Discussion of "Detection of Partial Blockage in Single Pipelines" by P.K.Mohapatra, M.H.Chaudry, A.A.Kassem, and J.Moloo

In the discussers opinion, the paper is of interest because it extends fast and reliable techniques for leak detection and sizing in pressurized pipes—i.e., those based on transient tests—to the diagnosis of partial blockage. With regard to the procedure proposed by the authors, the following comments can be made: i as pointed out in Ferrante and Brunone 2003, analysis of transient test data in the frequency domain may fail for some locations of the investigated irregularity and measurement section; ii the use of oscillating valves giving rise to transient tests can be challenging in water supply systems whereas it may be applicable in industrial systems, and iii the behavior during transients of valves jammed in a partially closed position has to be distinguished from that of the reduction of the internal diameter due to deposition of solid wastes. For the sake of brevity, in the present discussion only the third point will be examined by illustrating the results of some numerical experiments in which transients in a single highdensity polyethylene PEHD pipe L=35.42 m, D=93.3 mm, and a=345 m/ s are due to the instantaneous and complete closure of the end valve.