Parallel operation

Introducing parallel operations to the steps which limit the batch cycle time. 

Whether parallel operations, larger or smaller items of equipment, and intermediate storage should be used can only be judged on the basis of economic tradeoffs. However, this is still not the complete picture as far as the batch process tradeoffs are concerned. So far the batch size has not been varied. Batch size can be varied as a function of cycle time. Overall, the variables are... 

The configuration represents scheme of two incomings and one bus coupler. To avoid parallel operation, only two of these must be ON at a time. 

Thus, only three of the five interrupting devices can be switched at a time as required without causing a parallel operation between any of the two incomers. 

Code of practice for maintenance of electrical switchgear for voltages above 36 kV Speeificiition for voltage regulation and parallel operation of a.c. synchronous generators Methods of testing plastics... 

The governor can be set to make the machine run at a constant speed, even on load variations, with extremely quick and almost instantaneous speed control, and thus maintain a near-zero AN. In a parallel operation they can also control load sharing automatically and accurately. Power grids, receiving power from different sources, are extremely susceptible to frequency variations. Even a small Af of the order of 0.5 Hz, may cause the system to trip. A fast-actuating governor with low response time (as low as 0.5 second) can overcome such a situation by quickly regulating the speed of the PM. 

This device controls the generator and maintains a steady-stale armature voltage automatically within the predefined limits. It also serves to control the reactive kVAr loading during a parallel operation or when the machine is being used as a synchronous condenser for reactive power compensation through a quadrature droop control (QDC) as noted below. 

This is a scheme introduced in the AVR circuit to adjust the reactive power (kVAr) of a machine during a parallel operation or when it is being used as a synchronous condenser. It prevents a reactive circulating current, l. ... 

The higher the droop, the higher will be the load variation. When there is a difference in the full-load speeds the load sharing during a parallel operation will not be equal and the generators will operate underutilized. 

Parallel operation of capacitor bank C2 with an already switched capacitor C,... 

For smaller units, they are u.sed to limit only the inrush currents during a parallel operation and may be rated for 0.2% of the capacitors kVAr rating. They must be connected on the neutral side of a star-connected capacitor bank. Also refer to the notes below step 4 of Example 23.4. 

Introduction DG set Operating parameters Theory of operation Guidelines on the selection of a DG set Types of loads Starting of a DG set Proteetion of a DG set Parallel operation Procedure of parallel operation Recommended protection for a synchronizing scheme Load sharing by two or more generators Total automation through PLCs... 

Maldistribution of load in parallel operation of two or more eom-pressors. 

Check valves are required in the piping system at any point where backflow of gas after a shutdown has the ability to restart the compressor, running it backwards or, for that matter, even in the normal direction. Reverse rotation is totally bad, as many components of the various compressor types are not designed for reverse rotation, and there is some possibility, generally remote, that the compressor could reach a destructive over speed. Forward rotation is bad primarily because the intent was to stop the compressor, and it is now operating out of control. This is a problem, particularly if the shutdown was caused by a compressor failure indication, and the need to stop was to prevent further damage. In this mode, it is unlikely that the compressor can attain an overspeed condition. An application with a high potential for backflow is the parallel operation of two or more compressors. 

In parallel operation (sensible heat transfer), fluids A and B (Figure 10-30) flow in the same direction along the length of travel. They enter at the same general position in the exchanger, and their temperatures rise and fall respectively as they approach the outlet of the unit and as their temperatures approach each other as a limit. In this case the outlet temperature, tg, of fluid B, Figure 10-30, cannot exceed the outlet temperature, Tg, of fluid A, as was the case for counterflow. In general, parallel flow is not as efficient in the use of available surface area as counterflow. 

Parallel Operation ors,. Spore Reboiler Located as Mirror Imoge of Unit Shown... 

Figure 12-46D, Part 1. View toward inlet of 4 Vj-in. diameter brazed aluminum impeller. Note Regardless of the metal of manufacture, enclosed impellers with back-leaning blades are extremely useful in applications requiring a steep head-volume characteristic and the highest attainable efficiency. Applications include parallel operation with other compressors or boosting of another compressor s output. The power-volume curve will show a self-limiting feature at higher volumes. This feature is very beneficial when the driver has limited power available but operation throughout the full capacity range is required. (Used by permission A C Compressor Corporation.)...

Parallel operation of many fans in a system is common yet, it is a condition that must be analyzed to avoid improper and inefficient operation. 

A qualitative and somewhat quantitative indication of the case with which the two (or more) fans will parallel is represented by their limit curve of Figure 12-145. This curve is constructed by starting at pressure P corresponding to the system intersection A, and plotting the increments of Volume X, y, etc., to define the limit of available volume that the duct can accept and which the second fan must pick up as it comes on the line. For good parallel operation, the limit curve must intersect the combined static pressure curve, SP, at only one point. 

Although the analysis of parallel operation indicates that a fan may not operate satisfactorily, often it actually will operate, but under modified conditions. The effect of a slight difference in the individual fan ductwork can be enough to allow operation, or sometimes a change in damper setting will allow operation. Usually in such situations, efficiency will be reduced with a higher horsepower consumption. If the fans discharge toward each other in such a way as to affect each other s operation, the fans may actually operate at a reduced pressure, somewhere between the static and total pressure curves. ... 

Hagen, H. R, Parallel Operation of Fans, B. F Sturtevant Div., Westinghouse Electric Gorp. 

Bard, H. Parallel Operation of Fans, Flakt Products Div., Flakt, Inc., pub. date not known. 

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