Mixer mounting

Axial-Flow Fluidfoil Impellers For vessel volumes of 4 to 200 m (1000 to 50,000 gal), a turbine mixer mounted coaxiaUy within the vessel with four or more baffles should be the initial choice. Here also the vessel straight-side-height-to-diameter ratio should be 0.75 to 1.5. Four vertical baffles should be fastened perpendicularly to the vessel wall with a gap between baffle and wall equal to Df/24 and a radial baffle width equal to Df/12. 

Table 21-7 Recommended Beam Sizes" [in. x Ib/ft] for Mixer Mounting...

Vertical forces downward on a mixer mounting come from the weight of the motor, drive, shaft, and impeller. Vertical forces upward are caused by pressure... 

Butyl and polyisobutylene latices are very low in viscosity and therefore are normally compounded with quite simple equipment, typically a propeller mixer mounted on a closed tank. When maximum filler dispersion is required, ball mills or similar equipment may be necessary for part of the mix. 

A widely used type of pump—mixer—settler, developed by IsraeH Mining Industries (IMI) (115), is shown in Figure 13a. A unit having capacity 8.3 m /min (2000 gal /min) has been used in phosphoric acid plants (116). The unique feature of this design is that the pumping device is not required to act as the mixer, and the two phases are dispersed by a separate impeller mounted on a shaft miming coaxially with the drive to the pump. 

Planeta-iy Type. Paddles or whips of various configurations are mounted in an off-center head that moves around the central axis of a bowl or vessel. Material is mixed locally and moved inward from the bowl side, causing intermixing. This mixer handles dry materials or pastes. 

For suspension of free-settling particles, circulation of pseudoplastic slurries, and heat transfer or mixing of miscible liqiiids to obtain uniformity, a speed of 3.50 or 420 r/min should be stipulated. For dispersion of dry particles in hquids or for rapid initial mixing of hquid reactants in a vessel, an 11.50- or 1750- r/min propeller should be used at a distance Df/4 above the vessel bottom. A second propeller can be added to the shaft at a depth below the hquid surface if the submergence of floating hquids or particiilate solids is other wise inadequate. Such propeller mixers are readily available up to 2.2 kW (3 hp) for off-center sloped-shaft mounting. 

Banbury Mixer Preeminent in the field of high-intensity mixers, with power input up to 6000 kW/m (30 hp/gal), is the Banbury mixer, made by the Farrel Co. (Fig. 18-43). It is used mainly in the plastics and rubber industries. The top of the charge is confined by an air-operated ram cover mounted so that it can be forced down on the charge. The clearance between the rotors and the walls is extremely small, and it is... 

Two-Roll Mills These mills contain two parallel rolls mounted in a heavy frame with provision for accurately regulating the pressure and distance between the rolls. As one pass between the rolls does little blending and only a small amount of work, the mills are practically always used as batch mixers. Only a small amount of material is in the high-shear zone at any one time. 

FIG. 18-44 High-intensity mixer (a) bottom scraper (h) fluidizing tool (c) horn tool (d) flush-mounted discharge valve. Henschel Mixers America, Inc.)... 

Portable or fixed mixers up to 5hp normally use propellers and run at either direct drive speeds of 1,150 or l,750rpm or at single reduction gear drive speeds between 300 and 420 rpm. They may either be clamped on the rim of open tanks or mounted with a fixed assembly for open or closed tank operation. These mixers are the most economical and are usually used in tanks without baffles. They are rugged and long-lasting. 

Top entering mixers are heavy duty equipment. They are usually fixed to a rigid structure or tank mounting. Either radial flow or axial flow turbines may be used. Speeds vary from 50 to 100 rpm and usually require a double set of helical gearing or a single set of worm gears to achieve these low speeds. Therefore, they are more expensive than single reduction mixers. 

Figure 5-20 illustrates a vertical propeller mixer assembly, with vertical mounting with gear box and motor. Figure 5-21 is a typical right angle, vertical impeller shaft with horizontal gear and motor drive. 

The important dimensional features and/or ratios for a center-mounted mixer unit (vertical) are [29, 30] ... 

Dished bottom tank, center mounted mixer, 4 baffles... 

Baffles can be omitted when propeller mixers are top mounted at an angular off-center position (see Figure 5-23D) and vortex swirling is prevented. This is not recommended for large povver systems on large tanks, due to shaft fatigue. 

Code of Practice No. 4, Safe and Satisfactory Operation of Propane-Fired Bitumen Boilers, Mastic Asphalt Cauldrons/Mixers, and Hand Tools Code of Practice No. 7, Storage of Full and Empty LPG Cylinders and Cartridges Code of Practice No. 9, LPG-Air Plants Code of Practice No. 10, Recommendations for Safe Handling of LPG in Small Trailer Mounted Vessels, Skid Tanks and Small Bulk Storage Vessels Permanently Attached to Mobile Gas-fired Equipment... 

Propeller/paddle mixers are used to blend or agitate liquid mixtures in tanks, pipelines, or vessels. Figure 38.1 illustrates a typical top-entering propeller/paddle mixer. This unit consists of an electric motor, a mounting bracket, an extended shaft, and one or more impeller(s) or pro-peller(s). Materials of construction range from bronze to stainless steel, which are selected based on the particular requirements of the application. 

Installation of propeller-type mixers varies greatly, depending on the specific application. Top-entering mixers utilize either a clamp- or flange-type mounting. It is important that the mixer be installed so the propeller or paddle placement is at a point within the tank, vessel, or piping that assures proper mixing. Vendor recommendations found in O M manuals should be followed to ensure proper operation of the mixer. 

Mixers should be mounted on a rigid base that assures level alignment and prevents lateral movement of the mixer and its drive-train. While most mixers can be bolted directly to a base, care must be taken to ensure that it is rigid and has the structural capacity to stabilize the mixer. 

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