Valve Magazine - Spring 2008

Connections

Pipe can be provided with plain ends, threads or mechanical connections. Before the perfection of pipe welding techniques 75 years ago, most piping was supplied with threads on each end. Through the use of couplings and threaded pipe fittings, pipelines and piping assemblies were created. Making a leak-free connection on a 40-foot joint of 6-inch threaded pipe took quite a bit of muscle power, a bucket of “pipe dope” and a giant-sized pipe wrench!

Today, virtually all industrial piping is welded. Properly welded pipe joints have high integrity and they are much faster to make than by threading fittings to each piece of pipe. In the waterworks industry mechanical connections are used to join most large diameter water and wastewater lines. These mechanical connections employ a bell and spigot or

grooved-end design, combined with a resilient seal and bolting mechanism to lock the joint in place. Mechanical joints are also popular because they allow for a slight misalignment to permit pipe runs to dodge around obstacles without the use of curved pipe or excessive use of elbow fittings.

From Homes to Industry If you have walked through a house under construction or made a wrong turn down one of the big box store aisles, you have probably seen white plastic PVC piping. While not allowed in most industrial plants, the plastic pipe forms the basis of nearly all residential piping. PVC pipe as used in home construction is usually schedule 40, and it is welded to PVC fittings and valves using a plastic solvent. For some low-pressure, highly corrosive industrial applications, plastic

ISO 9001:2000

Our Reputation

is Stainless™

CIRCLE READER RESPONSE #31

pipe made of exotic materials such as Kynar and Kalrez is used.

Industrial facilities and power plants require a maze of piping that twists and turns in all directions. Small-diameter pipe is welded to fittings to achieve direction changes in the pipe runs, while larger pipe is bent. Steel pipe of virtually any size can be bent to any angle. This process creates what is called “ fabricated” piping that is formed to the exact geometry called for in the piping blueprints. The prefabricated pipe sections are then shipped intact to the job site where they are joined with other fabricated sections. This off-site fabrication saves time and money as well ensuring more accurate construction.