00:00:01.290 --> 00:00:02.550 - [Instructor] In this lesson, we'll talk 00:00:02.550 --> 00:00:04.550 about assembling and disassembling 00:00:04.550 --> 00:00:07.870 a plate heat exchanger and we'll also talk 00:00:07.870 --> 00:00:09.920 about some of the common maintenance tasks 00:00:09.920 --> 00:00:11.540 that you're likely to do when you 00:00:11.540 --> 00:00:13.900 disassemble the heat exchanger. 00:00:13.900 --> 00:00:16.120 When you think about it, the reason you disassemble 00:00:16.120 --> 00:00:17.540 the heat exchanger in the first place 00:00:17.540 --> 00:00:21.210 is usually because maintenance is required. 00:00:21.210 --> 00:00:22.800 You can see on this 3D model 00:00:22.800 --> 00:00:25.480 that it's been exploded into its parts. 00:00:25.480 --> 00:00:27.750 You can see each of the individual plates. 00:00:27.750 --> 00:00:29.590 Then we've got a plate stack 00:00:29.590 --> 00:00:32.880 and the frames, et cetera. 00:00:32.880 --> 00:00:35.480 If we play the animation, you can see 00:00:35.480 --> 00:00:37.940 it all being assembled. 00:00:37.940 --> 00:00:40.910 See the upper and lower guide bar going down. 00:00:40.910 --> 00:00:43.170 You'll see the plates sliding along. 00:00:43.170 --> 00:00:46.140 Plate stack comes along and the moveable frame 00:00:46.140 --> 00:00:49.460 comes on top of that to press it all together. 00:00:49.460 --> 00:00:51.750 Then the bars go on the side. 00:00:51.750 --> 00:00:55.093 And we're gonna use the nuts to tighten up the tie bars. 00:00:55.970 --> 00:00:59.053 So that is how a plate heat exchanger is assembled. 00:01:00.010 --> 00:01:02.840 Let's imagine for a moment we wanna take it apart. 00:01:02.840 --> 00:01:05.040 Before we even think about taking it apart, 00:01:05.040 --> 00:01:07.930 we need to ensure that when we put it back together, 00:01:07.930 --> 00:01:11.060 it's gonna be the same as it was before. 00:01:11.060 --> 00:01:13.540 There are two rules that every young engineer 00:01:13.540 --> 00:01:15.540 needs to know about. 00:01:15.540 --> 00:01:17.850 One of them concerns maintenance, 00:01:17.850 --> 00:01:21.140 in which case you leave it like you found it. 00:01:21.140 --> 00:01:23.480 And the other one concerns when you 00:01:23.480 --> 00:01:26.370 try to perform maintenance and you break something. 00:01:26.370 --> 00:01:28.350 And in that situation, you say 00:01:28.350 --> 00:01:30.273 it was like that when I found it. 00:01:31.220 --> 00:01:32.440 Okay, slight joke there. 00:01:32.440 --> 00:01:35.160 We should actually be putting the machine back 00:01:35.160 --> 00:01:37.320 or the component back as we found it. 00:01:37.320 --> 00:01:41.430 That is the correct way to perform maintenance. 00:01:41.430 --> 00:01:42.830 So what are we gonna look at 00:01:42.830 --> 00:01:45.030 when we look at our plate heat exchanger 00:01:45.030 --> 00:01:48.810 to ensure that we put it back the way we found it? 00:01:48.810 --> 00:01:52.550 Well the first thing we can look at is the plate stack. 00:01:52.550 --> 00:01:54.690 The plate stack, if we measure it 00:01:54.690 --> 00:01:57.510 from the moveable frame to the fixed frame, 00:01:57.510 --> 00:02:00.670 is going to be a certain length. 00:02:00.670 --> 00:02:02.140 Now if we measure that length 00:02:02.140 --> 00:02:05.150 and we also compare it to the value in the manual, 00:02:05.150 --> 00:02:08.540 we can ensure that when we reassemble the plate stack, 00:02:08.540 --> 00:02:11.430 the length remains the same. 00:02:11.430 --> 00:02:13.670 This ensures that we haven't overtightened 00:02:13.670 --> 00:02:17.280 the plate the stack or undertightened the plate stack. 00:02:17.280 --> 00:02:20.770 The plate stack itself will have a honeycomb structure 00:02:20.770 --> 00:02:23.360 and if you look at that, it's not very apparent 00:02:23.360 --> 00:02:26.730 on the R1 here, but if you look at it normally, 00:02:26.730 --> 00:02:27.940 you'll be able to see a pattern 00:02:27.940 --> 00:02:30.950 that carries on all the way through the plate stack 00:02:30.950 --> 00:02:34.510 and this honeycomb pattern will help you identify 00:02:34.510 --> 00:02:37.270 if the plates are in order or not. 00:02:37.270 --> 00:02:41.243 You'll also sometimes have tags on the side of each plate. 00:02:42.240 --> 00:02:45.030 If I go back a little bit here, see one plate 00:02:45.030 --> 00:02:47.380 might have a blue tag, the next one red, 00:02:47.380 --> 00:02:51.410 blue, red, blue, red, and we can check these tags 00:02:51.410 --> 00:02:55.090 to ensure that the plates are in the correct order 00:02:55.090 --> 00:02:57.233 when we reassemble the plate stack. 00:02:58.300 --> 00:03:01.970 If we actually just open up the plate stack for a moment, 00:03:01.970 --> 00:03:05.260 go along here, you will sometimes see 00:03:05.260 --> 00:03:09.260 an indication 'round about here, 00:03:09.260 --> 00:03:12.403 and it will say A and the model number of the plate, 00:03:13.469 --> 00:03:16.690 and the next plate will say B 00:03:16.690 --> 00:03:18.680 and the model number of the plate again. 00:03:18.680 --> 00:03:22.790 So you can also check A, B, A, B when you're assembling, 00:03:22.790 --> 00:03:25.830 but you may also be able to check the tags on the side, 00:03:25.830 --> 00:03:28.400 and you will be able to check the honeycomb structure 00:03:28.400 --> 00:03:30.503 on the side of the plate stack as well. 00:03:31.480 --> 00:03:33.850 Apart from measuring the distance 00:03:33.850 --> 00:03:37.047 00:03:37.047 --> 00:03:41.110 you can also put a line across the plate stack. 00:03:41.110 --> 00:03:44.870 It should be ideally all the way down the plate stack, 00:03:44.870 --> 00:03:46.537 although usually it's just here. 00:03:46.537 --> 00:03:50.180 And you can do another one that stretches down here. 00:03:50.180 --> 00:03:52.900 And that will also ensure that you've put the plates 00:03:52.900 --> 00:03:56.130 back in the correct order. 00:03:56.130 --> 00:03:57.940 So these are all things that you should be thinking about 00:03:57.940 --> 00:04:01.283 before you even take the plate stack apart. 00:04:02.260 --> 00:04:05.600 The other things that you need to ensure are the basics. 00:04:05.600 --> 00:04:09.160 Is the system drained down correctly? 00:04:09.160 --> 00:04:11.570 Are both systems, let's imagine for a moment 00:04:11.570 --> 00:04:15.910 we've got a hot water circuit and an oil circuit, 00:04:15.910 --> 00:04:18.140 are the two systems isolated? 00:04:18.140 --> 00:04:20.210 Are the pressures relieved? 00:04:20.210 --> 00:04:21.870 If we've got a hot water circuit, 00:04:21.870 --> 00:04:24.750 what sort of temperature is the hot water at? 00:04:24.750 --> 00:04:28.130 Do we need to wait and allow the hot water to cool down 00:04:28.130 --> 00:04:29.934 before we can work on it? 00:04:29.934 --> 00:04:32.740 So we need to ensure that both systems are isolated, 00:04:32.740 --> 00:04:35.590 the pressures are relieved, the temperatures 00:04:35.590 --> 00:04:37.550 are acceptable for people who are working 00:04:37.550 --> 00:04:39.680 on the plate heat exchanger. 00:04:39.680 --> 00:04:42.090 The fluids, are they corrosive? 00:04:42.090 --> 00:04:45.870 If they are, do people need protective clothing? 00:04:45.870 --> 00:04:47.730 Do we need to vent the area 00:04:47.730 --> 00:04:50.020 when we open up the plate heat exchanger? 00:04:50.020 --> 00:04:52.080 Et cetera, so there's a lot of things to do 00:04:52.080 --> 00:04:56.620 before we even take the plate heat exchanger apart. 00:04:56.620 --> 00:05:00.530 In addition to all that, we can have a look at the tie bars. 00:05:00.530 --> 00:05:03.310 Specifically, you wanna look along this area here 00:05:03.310 --> 00:05:05.750 after each of the nuts. 00:05:05.750 --> 00:05:08.380 The reason you wanna look along the tie bar 00:05:08.380 --> 00:05:10.730 is because you're gonna have to undo the knot 00:05:10.730 --> 00:05:12.760 all the way to the end of the tie bar. 00:05:12.760 --> 00:05:15.970 And you're gonna have to do that on all of the tie bars. 00:05:15.970 --> 00:05:20.040 Sometimes if the plate heat exchanger is an area 00:05:20.040 --> 00:05:21.790 that's not very clean, then you'll wanna 00:05:21.790 --> 00:05:24.400 get a wire brush onto each of these tie bars 00:05:24.400 --> 00:05:26.140 and clean them off. 00:05:26.140 --> 00:05:26.973 After you've cleaned them off, 00:05:26.973 --> 00:05:30.010 you'll wanna grease them up as well. 00:05:30.010 --> 00:05:32.050 You need to make sure there's no obstruction 00:05:32.050 --> 00:05:33.770 on your guide bar here. 00:05:33.770 --> 00:05:36.230 Maybe you need to clean it up and apply a layer of grease 00:05:36.230 --> 00:05:40.830 onto the upper and the lower guide bar as well. 00:05:40.830 --> 00:05:42.770 So consider all of these factors 00:05:42.770 --> 00:05:45.500 when planning to perform maintenance 00:05:45.500 --> 00:05:47.383 00:05:48.700 --> 00:05:51.950 Even if you've done the job 10 times before, 00:05:51.950 --> 00:05:54.840 always print out the checklist or get the manual 00:05:54.840 --> 00:05:57.350 and just read through it before you open up 00:05:57.350 --> 00:06:00.400 the heat exchanger itself, because once you open it up, 00:06:00.400 --> 00:06:01.950 it's out of service until you can 00:06:01.950 --> 00:06:04.290 put it back together again. 00:06:04.290 --> 00:06:07.140 If you've only got one plate heat exchanger in the system, 00:06:07.140 --> 00:06:09.780 then it most likely needs to be returned to service 00:06:09.780 --> 00:06:12.160 as quickly as possible, which definitely adds 00:06:12.160 --> 00:06:14.720 to the stress level of all the people involved 00:06:14.720 --> 00:06:16.410 if you need to put it back together quickly, 00:06:16.410 --> 00:06:18.760 but it just doesn't seem to wanna fit together. 00:06:19.670 --> 00:06:22.730 But let's assume for a moment we've done all the preparation 00:06:22.730 --> 00:06:25.757 and we know that we can open the plate heat exchanger 00:06:25.757 --> 00:06:28.150 and the stack and put it back together again 00:06:28.150 --> 00:06:30.080 and it shouldn't be an issue. 00:06:30.080 --> 00:06:33.553 So we'll open up the heat exchanger. 00:06:34.734 --> 00:06:36.110 And now if I go over here, 00:06:36.110 --> 00:06:38.140 you can see each of the plates. 00:06:38.140 --> 00:06:40.950 Now that we've opened up each of the plates, 00:06:40.950 --> 00:06:44.430 what we actually wanna do is spread them out. 00:06:44.430 --> 00:06:45.920 Normally you'll do this one at a time 00:06:45.920 --> 00:06:47.770 as they come off the plate stack. 00:06:47.770 --> 00:06:49.840 In fact, if I spin around this side, 00:06:49.840 --> 00:06:50.990 be a little bit easier. 00:06:52.610 --> 00:06:54.200 But you wanna spread them out 00:06:54.200 --> 00:06:57.320 and you want to clean each of the plate surfaces. 00:06:57.320 --> 00:07:01.010 Usually you will do this with a brush 00:07:01.010 --> 00:07:03.700 and a cleaning agent, and then you'll rinse them 00:07:03.700 --> 00:07:07.310 with water as soon as the cleaning agent has been applied 00:07:07.310 --> 00:07:10.570 and maybe done its work for a minute or so. 00:07:10.570 --> 00:07:13.330 The reason that you don't leave the cleaning agent 00:07:13.330 --> 00:07:16.050 on the plates very long is because the cleaning agent 00:07:16.050 --> 00:07:19.560 can damage the gaskets and it can also 00:07:19.560 --> 00:07:23.810 sometimes cause the glue that holds the gaskets in place 00:07:23.810 --> 00:07:26.510 to become less adhesive and the gaskets 00:07:26.510 --> 00:07:28.063 will literally just peal off. 00:07:28.910 --> 00:07:30.780 So if you're using a cleaning agent, 00:07:30.780 --> 00:07:33.350 make sure you apply it and let it do its thing 00:07:33.350 --> 00:07:36.080 for a little bit and then wash it off. 00:07:36.080 --> 00:07:39.490 If you're using a brush, then use a soft brush. 00:07:39.490 --> 00:07:42.770 You use a soft brush, maybe you can even use a brass brush, 00:07:42.770 --> 00:07:45.080 but don't go in there with pneumatic tools 00:07:45.080 --> 00:07:47.990 and a wire brush and try to scratch 00:07:47.990 --> 00:07:51.010 all of the plate completely clean. 00:07:51.010 --> 00:07:52.980 Sometimes you'll have stainless steel plates, 00:07:52.980 --> 00:07:55.140 sometimes you'll have titanium plates, 00:07:55.140 --> 00:07:57.340 sometimes you may have different materials, 00:07:57.340 --> 00:08:01.430 but generally, you want to treat the plates with care, 00:08:01.430 --> 00:08:04.010 remember they're quite thin, and there's no need 00:08:04.010 --> 00:08:05.170 to be attacking these plates 00:08:05.170 --> 00:08:07.700 with a stainless steel wire brush. 00:08:07.700 --> 00:08:09.950 And especially not with pneumatic tools, 00:08:09.950 --> 00:08:13.470 which may actually considerably damage each of the plates. 00:08:13.470 --> 00:08:16.550 So just treat them with care and try to pay attention 00:08:16.550 --> 00:08:19.680 that you don't damage the overall surfaces 00:08:19.680 --> 00:08:21.600 of each of the plates. 00:08:21.600 --> 00:08:23.140 Once you've cleaned all the plates, 00:08:23.140 --> 00:08:25.653 then the plate stack can be reassembled, 00:08:26.580 --> 00:08:29.510 and you can then check the diagonal lines 00:08:29.510 --> 00:08:31.290 that you put on the plate stack. 00:08:31.290 --> 00:08:32.740 You can measure the distance 00:08:32.740 --> 00:08:35.350 from the moveable plate to the fixed plate. 00:08:35.350 --> 00:08:38.020 And then you can check that there's a honeycomb structure 00:08:38.020 --> 00:08:40.230 or that the pattern is consistent 00:08:40.230 --> 00:08:43.200 throughout the entire plate stack. 00:08:43.200 --> 00:08:46.290 A common failure mode for plate heat exchangers 00:08:46.290 --> 00:08:50.500 is simple that the tie bolts are overtightened. 00:08:50.500 --> 00:08:53.310 Typically you may find a torque rating 00:08:53.310 --> 00:08:55.410 that you can use in the manual. 00:08:55.410 --> 00:08:56.243 But even if you don't have that, 00:08:56.243 --> 00:08:59.400 then you should also be able to measure the distance 00:08:59.400 --> 00:09:01.090 between the moveable plate and fixed plate 00:09:01.090 --> 00:09:03.700 and this is a good way to double check 00:09:03.700 --> 00:09:06.750 that you've assembled the plate stack correctly. 00:09:06.750 --> 00:09:09.460 The problem with overtightening is first, 00:09:09.460 --> 00:09:14.290 that people reassemble the heat exchanger incorrectly, 00:09:14.290 --> 00:09:17.890 and secondly, they just overtighten 00:09:17.890 --> 00:09:20.890 each one of these and pinch out a gasket, 00:09:20.890 --> 00:09:23.100 crush the corrugations, or perform 00:09:23.100 --> 00:09:26.133 some other damage to the heat exchanger. 00:09:27.338 --> 00:09:31.410 There will be in the manual a correct tightening procedure 00:09:31.410 --> 00:09:33.680 for the heat exchanger. 00:09:33.680 --> 00:09:36.790 Typically, if there are eight tie bolts, 00:09:36.790 --> 00:09:39.350 here we have six, let's image there was another two, 00:09:39.350 --> 00:09:43.070 one here and one here, what we'd actually do 00:09:43.070 --> 00:09:45.830 is we would tighten the center ones first 00:09:45.830 --> 00:09:50.100 a little bit and then we work on the outer ones next, 00:09:50.100 --> 00:09:52.630 and then the middle ones again, 00:09:52.630 --> 00:09:55.380 and then the outer ones again. 00:09:55.380 --> 00:09:56.460 But what we'd actually do, 00:09:56.460 --> 00:09:59.840 we would cross tighten the tie bolts. 00:09:59.840 --> 00:10:02.410 So we'd go here, one, 00:10:02.410 --> 00:10:06.010 two, three, four. 00:10:06.010 --> 00:10:07.810 And then we would tighten up here, 00:10:07.810 --> 00:10:12.240 one, two, three, and four, 00:10:12.240 --> 00:10:14.570 back at the top, and repeat. 00:10:14.570 --> 00:10:17.190 But it really depends on what the manufacturer 00:10:17.190 --> 00:10:19.330 tells you to do. 00:10:19.330 --> 00:10:21.550 Here we've got six tie bolts, so we'd have to 00:10:21.550 --> 00:10:24.680 think of how we could tighten these up correctly 00:10:24.680 --> 00:10:27.450 without pinching out the gaskets. 00:10:27.450 --> 00:10:29.510 So in my mind, I'd probably start here, 00:10:29.510 --> 00:10:34.510 one, two, three, four, five, six. 00:10:34.660 --> 00:10:37.110 And you'd do it incrementally. 00:10:37.110 --> 00:10:40.620 That means that perhaps one full turn here, 00:10:40.620 --> 00:10:44.723 one full turn here, one full turn here, and repeat. 00:10:45.830 --> 00:10:48.270 You can actually do more turns at the start, 00:10:48.270 --> 00:10:52.290 perhaps two, two, two, two, two, and two. 00:10:52.290 --> 00:10:55.610 But as the plate stack becomes thinner, 00:10:55.610 --> 00:10:58.050 as you start to push all those plates together, 00:10:58.050 --> 00:11:01.500 then you are not going to be doing two turns at a time. 00:11:01.500 --> 00:11:04.140 What you're actually gonna do is do one turn at a time, 00:11:04.140 --> 00:11:07.010 and then 1/2 a turn at a time, until the distance 00:11:07.010 --> 00:11:09.030 between the moveable plate and the fixed plate 00:11:09.030 --> 00:11:12.593 is the same as it was before you started maintenance. 00:11:13.700 --> 00:11:16.430 So that's how we assemble and disassemble 00:11:16.430 --> 00:11:21.290 the plate heat exchanger and also how we clean the plates. 00:11:21.290 --> 00:11:22.340 There is another option, though, 00:11:22.340 --> 00:11:25.550 that is a lot easier than taking the whole thing apart 00:11:25.550 --> 00:11:26.920 and that is simply to clean it 00:11:26.920 --> 00:11:29.433 when the plate stack is assembled. 00:11:30.650 --> 00:11:33.030 So what we would do here is disconnect 00:11:33.030 --> 00:11:35.740 each of the two systems here, 00:11:35.740 --> 00:11:40.740 and then we would pump or circulate cleaning fluid 00:11:40.750 --> 00:11:43.370 through the plate heat exchanger. 00:11:43.370 --> 00:11:45.006 That means that we connect a pump 00:11:45.006 --> 00:11:48.870 between this pipe here and this pipe here. 00:11:48.870 --> 00:11:51.630 Sometimes people call these portholes, by the way, 00:11:51.630 --> 00:11:52.690 and then we connect a pump 00:11:52.690 --> 00:11:56.980 between this pipe here and this one here. 00:11:56.980 --> 00:11:59.410 We would then turn on the pump 00:11:59.410 --> 00:12:01.780 and we would circulate the cleaning fluid 00:12:01.780 --> 00:12:04.710 through the heat exchanger and it would clean 00:12:04.710 --> 00:12:07.430 each of the plates. 00:12:07.430 --> 00:12:11.750 A common cleaning agent is sulfuric acid or sulf-acid. 00:12:11.750 --> 00:12:14.470 This tends to remove any organic material 00:12:14.470 --> 00:12:16.870 that has built up on the plate surface, 00:12:16.870 --> 00:12:19.940 but it will not damage inorganic material. 00:12:19.940 --> 00:12:22.050 So the seals, for example, 00:12:22.050 --> 00:12:24.840 the gaskets will remain unaffected 00:12:24.840 --> 00:12:27.000 and the plates will remain unaffected, 00:12:27.000 --> 00:12:29.500 but if you have any organic material 00:12:29.500 --> 00:12:32.560 that's accumulated within this fine space 00:12:32.560 --> 00:12:35.100 between each of the plates, for example seaweed 00:12:35.100 --> 00:12:37.610 in a seawater system, then the acid 00:12:37.610 --> 00:12:40.590 will attack the seaweed or the organic material 00:12:40.590 --> 00:12:43.253 and the plates will be effectively cleaned. 00:12:44.220 --> 00:12:46.420 If there's calcium or calc that's also built up 00:12:46.420 --> 00:12:48.480 on the plate heat exchanger surfaces, 00:12:48.480 --> 00:12:51.630 then you'll be able to dose it with a chemical 00:12:51.630 --> 00:12:55.470 in order to break down that calc. 00:12:55.470 --> 00:12:57.610 So there are different chemicals you can buy, 00:12:57.610 --> 00:12:58.940 not just from the manufacturer, 00:12:58.940 --> 00:13:00.540 but also on the open market, 00:13:00.540 --> 00:13:04.070 and usually they'll be acid or alkaline based. 00:13:04.070 --> 00:13:06.960 And you can use these chemicals to clean the plates 00:13:06.960 --> 00:13:10.320 without actually opening up the plate stack. 00:13:10.320 --> 00:13:12.520 Let's now go to the final lesson 00:13:12.520 --> 00:13:13.890 where we can do a short summary 00:13:13.890 --> 00:13:17.110 covering all of the topics that we have talked about 00:13:17.110 --> 00:13:20.443 and we can reflect a little bit on what we've learned.
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