Rate surge

Dies are shaping devices that operate at a rate that is directly proportional to the upstream pressure. Thus, if the pressure to the die is not constant then a variable rate will occur at the die opening, causing the dimensions of the product to vary. Rate surges at the die can be estimated from the pressure surges using the... 

A tank used to dampen liquid flow rate surges is known to exhibit second-order dynamics. The input flow rate changes suddenly from 120 to 140 gal/min. An operator notes that the tank level changes as follows ... 

Because RPSA is appHed to gain maximum product rate from minimum adsorbent, single beds are the norm. In such cycles where the steps take only a few seconds, flows to and from the bed are discontinuous. Therefore, surge vessels are usuaHy used on feed and product streams to provide unintermpted flow. Some RPSA cycles incorporate delay steps unique to these processes. During these steps, the adsorbent bed is completely isolated and any pressure gradient is aHowed to dissipate (68). The UOP Polybed PSA system uses five to ten beds to maximize the recovery of the less selectively adsorbed component and to extend the process to larger capacities (69). 

The special design of the Latham bowl allows for a specific blood cell separation known as SURGE. This technique makes use of the principle of critical velocity. The Latham bowl is filled until the huffy coat, ie, layer of platelets and white cells, moves in front of the bowl optics. At this point the machine starts to recirculate plasma through the bowl at increasing rates. The smallest particles, ie, platelets, ate the first to leave the bowl. Their high number causes the effluent line to turn foggy. The optical density of the fluid in the effluent line is monitored by the line sensor. A special algorithm then determines when to open and close the appropriate valves, as well as the optimum recirculation rate. 

These pipe walls are adequate for the rated working pressure plus a surge allowance of 100 Ihf/in . For the effect of laying conditions and depth of hiiry, see ANSI A21.51. 

The performance of a centrifugal compressor (discharge to suction-pressure ratio vs. the flow rate) for different speeds is shown in Fig. 11-87. Lines of constant efficiencies show the maximum efficiency. Unstable operation sequence, called surging, occurs when compressors fails to operate in the range left of the surge envelope. It is characterized by noise and wide fluctuations of load on the compressor and the motor. The period of the cycle is usually 2 to 5 s, depending upon the size of the installation. 

Rake-Lifting Mechanisms These should be provided when abnormal thickener operation is probable. Abnormal thickener operation or excessive torque may result from insufficient underflow pumping, surges in the solids feed rate, excessive amounts of large particles, sloughing of solids accumulated between the rakes and the bottom of... 

Figure 17.7(b) Typical value rating of equipmenf of surge impedances for HT mofors and transformers... 

It has been seen that smaller rating HT machines are more susceptible to steeply rising voltage surges, compared to larger ratings, due to their relatively w eaker interturn insulation and require more careful attention to their adequate protection. We attempt to explain this phenomenon as follows ... 

Lower ratings have low L and C and therefore have a higher (Figures 17.7 and 17.8) and do not help in dampening or taming the surges. 

Select the nearest voltage rating of a station class surge arrester (see also Section 18.8) from the manufacturer s catalogue, (Table 18.8) as 6 kV which has the following protective levels ... 

Unfavourable operatitig conditions will require a derating in the rating of a surge arrester or special surface treatment and better clearances. Refer to the manufacturer for the required measures and/or deratings. 

TOV is considered only to select the MCOV and the rated voltage, V, of the surge arrester. This is a reference parameter to define the operating characteristics of an arrester. It plays no part in deciding the protective level of the arrester, which is solely dependent on the transient conditions of the system, as discussed later. V, is used to make the right choice of an arrester and its energy absorption capability to ensure that it does not fail under the system s prospective traiisieut conditions. 

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