Internal wear of the batch mixer--part 3.Both the Banbury Banbury (băn`bərē), town (1991 pop. 37,463), Oxfordshire, central England, on the Cherwell River. Light industry and tourism are important to the local economy. mixer mixer, either of two electronic devices in which two or more signals are combined. In the type of mixer used in radio receivers, radar receivers, and similar systems, a signal is translated upward or downward in frequency. and the Intermix in·ter·mix tr. & intr.v. in·ter·mixed, in·ter·mix·ing, in·ter·mix·es To mix or become mixed together. [Back-formation from obsolete intermixt, from Latin have acquired an excellent reputation as being rugged and effective compounding devices, providing years of service for mixing a broad range of both rubber and plastics compounds. Over the years, applications have emerged that have caused the rapid wearing of specific components of the mixer. New materials of construction and design changes have been necessary to assure an acceptable longevity longevity (lŏnjĕv`ĭtē), term denoting the length or duration of the life of an animal or plant, often used to indicate an unusually long life. . With increased demands being placed on the performance of rubber and plastic products, new formulations, polymers, fillers, reactive reactive /re·ac·tive/ (re-ak´tiv) characterized by reaction; readily responsive to a stimulus. re·ac·tive adj. 1. Tending to be responsive or to react to a stimulus. 2. and chemical additives have been developed. Many of these new materials and formulations are extremely abrasive abrasive, material used to grind, smooth, cut, or polish another substance. Natural abrasives include sand, pumice, corundum, and ground quartz. Carborundum (silicon carbide) and alumina (aluminum oxide) are important synthetically produced abrasives. to mix, and some contain potentially corrosive corrosive /cor·ro·sive/ (kor-o´siv) producing gradual destruction, as of a metal by electrochemical reaction or of the tissues by the action of a strong acid or alkali; an agent that so acts. chemicals and emit TO EMIT. To put out; to send forth, 2. The tenth section of the first article of the constitution, contains various prohibitions, among which is the following: No state shall emit bills of credit. corrosive gases during the mixing process. The compounding of these new products requires the mixer to be manufactured using specific materials of construction based on the application. Besides the importance of selecting materials of construction that minimize mechanical wear and optimize optimize - optimisation corrosive resistance, the effect of these materials on the stick/ slip phenomenon required for efficient mixing and for a clean discharge from the batch mixer must also be considered (ref. 1). The compound must flow properly in the mixer to as sure efficient mixing, and must release from the internal surfaces of the mixer when the mix is complete. Improper
Although not covered not covered Health care adjective Referring to a procedure, test or other health service to which a policy holder or insurance beneficiary is not entitled under the terms of the policy or payment system–eg, Medicare. Cf Covered. within the text of this article, the design of the dust and fume fume Occupational medicine A solid suspension resulting from condensation of the products of combustion. See Inhalant Vox populi verbTo be in the midst of a mental mini-meltdown. collection system is also important and can have a dramatic effect on the life of the mixer. It is important that generated corrosive gases be quickly and safely removed from the mixing machinery. It is equally important that the dust and fume collection system be able to capture and handle the effluents from the mixing process, but not be so aggressive that critical components of the mix, such as light fillers or minor concentrations of critical powdered chemicals, are removed from the mixing chamber. In last month's Process Machinery column (March 2006), the batch mixer and the mixing process were examined, along with fume and dust removal. Wear observed in the mixer It is through field inspection of mixers and the standard practice of rebuilding machinery where the returned machine is cleaned, disassembled and inspected that we have been able to document wear and the effect of mixing on various mixer designs and materials of construction. Such innovations as replaceable throat and wear plates, rotor rotor: see generator; motor, electric. wear rings, as well as the use of specialty hard surface coatings Surface coating A substance applied to other materials to change the surface properties, such as color, gloss, resistance to wear or chemical attack, or permeability, without changing the bulk properties. for particular compounds, have been developed. Figure 13, displaying different components of a Banbury mixer, shows the effect of wear seen in different applications on specific materials of construction of the mixer. The categorizing of the type of wear is interpretive in·ter·pre·tive also in·ter·pre·ta·tive adj. Relating to or marked by interpretation; explanatory. in·ter  pre·tive·ly adv. and arbitrary. In fact, the wear observed in each
case is most likely a combination of various wear mechanisms imposed by
the mixing process.Sides Abrasive and corrosive wear has been seen in the body bore. Chemical wear has been seen on the mating parts of the sides, end frames, rotor end plates and the hopper A tray, or chute, that accepts input to a mechanical device, such as a disk duplicator or printer. In the days of punch cards, millions of cards were numerically or alphabetically organized by placing them into the hopper of a card sorter, taking them out of all the stackers and putting assembly. Rotors Abrasive wear is observed primarily on the leading and trailing angle of the rotor wing (rounding of the rotor wing tip) and at the start of the rotor wings at the rotor end plate. In cases where a porous porous /por·ous/ (por´us) penetrated by pores and open spaces. po·rous adj. 1. Full of or having pores. 2. Admitting the passage of gas or liquid through pores. hard surfacing has been applied for wear, corrosive wear has been seen as the corrodent Cor`rod´ent a. 1. Corrosive. n. 1. Anything that corrodes. penetrated the coating. Also, corrosive wear has been seen when a protective chemically resistant coating has been worn through and the base metal is exposed. Rotor end plate/end frame Abrasive wear has been seen on the face of the rotor end plate that is exposed to the mixing chamber. Corrosive-chemical wear has been seen between the mating parts between the rotor end plate and the sides/end frame of the mixer. Door top The door top has seen both mechanical and chemical wear on the working face of the door top. Impact wear is seen on the contacting face where it seals against the sides of the mixer. Weight rod History has shown that there is very little abrasive or impact wear on the weight. Chemical wear attacking the entire surface of the weight seems to be of most concern. There is a number of applications where the weight has to be constructed out of stainless steel stainless steel: see steel. stainless steel Any of a family of alloy steels usually containing 10–30% chromium. The presence of chromium, together with low carbon content, gives remarkable resistance to corrosion and heat. to prevent corrosion. Chromed weights have been supplied for the ease of cleaning. The base metal of these weights is cast steel. It now becomes an issue if a steel weight is used within a steel hopper rather than a cast iron weight within a steel hopper. Mixer hopper and throat and wear plates Replaceable throat and wear plates were designed because of severe wear observed in the lower part of the single piece hopper. The following questions must be asked when addressing the wear effects of compounding in the batch mixer: What potentially corrosive ingredients will be mixed and in what concentration? What (if any) corrosive by-products by-products materials generated incidentally to the production of a principal product in an industry or industrial enterprise. In the meat industry by-products include blood, bone, fat, bristle, hair, wool, hide, skin, hoof, horn and offal products prepared in various ways for use or gaseous gas·e·ous adj. 1. Of, relating to, or existing as a gas. 2. Full of or containing gas; gassy. vapors vapors, n.pl See inhalants. vapors Vapours Medical history An 18th century belief that nervous illness in ♀ resulted from vapors produced by the uterus which affect brain. will be generated during the mixing process, and how much will be generated (potential concentration)? What potentially abrasive ingredients will be mixed and in what concentration? Do I have product release problems which can be caused by the use of specific hard coatings or metals for the internal working surfaces of the mixer? Do I have a product that requires maximum heat transfer, dictating the use of a hard surface coating with good heat transfer characteristics? It is through communication with the machine manufacturer as to the application of the mixer that a mixer can be specified which will offer the longest service life for the proposed application. Currently, we have over 31 surface coatings and eight types of base metal options available to address issues of mechanical and chemical wear in selected parts of the batch mixer. Further, there are multiple materials such as specialty cast irons, various grades of carbon, tool and stainless steel available for use in the manufacture of the mixer. The first mixer bodies were produced primarily out of cast iron. Shortly thereafter, rubber hang-up issues in the mixing chamber resulted in the application of chrome (jargon) chrome - (From automotive slang via wargaming) Showy features added to attract users but contributing little or nothing to the power of a system. "The 3D icons in Motif are just chrome, but they certainly are *pretty* chrome!" onto the surface of the rotors, side and drop door for release. The inspection and eventual disassembly dis·as·sem·ble v. dis·as·sem·bled, dis·as·sem·bling, dis·as·sem·bles v.tr. To take apart: disassemble a toaster. v.intr. 1. of mixers showing signs of wear identified areas of the machine requiring different materials of construction, as well as the need for specialized spe·cial·ize v. spe·cial·ized, spe·cial·iz·ing, spe·cial·iz·es v.intr. 1. To pursue a special activity, occupation, or field of study. 2. hard coating in specific areas. As the rubber industry matured, higher speeds, shorter cycles, high torque requirements and the mixing of higher viscosity compounds forced a review of all mixer major components leading to the use of cast and wrought steel plate for many of the highly stressed mixer components. The mixing of highly abrasive materials, such as floor the formulations, silica silica or silicon dioxide, chemical compound, SiO2. It is insoluble in water, slightly soluble in alkalies, and soluble in dilute hydrofluoric acid. Pure silica is colorless to white. and Ti[O.sub.2], resulted in the rapid wear of the internal surfaces of the mixer. The use of iron, cobalt Cobalt, town, Canada Cobalt (kō`bôlt), town (1991 pop. 1,470), E Ont., Canada, NE of Sudbury, near Lake Timiskaming. Once a center for cobalt and silver mining, the area is now economically depressed. and nickel nickel, metallic chemical element; symbol Ni; at. no. 28; at. wt. 58.69; m.p. about 1,453°C;; b.p. about 2,732°C;; sp. gr. 8.902 at 25°C;; valence 0, +1, +2, +3, or +4. based hard surface coatings was introduced. Design changes were made which would allow relatively quick replacement of wearing components. Concurrently, it was discovered that in many applications corrosive effluent effluent waste from an abattoir carried away in liquid form. Disposal is a major problem because of the need to avoid pollution of waterways. See aerobic effluent treatment, anaerobic effluent treatment. gases were being generated within the mixer during compounding. These gases penetrated the porous chrome surfaces of the internal components of the mixer, causing a loss of the chrome, as well as the rapid loss of the base metal of the mixer. The corrosive gases/vapors also penetrated the mating area between metal parts, creating crevice corrosion Crevice corrosion is a corrosion occurring in spaces to which the access of the working fluid from the environment is limited. These spaces are generally called crevices. Examples of crevices are gaps and contact areas between parts, under gaskets or seals, inside cracks and seams, issues. Special (crack free) coatings have been and are being developed and tested to protect against specific corrosive agents. Due to wear, the design of the mixer has been changed and the materials of construction are now specific to the compounding application. Typical materials of construction are presented in table 6. The base metal used for specific applications depends on the tensile tensile, adj having a degree of elasticity; having the ability to be extended or stretched. and yield strengths, corrosion resistance and manufacturing requirements for specific components. The internal working surfaces of the mixer in most applications need some type of surface coating or treatment to protect the mixer against mechanical wear. Also, the surfaces of some of the structural components of the mixer which come in contact with high concentrations of the corrosive gases and vapors generated during the mixing process need protection as well. There is a number of options available that can be used to protect the base metal and extend the usable USable is a special idea contest to transfer US American ideas into practice in Germany. USable is initiated by the German Körber-Stiftung (foundation Körber). It is doted with 150,000 Euro and awarded every two years. life of the mixer. In all cases, the internal surfaces of the mixer contacting the mix must support the mixing mechanism of the batch mixer and must allow for a clean release of the product from the mixing chamber. Table 7 lists the categories of wear protection options that are currently available. Through exhaustive studies and years of data collection, it has become possible to establish specifications for the materials of construction for the batch mixer for specific applications. Figure 23 and table 8 present selected data of comparison for the materials of construction for an internal mixer for general purpose applications, an extreme mechanical wear application and for an extremely corrosive application. [FIGURE 23 OMITTED] Conclusions With the changing demands of the rubber and plastics industries, it is increasingly important that the compounder not only be aware of the type of mixer that is best for his application, he must also know the abrasive and corrosive nature of the products he is expected to mix. Knowledge of the effects of available base metal materials of construction, as well as that of the available surface treatments, can greatly extend the usable life of the mixer. It is through working with a qualified vendor of machinery that the proper selection of materials of construction can be made that will optimize the service life of machinery in application. References 1. "Effect of full-slip condition along rotor on the mixing efficiency of internal mixers', " Antec 2003, University of Louvain & Michelin Clermont-Ferrand, France. 2. Merriam Webster Webster, town (1990 pop. 16,196), Worcester co., S Mass., near the Conn. line; settled c.1713, set off from Dudley and Oxford and inc. 1832. The chief manufactures are footwear, fabrics, and textiles. On Line. 3. Elements of Physical Metallurgy metallurgy (mĕt`əlûr'jē), science and technology of metals and their alloys. Modern metallurgical research is concerned with the preparation of radioactive metals, with obtaining metals economically from low-grade ores, with , A.G. Guy Addison Addison, village (1990 pop. 32,058), Du Page co., NE Ill.; inc. 1884. An industrial suburb of Chicago, it manufactures machinery and plastic items. , Wesley Publishing. 4. Friction and Wear of Engineering Materials, I.M. Hutchings, 1992. 5. Handbook
This article is about reference works. For the subnotebook computer, see .
6. Dictionary of Scientific and Technical Terms, McGrawHill
Table 6--typical materials of construction
Description Type Comment
Cast iron, i.e., Multiple -- Low cost and high strength
-- Grey grades and
-- Ductile properties -- Difficult to weld and hard
-- Malleable surface
-- High tensile
-- Varying composition based
on application and use
Low and high alloy Multiple -- Medium cost to high cost
steels, i.e., grades and
properties -- Wide variety of strength,
-- Cast steels chemical resistance,
-- Wrought steels abrasion resistance
-- Tool steels
-- Stainless steels
Table 7--base metal protection options
Surface treatment - Quenching and tempering
- Shot peening
- Nitriding
Surface coating - Chrome and iron, nickel and cobalt based
matrix materials with different compositions
of boron, carbon, chrome, copper, magnesium,
molybdenum, silicon, tungsten and/or vanadium
Specialty plate - Iron, cobalt and nickel based alloys and
and castings composites
Table 8--Banbury mixer materials of construction
Mixer Standard Mixer Highly abrasive Highly
component applications corrosive
applications
Hopper sides, Cast iron and Cast iron and Stainless steel
charging door wrought steel wrought steel Base metal
and back door offers
No special Chromed surface protection for
protective for improved corrosive
coatings mechanical applications
required wear resistance
Floating Cast iron Cast steel Stainless steel
weight
No special FA # 27 (iron Base metal
protective based alloy) offers
coatings on bottom for protection for
required improved corrosive
mechanical wear applications
resistance
Replaceable Wrought steel Wrought steel Stainless steel
throat and
wear plates No special Chromed surface Base metal
protective for improved offers
coatings mechanical protection for
required wear resistance corrosive
applications
Rotors Cast steel Cast steel Cast steel
- Rotor tips
- Rotor body FA #12S (cobat FA #27 (iron FA #22 (cobalt
based alloy) based alloy) based alloy)
- standard FA #28A - FA #22 (cobalt
thickness (nickel based based alloy)
chrome alloy)
(coatings for
(coatings for (coating for extreme
mechanical wear extreme corrosive wear
resistance) mechanical wear resistance)
resistance)
Rotor end Wrought steel Wrought steel Stainless steel
plates
Standard chrome FA #26A (nickel FA #26B (nickel
on working face based alloy) based alloy)
(coating on (coating on
internal face internal face
for mechanical for mechanical
wear and corrosive
resistance) wear
resistance)
Drilled side Wrought steel Wrought steel Wrought steel
- Frame
- Liner (bore) Dual metallic Dual metallic Tri-metallic
steel liner steel liner and liner (steel,
and FA #13 FA #19 (iron stainless steel
(iron based based alloy) and FA #13B
alloy) iron based
(coating for alloy)
(coating for extreme
mechanical wear mechanical wear (special
resistance) resistance) construction
for mechanical
and corrosion
wear
resistance)
Drop door Cast steel Wrought steel Wrought steel
FA #27A (iron FA #26A (high
Chromed surface based alloy) nickel based
for product alloy)
release and (coating for
mechanical wear extreme (coatings for
resistance mechanical wear extreme
resistance) corrosive wear
resistance)
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