Equipment Features of PHLAUER™ Mixers
The outstanding feature of PHLAUER™ Mixers is predictable, repeatable and reliable performance. They are a premium investment over conventional mixers because we have more mechanism that also needs structural support. You can’t do what we are doing with eight paddles in a machine. You must be able to get a return on your additional investment. This comes from quality of your product, production volume, and savings in minor ingredients.
Many of our customers depend upon one machine to generate their entire revenue, so in addition to performance, the machine must have little down time. Our design target is 99.8% availability to work 24/7 on the mixer itself. Shearmakers will require yearly maintenance.
“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)
All bearings are sealed. The only lubrication required is on the motor, which on average needs grease every two years. We use best quality gearboxes and these should have the oil changed. Interval varies but typically every two years. We avoid chain drives.
The items that are the most maintenance on a mixer are the shaft seals and the discharge. This is why we invest more money in these items and want to explain more about them.
- Lip Seals
- Controlled Orifice Air Purged (COSAP) – Patented
- Packing Glands
Our drop bottom discharge is probably the most expensive in the world. We do not apologize for that: it works. When a competitor wants to cut cost, the discharge is where they start. The theory is that you only have to close the discharge when the mixer is empty, so if we just have a little lock that goes over top dead center (OTDC), we can cut the cost of air cylinders. That is true. We tried several types of OTDC locking devices and we could not get them to work on our test equipment, so we never put any on production machines. The basic problem is that as soon as you go over center, the pressure backs off. You can see that even on our side door clamps. When the pressure is not there, powders will leak. We learned that cement will go through a seal that is water tight.
There are many problems with designing discharges starting with the fact that you are trying to seal two “flat” fabricated surfaces. The first consideration that the surfaces have to be parallel. The second is the selection of gasket—it must have some compression so it will seal with your manufacturing tolerances and deflections. It must hard enough that it can be scraped clean and durable to stop the force of the door. We use BUNA N, 55 Durometer factory ordered and in inventory. Off the street, the durometer is 60 and is too hard. Thickness also plays a part in the amount of give, so we use ½” thick.
When the gasket does builds up with material, and normally it will, the door has to back off by that amount; and when the gasket is cleaned the door has to go back to its original position, in other words, self-adjusting. This is where OTDC fails miserably, and it’s adjust the turnbuckles or whatever. Some mechanisms have many pivot points that are not in bearings or bushed, and these wear.
Once we know how much the gasket compression is, all other tolerances and deflections must be kept within the number or the door will leak. Doors deflect from side to side, end to end, and the hinge shaft will have radial deflection, and in our system long shafts will bow in the center because of the pressure. The hinge shaft rotates in bearings and the shafts are sealed.
Drop Bottom Discharge 100 cu. ft. Double Rotor
We hold the weight of the load on the door with two air cylinders on each door, and don’t use the full stroke so they self-adjust. We use specific ratios as standard of the air cylinder torque vs. the load torque.
The drop bottom doors are made so they can be safely removed and re-gasketed. This is outlined in our Maintenance Manual.
There are a dozen other details that have to be done. If you would like to know more, please contact us.
We don’t like dead spots in a mixer so most of our discharges are flush inside. If you don’t need a drop bottom machine, buy a port discharge machine because they are so much easier to clean and maintain. We can also put as many as 3 port discharges on the machine to direct the product to multiple destinations, and all will discharge in 15 to 30 seconds.
Single Port Discharge with access doors to cleaning and maintenance.
Just in case you don’t think there is a difference in seals, take a look at this:
Material lost in 4 days of production. We got this fixed with our
packing gland system, and also some others.
All seals have a tolerance on the shaft wobbling called runout or Turn Indicator Radius (TIR), and skew which is the measurement of the seal being perpendicular to the shaft. Typical tolerances except for mechanical seals are less than 0.010” (0.25 mm) TIR, and less than 0.015” (0.38 mm) skew.
We set our standards at 0.005” (0.13 mm) TIR, and 0.010” (0.25 mm) skew. This means that the rotor and end plates have to be designed so they can be re-straightened, and develop manufacturing practices so you hope they don’t have to be re-straightened. False thinking is that the end plate doesn’t matter because bearings will self-align. That is true, but seals won’t self-align.
All our mixer shafts are slow speed, less than 60 rpm, but we have a high speed shaft on our Shearmaker, 3450 rpm. As a general rule we will use seal materials up to 50% of their surface speed rating without lubrication. All our seals run dry.
Lip seals are very useful for discharge door shafts and on small machines we will use two lip seals with air between them so we have an air purge that works at 10 psi and 2 cfm. Lip seals come in many materials now. Life is very good. We have had up to 5 years on sugar. However, when they do fail, the drive and bearings have to come off to change them.
Dual lip air purged seal
Controlled Orifice Air Purged (COSAP) – Patented
An air purge seal is a conveyance device that is supposed to carry the ingredients away from the seal. This needs a constant velocity.
You can’t accomplish this with air purged packing glands, chevrons or lip seals. The former is because you have one male follower that is supposed to give two different levels of pressure. The outside rings are supposed to hold air from escaping while the inside ones are supposed to be loose enough that air flows through at a constant velocity. Until we are convinced this will work, we will not build them.
The lip seals problem is that where you can see it (and this is a great hindrance in designing seals) the seal will build up pressure and blip.
The size of the blip varies, therefore the velocity varies.
We tried mechanical seals without success. There is no warranty on seals and some of them failed before they left the shop. There were no parts in stock. It got so our men didn’t even want to try to work with them. So we took them all back under warranty and changed to our own designs. Cost us 20K.
This is why we developed a seal that the blip or orifice can be controlled and therefore velocity would be a constant. We are inserting turbulent air and trying to make it laminar, and even NASA does not have a formula for this. Everything becomes empirical.
We solicited some help in both establishing the parameters for design and the actual design itself. We had some great contributions on both from engineers, shop people, and constructive criticism from our customers, which is always welcome. We went through 3 design phases—the first two were adjustable, and now we have a fixed design that can stand air interruptions. We also had to tighten our tolerances and manufacturing practices.
The COSAP is an assembly of several parts including a replaceable shaft sleeve. The sealing is a film of air around the shaft at a specific velocity. The input required 1 to 1.5 cfm @ 10-12 psi. A key component is a precision machined Orifice Plate.
This is particularly advantageous on high speed shafts with average life of 2 years. We can put a machine out with 10 Shearmakers to do 50 tons per hour, and the machine works without significant downtime for maintenance.
We also use it on slow speed mixer shafts where we have a solid to split replacement sleeve. It can be serviced without removing the bearings.
COSAP on a dual shaft mixer mixing a sugar
based product with fine powders.
It is cheaper than mechanical seals and replacement parts are in the hundreds of dollars, not thousands. They are not a replacement for other people’s mixers because they are not made to tight enough tolerances.
The problem with packing glands is that when they start leaking the shaft is compromised. And after a while, the shaft looks like this:
Before and after we repaired it with our system, and now
they don’t have to sweep the floor.
There are three definite upsides to packing glands:
- They are easy to repair. We can guide someone over the phone who has some mechanical ability.
- Seals never fail when the machine is idle. It always happens when you are in a production run. With the PG, you can stick another piece of rope in it in 10 minutes and be back in business.
- Repairs are usually comparatively inexpensive although good packing is getting pricy.
So why not tackle the downsides, which is what we did. First we spring-loaded it to prevent the start of leaking. We put a heat treated sleeve on the shaft, solid to split, to protect the shaft. The sleeves have a very long life—10 years? The receiver is split, so when you do a preventative maintenance recommended once per year, you can get complete access to clean the area. Once a month the spring washers should be kept tight without gaps.
Spring loaded packing gland with replaceable
heat treated shaft sleeve.
As inventors and innovators we have often led with our chin and we have had some bad experiences to get to what we offer today. Since starting with our patented rotor system in 1995, we have never had a real disaster and never took a machine back because it did not do what we said.
We started with a set of criteria to manufacture good machinery, and we have people trained, motivated and proud to turn out a good product. The better we get, the higher our customers set the bar, and we enjoy the challenge.
There are a lot of claims made and the difference with A & J is that we are hands-on.