Valve closure study

The motions of heart valves have drawn a considerable amount of auention from physicians and anatomists. One of the major reasons for this interest can be attributed to the frequent diagnosis of valvular incompetence in association with cardiopulmonary dysfunctionings. The first study exploring the nature of valve functioning, by Henderson and Johnson (1912), was a series of simple in vitro experiments, which provided a fairly accurate description of the dynamics of valve closure. Then came the Bellhouse and Bellhouse experiments (1969) and Bellhouse and Talbot (1969) analytical solution, which showed that the forces responsible for valve closure, are directly related to the stagnation pressure of the flow field behind the valve cusps. 

Leak Duratioa The Department of Transporation (1980) LNG Federal Safety Standards specified a 10-min leak duration other studies (Rijnmond Public Authority, 1982) have used 3 min if there is a leak detection system combined with remotely actuated isolation valves. Other analysts use a shorter duration. Actual release duration may depend on the detection and reaction time for automatic isolation devices and response time of the operators for manual isolation. The rate of valve closure in longer pipes can influence the response time. Due to the water hammer effect, designers may limit the rate of closure in liquid pipelines. 

Meisner JS, McQueen DM, Ishida Y, Vetter HO, Bortolotti U, Strom JA et al. Effects of timing of atrial systole on LV filling and mitral valve closure Computer and dog studies. American Journal of Physiology - Heart and Circulatory Physiology 1985 249 H604-19. 

The expander train supplier shall assist with the selection of the expander inlet and bypass valve configurations and closure rates by performing an open loop dynamic simulation study. For a main air blower train dais could be closed loop. 

A technical superintendent at TMI-2 who arrived on the plant at 03 45, subsequently said I had the perception that we were in a very unusual situation, since I had never seen the pressurizer level increase and stay at a high value and, at the same time, the pressure staying low. They [the pressure and the level] had always behaved in the same way . As a consequence of the described evaluation errors the primary circuit continued to lose water for hours and in addition the automatic core cooling system, correctly activated, could not perform its function of fuel integrity protection. It is now known that if the block valve had been closed after one and half or two hours or if the operation of the HPI only had not been arrested, even without the closure of the valve, the Three Mile Island accident would have been no more than a modest nuisance of operation. For completeness of information it has to be added that the possibility of an accident of the type of TMI-2 had been foreseen by some experts. If these foresights had been confirmed by in-depth theoretical studies and possibly by experimental tests, their results, duly made known to interested people, would have enabled the TMI-2 operators to correctly diagnose the fault and react correctly. 

The schematic diagram of HIPPS pilot model for the study is shown in Fig. 1. The wellhead is provided with a surface valve block, a master valve and a wing valve. A choke valve drops the pressure to the required operating pressure. In case of abnormal high pressure occurrence, pressure transmitters detect the overpressure and initiate the closure of HIPPS valves installed in series. The action of the HIPPS prevent further pressure rise. 

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