Read this guide to find out:
- The confusion and treachery of buying mixers.
- What is a mixture?
- How to measure the mixture quality.
- Fifteen steps you should follow in defining your project.
- Interviewing your potential vendors.
- Eight reasons why you should consider High Performance Mixers.
- Seven costly mistakes in choosing a mixer.
This is an educational service provided by:
Bliss Flower, A & J Mixing International Inc.
8-2345 Wyecroft Rd.
Oakville, ON, Canada L6L 6L4
1-905-827-7288; 800-668-3470; fax 1-905-827-5045
Contact us by email.
1. THE CONFUSION & TREACHERY
Are you confused by dry mixing and dry mixers? You are not alone. A good friend of mine who works in process said to me: “I just don’t understand mixers!"
That caused me to think about our industry. Most of the mixer manufacturers are in “Sell our Standard” or “Sell our copy”. They talk hardware but rarely can you find someone to talk mixing. Most will try to do anything without regard to your time and money. I once had a friend who had 14 companies to agree and did test his product. 13 failed.
There are dozens of competitors selling the “standard” or the “copy” all trying to get your business on price. Lowering prices is a simple concept—you just remove material and labor. We do it. Parts of the machine that cost the most to build are normally the ones that are attacked, and manufacturing tolerance widened, even if you are left with lost production and maintenance costs for life.
The ads all say a perfect mix. Some of the words in ads are “mined” by agencies who think they attract inquiries without regard to accuracy. I have seen my words in many ads when I know the equipment can’t deliver the claimed results.
The consultants in the business have pet strategies they want to sell. This year they started talking about a mixer patented in 1978, and where ours is 1998, it will be a long while before we are old enough to warrant their learning about us.
Do you hear any of them define what they call mixing, what size samples they are talking about and how to measure? I have never heard it. Yet I heard people who have opinions on all mixers except the one’s invented in the last 25 years.
There is also the capacity issue. Most ratings of mixer capacity are water fill, 100% rotor, or a line across the housing at the top of the rotor. No mixer will work at water fill and the manufacturer should give percentages of fill. A few manufacturers use the working capacity. Be sure to find the right value.
I have to say that dry mixing is a very complex subject. Don’t underrate knowhow. In my attempt to simplify, you may find statements for which there are exceptions. This guide is intended to help you with your selection so you do get your return on investment.
This market is a treacherous place for the occasional buyer. There are only a few, and we are one, that actually care about you and want you as a repeat customer with a smile. 98% of our business is repeat buyers. One company owns 24 machines; several have more than 5 machines. They buy them because they make more money.
2. WHAT IS A MIXTURE?
It is a mathematical ratio among the particles. If I have 4 particles in my hand, one being different, then I have a 3:1 ratio and a homogenous mix.
It would be nice if you could direct all the particles into that relationship. However, a mixer is a randomization device and all we can do is randomize to the best possible odds.
We believe that in addition to creating voids for particles to randomly roll together, that mixing also needs organized transportation. Speed of mixing and controlled void sizes helps overcome the tendency of particle to segregate by rolling apart. These traits will give you a homogenous mix.
3. HOW DO YOU MEASURE THE QUALITY?
First, you should decide on the size of the sample and how many samples. As a guide, your sample size should be the minimum amount that your product will be used, and large enough to mathematically contain the smallest ingredient. This is often overlooked, and you can’t ask a mixer to perform better than the ingredients that fill it.
Here are some ways:
3.1 Visual. This is not very accurate but can be useful. You can compare samples taken from the corners and the center and see if they look the same, either dry or wet.
3.2 Visual with an assist: Put color in the mixer and watch it disperse. When it appears to be mixed, jog the mixer and look for possible concentrations.
3.3 Draw test. Take a small sample like a teaspoon full and place it on a sheet of paper. Using a broad knife like a putty knife, press on the material a draw a thin film over the paper. This can show lumps of pigment, lumps of shortening, lumps of fumed silica, etc. This can tell you if you need more mixing time, and more shear.
3.5 Performance. This is useful for example in wall decorative compounds. If it runs on the wall, there is not a proper dispersion of the binder.
3.6 Spectrograph or similar. There are several devices that capture reflected light and can determine the color quality. These are frequently used in the colored cement products industry, an industry where we are probably the world’s best.
3.7 Statistical analyses among samples. This is easiest when you have particles that will screen apart. We frequently use tracers to check the mixing action. The caution here An educational service of A&J Mixing International Inc. Page 4 of 13 is to be sure you have a scale that will weigh the trace ingredient. We have a scale that weighs in grams and used a trace so small that it looked dispersed but the scale could not accurately weigh the screen off. We increased the trace and produced a result to Cv 5%, which is considered perfect for a randomized process, and that requires a High Performance mixer.
4. FIFTEEN (15) STEPS YOU SHOULD FOLLOW IN DEFINING YOUR PROJECT.
Be prepared to supply the following to your chosen vendors, and be prepared for questions that may be more specific.
4.1 What is your product? Many vendors have experience with the common ones. If it is something unusual, what are the ingredients, particle sizes, weights per cu. ft. and percent of the batch.
4.2 Any unusual characteristics such as lumps, sticky, etc.
4.3 Any liquids, temperature, viscosity, percent of the finish product. (We know more about applying liquids than any other vendor.)
4.4 Are you mixing it now? Which type of machine? What are the problems you want to overcome: quality, repeatability, reliability, volume?
4.5 How are the ingredients received? Bulk, bulk bag, bag?
4.6 How will the mixer be loaded? How much time required?
4.7 What will the mixer discharge to?
4.8 Does it take more than just mixing to make the product such as reaction, shear, particle reduction, heating, cooling
4.9 What is the volume you require per shift and minutes worked.
4.10 Do you have a fixed budget? What is the return on investment your company looks for?
4.11 Any restrictions such as aisle or building space.
4.12 What do you need from your vendor? System layout, controls, hoppers, etc.
4.13 Any specifications to be met such as food grade, wash down, explosion-proof, etc.
4.14 Material of construction: Carbon, Carbon/AR, Stainless Contact, all Stainless, Stainless/AR. Are there any chemicals including cleaning that will attack the metal?
4.15 When can you place orders, and when do you want to be operating. Be prepared to work with your vendor. “Team” jobs always work out better for both parties.
5. INTERVIEWING YOUR VENDORS.
You should ask if the vendor can make the equipment. Assuming they can, then ask for 5 things that they are doing to give their machines little downtime and maintenance.
The major maintenance costs are discharges and shaft seals. You should seek answers such as re-straightened end plates for proper seal skew presentation; re-straightened rotors to reduce wobble (TIR) on the shaft to under 0.005”; self adjusting discharge checked to be water tight; all helical drives, all sealed bearings.
Are their mixers designed to start under load? Will they customize their equipment to your exact needs? This can reduce your operating costs.
5.2 Mixing knowledge.
Do they know your product? Have any experience with it? What is the mixing performance level they would expect? Do they have demo equipment to show you? Any performance guarantees?
An educational service of A&J Mixing International Inc. Page 6 of 13
6. EIGHT REASONS WHY YOU SHOULD CONSIDER HIGH PERFORMANCE MIXERS?
The main reason to buy a High Performance mixer is to make more money. This money comes from both revenue and savings. First, let’s tell you what High Performance mixers do:
6.1 Mix to high accuracy Cv. 5% in 30 seconds (dual) to one minute (single) with predictable, repeatable, and reliable performance. This performance is based upon small samples. The sample only has to be big enough to mathematically contain the particles of the smallest ingredient. This means, for example, that the color of tile grout will look the same all around a bathroom tile. There are no dead spots.
6.2 No damage to ingredients. You can mix flakes, extruded pellets, detergent agglomerates without breaking them.
6.3 Ability to mix different sizes and weights of particles. The speed of mixing is faster than the natural forces of segregation can react. We also have discharging methods that keep the particles from segregating.
6.4 High and low liquid additions. We have done from 22 grams per tonne to 40%. We do both low pressure and high pressure spraying, and slug loading on some products.
6.5 High production. The highest operating is capable of doing 12,000 cu. ft per hour.
6.6 Shear or no shear at the flip of a switch. One customer said this allowed them to develop and make products that they had only dreamed about.
6.7 Ability to handle abrasive materials and combat accelerated wear. This comes from the short mixing times and the material of construction, or liners.
6.8 High quality machines built for 99.8% availability to work, customized for your application, low maintenance and easy to clean.
The economic gains come from quality and reduction of minor ingredients, and high volume in a smaller space. Powdered paint users can save 3% in minor ingredients. Pigment users get a savings ranging from 5 to 17% depending upon the color. We have taken a bay off a new building.
Here is a theoretical comparison to a ribbon mixer: (You can plug in your own numbers.)
|PHLAUER™ (pronounced flower) single rotor needs one minute to mix, typical to get Cv. 5%. Drop bottom discharge is 10 seconds. The balance of the cycle loading, assume 4 minutes. The total is 310 seconds. We should allow for inefficiencies, typically we would divide by 0.8 = 387.5 seconds.
3600 seconds/hour divide by 387.5= 9.29 cycles, and let’s say each batch is 1 tonne. Production is 9.29 tonnes per hour, 18,580 tonnes per year. If the machine costs $65,000, the investment is $3.50 per tonne.
A ribbon of the same size, same loading time, same discharge, but the mix time is 6 to 8 minutes, typical to get Cv.10% in minimum one pound samples. I’ll use 6 minutes and assume the ribbon is $40,000.
This cycle is 610 seconds divide 0.8= 762.5. 3600 divide 762.5=4.72 tonnes per hour x 2000 hours per year = 9,442.6 tonnes per year.
$40,000 divide 9,442.6= investment of $4.23 per tonne.
In this comparison we are using the same size and the same space. You also need to take your cost of space and heat, light, taxes, and maintenance and figure your cost per tonne.
It is also interesting to look at what it costs if you don’t buy High Performance. In ten years you lose the profit on 91,374 tonnes. At $5 per ton this is $456.870. The life of a mixer is 25 years.
Another alternative is to use a smaller High Performance mixer and get the quality for the same investment.
In High Performance mixers, equal specification, PHLAUER™ is the best quality and lowest priced. We have the only low speed single rotor mixer in the world that will mix to Cv. 5% in one minute. The volume of voids created on a mid-size mixer is equal to the batch size per revolution.
If you apply this reasoning that you want quality product at the lowest cost per tonne to other types of mixers, there are some machines that are a very poor return. One of the poorest is the vertical ribbon, which is really a liquid mixer being used in powders. Typically the vertical ribbon is half speed of a horizontal, and also half the ribbon. What is the volume of voids per time unit for particles to change place?
They occupy a tremendous amount of floor space. They say “easy to clean”. There is no ladder inside, how can it be reached? They have now tilted the ribbon to try to get material to fall off. They say no seal in the bottom, so no seal in the material. What about the valve? Does it not have a seal? Seals in material have been used for many years.
All verticals are poor mixers including the vertical augers.
There is no one mixer that can solve all mixing problems, so ability to get the job done is paramount.
7. COSTLY MISTAKES IN CHOOSING A MIXER
7.1 Buying on price.
7.1.1 If you are dealing with a vendor who has been in business 10 years, it is obvious that they are making a profit. There is not a great difference in cost, so if a machine is cheap chances are something is taken out to reduce cost.
Look for it to be under powered. There are a lot that won’t start under load. What do you do after a power interruption? Or after you have topped off the load with manually loaded ingredients? Some of these also hit the used market so be wary of used.
Here is a rule of thumb: The H.P. by itself doesn’t tell what the true power is. Look at the torque per cubic foot of capacity. Torque = HP x 63000/rpm/cu.ft. If it is less than 700 in. lbs, be wary, including ribbons and ploughs. If you have sticky materials or high internal friction like sand, you may want to be around 1,000 inch pounds
7.1.2 You can also see things like 80% of the rotor—balance missing.
7.1.3 Housings and rotors made to wide tolerances and not properly finished. This is an attempt to build cheap and the customer has quality, cleanout and cleaning problems. Housings also made so thin they wear out and drop bottom discharges won’t seal.
7.1.4 Discharges that go over center do not seal powders. Air purged packing glands don’t work.
You live with the maintenance cost for the life of the machine, typically 25 years.
7.2. Buying a machine that is too small and leaves you no flexibility for a recipe change.
7.3. Buying a mixer where the vendor tells you it will work at 40% overload and you are depending on that to get your production. At nearly every trade show we get someone asking how to make it work. The answer is reducing the load and they say they can’t. We can offer a retrofit in some cases.
I know where that came from and I have the original study from the University. They were bored and started to play with fill levels using corn meal and salt. They overfilled a machine and it took 45 seconds on swine ration to get close to the target. The advertised mix time is 15 seconds and at that mixing time the Cv. was 21.84. There were no ammeter, no dial indicator on the discharge cylinder mounts, and no one checking if the discharge was leaking when the mixer pulsed. They were just two students playing with a 500 liter mixer. Any mixing test should have the amps recorded.
The machines that are being put out do not have any extra torque on the discharge, any extra power, so you have to say “why do they have standards”. If a 1000 liter works at 1400 liters with 20 h.p., and 4” cylinders, why do they have a 1500 liter with 30 h.p. and 5” cylinders? Does this mean it takes 10 h.p. for 100 liters?
Also, if you are applying liquid, where do you get space to make spray droplets when you over fill?
It’s like buying a motorcycle as a family vehicle. Apply some judgment.
7.4. Buying a big machine that takes a long time to mix with the idea that the batch will all be the same, and if I take a sample, make an adjustment and mix again for 20 minutes, now for sure it is the same. If the mixer lacks organized transport, if I layer it across the top, for sure it will be mixed.
This is a misunderstanding of the dynamics of mixing, transportation, and the natural forces in particles that cause segregation.
Segregation: The biggest contributor is particle size differential. University of Bradford did studies that indicate that particles over 50 micron, if they have a 20% differential in particle size, they will roll apart. Less than 20 micron, weight of the particle is the major contributor. If you take a bottle and put ¼ salt and ¼ poppy seeds, put on the cover and turn it a few times in any direction and see that the salt always goes to the center.
Mixers try to overcome segregation. All mixers mix and demix, and as rule of thumb, the longer it takes the mixer to mix, the deeper the demix cycle.
Because the differential of size causing segregation is so small, every batch has its own mix curve and you don’t know where it is. There is therefore no logic that supports mixing any fixed time delivers the best result. The best result comes from a mixer that has enough transport and void creation to mix faster than segregation can occur. You are better off the have a smaller mixer that performs and have good control of the ingredients being entered. You will also find it a better investment because of savings building costs and lower operating costs. How would you expect to compete against a better product having a lower cost—investment, operating and less of costly minor ingredients like pigment?
7.5. “I’m going to test until I drop”. In bulk materials, a test or demo is priceless. Bear in mind that tests are expensive not only to do, but in many cases to analyze.
May we suggest that a logical process is to interview your vendors first. Pick one or more that appear to be prospective suppliers. Get your budget quotes first and make a further selection based on these quotes. Then test with the most likely to satisfy your project, and as soon as you have a successful test or demo, make your decision and buy.
The person I mentioned earlier who went to 14 companies and had 13 failures had a relatively inexpensive product and there was an initial simple draw test that gave a good indication before it went to a spectrograph. There was some apprehension because I was the new mixer on the block. They bought my first big mixer and put up a $5.5 million project around the one mixer. It is still operating.
7.6. All shear devices are the same. Most are a copy of a 1948 invention and utilize a motor with an extended shaft, and a tulip blade inside the mixer. There are some variations on the device inside. Objective is to make them cheaply.
There are two problems: the sealing options are limited because you can’t control the runout with the bearing so far from the seal. The second is that most are applied to ploughs and when they deviate from the tulip, the blades can’t all be the same length because they have to clear the plows. The short blades are ineffective, if our tests mean anything.
Our experience with liquid pedestals lead to the design or our pedestal and we have the bearing close to the seal, control the runout and that gives us sealing options. The best is our patented Controlled Orifice, Air Purged (COSAP). The sealing is actually a film of air.
Our blade design was develop through many hours of testing with masonry cement and red and black dyes until we could produce a consistent result in a fixed time. We succeeded and have the most aggressive shear on the market. All our blades are effective so we need fewer.
A co-operative program with our biggest customer who just ordered their twenty-fourth machine, lead to the seal arrangements and blade designs we have today.
7.7 Buying a high intensity mixer when you don’t need one because they use a lot of energy and create heat. If you don’t need friction heat that is used in compounding PVC, for example, or a lot of power for your mix, then you probably can get your job done better and faster for less investment and less operating cost.
Ploughs were designed in 1948 on the theory that mixing is a low level grind and therefore required high shear, shear being defined as imparting energy directly to the particle and possibly degrading it. Forberg with his 1972 invention proved with his fluidizing technique that mixing did not need shear, that it needed high particle movement, organized transport and space for particles to change place, hence the “fluidized zone”. Flower with his 1995 invention proved that high particle movement, organized transport and space for particles to change place could be achieved by mechanically creating the space so it was consistent, and that fluidization was not necessary to get an accurate mix. All three used the speed of mixing to overcome segregation in the mixer or demixing.
Ploughs in addition to being a higher investment, are harder to keep dust tight, can’t be loaded over the side; and because the movement inside is bi-directional off each plough, the transport is completely random making it difficult and a long time to discharge. Carry over is common. They are difficult to clean.
All of the above problems can be overcome by PHLAUER™.
One of our customers who now has 24 PHLAUER™ machines send their non-sanded colored products to plants having our machines because their plough won’t develop the color.
“We have three of your machines installed at this location and are awaiting delivery of a fourth unit. We were impressed that the scale-up from the test mixer was just as predicted. In addition, we are enjoying an average of 10% pigment savings over our previous mixer design due to the aggressive dispersal characteristics of your Shearmakers.” Tom Milan, Assistant Plant Manager. (Cement Products)
“I am Bliss’s oldest customer buying machines for nearly 25 years and we have had no downtime—maybe a day. It’s phenomenal. With your new high shear mixing we get a completely homogenous and lump free product in 30 seconds. We just ordered our fifth system—but I’m not loyal! Jim Piascik, Production Manager. (Powdered Metal)
“After talking with the mixer supplier’s reps, I was impressed with how helpful and supportive they were. I also liked that they could supply both the mixer and ancillary equipment. With the new mixer, we can make two, sometimes 3 batches per hour. (in the same space). It’s a huge productivity improvement.” Fred Gomez, Regional Operations Manager. (Cement Products)
“With A & J’s technology we are able to produce premium coffees that meet our exacting standards while significantly reducing our flavoring process time. We only wish that we had known about this technology sooner.” Charles Litterst, President.
“You have well designed machines and the personnel to support them. It has been a pleasure to work with everyone at A & J. The flexibility and accuracy of PHLAUER™ mixers allow us to produce a new range of products that we could only dream about before. The Price/Performance ratio is extremely favorable for us.” Edward Baranski (Food Additives)
“Appreciate your willingness and ability to customize the finish and capabilities of your equipment. It is performing beyond our expectations.” D. Novak, PE, DSc. (Detergent)
“A & J customized the mixer, stand and hopper to meet our needs exactly and fit the envelope of the old mixer. They recommended LESS equipment to do the same job.
An educational service of A&J Mixing International Inc. Page 12 of 13 Our new mixer replaced a 50-year old twin shaft unit, and does the job with 25% less horsepower in ½ the mixing time, and with better mixing results.” Rod A. Shaver (Gypsum Products)
“We like our mixer. It is very fast, and we like the product we get from it. I can honestly say that I believe A & J is concerned about my business. I look forward to working with you in the future and I would highly recommend your mixer. Looking back I wish I had bought the bundled package. The control options you were proposing in the beginning were very competitively priced. I just didn’t realize it at the time.” John Byrd. (Cement Products)
A & J will guarantee the performance of our mixers in any application where we have knowledge or have a successful test. We say the mixer will do what we say it will do or your money back.
Corporate law dictates that liability of such a guarantee be defined and the following are from our terms & conditions:
ARTICLE 5 -Warranty
5.1 Components produced by us are warranted to be free of defects in materials or workmanship for 18 months from the date of shipment, or 1 year from the date of installation. Warranty on purchased components will be transferred to the customer in full.
5.2 If you find a defect in material or workmanship during the warranty period, you must notify us within 10 days. We will, at our option, either repair or replace the component.
5.3 Obligations under this warranty are subject to the equipment being operated and maintained in accordance with our instructions and that it has not been altered in any way. The warranty does not include normal wear and tear, corrosion or misuse.
5.4 We warrant at the time of delivery that the equipment will be free of Liens and encumbrances. If there are any such Liens or encumbrances we will cause them to be discharged promptly when you notify us of their existence.
5.5 If performance is warranted as part of this proposal, it will be expressly written in our proposal. Any such warranty will be subject to the following i) We reserve the right to correct manufacturing errors. ii) The obligations under this performance warranty shall be considered fulfilled after 90 days of commercial operation; a controlled test which meets the warranted results; or the return of the equipment and refund of your purchase price. iii) We specifically exclude this warranty from the Ontario Sale of Goods Act and will not be responsible for any Losses, whatever the cause, in excess of the factory purchase price of the equipment supplied.
5.6 The expressed warranties we make to you in this Article 5 are the only warranties we will make. There are no other warranties whether statutory, oral, written expressed or implied and in particular there are no implied warranties of merchantability or fitness for a particular purposes.
5.7 The remedies we provide you in article 5 are the only remedies that you have in the event of a breach of warranty.
5.8 Warranty is void if payments are in arrears.
For further information visit our website, and call or email us for a Power Point presentation “High Performance Mixing”
We are very proud of our record. We have only had one personal injury reported to us 20 years ago, and that came from a man inside the mixer standing on the rotor with one foot trapped under it.
We discourage anyone from entering our mixers and provide proper access for the machine to be cleaned through side doors and covers. We have a side door design that can be put in the mixing zone without leaking. All our air cylinders are covered. We spare no expense when it comes to safety. We have the only Shearmaker that can be removed from the machine with the blades on so people do not have to go inside for maintenance.
Each time we have a new design, and there is any doubt, we have professionals from the Ontario Industrial Safety group, who are well respected, to check it for us and give us any comments.
Look at the equipment you intend to purchase from a safety point of view, both operating and maintenance. Look at weights of parts that may have to be removed, and look for a safe method to do it. I find it absolutely incredible what is being sold. We rebuilt one mixer that has an 18” x 12” door in one end and the mixer walls had to be scraped, so a man had to crawl inside.
ABOUT THE AUTHOR:
Bliss, & Lyndon—The Flower’s. Bliss has had 30 years experience; Lyndon, 11.
We own our technology and have a total of 4 patents and others pending. We are the people you can count on.
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