Wear issues of pumping units Oybek Ishnazarov, Abdusaid Isakov, Utkir Islomov, Umirzoq Xoliyorov and Dilshod Ochilov E3S Web Conf., 264 (2021) 04081 Published online: 02 June 2021 DOI: 10.1051/e3sconf/202126404081