Compressed air efficiency: A piping system solution

In the Asian and global power industry, maintaining the efficiency of a compressed air system is a constant battle, with leaks being a considerable source of the problem.

In recent years, compressed air lines constructed with press-to-connect and grooved mechanical piping have become popular for their ability to dramatically reduce the pipe joint as a leak source.

Press-to-Connect Systems
Press-to-connect piping systems join stainless steel pipe via a flame-free joining process that creates permanent joints in a matter of seconds.

Pipe is cut to size and deburred, marked for visual verification of full pipe-to-component engagement, then inserted into a lubricated coupling, fitting or valve. A handheld pressing tool is used to press the component containing seals onto the pipe-ends, providing a positive mechanical interlock and creating a precisely compressed, rigid joint.

Sealing is achieved by a combination of the mechanical interference between the component and pipe and the compression of the seal material. The mechanical strength of the joint is achieved through the crimping process.

When installed correctly, the elastomeric seals of a press-to-connect system significantly reduce the likelihood of leaks compared to threaded systems.

In addition to minimizing potential leaks at the joints, thereby increasing energy efficiency and reducing operating costs, press-to-connect systems offer several other benefits advantageous to industrial operations: installation that is up to five times faster than other joining systems and safer than welding, simple installation, and reduced total installed costs.

Most press systems offer several options for the seal material, including HNBR, nitrile, EPDM, fluoroelastomer and silicone, among others.

Grooved Mechanical Piping Systems
Although not as new as press systems—grooved mechanical piping has been around since the 1920s. Like press systems, grooved systems employ a mechanical joint containing an elastomeric seal, known as a coupling, to join pipe.

A grooved joint comprises four elements: grooved pipe, coupling housings, a gasket and nuts and bolts. The pipe groove is made by cold forming (roll grooving) or machining (cut grooving) a groove into the ends of a pipe. A gasket is positioned around the joint of two abutted pipe ends, then enclosed in the coupling housings.

The key sections of the coupling housings engage the groove. The bolts and nuts, tightened with a socket wrench or impact wrench, hold the housings together. In the installed state, the coupling housings encase the gasket and engage the groove around the circumference of the pipe to create a leak-tight seal in a self-restrained pipe joint.

The unique gasket design provides a triple-seal effect, creating a leak-tight joint. Gaskets are molded to fit over the pipe ends and seal between the grooves. They are slightly compressed as the coupling housing is tightened, which enables low-pressure sealing. The internal cavity is also energized by internal forces applying pressure downward on the sealing lips. The net effect is a pressure-responsive gasket that seals equally well at low pressures and at maximum rated coupling pressures.

In addition to creating leak-tight seals, grooved systems offer a number of additional benefits: installation that is up to 10 times faster than welding; safer installation through the elimination of flame and cutting; reduced total installed costs; ease of system maintenance and system expansion; accommodation of thermal expansion and contraction, deflection and seismic movement; and noise and vibration attenuation.

Grooved systems can be used on piping up to 60 inches in diameter, and pipe materials ranging from carbon, stainless and galvanized steel to copper, aluminum and plastic.

In short, press-to-connect and grooved mechanical piping systems are an ideal choice for compressed air lines because both joining methods practically guarantee a reduction, if not elimination, of air leaks through pipe joints compared to threaded systems, are much faster and safer to install than threaded and welded systems, and offer reduced total installed costs.  

Bill Lowar, Power Division Manager, Victaulic