One-Pump System

The IEX—Dual Column RP system configuration shown (Fig. 13.1) utilizes independent pumping systems for each separation dimension. One pumping system... 

One-pump systems Submersible turbine Moderate to high Unlimited Yes Yes ... 

Compared to other high-throughput systems in this parallel HPLC device, the use of a flow control unit with only one pumping system is a decisive factor. This setup guarantees stabilized flow in an extensible number of simultaneously operated separation columns and thus, in principle, can be combined with any other sophisticated column switching and detection system. A specific version of this instrument was adapted to preparative fractionation and purification of natural product extracts by... 

For many applications, provision is made to attach several dewars to one pumping system. The set of valves and the tube that connects them is referred to as the manifold. Care is necessary when connecting or removing a dewar to the system since the pumping of someone else s dewar can be disturbed. If using such a system, be sure you know the agreed-on rules. 

The above example is a simple one, and it can be seen that the individual items form part of the chain in the production system, in which the items are dependent on each other. For example, the operating pressure and temperature of the separators will determine the inlet conditions for the export pump. System modelling may be performed to determine the impact of a change of conditions in one part of the process to the overall system performance. This involves linking together the mathematical simulation of the components, e.g. the reservoir simulation, tubing performance, process simulation, and pipeline behaviour programmes. In this way the dependencies can be modelled, and sensitivities can be performed as calculations prior to implementation. 

This provides another criterion for testing whether a heat-pump system may be cost-effective. A power plant takes three units of to yield one unit of W. Therefore, to provide any incentive for less overall energy use, Q W must be far in excess of 3. 

The one-pass system consists of a feed tank, filter, pump, and membrane system (Fig. 6). The feed tank contains whiskey at approximately 100° proof. It is filtered through a cellulose filter and then pumped into the membrane system where the separation takes place. Dupont B-10 A ram id hoUow fiber membranes are used in series or parallel and are able to withstand the high pressures, 689—1034 kPa (6.8—10 atm), necessary to achieve separation. 

Collection and analysis of vibration signatures is a complex procedure. By looking at a vibration spectrum, one can identify which components of the pump system are responsible for a particular frequency component. Comparison of vibration signatures at periodic intervals reveals if a particular component is deteriorating. The following example illustrates evaluation of the frequency composition of an electric motor gear pump system. 

Be aware that in some cases, you ll have to live with cavitation. Many pumps suffer cavitation for reasons of inadequate design, hor example, when operating only one pump in a parallel system, this pump tends to go into cavitation. Pumps that perform more than one dut through a valve manifold tend to suffer cavitation. Pumps that fill and drain tanks from the bottom tend to suffer cavitation. The last pump drawing on a suction header tends to cavitate. And of course vacuum pumps and pumps in a high suction lift arc candidates for cavitation. 

By showing numerous impellers, motors and effieieneies for one pump, the family eurve has a lot of information crushed onto one-graph. So to simplify the eurve, the effieieneies are. sometimes shown as eoneentrie eireles or ellipses. The eoneentrie ellipses demonstrate the primary, seeondary and tertiary effleieney zones. They are most useful for eomparing the pump eurve with the system eurve. (The system eurve is presented in Chapter 8.)... 

This system, although simple, with only one pump, is more or less representative of all systems. This sy stem is eomposed of 180 ft of pipe 40 ft of 6 inch suction pipe, and 140 ft of 4 inch discharge pipe. 

Consider nil the mnthcmnticnl gXTntions required just to determine the H nnd Hf. This is n lot of ninth for one pump. Imagine the work to speeifi pumps for n paper mill or beer brewery or municipal water system. Now you can see why governments and pharmaeeutical eompanies contract consulting engineering companies to do this work and specifi the pumps. Finally, we can calculate the TDH of the system ... 

The system is designed so that two equal pumps are operating together side by side. The system can support the production of both pumps. If the needs of production are reduced, this system can operate with only one pump, simply by removing one pump from service (Figure 8-25). 

Here we see something interesting. Recause the system is designed for both pumps running in parallel, when only one pump is operating, this pump will run to the right of its REP. This situation brings it s own peculiar set of implications, not often understood in indu.stry. 

First, one pump running in a parallel system tends to suffer from cavitation because operation to the right of the BF.P indicates that the NPSHr of the pump rises drastically. To survive this condition, you should use dual mechanical seals on these pumps. Dual or double mechanical seals can withstand cavitation better than a single seal. There is a discussion on this in the mechanical seal chapter of this book. Many engineers perceive that parallel pumps are problematic becau.se they appear to suffer a lot of premature seal failure. Parallel pumps deserve double seals even if it s only a cold water system. 

Third, you would. suppose that parallel pumps are identical, that they were manufactured and assembled together. But it is possible that one pump of the pair is the dominant pump and the other is the runt pump. If you start the dominant pump first in the parallel system, and then decide to add the runt pump of the pair, the weaker pump may not be able to open the check valve. The pump operator perceives that the flow meter on the second pump is stuck or broken. This is because the second pump might be dead heading against a closed check valve, maintained that w ay by the dominant pump. If this situation exists, it may re.sult in premature failure of bearings and. seals, leading maintenance and operations personnel thinking that parallel pumps are problematic. 

The same previously mentioned critical tips apply, plus one more. Upon observing the system curve, with the pump curves, it appears that the operator can operate any one pump, or any two, or any three or four pumps. Actually there is no option to run three pumps in this... 

When operating just one pump in a parallel pump system. 

For positive displacement pumps, a bypass-type control valve should be furnished to set the primary lube system pressure. The valve should be able to maintain system pressure during pump startup and pump transfers, which includes relieving the capacity of one pump, while both are running. The valve should provide stable, constant pressure during these transients. Flow turndown of 8 to 1 is not unusual. Multiple valves in parallel should be used if a single valve is not suitable. The valve should be sized to operate between 10 and 90% of the flow coefficient (Cv). Additional pressure control valves should be furnished as required to pro ide any of the intermediate pressure levels. 

The natural frequency, co associated with the mode shape that exhibits a large displacement of the pump is compared with the fundamental frequency, of the wall. If co is much less than ru, then the dynamic interaction between the wall and the loop may be neglected, but the kinematic constraint on the pump imposed by the lateral bracing is retained. If nearly equals nr , the wall and steam supply systems are dynamically coupled. In which case it may be sufficient to model the wall as a one-mass system such that the fundamental frequency, Wo is retained. The mathematical model of the piping systems should be capable of revealing the response to the anticipated ground motion (dominantly translational). The mathematics necessary to analyze the damped spring mass. system become quite formidable, and the reader is referred to Berkowitz (1969),... 

The two primary pumps with AC and DC pony motors flow 18,000 gpm of heavy water through the core for cooling. Following 60 MW operation, for 3 minutes, forced flow is needed to remove the decay heat. Upon loss of pony motors and primary pumps, forced flow is established through the shutdown cooling water system consisting of two pumps in parallel - one pump running and the other on standby. 

Pumps are operated in parallel to divide the load between two (or more) smaller pumps rather than a single large one, or to provide additional capacity in a system on short nodce, or for many other related reasons. Figure 3-35 illustrates the operational curve of two identical pumps in parallel, each pump handling one half the capacity at the system head conditions. In the parallel arrangement of two or more pumps of the same or different characteristic curves, the capacities of each pump are added, at the head of the system, to obtain the delivery flow of the pump system. Each pump does not have to carry the same How but it will operate on its own characteristic curve, and must deliver the required head. At a common tie point on the discharge of all the pumps, the head will be the same for each pump, regardless of its flow. 

The lubricating oil system for a turbine is very important and is nearly always provided with a dual pumping arrangement. One pump can be driven directly off the turbine shaft and the other by separate electric motor or steam turbine. In another arrangement, one pump can be separately electric driven and the other separately steam turbine driven. Twin coolers are often provided in the dual system to... 

In Oxalobacter formigenes, oxalate and its decarboxylation product formate form a one-to-one antiport system, which involves the consumption of an internal proton during decarboxylation, and serves as a proton pump to generate ATP by decarboxylative phosphorylation (Anantharam et al. 1989). 

These batch procedures for enrichment and successive transfer may be replaced by the use of continuous culture. This may be particularly attractive when the test compound is toxic, when it is poorly soluble in water, or where the investigations are directed to substrate concentrations so low that clearly visible growth is not to be expected. These problems remain, however, for subsequent isolation of the relevant organisms. One considerable problem in long-term use arises from growth in the tubing of the pump system that is used to administer the medium and should be renewed periodically. 

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