Malleability, construction materials

Pumps may also be classified according to the primary construction materials. As illustrated in Figure 3.3, pumps are classified as metallic or nonmetallic, depending on the material used for the eluent flow path. The most commonly used material for HPLC pumping systems is 316 stainless steel because of its mechanical strength, corrosion resistance, good thermal stability, and malleability only a handful of HPLC solvents, such as hydrochloric acid, will cause damage to 316 stainless steel. 

As we have seen, the characteristics of metals that permit them to function as enormously versatile construction materials are their ductility, malleability, and strength. The last of these characteristics needs no explanation at this time, but the first two are related to the ability of the metal to be fabricated into a desired shape. Metals vary widely in these characteristics, and a metal or alloy that is well suited to one use may be entirely unsatisfactory for another. Addressing this branch of applied science is beyond the scope of this book, but a book on materials science provides a great deal of information that is relevant for students of inorganic chemistry. 

Typical applications for this type of conveyor are in the heavy duty areas of mining or minerals processing or power generation. Their simple geometry and robust nature make them ideal for handling materials such as hot cement, clinker and ash or wet mineral ores, coal and grain. Construction materials may be malleable iron or hardened steel for heavier duties. 

Acid Pumps.—When an acid or other corrosive substance is to be handled by a pump no material should be used that is attacked by the substance. For this reason pumps may be constructed either wholly of brass, bronze, rubber or even stone ware, or wholly of iron or they may be merely bronze fitted, which means that certain working parts such as pistons, rods, pump pistons, etc., are made of bronze or bronze lined. In ordering bronze or brass-fitted pumps it should be clearly specified what parts should be made of bronze or brass. In an all-iron pump the pump cylinder is bored to size and has no lining. The valve seats and stems are made of malleable iron. 

Effect of temperature on choice of material of construction and roll design Modern roll presses will often handle hot materials because either the material is produced hot or has been heat processed, e.g. dried, and must not be cooled, or a hot binder has been added, or use of the higher plasticity or malleability of hot (mostly metallic) materials is being made. In the last case, temperatures of the feed material may be as high as 1000°C. 

In mediaeval times, wort was boiled in iron cauldrons over open fires but as the scale of production increased, the vessels were covered over and fitted with a chimney or stack to carry steam out of the building. To construct these more complex vessels, copper, rather than cast iron, became the material of choice because of its malleability, superior conductivity and better resistance to corrosion. Accordingly, vessels in which wort boiling is carried out are often called coppers , even if the metal of construction is not copper. Other terms used are kettles or wort boilers. ... 

Aluminium is a silver-white metal which is very light it is a good conductor of heat and electricity, malleable (easily beaten or rolled into sheets) and ductile (readily stretched) and of a high tensile strength. The metal slowly oxidizes in moist air, a thin protective film of oxide being formed. It is attacked by dilute hydrochloric acid, concentrated sulphuric acid, sodium hydroxide, potassium hydroxide, and brine, but is almost unattacked by nitric acid in all concentrations. Its alloys with copper are called aluminium bronzes. Its many uses as a material of construction, as the metal or its alloys, include hoppers, drums, ventilation hoods, and ducting, utensils, and electric conductors. 

Important physical properties of the material being elevated are particle size, lump size, moisture content, angle of repose, flowability, abrasiveness, friability, and so on. The design of the buckets has to do, principally, with capacity and ease of discharge. They may constructed out of malleable iron or steel and can be shaped with either sharp or round bottoms, as illustrated in Figure 3.27. 

---