Closure time

Figure 4-90. Predicted overspeed versus valve closure time.

The pressure response during a fracturing job provides important information about the success of the operation. The fluid efficiency can be estimated from the closure time. 

Figure 4 shows the final ventilation system protection scheme. It should be noted that even with a blast valve that closes in a few milliseconds there will be some reduced shock pulse that "leaks through" during closure of the valve. The peak value of this shock is a function of losses occurring as the shock passes through the valve and the duration is the valve closure time. The leakage shock was predicted using the blast valve manufacturers test data. 

Patients using eye drops are advised to pull down the lower eye lid gently and instil the drops in the pocket formed without touching the dropper with the eyelid. The patient must be advised to keep the eyes closed for as long as possible, closure time being at least 1-2 minutes. 

Figure 1-20 Explanation of closure time, closure age, and closure temperature (Tc). (a) The cooling history, (b) " Ar accumulation history. The long dashed line shows the accumulation of " °Ar if there were no Ar loss since formation. The thin solid curve shows a real accumulation history. The short dashed line shows how the age is obtained from the present-day " °Ar/" °K ratio. For a mineral grain cooling down from 1200 K, when the temperature is between 1200 and 1037 K (at 5 Myr), all °Ar is lost once produced. Then from 1037 to 571K (at 30 Myr), there is partial loss, and the loss becomes smaller and smaller. Below 571 K, essentially all newly produced " Ar is retained. When °Ar/ °K ratio is determined, one calculates the age based on the present-day °Ar/" °K ratio and the age corresponds to the time of closure ta about 20 Myr). That is, the age is 130 Ma, although the mineral formed at 150 Ma. The temperature at t— 20 Myr is the closure temperature ( 704 K). Adapted from Dodson (1973).

Dodson (1973, 1986) adopted that at closure time U, the accumulation of Ar is zero (C=0), leading to... 

When the threat is removed, the PLZT is re-energized and the open state is restored. The open and closed states of the device have typically 20% and 0,006% transmission respectively. Closure time is less than 150 microseconds. 

Xe and radiogenic Xe in the upper mantle are derived from the lower mantle. This lower-mantle compositions, obtained by subtracting from MORE xenon the U-derived Xe produced in the upper mantle, corresponds to closure times that are similar to that of the atmosphere, indicating that early losses occurred from the deep mantle as well (Porcelli et al, 2001). These losses must have been prior to the assumed closed-system evolution. 

Once the charge is properly placed in the mold, it is closed quickly to contact the top surface of the charge. Mold closure is a critical factor delay in closure time may cause some precure owing to the gelation of the top surface, occurring before the part is molded, and faster closure rates trap air, which induces surface imperfections, which is undesirable. A 10-sec closure time has been suggested as optimum to avoid any precure. 

Fig. 4-3. Long-term trend of methane in air bubbles trapped in the great ice sheets, corrected for firn closure time. Squares are results of Robbins et at. (1973) from Greenland and the Antarctic open circles are results of Craig and Chou (1982) from the Antarctic filled circles and triangles are data of Rasmussen and Khalil (1984) from Greenland and the South Pole, respectively. The asterisk indicates an average global value for the late 1970s.

The use of real-time bottomhole treating pressure enables the qualitative analysis of fracture propagation. Treatment design parameters such as fluid loss coeffident, fracture height, length, width, and closure time can also be determined with pressure decline analysis. 

Figure 2. The abundances of Xe and Xe in the atmosphere are much lower than produced by parent nuclides in the Earth and Earth-forming materials. This has been interpreted as due to losses to space of daughter nuclides until some closure time, after which daughter Xe is retained by the Earth, (a) Abundance of Xe produced from after the time of closure. The amount of Xe in the atmosphere is consistent with complete loss of Xe from the Earth for the first 80 Ma. (b) The Xe in the atmosphere from similarly reflects early Xe losses.

Figure 2, continued, (c) The and systems can be combined to obtain a Xe-Xe age. The slope of the line from the initial (i.e., nonradiogenic) atmospheric composition and through the present atmospheric composition is equal to the Xe/ Xe ratio of the present atmosphere, and is directly related to the closure age. The Xe-Xe age does not depend upon the absolute abimdances of Xe isotopes in the atmosphere. Using U-free MORE from either Kimz et al (2000) (upper value) or model calculations (Porcelli and Wasserburg 1995a). the MORE source has a similar closure time. 

The engineered safety features, for example, have been optimized for the removal of elemental and organic iodine, while the closure time of the isolation valves has been established on the basis of the immediate release from the core. The Technical Information Document 14844 (TID) releases, as they were then named, have been used for the verification of the resistance to radiations of equipment inside the containment, as well as for the evaluation of control room habitability after an accident and for the design of liquid and gas sampling systems. 

Maximum superficial condensate velocities are about 25 m s . In a given line, the velocity increases as the pressure drops and more liquid vaporizes. Vendors of steam traps and condensate systems can provide guidance and line-sizing charts. Water lines usually have velocities up to 3ms . The designer must consider water hammer as well as velocity and pressure drop. Selection of valves and their closure time becomes important. Compressed air usually is transported at 5-8 m s. ... 

Coolant inventory Guard vessel Isolation valves Passive Passive GV integrates primary systems except clean-up. Quick-acting (5s closure time) valves,... 

The required closure time for the Low Volume Purge isolation valves is justified (see CESSAR-DC, Section 6.2.4) by an analysis of ... 

Isolation valve closure times are designed to limit the release of radioactivity and are consistent with standard valve operators, except where a shorter closure time is required. 

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