Pressure spikes

Pressure Spikes - They re inherent in the design of many systems. 

Dynamic simulation models include fluid inertia and compressibility and exchanger shell expansion to determine the pressure spikes associated with... 

Stage 1 may last less than one second to several seconds. It is characterized by a very fast transient and a pressure spike immediately after the tube rupture. After the low-pressure side fills with high-pressure fluid, the transition to stage 2... 

API RP-521 reeommends transient analysis for exchangers with wide difference in design pressure (such as cases where the two-thirds rule was not applied) because the pressure in the low pressure side of the exehanger ean spike to a level that exceeds the pressure predicted by a steady state analysis when it is liquid-filled. This pressure spike is due to pressure buildup before the liquid is accelerated out of the low pressure side and/or before the relief device opens fully. API RP-521 recommends that the basis for the tube rupture be a sharp... 

The pressure spike introduces a disruption in the flow. Depending on the local conditions, the excess pressure inside the bubble may overcome the inertia of the incoming liquid and the pressure in the inlet manifold, and cause a reverse flow of varying intensity depending on the local conditions. There are two ways to reduce the flow instabilities reduce the local liquid superheat at the ONB and introduce a pressure drop element at the entrance of each channel, Kandlikar (2006). Kakac and Bon (2008) reported that density-wave oscillations were observed also in conventional size channels. Introduction of additional pressure drop at the inlet (small diameter orifices were employed for this purpose) stabilized the system. 

The pressure profile and film shape with or without micropolarity are shown in Figs. 10-17. The polarity does not alter the positions of the second pressure spike and the minimum thickness, and it has a minor influence on the pressure profile and the film shape. In the case of the pressure profile, the micro-polarity affects the pressure distribution in the vicinity of the second pressure spike. It should be noted that, in Figs. 10 and 12, the second pressure spikes are not clear enough due to low velocities. With an increase in character-... 

Fig. 10—Pressure profile near the second pressure spike for v = 10 mm/s and N=0.S.

Filter-cakes are hard to remove and thus can cause considerable formation damage. Cakes with very low permeability can be broken up by reverse flow. No high-pressure spike occurs during the removal of the filter-cake. Typically a high-pressure spike indicates damage to the formation and wellbore surface because damage typically reduces the overall permeability of the formation. Often formation damage results from the incomplete back-production of viscous, fluid loss control pills, but there may be other reasons. 

Fig. 5. Pressure spikes induced by shaking low/ dense fluorocarbons in vitro.

Unlabeled Uses Postcycloplegic intraocular pressure spikes, intraocular pressure from post cataract surgery. 

Hauver concluded that pressure-time measurements with a sulfur transducer in contact with detonating Baratol gave clear evidence of an initial pressure spike, and lends addnl confirmation to the hydro-dynamic theory of deton proposed by von Neumann and others. The sulfur transducer appeared capable of good resolution over that portion of the pressure-time curve corresponding to the reaction zone, and may offer a method for investigating the reaction process Refs 1) S. Joigneau J. Thouvenin, "Electrical Conductivity of Sulfur Under the Action of a Shock Wave , CR 246, 3422-25 (1958) 2) G.E. Hauver,... 

It predicts ignition delay times for space rocket engines and ignition pressure spikes (Ref 40)... 

As the sloughed particles travel downstream, they bridge across the flow channel (Point F) to form a plug, with the corresponding upstream pressure spikes as shown in the final period of the top of Figure 8.9. 

Pressure pulsations can make an SRV relieve below set pressure when the pressure spikes perhaps reach set pressure. These spikes have such high frequency that they are unseen on charts or gauges. Nevertheless, they do art on the SRV, making it vibrate at high frequency. 

Pressure spikes at inlet (actual oscillograph recording)... 

Pressure spikes measured before and after a pulsation dampener... 

In particular, vibrations and pulsations due to positive-displacement compressors can cause premature opening when the forces within the valve are anywhere near equilibrium and are acting as another upward force. For pilot-operated valves, some manufacturers provide pulsation dampeners in their pressure pick up lines so that the effect of these pressure spikes are compensated. As can be seen in Figure 6.21, for spring-operated SRVs, unfortunately, no provisions can be taken to compensate for this effect. 

In these cases, it is possible to use a pilot-operated valve fitted with some sort of pressure spike compensator before the fluid enters the pilot. If the set pressure of the valve is lower or very dose to the highest compressor pressure spike, the valve may leak or even pop. The pressure surge compensator dampens any spikes of pressure before they enter the pilot, so the valve reacts to the average pressure and remains stable and tight. This compensator can be built into the supply line to the pilot and has an effect on the pilot, as shown in Figure 9.2. 

Pressure at the entry of the pilot valve after having passed a pressure spike compensator... 

Valves should have adequate actuation time. A solenoid valve closing in 40 milliseconds in a stream pressurized to 50 psig will generate a total pressure spike of about 490 psi.4... 

There are two different kinds of life-threatening adverse events associated with drug withdrawal physical risks and emotional risks. The most common physical risks are seizures and blood pressure spikes. The most common emotional risks are violence against self and others and manic or psychotic reactions. 

It bears repeating that any mood stabilizer that is also approved for use as an antiseizure drug presents the risk of dangerous withdrawal seizures, and any mood stabilizer used as a treatment for hypertension presents the risk of dangerous blood pressure spikes during withdrawal. Some of these drugs are listed in the appendix. 

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