Fluid transient analysis is one of the more challenging and complicated flow problems in the design and the operation of water pipeline systems (wps). When transient conditions "water hammer" exists, the life expectancy of the wps can be adversely impacted, resulting in pump and valve failures and catastrophic pipe ruptures. Transient control has become an essential requirement for ensuring safe operation of wps. An accurate analysis and suitable protection devices should be used to protect wps. This paper presents the problem of modeling and simulation of transient phenomena in wps based on the characteristics method. Also, it provides the influence of using the protection devices to control the adverse effects due to excessive and low pressure occur in the transient. The developed model applied for main wps: pump combined with closed surge tank connected to a reservoir. The results obtained provide that the model is an efficient tool for water hammer analysis. Moreover; using the closed surge tank reduces the unfavorable effects of transients. Flow Transient, Water hammer, Pipeline System, Closed Surge Tank, Simulation Model, Protection Devices, Characteristics Method. I. INTRODUCTION N a wps, the flow control is an integrated part of the operation, for instance, opening and closing the valves, starting and stopping the pumps. When these operations very quickly performed, they shall cause the hydraulic transient phenomena. Transients can introduce large pressure forces and rapid fluid accelerations into a wps. These disturbances may result in pump and device failures…etc. Several methods have been introduced and used to analyze water hammer problem like the energy [1], arithmetic [2], graphical, characteristics, algebraic, implicit and linear analyzing [3]6[5], Euler and Lagrangian based method [6], and decoupled hybrid methods [7]. Karney used the characteristics with some modification to obtain more efficient calculations of transient in simple pipe system [8], while Tezkan used this method to analyze the transient in complex pipe systems [9]. Kodura and Weinerowska, Karney and Mclnnis , Sirvole and Itissam Abuiziah is Ph.D student, with the Rural Engineering Department, Institute of Agronomy and Veterinary Hassan II, Rabat, Morocco (e6mail: itissam2002@yahoo.com). Ahmed Oulhaj, Karima Sebari and Abbassi Saber Anas are with the Rural Engineering Department, Institute of Agronomy and Veterinary Hassan II, Raba, Morocco. Driss Ouazar is with the Civil Engineering, Ecole Mohammadia d'Ingénieurs, Rabat, Morocco. Jung compared between the results obtained for both simple and complex pipe systems by using the method of characteristics, and the results are more accurate in the simple systems [1], [10]6[12]. The characteristics method has been used to study the oil pipe systems [13] and cooling networks in nuclear plants [3], [14]. Recently Nabi used this method to analyze real pipe systems in Pakistan; also they studied the effect of installing the protection devices on the pipeline systems [15]. To reduce the dangerous effects of water hammer; the surge devices have been added to the pipeline systems. Most of these protection equipments aim to protect against unfavorable large pressure fluctuations tend to maintain the pressure at a nearly constant value at some fixed places, or tend to keep the pressure from exceeding a predetermined value [3], [16], [17]. Several criteria can be adopted to determine which surge devices are to be used such as the effectiveness, dependability, evaluation of cost character and frequency of maintenance requirement over an exceeded period [5]. Air chamber is a relatively small pressurized reservoir that contains water and air. Generally, it is connected to the main pipe just at the discharge point of the pumps. Its primary purpose is to prevent the negative pressures and the column separation downstream the pumps [18], [19]. After the energy failure, the liquid drains from the air chamber to the pipe and the air volume inside the chamber expands causing a pressure drop. The magnitude of such pressure drop is dependant of the initial air volume as well as the air thermodynamic process [19], [20]. When the pump power fails, the flow begins to advance in reverse and the retention valve instantly closes to protect the pump. After that, the liquid come into the air chamber [3]. The system oscillates and ultimately comes to rest. The period of the oscillation and the associated head fluctuation depends on the size of both the air chamber and the system. It is important that the tank be large enough that it never empties and allows the air to flow into the pipe [20]. The air chamber has many advantages of use [3]:  Air volume necessary to keep the maximum and minimum pressures is relatively small.  Air chamber can be installed to level ground. This fact reduces the foundation costs and it brings a greater resistance against wind forces and earthquakes.  Air chamber can be installed very close to the pump. I. Abuiziah, A. Oulhaj, K. Sebari, D. Ouazar, A. A. Saber Study on Status and Development of Hydraulic System Protection: Pump Combined With Air Chamber I World Academy of Science, Engineering and Technology International Journal of Civil and Environmental Engineering Vol:7, No:11, 2013 889 International Scholarly and Scientific Research & Innovation 7(11) 2013 ISNI:0000000091950263 Open Science Index, Civil and Environmental Engineering Vol:7, No:11, 2013 publications.waset.org/9997282/pdf