What would the take-off be for an 18" pipe in a 90° butt weld ell?

When calculating the take-off for a pipe fitting, such as an 18" pipe with a 90° butt weld elbow, the take-off primarily refers to the length of the pipe that will need to be cut from the straight run to accommodate the fitting. For a standard 90° elbow, the take-off length is typically equal to the nominal pipe size.

For an 18" pipe, the standard practice is that the take-off for a 90° butt weld ell is 18 inches. This is based on industry standards, which specify that the take-off length for a fitting like this generally matches the nominal diameter of the pipe being used.

Thus, in this scenario, the correct take-off for an 18" pipe in a 90° butt weld ell is indeed 18 inches, aligning with established pipefitting conventions for these types of fittings.