EXPANSION LOOP

 EXPANSION LOOP 

        ΔL = C x L x (Tf - Tg) x 12in./ ft. 

Where C= coefficient of thermal expansion

            L= Distance between to fixed points

            Tf = temp. of fluid

              Tg = temp. of ground

1. Loop width should always be based on utilizing existing supports.
2. Thermal expansion must be allowed for when spacing adjacent loops.
3. Loop width does not have to be near 20 feet just because the loop nomographs happen to use that number. Loop width has only a secondary effect on results.
4. Minimum loop height depends on the berthing of the line with respect to the location of the loop support.
5. Loops cannot extend too far beyond existing support or the overhang will cause the loop to “lose its balance.” This sets the maximum allowable loop height.
6. The first two points have more influence on loop design than stress formulas, from the piping point of view.
7. Three-dimensional loops are widely used because this arrangement does not block the routing of low-temperature lines under the loop.
8. Vertical loops are placed at road crossings and sometimes are nonsymmetrically located due to the location of the road

GUIDELINES FOR LOOP SIZING 

1. The expansion loop is usually located on the side of the hottest line

2. The expansion loop, as a rule, should be located in the center of the distance between two anchors.

3. The height of the expansion loop is normally twice the width. The exception to this rule occurs when more than one line runs parallel in a common trench. The dimensions of the loops for the additional line must be increased to allow nesting of the loops.