Calculation of pressure loss and critical velocity for slurry flows with additive agents in vertical polyethylene pipelinesYevhen Semenenko, Stepan Kril, Olha Medvedieva, Nina Nykyforova and Larysa TatarkoE3S Web Conf., 109 (2019) 00083DOI: https://doi.org/10.1051/e3sconf/201910900083