Strength Design

Balanced bellows PR valves need not be restricted to the same built-up back pressure limit (10% of set pressure) as are conventional valves, since they are not subject to chattering from this cause. However, maximum back pressure is limited by capacity and in some cases by the mechanical design strength limitations of parts such as the outlet flange, bellows, or valve bonnet. 

Prevent loss of containment due to exceeding equipment design strength. 

All the nickel alloys are readily fabricated and welded. Their design strengths allow use to elevated temperatures and with relatively thin wall thicknesses. The Nickel Institute (http7Avww.nickelinstitute.org) has excellent publications available that detail the properties and fabrication requirements for both stainless steels and nickel-based alloys, as does SSINA (http //www.ssina.com) and so do many of the manufacturers of these alloys. 

For design purposes it is necessary to decide a value for the maximum allowable stress (nominal design strength) that can be accepted in the material of construction. 

In the British Standard, PD 5500, the nominal design strengths (allowable design stresses), for use with the design methods given, are listed in the standard, for the range... 

The vessel wall thickness must be sufficient to ensure the maximum stress intensity does not exceed the design stress (nominal design strength) for the material of construction, at any point. 

Dynamic Strength. The dynamic design strengths for steel reinforcing and concrete are equal to their static design strengths times the appropriate Dynamic Increase Factor (DIF). 

Frame Loads. The window frame must develop the static design strength of the glass pane, r, given in Table II. Otherwise, the design is inconsistent with f rame assumptions, and the peak blast pressure capacity of the window assemblies will produce a failure rate in excess of the prescribed failure rate. This results... 

Table II. Static Design Strength, r Cpsi), for Tempered Glass ...

Glass Size, Static Design Strength (psl) for a Window thickness, t, of - ... 

The A SI LRFD Cold-Formed Steel Design Manual (AISI 1991) is used as the basis for blast resistant design. Strength reduction factors are not applied (i.e. [Pg.57]

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