Ultrasonic guided waves in elastic bare pipes are studied from a theoretical point of view. Dispersion curves of both axisymmetric and non-axisymmetric waves are presented. The parameters of 4-channel focusing are calculated by a phased array focusing algorithm. Experimentally four defects are detected in a cased pipe inspection. The defect probability of detection is highly improved by applying the phased array focusing technique. Guided wave dispersion curves in coated pipes are calculated using a 1-D Semi-Analytical Finite Element (SAFE) technique. This theoretically driven hybrid SAFE method has perfectly tackled the guided wave problem in coated pipes, including dispersion curves (phase velocity dispersion curves and attenuation dispersion curves) and wave structures. The time delays and amplitudes of the 8-channel focusing in an 8 in sch40 coated pipe are calculated by the SAFE algorithm and input to the FEM simulation in ABAQUS®. Focusing performance is improved up to 67% by applying the coated pipe parameters compared with the bare pipe parameters.