Requirement in resist design

Metal can cover many requirements in seal design it may be used for faces and other parts such as rings and bellows. The specification of the metal depends on the degree of corrosion resistance necessary, the thermal expansion and the material of the mating face. 

All three types of valves described above are on-off type devices (binary devices). A basic requirement in the design of these valves is that they offer minimum resistance to flow when open. For many types of calculations it is often justifiable to neglect pressure losses through such devices. But such a simplification cannot be applied to flow control valves. With these devices the control of flow is accomplished either by a constriction or by a diversion. In either case an additional resistance to the flow is introduced. Globe, angle, cross, and needle valves are typical devices of this type. Specific pressure drop correlations should be developed for such devices and used whenever possible. One such correlation used by Stoner (S5) takes the form... 

Certain operations require that the workspace be at a lower pressure than surrounding workspaces, e.g., radioisotope laboratories. In these cases, the exhaust flow rate should exceed the supply flow rate, but this excess should he within 10%. The additional resistance resulting from this imbalance should be considered in the design of the exhaust system, specifically in the selection of exhaust fans. 

Aluminum has many of the characteristics and qualities required for fluid power lines. Is has high resistance to corrosion and is easily drawn or bent. In addition, it has the outstanding characteristic of lightweight. Since weight elimination is a vital factor in the design of aircraft, aluminum alloy tubing is used in the majority of aircraft fluid power systems. 

In addition to spacing criteria, many standards provide requirements for building design and construction to provide fire resistance and protect occupants. Table 3.2 summarizes typical key references for fire protection and evaluation. 

For low-hazard situations, blast-resistant design is not required because a fire is more likely than an explosion in case of a flammable vapor release. Where little or no explosion hazard (low hazard) exists, it is only necessary to meet conventional building code requirements, including those for fire protection. 

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