b'Process Industries | Engineer Innovationlike throttling, reduced pump speed, orstart class 1increased pipe diameter, the investigationno measure requiredis completed for this pipe.^ ^ Yes class 2Exit 3: At the last stage, a dynamicP ref. P cc. end - limit ow (e.g. by orice)simulation is performed in order to get a- reduce pump performanceless conservative prediction of the peakno - increase nominal diameterpressure. If this is still above theReduce vacceptable value, an investigation loop isClass 3 (only few cases)started to assess multiple mitigating- hydraulic dampertechniques like hydraulic damper, slower^ ^ YesP ref. P cc. end - slower valve closingvalve closing etc. - venting valve (against cavitation)no - change of valve characteristicsCase Study: Assessment of mitigation- etc.techniques for pressure surgedynamic (Simcenter A tanker barge is filled with 60 m/hsimulation Flomaster)methylene chloride through a 530 m long pipe PN16 via a pipe bridge, figureYes5. The resulting flow velocity is 3 m/s.^ ^The wave propagation velocity is aboutP P endref.cc.900 m/s, leading to a signal return timenoof 1.2 s. In case the ship begins to drift, anofurther measures valve at the pier closes automatically^within 1 second. to reduce P sim.Exit 1 Criteria: Check qualitative maximumFigure 4: Practical approach flow chartpressure expectedMethylene^p= p+ p chlorideref. operation Jouk. P vap= 0.48 bar 530 m,80 mm, PN16 valve shuts automaticallyif ship drifts off^ 3 m/s60 m3/hp= 77.6barg + va =44.2bargref. 9 m p = 7.6 bar15 m^p =16barfor a PN16 pipe. Since pacceptable ref. p , further investigation is acceptableneeded.Simcenter numericalExit 2 Criteria: Check if peak pressure canFlomaster simulationmodelbe reduced by simple meansAnalysing this is often a matter of practical concerns. The peak pressures could be reduced by lowering the flow velocities. To obtain this, either the pipe diameter is increased or the flow rate isFigure 5: Case studyvalve closure in ship loading linelimited to the required value. Pump speed can be varied but given the hydrostaticStatic Pressure Upstream of Ball Valveand friction head in the pipe, it isP max= 43.4 barg! P Jouk.= 35.6 barg t return= 1.2simportant to consider that the flow may slack if there isnt enough back-pressure40 bargmaintained in the pipe. In this case, static pressureapplication of a throttling element (e.g.30 bargorifice) at the end of the line is favorable.20 bargExit 3 Criteria: Evaluate alternatives tocavitationmitigate high pressures10 barg1,2 sAt this stage, it becomes necessary to0 barghave a detailed model set up in0 s1 s2 s3 s4 s5 s6 s7 s8 sSimcenter Flomaster as shown in Figuretime5 to evaluate mitigation techniques. WeFigure 6: Status quo (valve closes uniformly in 1 second)53'