Contents lists available at ScienceDirect Journal of Natural Gas Science and Engineering journal homepage: www.elsevier.com/locate/jngse An experimental study of the effective parameters on automatic line-break control valves action in natural gas pipelines Mehdi Mahmoodi * , Mofid Gorji Bandpy Department of Mechanical Engineering, Babol Noshirvani University of Technology, Babol, Iran ARTICLE INFO Keywords: Automatic control valve Line-break Gas pipeline Operating pressure Orifice diameter Pressure drop rate ABSTRACT The automatic line-break control valve (LBV) is a robust self-contained pipeline monitoring system which is widely used to prevent gas releasing upon rupture or large leakage event in the oil and gas pipelines. The differential pressure set point (DPS) at each valve location is the main criteria for value setting in LBV action. If the DPS is not properly adjusted, the LBV may mistakenly close or it may not take any action at proper time. In this study, the effect of characteristic parameters such as orifice diameter (OD), pipeline operational pressure (POP) and pipeline pressure drop rate (ROD) due to rupture or major leak was experimentally investigated on DPS. 100 different conditions with triple set of typical mentioned characteristic parameters were chosen. For each condition, the differential pressure (DP) was measured over 180 s by statistically analyzing the experi- mental results. Therefore, 100 maximum DP values (DPSs) were obtained. The attainable time to DPS depends only on OD and is independent of the POP and ROD and decreases by increasing the OD. The DPS increases by increase in ROD or decreasing OD or POP parameters. Because of using nitrogen gas instead of natural gas due to safety reasons and the uncertainties, the DPS results can be practically applied by adding a safety factor of 10%–15%. Finally, the diagram of DPS with respect to ROD was provided for different POPs and ODs. The diagram can be used as a basis for designing and regulating of LBVs installed on gas transportation pipelines. 1. Introduction Automatic line-break control valves are installed on oil and gas pipelines for several reasons. For example, LBVs can be used in zones with no access to national electricity network, hazardous or impassable area enclosure, passive defence conditions or to protect different eco- systems such as rivers, ground waters and fertile lands. The goal of LBV installation is automatic operation, remote control or required large force for changing the control valve position (Nesbitt, 2011; Zhang, 2010). The rupture or leak detection ability depends significantly on transmission system configurations, operating transients and philo- sophy, which means that the selection of any detection system must be based on a thorough analysis of the pipeline system (Chan, 1980). Millions of liters of oil and gas are transported through pipelines each day. Inaccurate or incorrect operation of LBVs can cause huge disaster in pipelines. The high cost of required experimental testing, sensitive design, passive defense and strategic role of LBVs are the reasons for few reliable experimental data in this field. Several studies on leak (Harriott, 2011; Noguerol, 2011; Reddy et al., 2011; Yan et al., 2015; Chen et al., 2017; Ebrahimi-Moghadam et al., 2016) and ruptures de- tection (AL-Rasheed et al., 2010; Lacerda and Elias, 2010; Peekema, 2013; Richards, 2013) in gas pipelines have been reported. However, there are only a few studies on setting the DPS value of LBVs (Wang and Zhang, 2004; Doostaregan, 2013; Wang et al., 2013) especially about how the value settings might differ between gas pipelines. The LBV requires detailed and accurate setting due to great sensi- tivity on the rate of pressure variation over time in different pipeline conditions. The pressure drop rate due to frictional losses in a piping configuration is called normal pressure drop rate. This pressure drop should not cause the LBV to act. The maximum differential pressure between two sides of diaphragm valve is DPS. LBV will be regulated with certain DPS for different conditions. As mentioned, DP depends on several parameters such as POP, ROD and OD. The orifice in line-break detection system is the most important section of a LBV. Sensible pressure drop occurs by a pipeline rupture or large leak. The corre- sponding ROD can be observed at the adjacent control valve location. The DPSs of LBV are usually adopted based on experience or estimated values derived from pipeline steady flow over a long time (Lorusso, 2012; Phan and Sawin, 2012; Zuo et al., 2015). In this study, the effect of critical parameters such as POP, ROD and OD on DPS of LBV with a Scotch-yoke actuator were experimentally studied. Understanding the effects of these parameters is critical to https://doi.org/10.1016/j.jngse.2018.01.006 Received 18 February 2017; Received in revised form 4 January 2018; Accepted 4 January 2018 * Corresponding author. P.O.Box 484, Babol University of Technology, Babol, Mazandaran, Iran. E-mail address: mmahmoodi@stu.nit.ac.ir (M. Mahmoodi). Journal of Natural Gas Science and Engineering 52 (2018) 59–81 1875-5100/ © 2018 Elsevier B.V. All rights reserved. T