Operation window

Fig. 20. Example of constraint control operating window for a distillation column, where (-----) is the vessel pressure limit, and ( ) represents constant...

The way that a pump receives the liquid into the impeller determines the available combination of discharge flow and head that the pump can generate. Hssentially, it determines the operating window of the pump. 

This operating window is quantified or rated by the term Suction Specific Speed, Nss . The Nss is calculated with three parameters, the speed, the flow rate, and the NPSHr. These numbers come from the pump s performance curve, discussed in Chapter 7. The formula is the following ... 

In the numerator we have the speed and the flow. If we were comparing similar pumps into an application, these multiplied numbers would mostly be a constant. In the denominator we have the NPSHr of the pump (or competing pumps under comparison for an application). As the NPSHr of the pump goes down, the Nss value rises. As the Nss value increases, the operating window of the pump narrows. 

By using these N,ss values, we ean interpret the Nss Graph, and get a picture of the operating window ofthe.se three pumps. To interpret the graph we start on the left eolumn at the flow in gpm. In Figure 6-15, we draw a line from the flow to the Nss value of the pump, and then reference downward for water, or upward for hydroearbons. 

The operating window is the effective zone around the BH.P on the pump curve that must be respected by the process engineer and/or the operators of the pump. How far away from the BHP a pump can operate on its performance curve without damage is determined bv its impellers suction specific speed. 

There is more information on this in Chapter 9. Dual volute casings tend to equalize the radial hydraulic forces around the pump impeller, thus expanding the operating window of the pump. The Ns is a guide in selecting the adequate volute design. 

Consider the following graph. Figure 9-14. Radial loading on the shaft rises if the pump is operated too far to the left or right of the be.st efficiency zone. Another interpretation of the. same concept is to. say that the maintenance and problems rise when the pump is operated away from its BEP. Many pumps have a rather narrow operational window. These pumps can be very efficient if they are correctly specified and operated. This is discussed completely in Chapters 7 and 8 Pump Curves and System Curves. 

Some pump manufacturers use a different taetie to expand the operating window of their products. This is why the dual ohite pump exists. The dual volute pump is designed to operate over a wide range of flows and heads. 

Link operating factor (fan operation, window opening)... 

Provide good draft-proofing strip around the door and operable window frames, leaving sufficient fresh air ingress for any combustion appliances. 

A chimney should not be less than 3 m from any area where there is access (i.e. ground level, roof areas or operable windows). 

The outlet must not be within 20 U/F of an operable window on the emitting building. 

The operational window of a fluidised bed process is defined by the minimum fluidisation velocity, Uml, at which a settled bed of adsorbent beads starts to fluidise and the terminal velocity ( /t) at which the bed stabilises and adsorbent beads are entrained from the bed. 

In light of the many types of behavior plastics that can manifest and the considerable effect this behavior can have on the performance of the finished product, it behooves designers to become familiar with specific behavior characteristics of each plastic considered for an application. Recognize potential problems. A major cause for problems is not of poor product design but instead that the processes operated outside of their required operating window. This subject will be reviewed latter in this Chapter under PROCESS CONTROL... 

Much progress has been made in widening the operating windows. Stabilized supports have been developed which can tolerate occasional temperature excursions to 2000°F, but even this temperature may be... 

A potentially large operating window in supercritical region. 

Occupants like the operable windows in the original and the new facade, but it is noisy with the windows opened. Lighting is good but acoustics are a problem. Rolling and moveable partitions are commonly used—usually without a ceiling. 

The OSC materials are able to increase the efficiency by enlarging the operating window of TW catalysts [50,51], NOx reduction in TW catalysts is closely coupled to oxidation reactions since there is a competition between NOx and 02 reaction on the reducers present in the exhaust gases [52], We will first examine the effect of these OSC materials on the oxidation efficiency of TW catalysts. 

Figure 8-6 Effect of suction speed on stable operating window due to recirculation. (Numbers on the curves are the values of the suction specific speed, Nss.) (From Raymer, 1993.)...

As a result of the kinetics and the equilibria mentioned above, all iodide in the system occurs as methyl iodide. The reaction in Equation (2) makes the rate of the catalytic process independent of the methanol concentration. Within the operation window of the process, the reaction rate is independent of the carbon monoxide pressure. The selectivity in methanol is in the high 90s but the selectivity in carbon monoxide may be as low as 90%. This is due to the water-gas shift reaction ... 

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