Liquid Analysers pt 2

Sean continues the conversation with Nick Crowe about the misconceptions we hear regarding liquid analyzers. Are analyzers and sensors warranted? Is it easier to just replace than maintain sensors?  Is it necessary to calibrate a rebuilt unit? 

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[00:17] - Sean 
This is a Yokogawa Australia New Zealand podcast. Welcome back to Yokogawa Debunks. Conversations with industry experts to demystify misconceptions we're hear in process instrumentation and industrial automation. I'll be a host today, Sean Cahill, and thank you very much for joining us. Now, in our last episode, we kicked off our conversation with Nick Crowe of Yokogawa, who is a product manager for analytical products, about one typical misconception many users have, liquid analysers have. And it's the idea that liquid sensors require no maintenance and no intervention. 

[00:53.] - Sean 
Today, we continue to dissect this idea with him, so Nick welcome back. 

[00:59] - Nick 
Thanks Sean, it’s great to be back.  

[01:00] - Sean 
Now moving to some of the conversation from the from the last session, we found that often the focus can turn to that of sensor life. Is there any warranty on analysers and sensors? 

[01:12] - Nick 
Well, the short answer to that surely is no. We can warrant the analyzer, but the actual sensor itself, you really can't. So, when we think about the things that we talked about in the previous episode there, where we have to have our for liquid analysers, we have to have our sensor in contact with the process. And we mentioned that, you know, different process parameters can affect that sensor in different ways. Well, that all has an impact on the life. 

[01:41] - Nick 
And what happens is that it ages the sensor at different rates. So, what we're trying to do when we do the maintenance is determine how quickly that sensor has aged. I mentioned previously high temperature applications, they will age a sensor particularly fast because liquid analysers, we're generally making a measurement of a chemical and we know that chemical reactions happen much faster at high temperatures. So, it makes sense that it will age it quickly. But also when it comes to to warranty, you know, what constitutes a failure? 

[02:19] - Nick 
So, for some people, perhaps a slow response time of a sensor might not be important. It might not matter if they're making a measurement in a large tank or something like that that has a great volume of liquid. But for other people, a slow response time can be critical to their operation. So for them, it would be considered a failure and for the other people it wouldn't. So, it really is very difficult to to put a warranty on a sensor. 

[02:46] - Nick 
So, I mean, hopefully those reasons make it clear why we don't. And I suppose the other question we have to ask ourselves is how long could you reasonably put a warrant on on a sensor for? 

[02:58] - Sean 
So with this in mind Nick, if a client has a high maintenance installation, for example, does it then become cheaper just to replace the sensor rather than to maintain it? 

[03:08] - Nick 
I think in some cases it could be. So, we have some sensors that are designed to be disposable. So once they're used up, you dispose of it and put a new one on. And if we're using that particular type of sensor in an appropriate service, say, you know, nice potable water installation where we might get, you know, 18 months, two years sensor life out of it, is probably cheaper for those guys to do the replacement rather than try and spend a great deal of time and effort to recover that sensor.  

[03:43] - Nick 
But if someone's got a harsh application where they're getting through sensors a lot, perhaps they need to consider a different type of sensor and then they can perform work on it and keep that sensor going as long as they can. But, yeah, I guess you really have to weigh up how frequently you are going through sensors and the cost of your maintenance staff and time and effort they're spending out there doing the work. 

[04:09] - Sean 
So you mentioned there that some sensors are designed to be disposable. Well, you said some. So, does that mean that some sensors can actually be rebuilt? 

[04:17] - Nick 
Yeah, yeah, that's right. So, when we consider the common analytical measurements, pH, conductivity, dissolved oxygen and, you know, suspended solids and things like that. So, a pH or a DO sensor, for example, yeah that can be rebuilt. So, a pH meter, for example is made up of three elements, a measuring element, which we call the glass, a reference element, and a temperature element. Now, generally, when a probe expires, only one of those elements has passed out. 

[04:51] - Nick 
So maybe the glass is broken or the reference junction has become clogged and can't be recovered. In those high turnover applications. Sometimes it's better to look for a sensor that's rebuildable and then we can replace just that reference junction and that becomes really quite a cheap sensor to own and to maintain as well. Dissolved oxygen, for example, we mentioned, that has to have an electrolyte and a membrane, and both of those elements can be replaced. And when you do that, it gives you an opportunity to prolong the life expectancy of that sensor. 

[05:24] - Sean 
OK, so if I replace only the junction or the reference probe, I guess, does this mean that I won't have to calibrate it?  

[05:32] - Nick 
Unfortunately, no. You do still have to perform a calibration. So, as I mentioned, the pH sensor is made up of three elements. And when we perform a calibration, we're providing the analyzer converter with information on the condition of the pH probe. So remember, if we replace one of those elements essentially, we've changed the condition of the entire probe, so, yeah, that is something that we've noted some people tried to get away with to reduce time. 

[06:04] - Nick 
But really, you do have to perform that calibration if you replace any one of those elements. 

[06:09] - Sean 
So, look, I mean, I think what you're saying is that there is a degree of flexibility here with your your probe selection. You probe maintenance. But at the end of the day, you've really got to come back to basics by calibrating the device. Now, Nick, I just want to move the conversation onto a slightly different part of the topic here. And it's in relation to that of digital sensors and smart sensors. You know, in the in the world of liquid analytics, where do they fit in? 

[06:35] - Nick 
Well, we we've witnessed, you know, in in recent times an increased uptake of the smart sensors. And they've been around for for, you know, perhaps over a decade now. As I mentioned, that really is in the recent years they've started to really pick up. And I really wonder if it's because of the the uptake of digital transformation and the the continuous desire for extra data. So the benefit that smart sensors bring really is they change the way that we do our maintenance. 

[07:08] - Nick 
Unfortunately, you still have to do the maintenance because it doesn't matter how smart the sensor is, it's still making its measurement in the same way. It's just transferring the information that it's gathered in a different way. But as I mentioned, it enables us to change the way we do our maintenance. We don't have to do the maintenance in the plant anymore. So I guess that's a benefit that some people might find attractive. They're able to take a smart sensor back to a workshop or a laboratory and perhaps hand the responsibility for maintenance and calibration over to someone else. 

[07:40] - Nick 
And then when that's been performed, you can take it back out to the plant and plug it in. The analyzer recognizes all the new data over a few seconds and starts measurement again. But I think what the real benefit is, if you are utilizing the data that they can gather, because having the smart sensor, you have much greater visibility into the condition of the sensor and it enables you really to improve your maintenance planning, you are perhaps better utilize the maintenance staff because they'll be able to see (a) if a sensor does need maintaining and (b) if it doesn't need maintaining, they'll also be able to see what needs to be done. 

[08:22] - Nick 
So they go out to plant prepared with relevant and appropriate tools and they can get their job done a lot quicker. And as I mentioned, when you can see if a sensor needs to be done, perhaps you can extend that period between maintenance that everybody's trying to achieve. But yeah, so hopefully that kind of explains the benefits that digital sensors can bring and the different options between the traditional analog and the new smart sensor types. 

[08:51] - Sean 
Like I think you have. You've explained very well there that there is some great advantages to be had with the newer smart sensors, not only with the diagnostics they provide, but but also when it tackles this topic again of maintenance and the requirements of maintenance and and why you should maintain. So I think this is a great way to to close out this session, because it backs up everything not only from earlier in this podcast, but also from the previous one. 

[09:17] - Sean 
So we've come to the end of this podcast, and Nick I just let's say once again, thank you very much for joining us today. 

[09:22] - Nick 
Thanks Sean. It's been really good to have an opportunity to to talk about this. Yeah. Sensor life is often a hot topic. So, yeah, hopefully this information will help help some people realize if they analyzer is normal or abnormal. 

[09:37] - Sean 
Thanks again, Nick. And look, if you'd like to know more about the Yokogawwa liquid sensor's, please follow the links that we've provided with the podcast or leave any comments in the in the sections of this episode until next time. Thank you very much for joining us on Yokogawa Debunks. Goodbye.