for the startup and shutdown of a
00:08:25.280 00:08:25.290 typical shell and tube heat exchanger we
00:08:27.770 00:08:27.780 also looked at some operator
00:08:29.300 00:08:29.310 responsibilities associated with
00:08:31.250 00:08:31.260 operating a shell and tube heat
00:08:32.570 00:08:32.580 exchanger now let's try a few practice
00:08:35.240 00:08:35.250 questions when the cooling water pump is
00:08:37.490 00:08:37.500 started cooling water will fill the
00:08:39.620 00:08:39.630 00:08:42.200 00:08:42.210 00:08:43.730 00:08:43.740 00:08:45.950 00:08:45.960 00:08:48.320 00:08:48.330 00:08:50.600 00:08:50.610 00:08:52.520 00:08:52.530 00:08:54.830 00:08:54.840 00:08:57.130 00:08:57.140 00:08:59.960 00:08:59.970 inlet valve the rest of the way at that
00:09:02.480 00:09:02.490 point he informs the control
00:09:04.489 00:09:04.499 that the shell side is lined up and that
00:09:07.069 00:09:07.079 they can establish the proper flow rate
00:09:09.019 00:09:09.029 through the shell to shut down the heat
00:09:11.569 00:09:11.579 00:09:14.029 00:09:14.039 00:09:17.059 00:09:17.069 00:09:20.719 00:09:20.729 00:09:23.359 00:09:23.369 00:09:27.169 00:09:27.179 00:09:29.209 00:09:29.219 process fluid as the tubes become
00:09:31.579 00:09:31.589 blocked or fouled the differential
00:09:33.619 00:09:33.629 pressure will increase above the normal
00:09:35.629 00:09:35.639 value once again the cause of the
00:09:37.999 00:09:38.009 problem should be investigated and
00:09:39.649 00:09:39.659 supervisory personnel should be informed
00:09:42.039 00:09:42.049 fouling is a term that's often used to
00:09:44.509 00:09:44.519 describe the build-up of deposits on the
00:09:46.669 00:09:46.679 internal surfaces of the heat exchanger
00:09:48.979 00:09:48.989 when fouling occurs the result is an
00:09:52.039 00:09:52.049 additional layer of material that heat
00:09:54.049 00:09:54.059 must pass through this additional layer
00:09:56.479 00:09:56.489 reduces the ability of the unit to
00:09:58.639 00:09:58.649 transfer heat also if the buildup
00:10:01.399 00:10:01.409 becomes excessive the flow of fluids
00:10:03.679 00:10:03.689 through the unit may be restricted
00:10:05.439 00:10:05.449 fouling can be caused by many things one
00:10:08.539 00:10:08.549 common cause is impurities in the fluids
00:10:11.269 00:10:11.279 passing through the heat exchanger for
00:10:13.549 00:10:13.559 example in a process that uses water
00:10:16.179 00:10:16.189 impurities such as calcium can come out
00:10:18.949 00:10:18.959 of the water and form an additional
00:10:20.960 00:10:20.970 layer of material another source of
00:10:23.509 00:10:23.519 fouling is small plants and animals that
00:10:25.669 00:10:25.679 enter the heat exchanger many forms of
00:10:28.339 00:10:28.349 algae and bacteria can live and grow
00:10:30.710 00:10:30.720 inside the unit and form a layer of
00:10:33.019 00:10:33.029 slime on the internal surfaces of the
00:10:35.089 00:10:35.099 heat exchanger gases dissolved in the
00:10:38.059 00:10:38.069 fluids that flow through a heat
00:10:39.379 00:10:39.389 exchanger can also cause fouling for
00:10:42.109 00:10:42.119 example some gases react with the metal
00:10:44.689 00:10:44.699 inside a unit to cause a type of
00:10:46.429 00:10:46.439 corrosion the corrosion forms a layer
00:10:49.099 00:10:49.109 that acts as an insulator just like
00:10:51.319 00:10:51.329 impurities or algae different techniques
00:10:54.679 00:10:54.689 can be used to minimize fouling for
00:10:56.899 00:10:56.909 example filters and screens can be used
00:10:59.329 00:10:59.339 to remove particles from the fluids
00:11:01.279 00:11:01.289 before they enter the heat exchanger
00:11:03.019 00:11:03.029 fouling can sometimes be minimized by
00:11:05.689 00:11:05.699 adding chemicals to the fluids passing
00:11:07.879 00:11:07.889 through a heat exchanger for example
00:11:09.949 00:11:09.959 chemicals such as chlorine are often
00:11:12.439 00:11:12.449 added to cooling water to reduce the
00:11:14.659 00:11:14.669 amount of algae or other organisms
00:11:16.639 00:11:16.649 inside a unit
00:11:17.870 00:11:17.880 in some situations fouling can become
00:11:20.689 00:11:20.699 bad enough to restrict the fluid flow
00:11:22.639 00:11:22.649 this problem may show up on the heat
00:11:24.920 00:11:24.930 exchangers instruments as an increase in
00:11:27.439 00:11:27.449 the pressure drop or as a gradual
00:11:29.600 00:11:29.610 decrease in the flow through the
00:11:31.160 00:11:31.170 affected side of the unit
00:11:32.600 00:11:32.610 fouling may also affect the temperature
00:11:35.180 00:11:35.190 of both fluids passing through the heat
00:11:36.980 00:11:36.990 exchanger when fluid flow is restricted
00:11:39.740 00:11:39.750 the heat exchanger must be cleaned one
00:11:42.710 00:11:42.720 way that heat exchangers can be cleaned
00:11:44.480 00:11:44.490 is by using chemicals when this is done
00:11:46.939 00:11:46.949 a chemical solution is passed through
00:11:48.949 00:11:48.959 the heat exchanger to dissolve the
00:11:50.990 00:11:51.000 fouling on the walls of the tubes
00:11:53.079 00:11:53.089 fouling on tube walls can also be
00:11:55.790 00:11:55.800 removed by scraping or by spraying with
00:11:58.400 00:11:58.410 high-pressure water or steam however
00:12:00.949 00:12:00.959 these methods require the heat exchanger
00:12:03.379 00:12:03.389 to be shut down and taken apart in some
00:12:06.410 00:12:06.420 heat exchangers cleaning can be
00:12:08.180 00:12:08.190 accomplished using a technique called
00:12:09.800 00:12:09.810 back washing back washing is the
00:12:12.710 00:12:12.720 reversing of flow through the heat
00:12:14.509 00:12:14.519 exchanger this technique is effective in
00:12:17.090 00:12:17.100 temporarily dislodging materials from
00:12:19.280 00:12:19.290 the ends of the tubes and the tube
00:12:21.170 00:12:21.180 sheets tube leakage is a problem that
00:12:24.379 00:12:24.389 can seriously affect the operation of a
00:12:26.540 00:12:26.550 heat exchanger it's usually caused by
00:12:29.090 00:12:29.100 the failure of a tube as a result of
00:12:31.460 00:12:31.470 overheating erosion or corrosion
00:12:34.569 00:12:34.579 corrosion is the wearing away of tube
00:12:37.460 00:12:37.470 metal caused by the flow of fluids or by
00:12:40.160 00:12:40.170 solid impurities in the fluids some
00:12:42.920 00:12:42.930 fluids that pass through a heat
00:12:44.240 00:12:44.250 exchanger may contain abrasive particles
00:12:46.490 00:12:46.500 as these fluids flow through the heat
00:12:48.559 00:12:48.569 exchanger the particles come into
00:12:50.480 00:12:50.490 contact with the tube metal and erode
00:12:52.610 00:12:52.620 the tubes eventually the tube wears away
00:12:55.309 00:12:55.319 in a spot and a leak forms corrosion
00:12:58.490 00:12:58.500 chemically deteriorates to metal to
00:13:00.769 00:13:00.779 create a leak corrosion is caused by a
00:13:03.439 00:13:03.449 chemical reaction between the metal in
00:13:05.509 00:13:05.519 the heat exchanger and either the fluid
00:13:07.699 00:13:07.709 passing through the unit or impurities
00:13:09.949 00:13:09.959 in the fluid the corrosion weakens the
00:13:12.350 00:13:12.360 metal until a leak forms the biggest
00:13:15.199 00:13:15.209 problem that can result from leaks in a
00:13:17.240 00:13:17.250 heat exchanger is the mixing of one
00:13:19.429 00:13:19.439 fluid with the other fluid for instance
00:13:22.100 00:13:22.110 if cooling water mixes with oil and a
00:13:24.710 00:13:24.720 lube oil cooler the water could damage
00:13:27.019 00:13:27.029 the equipment that the oil lubricates to
00:13:29.870 00:13:29.880 prevent this type of damage from
00:13:31.400 00:13:31.410 occurring leeks must be detected one way
00:13:34.249 00:13:34.259 to check for tube leaks is to take and
00:13:36.439 00:13:36.449 analyze a sample of the lower pressure
00:13:38.449 00:13:38.459 fluid when a leak occurs the
00:13:40.790 00:13:40.800 high-pressure fluid leaks into the
00:13:42.619 00:13:42.629 low-pressure fluid in some cases you may
00:13:45.860 00:13:45.870 be able to tell there's a leak by just
00:13:47.600 00:13:47.610 looking at the sample in other cases a
00:13:49.850 00:13:49.860 lab test may be required to prevent
00:13:52.910 00:13:52.920 leaks in some applications the process
00:13:55.100 00:13:55.110 fluids pass through filters or strainers
00:13:57.860 00:13:57.870 to remove impurities that can erode the
00:14:00.139 00:14:00.149 tube metal also chemicals may be added
00:14:02.809 00:14:02.819 to the fluids to control corrosion
00:14:04.720 00:14:04.730 another method of controlling corrosion
00:14:07.400 00:14:07.410 involves using a device called a
00:14:09.439 00:14:09.449 sacrificial anode when a sacrificial
00:14:12.110 00:14:12.120 anode is used impurities in water tend
00:14:15.019 00:14:15.029 to react more readily with the anode
00:14:17.119 00:14:17.129 than with the metal of the heat
00:14:18.650 00:14:18.660 exchanger so the sacrificial anode
00:14:21.050 00:14:21.060 corrodes while the heat exchanger is
00:14:23.389 00:14:23.399 less affected heat exchangers that are
00:14:25.790 00:14:25.800 used with water often have sacrificial
00:14:28.100 00:14:28.110 anodes made up of zinc plates mounted
00:14:30.290 00:14:30.300 inside when a leak does occur some type
00:14:33.559 00:14:33.569 of corrective action must be taken if
00:14:35.840 00:14:35.850 only a few tubes in a heat exchanger
00:14:37.429 00:14:37.439 have leaks it may be possible to plug
00:14:40.370 00:14:40.380 the affected tubes this prevents the
00:14:42.740 00:14:42.750 tube side fluid from passing through
00:14:44.569 00:14:44.579 those tubes and effectively eliminates
00:14:47.240 00:14:47.250 the leak
00:14:47.870 00:14:47.880 however plugging tubes reduces the heat
00:14:50.660 00:14:50.670 exchangers heat transfer capacity if a
00:14:53.900 00:14:53.910 lot of tubes are leaking the unit will
00:14:55.999 00:14:56.009 have to be shut down and the affected
00:14:58.189 00:14:58.199 tubes will have to be replaced when air
00:15:01.540 00:15:01.550 non-condensable gases or other vapors
00:15:04.069 00:15:04.079 are trapped inside a heat exchanger they
00:15:06.259 00:15:06.269 can prevent the unit from operating
00:15:08.269 00:15:08.279 efficiently this is because the air or
00:15:10.759 00:15:10.769 gas can either blanket the tubes or
00:15:13.309 00:15:13.319 block the tubes off and prevent fluid
00:15:15.679 00:15:15.689 from flowing through them the effect is
00:15:18.110 00:15:18.120 the same as the effect created by
00:15:19.610 00:15:19.620 fouling less heat can be transferred
00:15:21.920 00:15:21.930 across the tubes gas trapped on the tube
00:15:25.129 00:15:25.139 side of the heat exchanger can block off
00:15:27.350 00:15:27.360 tubes and prevent fluid from passing
00:15:29.420 00:15:29.430 through them gas trapped on the shell
00:15:31.819 00:15:31.829 side can displace the shell side fluid
00:15:33.889 00:15:33.899 at the top of the heat exchanger this
00:15:36.259 00:15:36.269 can reduce the amount of tube surface
00:15:38.179 00:15:38.189 area that is exposed to the shell side
00:15:40.220 00:15:40.230 fluid and thus reduce the amount of heat
00:15:42.620 00:15:42.630 that can be transferred there are men
00:15:44.900 00:15:44.910 ways that air or other gases can get
00:15:47.060 00:15:47.070 trapped inside a heat exchanger for
00:15:48.800 00:15:48.810 example this can happen during the
00:15:50.960 00:15:50.970 startup of the unit during startup the
00:15:53.930 00:15:53.940 heat exchanger should be vented to
00:15:55.700 00:15:55.710 remove unwanted gases if the vetting is
00:15:58.400 00:15:58.410 not complete gases will remain inside
00:16:01.100 00:16:01.110 the unit another source of gases as the
00:16:04.010 00:16:04.020 process itself in some situations the
00:16:06.650 00:16:06.660 process can produce vapor bubbles as the
00:16:09.680 00:16:09.690 process fluid passes through the heat
00:16:11.510 00:16:11.520 exchanger the vapor collects inside the
00:16:14.180 00:16:14.190 unit when maintenance is performed on
00:16:16.580 00:16:16.590 process equipment air may be trapped in
00:16:19.040 00:16:19.050 the piping or shell as the equipment is
00:16:21.080 00:16:21.090 put back together when the equipment is
00:16:23.240 00:16:23.250 restarted the air can make its way to
00:16:25.460 00:16:25.470 the heat exchanger and become trapped
00:16:27.260 00:16:27.270 inside no matter how error other gases
00:16:30.500 00:16:30.510 get trapped inside a heat exchanger they
00:16:32.780 00:16:32.790 can cause it to become air bound or
00:16:34.730 00:16:34.740 vapor bound there are several symptoms
00:16:37.040 00:16:37.050 to indicate this for example when
00:16:39.530 00:16:39.540 trapped gas blocks flow to some of the
00:16:41.600 00:16:41.610 tubes the outlet temperatures of the two
00:16:44.090 00:16:44.100 fluids may change this is because the
00:16:46.610 00:16:46.620 gas is restricting flow into the tubes
00:16:48.680 00:16:48.690 and the restricted flow causes less heat
00:16:51.680 00:16:51.690 transfer surface area to be available
00:16:53.860 00:16:53.870 the decrease in heat transfer surface
00:16:56.690 00:16:56.700 area will cause the outlet temperature
00:16:58.910 00:16:58.920 of the process fluid to increase since
00:17:01.340 00:17:01.350 less heat will be removed from the fluid
00:17:03.610 00:17:03.620 there are also situations where the
00:17:06.050 00:17:06.060 pressure inside a heat exchanger may be
00:17:08.030 00:17:08.040 affected for example this can occur in
00:17:10.700 00:17:10.710 heat exchangers that are used to
00:17:12.290 00:17:12.300 condense processed vapors in this
00:17:14.780 00:17:14.790 situation non condensable gases
00:17:17.150 00:17:17.160 partially fill the unit reducing the
00:17:19.730 00:17:19.740 amount of heat transfer area that the
00:17:21.860 00:17:21.870 process vapor can come in contact with
00:17:23.780 00:17:23.790 in turn this reduces the amount of vapor
00:17:26.960 00:17:26.970 that can be condensed the flow of vapor
00:17:29.510 00:17:29.520 will start to decrease and the pressure
00:17:31.760 00:17:31.770 inside the unit will start to increase
00:17:34.570 00:17:34.580 regardless of how gases get into the
00:17:36.980 00:17:36.990 heat exchanger the unit must be vented
00:17:39.320 00:17:39.330 to allow them to escape repeated venting
00:17:42.170 00:17:42.180 may be necessary to ensure that the heat
00:17:44.390 00:17:44.400 exchanger remains free of air and other
00:17:46.790 00:17:46.800 undesirable gases however excessive
00:17:50.720 00:17:50.730 venting can cause its own problems for
00:17:53.210 00:17:53.220 example each venting may allow a small
00:17:55.520 00:17:55.530 amount of the process fluid to be lost
00:17:57.440 00:17:57.450 from the process
00:17:58.640 00:17:58.650 this reduces the efficiency of the
00:18:00.440 00:18:00.450 process venting may be only a temporary
00:18:02.780 00:18:02.790 fix if the source of the gas is the
00:18:05.720 00:18:05.730 process there may be a problem with the
00:18:08.030 00:18:08.040 process or with one of the components in
00:18:10.310 00:18:10.320 the process in this topic we looked at
00:18:12.770 00:18:12.780 some of the basic problems that can
00:18:14.450 00:18:14.460 affect a typical heat exchanger
00:18:16.000 00:18:16.010 including fouling tube leaks and air and
00:18:19.280 00:18:19.290 vapor binding we also looked at the
00:18:21.500 00:18:21.510 causes and effects of these problems and
00:18:23.450 00:18:23.460 we saw how they can be dealt with
00:18:25.370 00:18:25.380 let's take a moment now and try some
00:18:27.440 00:18:27.450 practice questions
00:18:28.520 00:18:28.530 00:18:30.830 00:18:30.840 00:18:33.230 00:18:33.240 00:18:35.330 00:18:35.340 00:18:37.790 00:18:37.800 00:18:40.010 00:18:40.020 00:18:41.990 00:18:42.000 inside a unit corrosion chemically
00:18:44.510 00:18:44.520 deteriorates tube metal to create a leak
00:18:47.050 00:18:47.060 corrosion is caused by a chemical
00:18:49.220 00:18:49.230 reaction between the metal in the heat
00:18:51.140 00:18:51.150 exchanger and either the fluid passing
00:18:53.510 00:18:53.520 through the unit or impurities in the
00:18:55.520 00:18:55.530 fluid the corrosion weakens the metal
00:18:57.950 00:18:57.960 until a leak forms regardless of how
00:19:00.590 00:19:00.600 gases get into the heat exchanger the
00:19:02.810 00:19:02.820 unit must be vented to allow them to
00:19:04.730 00:19:04.740 escape repeated venting may be necessary
00:19:07.310 00:19:07.320 to ensure that the heat exchanger
00:19:09.620 00:19:09.630 remains free of air and other
00:19:11.480 00:19:11.490 00:19:15.410 00:19:15.420 00:19:17.900 00:19:17.910 00:19:20.210 00:19:20.220 00:19:22.100 00:19:22.110 from the process this reduces the
00:19:24.230 00:19:24.240 efficiency of the process
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Engineering company LOTUS®
Russia, Ekaterinburg, Lunacharskogo street, 240/12

Phone: +7 343 216 77 75

E-mail: info@lotus1.ru

Sales phone

Russia: +7 343 216 77 75

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