Constructing industrial parks with DH (district heating) systems has become a main way to develop modern industry, which requires strict security and reliability of heating networks. Industrial steam heating networks are usually ring-shaped with multiple heating sources, and the working conditions would be changeable due to the high frequency and a wide range of load variation of heating consumers. Under a specific working condition, low steam velocity for a long time (namely "steam stagnation") in certain pipes will result in CIWH (condensation-induced water hammer) which will threaten the security of the whole DH system. In this paper, a hydraulic calculation model is built to study the steam flow regime considering heat dissipation and condensation in pipes, an operation optimization method is proposed to help eliminate steam stagnation through optimizing the heat load distribution of each heating source, a general software system entitled "HEATNET" is presented to realize online hydraulic calculation and operation optimization for arbitrary structured heating networks. The practical application of HEATNET in Shanghai chemical industry zone shows that heat dissipation and condensation in pipes would influence the overall hydraulic calculation of steam heating networks and it can prevent CIWH and improve the security and reliability of steam heating networks. (C) 2015 Elsevier Ltd. All rights reserved.