Planning For Heat Expansion

Heat expansion can be quite significant on long runs of pipe, especially those in a pipe rack. To absorb the expansion of pipe in a rack, pipe loops are often incorporated. Figure 11-4 shows a pipe loop as a U-shaped routing of the line designed to contain the expansion of the pipe. Loops are typically located near the midpoint of a long run of pipe. Expansion will cause the two ends of the pipe to grow toward one another resulting in the distortion of the loop as shown in Figure 11-5.

When multiple loops are placed at the same location, as shown in Figure 11-4, adequate line spacing requires the deflection of each loop be calculated to avoid interference.

Lines resting on T-supports must be designed carefully as well. If a line is positioned too close to the end of a support, expansion may push the pipe off the support (see Figure 11-6). Situations like this may require a cold spring or a longer T-support.

When multiple lines resting adjacent to one another turn in the same direction, attention must be given to the fact that one line can grow while the other does not. In Figure 11-7 assume lines 105 and 106 are both expanding at the same rate and in the same direction. As they both grow, adequate line spacing will be maintained. But what if line 106 was a cold line and did not grow at the same rate as line 105? Expansion from line 105 would cause interference with 106. To avoid this, the line spacing dimensions X and Y in Figure 11-7, must be calculated to reflect the conditions of one line being hot and the other cold. Calculations using the hot/cold scenario will guarantee adequate spacing at all times.

Cold Loop Piping
Figure 11-4. Piping loop. Courtesy Nisseki Chemical Texas Inc., Bayport, Texas

AVOID PLACING A PIPE NEAR THE END OF AN OPEN SUPPORT.

Figure 11-6. Pipe expansion on T-supports.

TREAT ONE PIPE AS HOT AND THE OTHER COLD WHEN CALCULATING UNE SPACING FOR TWO PIPES EXPANDING IN THE SAME DIRECTION.

Figure 11-5. Pipe loop distortion.

Figure 11-7. Hot and cold line spacing.

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