b'Engineer Innovation | Process IndustriesMethylenechloride first assess the status quo i.e. where the valve shuts automatically in e. g. 1 s and 9 m 500 L observe the pressure behavior. membrane vessel3 barg N 2pressureThe simulation results for the status-quo as shown in figure 6 imply that: SimcenterFlomasterThe Joukowski shock fully develops, modelsince the valve is completely closed, when the signal reflection arrives. The negative reflection wave causes a pressure drop down to the vapour pressure of about 0.4 barg. This means, cavitation occurs.Multiple very sharp pressure peaks are Figure 7: Application of hydraulic accumulator as damper caused by collapsing of the cavitationDamper reduces P maxfrom 43.4 barg to 12.3 barg! (i.e. 70 percent reduction)\\ bubbles. Disadvantages: expensive and high maintenance requirementsThe predicted overall maximum peak pressure is about 43 barg! This is high Static Pressure Upstream of Ball Valve above the pipes pressure rating of 16 without damper barg. 40 bargOne possibility to reduce the surge30 barg with damper effect is to apply a hydraulic damperstatic pressureto the pipe. Therefore, to assess the 20 barg impact of this technique, we add a500 L membrane vesselpressurized10 barg with 3 barg of nitrogen to the model (figure 7). 0 barg0 s5 s10 s15 s20 s25 s30 s35 s40 stime The analysis time for such networks is Figure 8: Results with and without damper typically less than a minute and quickly reveals some key insights into how this Closure time increased by x10 to 10s change impacts the transient pressure P maxreduced by 1.5 (only.) to 20 bargbehaviour (figure 8).Static Pressure Upstream of Ball Valveuniform uniform The hydraulic damper clearly reduces the 40 barg t closure= 1s t closure= 10s maximum pressures below acceptable 32 barg limits and also effectively avoids static pressure24 barg cavitation. However, in practical terms, such dampers are often highly costly and 16 barg require regular maintenance and 8 barg inspections of the gas content and 0 barg membrane condition. 0 s2 s4 s6 s8 s10 s12 s14 stime As a next step, we attempt to assess the Figure 9: Impact of 10s uniform closure time influence of slower valve closing profile and see whether this technique can be Ball valve characteristics Comparison of valve characteristics used to reduce maximum pressure below in terms of loss coefcientin terms of ow coefcient K v(analogeous ro C v ) the acceptable limit and avoid the hydraulic damper. Therefore, we run a simulation with a closing time elongated from 1 s to 10 s (figure 9). The resulting maximum pressure does not reduce satisfactorily and still reaches 28 barg, considerably higher than the acceptable value. At this stage, it is worth considering why the elongated closure was so ineffective. Figure 10: Non-linear valve characteristics Frequently, the non-linear valve 54'