This report describes the work undertaken to numerically model the hydrogen diffusion in in-service fillet welds across a wide variety of pipe attributes, welding conditions, and thermal conditions. The document includes recommendations for post-welding nondestructive examination (NDE) delay times that correspond to time-to-peak-hydrogen (TTPH) and time-to-critical-hydrogen (TTCH) at four common locations around a fillet weld where hydrogen induced cracking is likely to occur.