Awarded as the best online publication by CIDC

Knowing Expansion and Contraction of Piping Systems

Reasons behind thermal expansion and contraction in piping systems
One of the most powerful dynamic forces acting on piped services is thermal expansion and contraction. All piping materials expand or contract when pipes are exposed to higher or lower temperatures than the installation temperature. If a pipe run is fixed at both ends and heated, the expansion of the liner pipe due to temperature change will cause compressive stresses in the pipe material. If the resulting stress is strong enough to exceed the pipe material’s allowed stress, the pipe, supports, or piping components may be damaged. Depending on the extent of the damage, the facility may be forced to shut down for a period of time to make repairs or replace the piping system. Because piping systems frequently transport hot fluids, piping stresses and flexibility analysis must be carefully executed to minimize difficulties.


Design Factors To Consider
To design for pipe expansion or contraction, one must first understand the pipe material properties listed below:

Types of Expansion Joints in Pipes
In industrial applications, a variety of expansion devices are used. Thermal expansion and contraction induce variations in piping systems as they heat and cool. The length of the piping run, the temperature differential, and the pipe alloy all influence thermal expansion. Because this thermal expansion and contraction can put a lot of strain on the piping system, different approaches have been used to compensate. Let’s look at the most typical expansion joints used in piping systems.

Slip-Type
Slip-type joints compress when the pipe expands into them. A sleeve that slides into an outer shell accommodates this expansion. Sealing materials are wrapped around the sleeve inside the body to prevent leaking through the slip joint. Slip joints come in a wide range of forms and configurations. However, they have several fundamental flaws. Only axial movement can be accommodated by slip joints (compression and elongation). The ability of slip joints to withstand thermal stress is limited, and the packing material must be maintained and replaced regularly to avoid leakage. This maintenance is frequently neglected, resulting in income loss due to leaking steam or other media.

Fig 1: Slip-type joint
Fig 1: Slip-type joint
Courtesy: passuite.com

Pipe Expansion Loops
A pipe expansion loop is one of the most frequent expansion devices. Pipe sections that run perpendicular to the piping system are installed. The resulting pipe expansion loop accommodates thermal movements. Pipe expansion loops must be installed with care to ensure that the pipe, elbows, and welded joints can withstand the pressures. Pipe expansion loops don’t need to be maintained, but they take up a lot of room in the piping layout.

Fig 2: Pipe Loop Expansion joint
Fig 2: Pipe Loop Expansion joint
Courtesy: Spiroflex

Bellows Type
Metal expansion joints are the most adaptable expansion joint pipe fittings. They are made up of one or more metal bellows that are convoluted to offer flexibility. A metal bellows expansion junction combines the advantages of pipe loops and slips joints while avoiding the drawbacks of both. Expansion bellows, like pipe loops, can absorb thermal, mechanical, or seismic movement in any direction while requiring minimal maintenance. Although non-metallic joints are less expensive, they have poor temperature resistance and pressure absorbing qualities. When installed outside, metal expansion joints are more resistant to sunlight, ozone, temperature extremes, and corrosive atmospheres than non-metal expansion joints.

Fig 3 Bellows Type expansion joint
Fig 3: Bellows Type expansion joint
Courtesy: adscomfg.com

Designs to tackle this Problem
In order to avoid major difficulties, piping stress and flexibility analysis must be handled throughout the design stage. If left untreated, snaking pipes or tension on pipe joints could eventually lead to leaks or burst pipes, as well as all of the associated damage that a failure could entail. Hence, the piping stress and flexibility analysis can be done in the following ways:

Conclusion
These mechanisms are very important in civil engineering, especially when designing pipes. Even small changes in pipe systems can bring a big difference in the design, leading to defects. If all these are known properly, money can be saved in repairing. Thus, every civil engineer must be well equipped with modern design factors, criteria, and recommendations.

References

Share this post

Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

If you have a query, you can ask a question here.

Leave a Reply

Your email address will not be published.

Ask a question