Pumping time

A. Since tire applied field is red detuned, all A have negative values. Now in order for tire cooling mechanism to be effective tire optical pumping time tp should be comparable to tire time required for tire atom with velocity v to travel from tire bottom to tire top of a potential hill,... 

When equipment receives impulses at its own natural frequency of vibration, excessive vibration (resonance) occurs, and this can lead to rapid failure. A control valve was fitted with a new spindle with slightly different dimensions. This changed its natural frequency of vibration to that of the impulses of the liquid passing through it (the frequency of rotation of the pump times the number of passages in the impeller). The spindle failed after three months. Even a small change in the size of spindle is a modification [24]. 

PUMP TIME RELATED FAILURE DATA SHEET... 

Figure 6.5 Example Pump Time-related Failure Rate Data Worksheet. From Science Applications International Corporation.

Table 4. Typical pumping times for reaching vacuum (system without sample)...

Pumping time From normal pressure To medium vacuum approx. 1 x 10-3 torr To high vacuum approx. 1 x 10-6 torr... 

A peristaltic pump pulls the sample stream to each of the module detectors for a selected time period this is the Pump Time . TTie peristaltic pump then stops and the detectors are allowed to come to equilibrium this is the Measure Time . At the end of... 

The size of the ballast volume depends on the total quantity of gas to be pumped per unit of time. If this rate is very low, the rule of thumb indicates that 0.51 of ballast volume allovi/s 1 min of pumping time with the backing pump isolated. 

An extreme example of the discrepancy between true pressure pT and indicated pressure pi in pressure measurement is the admission of air to a vacuum system with argon from a pressure cylinder to avoid moisture (pumping time). According to Fig. 3.11, one would obtain a p, reading of... 

With care, which usually means longer pumping times and greater rigour in the preparation of the experiments, the level of the impurities, such as water in liquid reagents or solvents, can be reduced to below 10" mol 1" ... 

Equation (1.7) is the general equation for any individual component of the system under molecular flow conditions and with it one can calculate the overall pumping time for a system, if the conductances of the individual components of the system are known. The effective pumping speed at any point along the vacuum line is given by ... 

Fig. 4.7. The first-order rate constant as a function of the initiator concentration for the polymerisation of styrene in nitrobenzene by various salts for details see text and the table below. The pumping time, /p, determines the concentration of residual water which neutralises some of the initiator. In this instance the impurity acts as an inhibitor , in contrast to the examples in Figs. 4.5 and 4.6...

As an example, consider the time required to pump a large air lock with a volume of 50 L from a pressure of 760 to 0.5 torr. The free-air capacity of a widely available pump is 140 L/min, but three-fourths of this is a more reasonable average pumping speed for the above pressure range. Insertion of these numbers into Eq. (3) gives a pump-down time of 3.5 min. This value may somewhat underestimate the pumping time, but the calculation illustrates a method for approximately matching the pump to the patience of the experimentalist. 

Although a solution of HF, or a mixture of HF and HN03, can remove the tungsten stain, it also removes some of the glass, which can etch the glass and thereby increase pumping time due to increased surface area. If the HF solution is left too... 

Table 7.4 The Relation of Tube Length and Diameter to Pumping Time (see Fig. 7.8)°...

This determination is assuming that you have a perfectlydesigned vacuum system with no narrow passageways, no extra chambers, no bends, no contamination, and no traps, baffles, or stopcocks. Not much of a vacuum system, but it sure would be fast. Because you are working in the real world, the real pumping time will be slower. To compensate for this slower time, it can be helpful to multiply the above result by 2 or 3 to ensure that the pump will be adequate to handle your system s needs. However, as a tool for approximating the minimum size needed, the above formula is usually sufficient. The final decision of what pump to purchase, as in all selections, will depend on what you are willing to settle for and/or what you can afford. (More information on pump speeds is provided in Sec. 7.3.10.)... 

To demonstrate the value of this system, suppose you have a mechanical pump who s general lower range is 2 torr (in an acceptable pumping time period ). By the third evacuation and purging, the amount of residual air is 2 x (2/760)2, or about 10 5 torr.23... 

Low speed (extra long pumping time) Low heat input Check heater. 

Precalcination reduces the rate of dissolution of MgO substantially, and as we shall see later in this chapter, a slurry of MgO and H3PO4 or an acid phosphate can be mixed for several minutes before the exothermic acid-base reaction kicks off. Often, large-scale production of ceramics, such as oil well cements, requires hours of pumping time (see Chapter 15) or long setting times. Even in a production line of refractories that produce castables of consistent quality, the reaction slurry must have a storage life of a few hours. In such cases, chemicals are added to retard the reactions in the slurry. 

Calcined MgO is a requirement for forming practical Mg-based ceramics, while boric acid addition is not essential in several systems such as formation of MgKP04-6H20, unless the mixing and pumping times of the slurry need to be extended for several hours. We will be discussing various Mg-based ceramics that have been developed using these methods. 

Using this approach, ANL and BNL have identified slurry compositions for a range of depths and temperatures of relevant oil, gas, and geothermal wells. The pumping time and slurry compositions are presented in Table 15.2. 

Well Conditions Pumping, T(° ) Sluixy Components (g) Pumping Time (h min)... 

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