Bonds and Connections How to use Cement for Save Connections in Pipeline Engineering
Solvent cementing is an ideal and proven jointing method for numerous applications in industrial pipeline engineering, one example in particular being pipelines used to transport aggressive chemical media. Two examples in the article demonstrate the advantages of this method.
Cementing is one of the oldest jointing methods known to man. Even in primeval times a distillate made of birch bark was used to fasten arrowheads. Since then, many materials have been used to manufacture adhesives. The first patent for adhesives was issued in the middle of the 18th century. In the early 20th century, the development of synthetic substances paved the way for industrial adhesives. The breakthrough for cement bonding in industrial applications was the manufacture of cyanoacrylate adhesives, first achieved in 1960. Adhesives have become indispensable in industry and private households. There are no less than 250,000 types on the market today.
Cement bonding is a highly developed jointing technology and therefore used in applications with stringent specifications, such as the automotive industry, aircraft construction or pipeline engineering. The primary focus is on quality and safety demands.
In the past, only insulation and interior paneling were glued in automobiles; in the meantime, however, body parts, brake linings and other bearing components are joined lastingly with adhesives. The applications in aircraft construction indicate that adhesives are indeed resilient; the joints withstand temperatures far below freezing, intense UV radiation and the enormous forces caused in turbulence.
Cements for piping systems
Easy and fast installation, low maintenance costs and absolute resistance to corrosion and incrustation are what make plastic piping systems an attractive alternative to metal systems. ABS, PVC-C and PVC-U are solvent cementable plastics.
When constructing industrial piping systems, it is essential that the connections between pipes and fittings or valves are not only easy and quick to assemble, but also 100 % dependable under critical application conditions. The conveyed media can reach temperatures between -60 °C in cooling applications and 70 °C in chemical processes. Pressures up to 16 bar are also not uncommon. When acids, alkalis and other chemicals are used, the solvent cement joint must be just as resilient as the piping component itself. A reliable and completely leakproof connection must be guaranteed throughout the entire lifetime of the system, which is often 20 years or more.
The bonding process with cement is often referred as “chemical fusion”. The term accurately describes the process because the material of the pipes and fittings is liquefied and then bonded cohesively like in the fusion process. Such a homogenous joint is achieved largely through the composition of the cement. The solvent cements used by GF Piping Systems contain up to 20 percent of the raw material from which the fittings and pipes are made. In conventional fusion, heat is applied. In cement bonding, the solvent in the adhesive causes the liquefaction.