Pump-around systems

For a fired reboiler, a pump-around system is used with an FRC to maintain constant flow. There will be a low flow alarm plus fuel shutoff. There will also be a high flow alarm plus fuel shutoff, since a tube rupture would reflect itself in a high flow. 

FIGURE 13.3 A "pump around" system to minimise heat exchanger fouling... 

Pump-around system—consists of a series of piping, storage tank(s), valves, gauges, and a pump. 

Steam-generation system—a complex arrangement of boiler systems designed to convert water to steam. These include pump-around systems, advanced process control systems and instruments, fuel systems, and compressor systems. 

New technicians often have difficulty determining which pieces of industrial equipment go together when asked to develop a simple flow diagram. Using a simple pump-around system, technicians can learn how to perform equipment line-ups, start-ups, operational checks, and shutdowns. The... 

Identify the equipment used in a pump-around system. 

Sample Problem Calculate the flow rate (FR) of the following pump-around system. 

In an excimer laser the mixture of inert gas, halogen gas, and helium, used as a buffer, is pumped around a closed system consisting of a reservoir and the cavity. 

Also for these pumps, multistage systems (e.g. Varian TriScroll Pump) are used which allows for final pressure around 10 2torr and pumping speed of about 30m3/h (see Fig. 1.10). The typical application of scroll pumps systems is the backing for turbomolec-ular pumps (see Section 1.6.6). 

Following are some examples of passive safety systems to reduce the likelihood of explosions in storage units. The use of baffles in a high-pressure storage vessel can cool the tank wall above the liquid surface via liquid pumped around by vapor bubbles, extending the time for fire fighting. Fire resistant tank insulation is also effective in delaying a BLEVE. 

This type of traveling wave tube with cold cathode has been developed and met reasonable performance. However, a good system pumping around the cathode was difficult to achieve in the small enclosed spaces. 

Motionless mixers (and inline mixers in general) present an alternative to the more traditional agitated vessel. These devices are particularly useful for the continuous processing of chemicals but are also incorporated as part of a batch system in pump-around loops. 

The internal modifications to retrofit the distillation system consider the distillation column and its internals. In this level of retrofit, some changes are made in the internals or nozzles of the main column and the side strippers. Moreover, the reboilers and pump around loops are examined and adjusted as required. Therefore, more complex modifications are required at this level that lead to higher investments. The objective of these modifications is to find out the ideal distribution of stages for each section in the main column [4]. This ideal design is applied to the existing column by modilying its internal to the niinimrim extent to reduce the costs. 

The large amount of seed presents a high-growth area from the outset of the operation. The initial presence of the seed avoids the issue of when to add it to prevent seed dissolution and homogeneous nucleation. Note that for this process, the size of the particles does not need to decrease, as steady-state particle size distribution is reached at the low but finite natural attrition rate achieved in the pump-around and agitation systems. 

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