Plough Shear Mixer

Plough shear mixers are widely used to mix many thousands of products, from flour powder and plastic resins to chemical additives and cosmetics. Plough Shear Mixer is designed for heavy duty blending of both dry and wet materials. The choppers in the bottom of plough shear mixer could break the lumps and little balls when adding liquid additives during mixing.

Key Design Considerations

Drive design The first variables to consider in powering the blender are always product density, volume and moisture content. But from that point on we must consider the needs of each application individually. Specifying the right drive requires effective communication between the equipment manufacturer and buyer to identify key process needs. Slow-speed starting – Over the years, many plough mixers were built without any provision for starting at slow speed. Unfortunately, a dead load start presents many disadvantages, all of which increase costs. The buyer must choose between using an over-sized motor that is capable of delivering the peak horsepower needed to get the batch moving or a smaller motor that is appropriate for powering the blender once it is running. The first choice is wasteful, since the larger motor is a glutton for power and its initial purchase price is high. The second choice is risky, since the high torque at start-up over-stresses the system and eventually causes maintenance problems. Electronic starting systems offer a more practical choice. Electronic soft start controllers can be programmed to allow a slow start under full load and protect the system against a spike in start-up torque in the drive train. Experience tells us that they are more reliable, require less ongoing maintenance, and cause less downtime.
Another alternative is to rely on a variable frequency drive (VFD) to start the blender at slow speeds. New generation VFD’s are capable of safely soft starting mixer even with high-density applications. They also provide convenient speed control anytime during the blending and discharging cycles unlike electronic soft starters that allow slow speed only when starting. The functionalities for soft start, overload protection, adjustable starting torques and speed control make VFD’s the best performing and cost-effective option.
Variable speed blending – The ability to blend at varying speeds can be extremely advantageous in many circumstances. It is essential for virtually any R&D application. It can also be useful in any plant where numerous products are blended and changeover is common on the process line. By adjusting the peripheral speed of the plough, you can “tune” the blender to reach the greatest possible efficiency for each product. When blending friable materials, in particular, the variable drive allows you to blend at a speed just below the threshold at which the material will start to degrade. Direct drive vs. belt drive – Today, a direct drive is usually the most efficient choice, since it is extremely compact and reliable. A belt drive system suffers from losses in horsepower and efficiency through belt slippage. Belts also impose overhung loads which can limit the longevity of motor/reducer bearings. Their limited flexibility typically cannot accommodate high start/stop blending cycles. Belts “stretch” during their life especially when new so a plough shear mixer system would require tension adjustment when first installed and as the belt wears or stretches. By comparison, direct drive systems deliver better operating efficiency, performance and many practical advantages. Because overhung loads on the motor and reducer-shaft bearings are eliminated in one-piece motor reducers, service life is longer. Maintenance required to align and adjust belts and couplings is eliminated as well. Plough shear mixer design and interior finish. At first glance, plough design are new in recent years. Naturally, the plough is specified to provide sufficient surface area and peripheral speed to move the bulk.
For every minute that your blender is committed to discharging and cleaning, production is sagging. So, efficient discharge has become another important focus in plough shear mixer design. Fast discharge is a function of axial pumping action – and the discharge valve design. Complete discharge requires close clearances and a clean design in the interior trough.
All interior angles must be radiused to prevent material from collecting in corners. Clearances should be 1/8” or less at the bottom of the trough. Welds should be ground and polished, even for non-sanitary applications. Seals and valves. Recent developments in seals, packing systems, and shaft design have made plough mixer more reliable and versatile. This is a welcome development, since the shaft and packing in a plough mixer are submerged in the product zone. Improved seal integrity always helps to insure against contamination. Especially when blending abrasive materials, and when contamination is a critical concern, air-purged seals help to prevent material from attacking the packing material and shaft. (Nitrogen is used when blending materials that are prone to oxidation.) In industries that require sanitary blending, Teflon o-rings are commonly used to provide a seal that is reliable and easy to clean quickly. In many pharmaceutical applications, for example, the split packing is easily opened and cleaned after every batch.
The valve most often specified for a plough shear mixer is a pneumatically-actuated sliding gate valve. But for special applications – vacuum operation, for example – alternative valves are sometimes required. A spherical disk valve provides a positive seal during vacuum blending, while it also offers a large discharge port for fast discharge.
After choosing the desired features you should contact the manufacturer and run a test on your product, in the manufacturers Test Center or in your own factory. Nothing beats the satisfaction of knowing that you have chosen the best possible design for your requirements.