Piping systems, design pressure

Over-pressure, a pressure exceeding the system design pressure, is one of the most serious hazards in chemical plant operation. Failure of a vessel, or the associated piping, can precipitate a sequence of events that culminate in a disaster. 

The code also excludes piping systems designed for internal gauge pressures at or above zero but less than 0.105 MPa (15 Ibf/inU provided the fluid handled is nonflammable, nontoxic, and not damaging to human tissues, and its design temperature is from -29 C (-20 F) through 186 C (366 F). Refer to the code for definitions of nonflammable and nontoxic. 

Piping systems designed for pressures less than 15 psi gage that handle fluids that are nonflammable, nontoxic, and not damaging to human tissues and are at temperatures between —29°C (—20°F) and 186°C (366°C) ... 

The 42-in. and 30-in. pipe diameter are selected to obtain coolant velocities which provide a reasonable balance between erosion-corrosion, pressure drop, and system volume. The surge line is sized to limit the frictional pressure loss through it during the maximum in-surge so that the pressure differential between the pressurizer and the heat transfer loops is no more than 5 percent of the system design pressure. The spray line sizing is discussed in Section 5.4.10. 

There are two types of pressure test. The first is a tightness test, used after the equipment has been opened but not modified in any way. Typically this type of test is conducted after the item was opened for cleaning, inspection, or routine maintenance. The test ensures that the equipment is leak-free but it does not test the integrity of the vessel or piping itself. Tightness tests are never conducted at a pressure above the equipment or system design pressure or the relief valve set pressure. 

Helium system design pressure and temperature will be o psig and l().aO°F. fl he entire loop is of all-welded construction to minimize helium leakage and leakage of olatil< fission products. should. a rupture of the reactor c.s.scl or piping gi c volatile fission products access to (his loop. 

The minimum thickness of a pipe wall (fm), prior to bending, required for the system design pressure was calculated using the following equation ... 

The code prescribes minimum requirements for the materials, design, fabrication, assembly, support, erection, examination, inspection, and testing of piping systems subject to pressure or vacuum. The scope of the piping covered by B31.3 is illustrated in Fig. 10-124. It applies to all fluids including fluidized sohds and to all seivdces except as noted in the figure. 

Design Conditions Definitions of the temperatures, pressures, and various forces applicable to the design of piping systems are as follows ... 

Design Pressure The design pressure of a piping system shall not be less than the pressure at the most severe condition of coincident pressure and temperature resulting in the greatest required component thickness or rating. 

Vacuum pump capacity is conventionally based on the total cycle and expressed as mVh-m" (cfi7i/ft ) of filter area measured at pump inlet conditions. Thus, the gas volumes per unit area passing during each dry period in the cycle are totaled and divided by the cycle time to arrive at the design air rate. Since air rate measurements in the test program are based on pressure drop across the cake and filter medium only, allowance must be made For additional expansion due to pressure drop within the filter and auxiliary piping system in arriving at vacuum pump inlet conditions. 

To minimize nucleation, piping systems should be designed to maintain absolute pressure as high as possible. 

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