The effect is that instead of being stressed from 0 F to +1 F units of force, the piping is stressed from -½ F to + ½ F units of force. At working temperature and having fully expanded, the piping is stressed in the opposite direction. When warmed through half of the total temperature rise, the piping is unstressed. The pipes are left short by half of this amount, and stretched cold by pulling up bolts at a flanged joint, so that at ambient temperature, the system is stressed in one direction. The total amount of expansion is first calculated for each section between fixed anchor points. The amount of movement to be taken up by the piping and any device incorporated in it can be reduced by ‘cold draw’. The steam main will be operating at a higher temperature than that of the condensate main, and the two connection points will move relative to each other during system warm-up. Here, the difference between the expansions of the two pipework systems must be taken into account. In other installations, however, it will be necessary to incorporate some means of achieving this required flexibility.Īn example on a typical steam system is the discharge of condensate from a steam mains drain trap into the condensate return line that runs along the steam line (Figure 10.4.2). In many cases the flexibility of the pipework system, due to the length of the pipe and number of bends and supports, means that no undue stresses are imposed. The pipework system must be sufficiently flexible to accommodate the movements of the components as they expand. For this example an approximate expansion of 330 mm is indicated. Where the diagonal temperature difference line of 250☌ cuts the horizontal pipe length line at 100 m, drop a vertical line down. Temperature difference is 265 - 15☌ = 250☌. Find the approximate expansion from 15☌, of 100 metres of carbon steel pipework used to distribute steam at 265☌. If the pipe is installed at 10☌, determine the expansion using Equation 10.4.1.Īlternatively, the chart in Figure 10.4.1 can be used for finding the approximate expansion of a variety of steel pipe lengths - see Example 10.4.2 for explanation of use. The amount of the expansion is readily calculated using Equation 10.4.1, or read from an appropriate chart such as Figure 10.4.1.Ī 30 m length of carbon steel pipe is to be used to transport steam at 4 bar g (152☌). This will create stress upon certain areas within the distribution system, such as pipe joints, which, in the extreme, could fracture. It follows that they expand, especially in length, with an increase from ambient to working temperatures. Pipes carrying hot fluids such as water or steam operate at higher temperatures. All pipes will be installed at ambient temperature.