Valvesw hich are connectedt o long pipelines in a large hydraulic system are occasionally closed very rapidly owing to unavoidable circumstances. The instantaneous stoppage of the flow in the pipeline causes the oil hammer phenomenon resulting in pressure rise which must be properly suppressed from the viewpoint of safety of the pipeline system.
In this research, suppression of the oil hammer due to the instantaneous valve closure at the downstream end of the hydraulic line is considered and for this purpose the accumulator and its entrance choke are installed at the upstream side of the valve.
The suppressing method are analyzed experimentally and theoretically to get the optimum value of the parameters of the accumulator and its choke.
The simples traightforward procedure to determine the optimum parameters are established and its effectiveness are confirmed by the additional experiment.

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In a working pneumatic cylinder, the air temperature at an outlet port of the cylinder decreases rapidly by the sudden expansion of the air, and at an inlet port it increases rapidly by the sudden compression of the air. In a pneumatic system composed of a pneumatic cylinder and speed controllers, the amount of heat absorbed and released is not always balanced during the ascending period and the descending period of the piston. Thereby, during the continuous operation of this system, the temperature of speed controller body connected to the one side of the pneumatic cylinder becomes gradually high, and the temperature of the other speed controller body becomes gradually low. Therefore, if the system is operated in the low temperature environment, freezing occurs at the throttle of speed controller and the piston speed changes or the motion of piston stops occasionally. If the system is operated in the high temperature environment, the temperature reached by the speed controller body is high enough to be dangerous for the human body or in decreasing the packing lifetime.
The temperature characteristics of the pneumatic system is closely connected with the pressure change in the cylinder. In this report, the temperatures of air in the cylinder and the speed controller have been measured, and the relationship between the temperature and the pressure in the cylinder has been derived experimentally. Furthermore, the temperature of speed controller body has been measured during the continuous operation and the influence of the effective area of speed controller and the load on the temperature change of the speed controller body was clarified.

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An approach is made for the analyses of the transient responses of pneumatic and oil pipe lines. The algorithm based on the characteristics grid method considers the variations of the density, pulse wave speed and kinematic viscosity of the fluids due to the pressure changes in pipes.
The numerical results are compared with the experimental results or the ones ob t ained by other analyticalm ethods for problems of this type and discussed to obtain the following conclusions: The approach is effective in predicting the transient responses of pneumatic pipe line. And also, in oil pipe lines, it obtains excellent results inclusive of the severe pressure changes due to high-pressureo peration of the directional control valve.

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