Reliable Pumps for Abrasive Material


Written by:
Sergio Avila, Pump Solutions Group

Solid-body plastic AODD pumps deliver the operational ability required for challenging abrasive-handling applications.

The originator of the epigram, “Laws are like sausages; it’s better not to see them being made,” is unknown although it is generally attributed to the 19th century German statesman Otto von Bismarck. The sentiment that it portrays, however, is easy to grasp: While we may like and respect the outcome, sometimes it is best not to know how it was reached.

This can also apply to the manufacturing industry. The shine on the chrome of an automobile or a mirror-like reflection on the surface of a highly glazed piece of pottery may dazzle, but most consumers really have no idea just how harsh the manufacturing conditions are to produce the desired end result. Innumerable objects that we see and use in our daily lives only achieved their final form after a harsh production process that may have included the use of any number of abrasive media to create the finished product.

This article examines several manufacturing applications or components in which abrasive chemicals are used and the best type pump technology to incorporate in those processes. Choosing the right pump will not only ensure that the desired final product is produced, but that the entire manufacturing process will be completed efficiently and effectively at a cost-conscious rate and with a minimum of pump maintenance and downtime.

Abrasive Material Challenges

While consumers may be blissfully unaware of the trying conditions required to produce their favorite piece of jewelry or the ink that is used to print the words on their daily newspaper, the manufacturers of those, and thousands of other products, are not. The conditions in which their products are created must be a front-of-mind concern for manufacturers, as are the specific pieces of equipment that are used to complete the process.

Examples of the types of manufacturing processes or components that can require abrasive chemical compounds are discussed in this section.

Pickling Baths

When metal is “pickled,” in a process that is also known as tarnision, a surface treatment is used to remove any impurities, such as inorganic contaminants, stains, rust or scale that can discolor the steel. The pickling bath, or tarnision liquor, that is used to facilitate this treatment primarily consists of hydrochloric acid, although steels with an alloy content greater than 6 percent must be pickled in two stages—the initial hydrochloric acid stage, followed by submersion in another strong acid, such as nitric, phosphoric or hydrofluoric.

An AODD pump in a slurry transfer application in Korea

In jewelry-making, pickling is used to remove the oxidation layer from copper, which occurs after heating. The waste product from steel pickling, known as pickling sludge, includes:

  • Acidic rinse waters
  • Metallic salts
  • Waste acid

All the components that make up this pickling sludge make it a hazardous waste that needs to be neutralized with lime before it can be disposed of in a landfill.

Silicon Carbide Slurry

Slurry is a generic term for any thick suspension of solids in a liquid. Silicon carbide slurry is used in a variety of applications in the construction, ceramics, paper and explosives industries, among many others. It is made from a mixture of powdered silicon carbide that is suspended in polyethylene, diethylene glycol or an oil-based fluid. Silicon carbide is an extremely hard, durable, heat-resistant compound.

Grains of silicon carbide can be sintered together to help form hard ceramics that can be used in the manufacture of such diverse products as:

  • Solar cells
  • Car brakes
  • Bulletproof vests

Because of its degree of hardness, silicon carbide is often used as a cutting liquid, or slurry, in the manufacture of solar cells and wafers.

Most silicon carbide slurries are mixed by the manufacturer, who purchases the silicon carbide powder by the size of the “grit” needed and then mixes it with the preferred liquid. Once the slurry is created, it is pumped to storage tanks until needed.

Electroplating

Electrodeposition is the name of the process used in electroplating. In the electrodeposition process, metal ions in a solution are transferred via an electric field to coat an electrode. It is primarily used to deposit a layer of material, such as a metal, on an object in an attempt to give it a preferred property—such as wear resistance, lubricity or corrosion protection.

The electrodeposition process occurs when the components are introduced to an electrolyte solution that contains one or more dissolved metal salt(s) and other ions that enable the flow of electricity. Depending on the object to be plated, the electrolyte solution can be extremely abrasive.

Printing Inks

Printing inks are divided into two categories: writing inks and printing inks. They are further divided into two distinct subcategories—ink for conventional printing (where an image is transferred to the paper or object to be printed via mechanical plate) and ink for digital, non-impact printing (electrophotographic and ink-jet technologies).

Many components that make up inks can be abrasive. Color inks, for example, are made with a solvent that is generally produced from petroleum distillates, linseed oil or soybean oil, while the pigments are made of dyes. Titanium dioxide can be used to adjust the color characteristics of color inks. All inks may also contain additives such as:

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