Piping arrangements system

This facc-to-facc double seal is quite versatile (Figure 13-21). It is reeommended in a wide range of applieations depending on the piping arrangement of its support system. 

A pressure switch located so as to sense falling pressure at the earliest moment should be used to activate the standby pump. The switch should be so connected to the system as to permit testing the startup circuit without shutting down the compressor. Figure 8-8 shows four piping arrangements. The figure at b would be the recommended method. 

The availability of pre-action systems depends heavily upon the availability of the associated independent detection system. To compensate for this, systems should be designed so that the valve can be opened manually, both locally and at a constantly attended location. In addition, because of the complex mechanical valve arrangement, pre-action systems are less reliable than wet and dry pipe sprinkler systems. 

All commercially available fractionation processes can give comparable performances. Basically, each process uses a deaerator, heat source, fractionation column, condensing system, and vacuum source. These processes may differ in the internals of the column, in the manner of evaporation and condensation, and in the piping arrangement for better heat recovery, but they can give equally good results. 

Fig. 8. Piping arrangement of a bench-scale batch dispersed air flotation system.

The characteristics and complexity of flow pattern are such that most flows are described by a set of empirical or semi-empirical equations. These relate the pressure drop in the flow system as a function of flow rate, pipe geometry, and physical properties of the fluids. The aim in the design of fluid flow is to choose a line size and piping arrangement that achieve minimum capital and pumping costs. In addition, constraints on pressure drop and maximum allowable velocity in the process pipe should be maintained. These objectives require many trial and error computations, which can be performed well by a computer. 

One of the advantages claimed for the technology in comparison with the sponge rubber ball system, is that it requires less maintenance. A major disadvantage perhaps in some situations more than others, is the momentary interruption in flow while the flow reversal is accomplished. The disruption of steady state conditions in the plant operation may be difficult to accommodate and could have implications for product quality. The cost of the complex piping arrangements and the control system could be expensive, particularly in a retrofit... 

A poorly piped variation of this system (Fig. 17.5e) caused pressure fluctuations and inability to keep column pressure constant in one case (194). The author is familiar with two more troublesome cases with a similar piping arrangement, while a fourth similar case was reported by Hollander (164). With the Fig. 17.5e scheme, subcooled liquid mixes with dew point vapor. Collapse of vapor takes place at the point of mixing. The rate of vapor collapse varies with changes in subcooling, overhead temperature, and condensation rate. Variation of this collapse rate induces pressure fluctuations. The above problem (194) was completely eliminated by separating the liquid line from the vapor line, and extending the liquid line well below the liquid surface. The vapor line entered at the previous inlet. 

The final vent from the system should be regarded as a point of possible chlorine emission. It should be at a high level and away from personnel traffic and ventilation system intakes. Particularly when the low-pressure scrubbing device is a packed bed, booster fans may be added on the tail pipe. The piping arrangement around the fans then should avoid low points that could collect liquid. As with any vent manifold, the designer of a system serving several different units should take precautions to avoid mixtures in headers that may lead to undesirable side reactions. 

The optimum liquid level depends upon the system. The optimum can be predicted with confidence, but the final point must be established by observation since two-phase pressure drops, product composition, and piping arrangements cannot always be precisely calculated. For most systems the optimum point results when the evaporator liquid level is approximately half the distance between the two tubesheets. 

The design of the System 80+ Main Steam system adequately addresses dynamic loads caused by condensation-induced water hammer and has piping arrangement and drainage provisions to protect against water entrainment. These are described in CESSAR-DC, Sections 10.3.2.2D, M, N, and P. 

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