Individuals with access to two dial indicators will find these tools extremely useful in measuring concentricity. Place one indicator on the east side of the tubing and the second indicator on the west side. Observe the readings and determine when the indicators cancel each other out. Rotate the tubing a full 90 degrees so the indicators point north and south. Add the indicator readings to determine the concentricity tolerance. Those who do not own dial indicators must use the concentricity formula to determine the pipe's tolerance.
An optical comparator is ideal for locating the thickest and thinnest sections of pipe wall; however, many people are unfamiliar with this tool. A micrometer is more readily available and because a micrometer is often used in various high school chemistry and physics experiments, more people have experience using this implement. Attempt to locate the thickest and thinnest points in the tubing by sight and conduct a trial and error test with the micrometer to determine the precise minimum and maximum width of the pipe or tube's wall. Record both values.
The formula for concentricity is simple, but determining the value of the variables is difficult for those who are inexperienced in using dial indicators or comparators. To determine concentricity, divide the minimum width of the tube or pipe by its maximum width. Multiply the quotient by 100 percent. Concentricity is always represented as a percentage, and a product of 100 indicates the pipe or tube in question is fully concentric, which is ideal for any function.
Depending on the function and purpose of the pipe or tubing, quality control tolerance standards exist that must be adhered to strictly. Compare the concentricity percentage determined by the solution to the formula. The percentage of the tube or pipe's concentricity must be higher than the tolerance percentage; for example, if concentricity is calculated to be 85 percent, it will support a function with a minimum tolerance of 80 percent.