Comparison analysis on the scheduled venting modes of gas pipelines

Venting system is an important facility of long-distance gas pipeline, and it plays an important role in ensuringthe safety of pipeline maintenance and repair and reducing the damage of pipeline accidents. To select a reasonable ventingmode on the basis of existing venting facilities is favorable for reducing the adverse effects of venting and ensuring thesafety of operators. In this paper, the venting flow, temperature and pressure changes of 5 venting modes (i.e., single-stageventing, two-stage venting, three-stage venting, six-stage venting and constant rate) were simulated by the software TGNETafter the venting facility and process of the gas pipeline were simplified rationally. Then, the Mach number, noise intensityand natural gas diffusion radius corresponding to the maximum venting rates in different venting modes were calculatedby FLARENET and PHAST. It is shown that during the scheduled venting, the more frequently the venting valves areoperated, the stabler the venting rate of natural gas is and the less the adverse effect of temperature drop, noise and naturalgas diffusion is. Therefore, it is recommended to adopt the constant-rate venting as the preferred venting mode of natural gaspipelines. If the conditions of constant-rate venting cannot be met, it is necessary to regulate the opening of venting valves asmany times as possible in order to reduce adverse consequences of venting.