Piping Design Factors

In piping design, the three conditions that lead to corrosion problems are (i) water traps (ii) dead legs (iii) high velocities. 

Water traps are low sections of the piping system where water stagnates and causes corrosion. Pitting corrosion occurs in water traps. This form of corrosion can be countered by minimizing the low sections through slanting the pipe or by installing drain valves at low points that are periodically drained. 

Velocity effects are cavitation and erosion-corrosion. In general, fluid piping should be designed with large diameters to transport the quantity of material 

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A heavier wall thickness than is required by the pipe design factor, F, in accordance with Table PL-3.7.1(b)(6)-l or Table PL-3.7.1(b)(6)-2, may be used. 

Larger flaws can be tolerated in X60 as compared to X80 for the same diameter of the pipe. This is because the wall of the X80 pipe is thinner than X60 at the same MAOP = 1500 psi for the same design factor DF = 0.72 or SF = 1.39. 

Class 1, Division 2. This Division is a Location Class 1 where the design factor of the pipe is equal to or less than 0.72 and has been tested to 1.1 times the maximum operating pressure. [See Table PL-3.7.1(b)(6)-2 for exceptions to design factor.]... 

F = design factor obtained from Table PL-3.7.1(b)(6)-l or Table PL-3.7.1(b)(6)-3 as applicable, depending upon the fracture control option specified in (b) below used in the design. In setting the values of the design factor, F, due consideration has been given and allowance has been made for the various underthickness tolerances provided for in the pipe specifications listed and approved for usage in this Code. 

Table PL-3.7.1 (b)(6)-2 Design Factors for Steel Pipe Construction (Used With Option A)...

D = outside diameter of pipe container or bottle, in. F = design factor [see para. PL-3.7.1(a)]... 

NOTE The twice nozzle load requirement is a pressure casing design criterion. Allowable nozzle loads for piping designers are the values given in Table 4. Other factors such as casing support or baseplate stiffness affect allowable nozzle loads. 

Design Factor Pipe Reactor Vessel Reactor... 

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