Have You Automated Viscosity Measurement?
What Century Is It?
What are you using to measure viscosity in your manufacturing process?
If the answer is “just a Zahn cup”, then I only have one other question for you:
Why aren’t you using a rotary dial phone?
Did I just ask you to ditch your iPhone or your Android? Of course not. I wouldn’t do that. We rely on smartphones for our personal and professional survival each day, and we feel helpless if we leave the house without them.
A smartphone’s technology is invaluable because it allows us to work, shop, play, communicate, and tend to our obligations.
The Zahn Cup was originally patented in 1938 by Erwin A. Zahn. Zahn cups measure drain time of a liquid through a known orifice size to determine how thick it is – its viscosity. Meanwhile, in 1934, the first handset telephone was used by independent phone companies. Its official name was the “round base rotary dial monophone”. Some might recognize it better as the Shirley Temple phone.
Shirley Temple? Who’s that? If you think the reference is outdated, then I’m guessing you’ll agree that the rotary dial phone is outdated as well.
I was born in 1978. Growing up, I can remember when my dad bought a “portable” phone for his business. (Portable meant that it was in a suitcase – a very heavy suitcase.) I also remember when caller ID, call waiting, and speed dial were features that made your family cool if you had them. And let’s not forget when the cordless phone came out, making our lives easier and our conversations a little more private.
Those were just common household phone innovations that made the everyday person’s life more convenient. We could probably write a novel about the cell phone and how it has changed our lives.
I won’t digress too far, but let your imagination wander for a bit and think about the things that you do on your mobile device every day. Some of you reading this might not even know a life without daily smartphone use.
Let’s pivot now to a few things we wouldn’t dare use to conduct business.
Picture this hypothetical scenario: you need to write a proposal and get it to your customer, who is three states away.
You write your proposal by hand, then dictate it to an assistant to type out on their typewriter, because it would take you three times as long to use the typewriter. Oh, nevermind – you don’t have an assistant to do clerical work.
Okay, so now you’ve figured out the typewriter and are ready to send it off. Since we’re still stuck in the Stone Age, there’s no email. So you have to arrange for the mail service to send this multi-page document. That’s right – no click to send in a matter of seconds, to be reviewed in a matter of minutes or hours. Three to five business days later, your customer receives the proposal.
Must we continue? My brain hurts just thinking about this lengthy and painstaking process.
Now take that headache and multiply it by your number of employees and/or processes. How efficient and profitable would your business be? Would you still be in business? Would you have a job?
Let’s revisit our opening sentiment. – if you’re only using a Zahn Cup to measure viscosity in your manufacturing process, you may as well be using a rotary dial phone.
But you wouldn’t dream of using a rotary phone instead of your cell phone, would you?
So why are your operators still using a tool that was invented in 1938 to measure viscosity?
Are there viable alternatives? Could you be taking advantage of newer technology?
Let’s explore why you shouldn’t rely solely on the Zahn Cup and talk about some alternatives.
Why the Old Ways Are…Well, Old
Remember: a viscosity measuring cup is used to measure the drain time of a liquid through a known orifice size to determine how thick it is. So a user would take the Zahn Cup and dip the cup into the tank or vessel that contains the fluid being measured. They would then hold the cup up and let it hang straight down from their finger on one hand and hit the start button on a stopwatch with the other. This is where it gets a little tricky.
The user must now watch the fluid as it drains from the cup. Once the user sees the first break in the fluid, they are supposed to stop the timer and record the measurement in seconds. This, of course, assumes the user is following this procedure to the letter and not waiting until most of the fluid has left the cup.
Do you see any challenges with this process? We definitely do.
First, you have to make sure that the correct cup has been selected based on the viscosity of the fluid that you are using. (Unfortunately, many people use the wrong cup because they don’t know better.)
Second, the material has to be easily accessible for these measurements to take place. We know of one operator that takes 30 minutes just to get into the tank. And they have thirteen tanks in their process. So that realistically comes out to just one measurement per day per tank. Even then, the best case scenario is measurements at 30-minute increments. Is such little data even useful?
Human error plays a part, and so does variation. Most processes have multiple shifts, which means it’s not the same person taking all the measurements. So add variation in detail and diligence across users into the equation.
But by far the most important element we miss by using a Zahn-type cup is the ability to measure viscosity at the point of application.
If you’re measuring the viscosity of your kitchen paint, the paint itself could be hundreds of feet away from the gun, bell, or coater that’s applying it. Experienced engineers and operators know that the fluid is being subjected to things like high-speed flow, heat from pumps, and shear from bend radius in a pipe, to name a few. The outcome? We don’t actually know the most crucial piece of data: our fluid’s viscosity when it’s laid on our product.
An often-overlooked side of this is that when a fluid moves through a cup, its shear rate is different from when it’s flowing through a pipe at a higher rate of speed. Why is this important? Because most water or solvent additions are made in the kitchen under these conditions.
Is it fair to say that you may not be getting the desired viscosity on the part you’re coating? Think about it and decide for your own process. As we know, not all processes are created equal – even for the same application. It’s definitely something to consider.
At this point, we’ve bashed your Zahn Cup and basically said that you’re measuring viscosity with the industry equivalent of a Shirley Temple and a typewriter. But we know we can’t do that and not provide an alternative for this modern era. After all, we want to take some burden off of your operators and help the decision makers sleep a little better at night knowing they’re using the most cutting-edge technology.
Can you guess what we’re referring to?
If you guessed devices that measure viscosity automatically (also known as viscometers), you’re right!
These can be placed in line, in a tank, or even used on a lab benchtop. For our purposes, we’re mainly talking about the ones that can give you real time data, all day, every day. Viscometers can also be placed close to the point of fluid application to give you an accurate depiction of what’s happening during your process.
Technology Helps
“But we’ve tried those before. They didn’t work.”
I can’t say I haven’t heard that response before. It’s true that if you try a new technology and it doesn’t work, most of the time the technology gets blamed. Usually, though, the technology is not at fault. It might not work because its operators were poorly trained. It could also be because of unrealistic expectations – maybe what was promised (or what was thought to have been promised) was miscommunicated. And in some instances – though they are few and far between – the equipment itself might actually be defective.
This next one might come as a harsh truth, but sometimes, the reason the technology doesn’t work is us: the end users. We can also have operators who are stuck in their ways and don’t want to learn or use something new. They’ll find ways to ensure it doesn’t work.
Why should we automate our viscosity measurement process? Not only can you record accurate, real-time data 24/7, but most sensors will also measure temperature. Once you’re tracking what’s happening in your process, you can start to tie defects to causes. This kind of data will help you make informed decisions about how to further improve your processes.
Your operators will thank you for not making them manually perform this tedious, thankless task. In doing so, you free them to devote more time and energy to other parts of the process.
Most of all, you will thank yourself when you see higher consistency and better product going out the door because you actually know what your fluid viscosity is.
When you’re ready to swap that rotary phone for a smartphone, you know where to find us.