Mixer Blades

[matthewcsmith]

I've been casually working on a project for a few years now off and on. I've been told several times that plastic blades would do well in our mixers. We are mixing mostly alumina grain based concrete type mixes with very low water content (4-8%).

I have done some trials with nylon & UHMWPE with no success. Does anyone have an experience or know of a company who might be able to help us?

Thanks!

 

[concretemasonry]

I was in the concrete block business for many years and looked for materials that are resistant to the abrasion caused in low moisture (zero slump) concrete mixes.

We used normally available products and worked with "plastic" manufacturers for use in applications in molds (where a single mold is subject to extreme vibration at the cost of $20,000/mold) and to be used on troughs for feeding where there was no continuous vibration or pressure some plastics worked well IF they could be attached compatiibly to the supporting structure and the associated temperature variations.

When it came to mixers (blades and liners), there is nothing that can be equal to the traditional proper (heat treated) liners and blades attached properly. The wear life is good and is predictable, which is great in a manufacturing situation from a scheduling standpoint. Plastic does not have the compatible properties to be attached to rigid frames subjected to vibration and possible temperature variations.

The particle shape of the larger particles is particularly important when it comes to wear under uniform conditions.

We tried hard to be progressive, work with plastics suppliers and the the best options. Apparently plastics manufacturers make a product and then try to find a market for it. The failure modes and unpredictable life of cast or formed blades using plastic coatings/protection is unpredictable if you are in a critical production situation and not just an intermitant situation.

If you have a mixer(s), contact the mixer supplier for assistance. They know more about mixing (especially flow over blades) and wear and constantly trying to find a best way to improve their products. Most have done a lot of actual testing with different blade/drum products/systems in plants that use similar mixer types (band and centrifugal).

Dick

dick

 

[matthewcsmith]

Thanks for your comments Dick.

I've spoken with the OEM and currently purchase metallic blades from them. You are absolutely correct, the metallic blades wear very predictably. The material they are cast from (of unknown chemistry) is incredibly hard (700 BHn) according to one of our foundrys.

Maybe these are as good as it gets!

 

[concretemasonry]

After working for a concrete products company for 20 years, I worked for equipment manufacturer that had been making mixers and replacement blades for over 70 years.

They had their own foundry and heat treating facilities and sold in over 100 countries. Some designs were for a steel shaft and structure with bolt on replacement steel blades ( ribbon/drum mixer of 40 to 120 cf). To protect their market position, they were constantly looking for possible competitive products, but could not find any equal the traditional steel blades made from the proper steel. Many plants schedule blade replacement and liner replacement well in advance to coincide with production requirements. Nothing is worse than an emergency shut down in a concrete products plant.

You will find higher blade and replacement costs on pan/centrifugal mixers, but the mixer type usually depends on the optimum mixing cycle time to achieve ultimate uniformity, especially is the aggregates are dry.

Good luck on your research.

Dick