How Tube Fittings Save Installation and Maintenance Costs Part 1

Posted by John Comi | Jul 17, 2014 7:30:00 AM 0 Comments

Recently, I have been involved in discussions about substituting tubing and tube fittings in systems that are usually built using welded pipe and pipe fittings.  This is not a new topic, but as system designers and equipment manufacturers continue to look for ways to save money, tube fittings provide a proven method for reducing installed cost while maintaining reliability.

The Welding Tradition

Navy Welding Pipe

Traditionally, welding has been used to make “leak-tight” connections in demanding applications.  It offers a permanent leak-tight connection that resists vibration and extreme temperature and pressure changes. Until recently, the US and Europe have had an adequate source of trained welders and ample supplies of inexpensive pipe and weld fittings.  For these reasons, welded pipe has been specified, especially in the oil & gas, chemical, and paper industries. 

An Opportunity to Reduce Time and Cost

While welding is a proven method, it is also time consuming and expensive when compared to making tube fitting connections.  Advances in machining technology and metallurgy have closed the reliability gap between tube fittings and welding.  In addition, a shortage of trained welders has driven both the time and cost of welded systems.Therefore, OEMs, contractors and process system designers have an opportunity to reduce equipment and system CAPEX and OPEX costs by converting from welded pipe connections to tubing and tube fitting connections.

Comparing Tube to Pipe

Engineers and system designers considering changing over pipe systems to tube systems must also compare the technical merits of tube and tube fittings to pipe, pipe fittings, and welds. When comparing tube systems to pipe systems, tube systems:

  • Tubing has higher working pressures when compared to pipe of the same nominal size and wall thickness.  Welds and tube fittings are both rated to the maximum working pressure of the pipe or tubing they join.
  • Tubing weighs significantly less than pipe.
  • Tubing can be bent reducing both the number of fittings used and the number of potential leak-points in the system.
  • Stainless steel coiled tubing (available up to 3/4 in) can create continuous runs of tubing up to 600 feet.  This is especially important in applications, such as CNG fueling stations and some hydrocarbon lines that do not allow fittings.
  • Tubing has smoother internal surfaces.
  • Welded pipe and tube systems both perform well in systems with high vibrations, pressure fluctuation and thermal cycling.  Most quality tube fitting manufacturers can provide third-party test reports for these properties.

Tube vs. Pipe - Pressure/Strength

 

 

Tube/Pipe

Nominal Size

Wall (in.)

Pressure 
psig (bar)

Tensile Strenth
 PSI (N/mm2)

Schedule 40 

1.000

0.133

1575 (1080)

40000 (275)

Tubing

1.000

0.083

3100 (2130)

75000 (516)

Schedule 80 

1.000

0.179

2601 (179)

40000 (275)

Tubing

1.000

0.120

4700 (323)

75000 (516)

 

Tube vs. Pipe - Weight

 

Tube/Pipe

Nominal Size

Weight

Schedule 40 

1.000

0.133

Tubing

1.000

0.083

Schedule 80 

1.000

0.179

Tubing

1.000

0.120

 

Safety

Safely is always a critical concern.  On the installation side, tube fittings are much safer to install.  Unlike welding, installing tube fittings does not have an open heat source making it more suitable for explosive and flammable applications.  In additions tube fitting installation does not include the use of purge gases.  This makes them ideal confined spaces. 

On the operational side, properly installed tube fitting deliver leak-tight performance in applications having vibration and extreme temperature and pressure cycling.  Leading manufactures can provide ASTM F-1387 testing and other certifications and approvals to demonstrated that tube fittings can perform in many applications that have traditionally used welded pipe.

Conclusion

On a performance basis, tubing and tube fittings represents a viable replacement for many applications a variety of industries that have traditional used welded pipe and pipe weld fittings. In our next blog, we will discuss the hard cost and installation cost differences between weld pipe and tube systems. 

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Topics: Tubing, Tube Fittings


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