Common symbols used in piping drawings include function symbols, such as two circles, side-by-side, indicating instrument sharing in common housing and a diamond with a P in the middle indicating a purge or flush device. Pipe- and valve-end symbols include a curved 90-degree angle opening to the right with one smaller vertical line on each side, which represents a screwed pipe, or two triangles, vertically tip-to-tip with straight lines extending from their bases, which stands for screwed valve.
Flow symbols include a circle containing the letters FE with a line extending from the bottom of the circle, looking like a balloon on a string, that floats slightly above a horizontal line. The horizontal line usually contains a shape at its center, such as a square containing an open triangle pointing to the right, the full symbol in this case representing a vortex sensor.
Line symbols used in piping design drawings include a straight line, representing an instrument supply or connection to process and a straight line with three diagonal, right-leaning lines intersecting it at equal distances, indicating an undefined signal. A straight line with three Ls intersecting it, equal distance apart, indicates a hydraulic signal. A straight line with three equally spaced Xs intersecting it indicates a capillary tube and with three S shapes intersecting it horizontally, an electromagnetic or sonic signal.