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Maintenance of Industrial Refrigeration Systems - Andy Smith

Maintenance, Aftercare, Vibration and Condition Site Monitoring of Industrial Refrigeration Systems - Transcript

Morning everyone, I’m the Branch Manager at Star Manchester. I’ve worked for Star Refrigeration for about six and a half years. I’ve been in the industrial refrigeration sector for most of my working life and I did start off as an apprentice service engineer, so I’d like to think I’d bring a practical approach to the actual reduction of operation costs and energy consumption. Probably one of the most used slides that we’re going to talk about today is the Total Cost of Ownership of a refrigeration plant. That’s an industrial plant - some of these can be scaled down to a lower level. I think what’s quite interesting for the first three presentations – whether it’s refrigerant choices, equipment selection, or how we use that heat – a lot of that is talking about how we use those first sections here. How do we use that capital? What do we choose, what specification?

What I’m going to be talking about in general today is the aftercare, maintenance, service costs, breakdown, replacement components. But what I’m going to tell you today is by choosing this, it has a big effect on this, which is your energy consumption,. That’s the Total Cost of Ownership, and what we’re looking at is a 20 year cycle. So, what can we do that’s slightly different? Let’s turn the clock back, for us anyway.

What we’re talking about now is aftercare: type A maintenance, or an aftercare system. This is what we would call a traditional maintenance system. So, what have we got here? We’ve got reasonable reliability, efficiency, total operating costs, energy costs, breakdowns and so forth – quite high. What do we look at so it’s slightly different? We’ll look at what we would call a type B aftercare system, and this is a condition based maintenance system. And what we’re doing here is, by changing how we deliver aftercare to your refrigeration plant, we’re increasing the reliability, increasing the efficiency, and therefore reducing your operating costs and all the benefits that come with that. So, that’s the theory side. Let’s see what we can do in practice.

This installation was a main plant, quite a large ammonia plant running 24/7. One of our traditional customers asked us to look after this plant – it wasn’t a Star installation. From the maintenance, service and operations department, we look after a multitude of equipment, whether that’s a Star designed system, or someone else’s. So, let’s look at type A.

This is the energy cost based on the month’s usage with a traditional type A based maintenance system. We came on the scene back in January, and what our customer found was – in the summer months here, June and July – they’re saving over £10,000 a month on energy costs. Now again, that is not a Star design. All we’re doing here are some very low cost adjustments. We're maybe re-commissioning the plant and looking at what it is needing now, compared with what it was doing or what it was designed for a number of years ago. A type A system, again, is a traditional maintenance system, labour intensive. Fixed schedule maintenance systems are quite invasive, that we’ve seen in the past. Let’s compare that with a condition based maintenance system.

We’re going to talk about five elements this morning, five elements of what we would say are condition based. The first element is vibration monitoring. That can either be fixed installation, or as in the picture here, it shows a little portable handheld device. I’m not going to talk about vibration monitoring too much because I’ve actually got a demonstration after lunch, if you’d come and have a look at how that system works as well. And then we’re looking at performance checking – how is the system performing today compared with how it was designed, or how you’re operating it? Again, that can be done in a number of ways. That can be very traditional, logging the plant, taking that information back, interrogating that and looking for where the weaknesses are. In this instance, we’re using a piece of equipment called a Climate Checker. I’m not going to talk too much about that system, because we’ve got a video to watch after my presentation which shows you how that works.

But also, that can be pulling that information off-site for us to monitor weekly. We’ve got some graphs at the back of our site monitoring system, and we can see where the performance falls off a plant, and where we have to go and do some invasive work on some compressors and so-forth. We’ve got laser alignment, so we can have a look at that. The last two segments are oil samples here, and also refrigerant quality checks. This one is what we would call an ARQ which is an Ammonia Refrigerant Quality check.

Moving on to oil. Again, we’ve got some oil samples at the back here. We work on a RAG system – Red, Amber, Green. When I came to Star six and a half years ago, we were already using this system. We work in partnership with a number of suppliers. The problem is, is that they didn’t know what we want as refrigeration engineers. So, over the last six years we’ve been working with them to work out these actual tolerances. This is quite an old system, again it’s not one of our installations. It’s a processed system that uses R22, which is a problem. What are they going to do in a few months time?

So, what do we see here? We see that there is an alert here because there is quite a high iron content. And on the same sample number four we’ve got free water. We see a viscosity change. This is running on a mineral based oil, which is traditionally what we used to do, but we’ve moved away from minerals. Minerals are quite susceptible to contamination and we see the viscosity changes now, so we’ve got no alert on that. We’ve still got a high water content. And this thing here, you can see it says “PQ”, that’s basically a magnetic field Particle Quantifier. So what we see is we’ve got small iron particles – probably below 200 microns – and relatively large iron here. That’s quite bad. We took another sample, and we’re still getting some samples here. We’ve recommended that the customer shuts the plant down and we do a full oil and filter change, which is a major undertaking on this plant.

So everything’s running fine, great. And we see in sample six, everything’s running fine. But what happens in sample seven? We’ve got water back again. We’ve got debris, and we’ve got free water in the actual oil sample. Nobody’s done anything to the plant. We’ve not taken anything apart, chopped a pipe, or changed anything. So what’s actually happened? With this system, the actual customer controls the refrigeration plant. He stops and starts the machine, he controls the refrigerant levels in his surge drum – and what we actually found was, when we were not on site, was that they had a problem with the control system that caused a flood-over of refrigerant to the compressor. The compressor stopped on its safe disk, which is fine, but what did that do? Well, because it’s a surge drum, all the dirt and water from the whole time that the system’s running is collected there. It’s washed over back to the machine, and that’s the reason why here we can see high water content here and free water there. So what we seen in an oil sample is actually a controls problem. We recommended that the customer changes his controls, based on what we found here.

Let’s look at another oil sample. This is a Star installation – this is a relatively new system, circa 2010. Again, part of our maintenance proposal, and what we provide this customer is regular oil samples. But we’ve got a problem – we keep getting high oil insolubles here. Insoluble is just general muck in the system. On this level of oil analysis, what we do is, we just measure that figure. If we want to, we can take a further sample and we can get a crystalline structure. Actually, on here, we were getting a crystalline structure building up. We take another oil sample. It’s still bad, so we recommend to the customer that we change his maintenance. We look at his five year plan. We have the equipment down, and we do an oil and filter change. And here we go. Everything’s back to normal, everything’s great.

Then we do another oil sample, and what happens again? Now again, nobody has done anything to this machine. We’ve not added new oil, we’ve not taken anything apart, but somehow it’s generating a high insoluble. What we found – and it took us a wee bit of time – is that on the third stage of oil separation, we have these coalescer filter arrangements here. We compared that with a new one that this bonding had melted, and changed this bonding arrangement here, and that was the problem. We’ve got, again, a new coalescer here that you can see. What we’re seeing with oil samples is that some components are failing early, because someone’s changed the mix, or some things can be delayed. You don’t have to do oil and filter changes every year just because your dad used to do it. That’s what it’s like sometimes.

Now we come to refrigerant quality checks and site monitoring – in about 2009/2010, we took a decision to do a national survey of ammonia systems throughout the UK. I don’t know if you know there’s nine branches, and that’s really why we chose nine sites. So what did we find? Well, we found that four systems had a water contamination of 1% or below. Which is acceptable, as long as you monitor that. We found one system had ammonia carbonate. What that is, is when you evaporate the refrigerant and you’re left with this white powder wax that clogs up valves, clogs up heat exchangers, costs you a lot more to run. The system breaks down, and you lose performance on the plan. This was due to the guy using secondhand equipment to save money. So, I put that equipment in on an ammonia plan – but what they hadn’t done was paid attention to changes in the coalescers. That was saturated with old oil on a synthetic refrigerant. That oil, mixing with ammonia, turned it to ammonia carbonate, and that was being pumped around the system. I think it took him about 18 months to clean the system. They got to the point where they actually stopped the plant, took everything out, and poured all the system out. But what we also found as well, we actually found that four systems were contaminated between 1 ½-24% water in the refrigeration system.

So what does that cause you? If we’re just looking at one thing, we’re looking at energy. For every 1% water in an ammonia system, you’re going to lose cooling capacity. You’re going to lose 1½-2%. But also, coupled with that, is the increase in energy costs. 1% water increases your running costs by 1%. That’s just one part of it. You’re going to get component failure. You’re going to get your oils breaking down very quickly. What you find when you track oils is that it doesn’t just slowly deteriorate – especially the synthetic oils. Although they last longer, what they do is fall off a cliff. So, when you’re doing oil samples, you have to do them regularly. Once a year is not enough. Once every six months is not enough. Really, true condition monitoring on oil samples is once a month. That is not always practical on some systems, and you have to take a view on that. But really, you’ve got to be looking at those sort of things anyway.

The worst system we found was a traditional ammonia two-stage system in the food industry. He had spiral freezers, he had a cold store, and he had two surge drums. In this instance, we say surge drum A and surge drum B. Surge drum A had a contamination of about 10-12% and surge drum B had a contamination of about 20-24% water in his ammonia. So, what did he find? Well, he took 118 litres out of drum A, and he took out over 500 litres of water. If anybody knows a bit about refrigeration in the room, we took over half a ton of water out of his ammonia plant. We took out that much water that he had to put more ammonia in, because the system was running short. The customer was monitoring a couple of things – he was actually monitoring the pumped liquid temperature, that’s the temperature as it entered the spirals. He was also monitoring his cold store temperature, and obviously he was monitoring his energy costs, to a degree. After a period of time, we took that water out – which, in this instance, took over six months. He noticed the temperature difference between the actual temperature and between his liquid temperature, and the saturation reduced down. But also – and we didn’t plan on this – his cold store temperature came down. He only told us, right at this point, that he had been having problems for a number of years maintaining his cold store temperature. He also found that his energy costs went down.