8/18/2019 Defining Soil corrosion Points in AutoPIPE

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Defining Soil Points in AutoPIPE

 The process of defining a buried piping system is a combination of user defined piping points, and internally generated (by AutoPIPE)soil points. The user only needs to define piping points for identifying the following critical parts of a buried piping system:

1. As required by changes in the system geometry.

2. For specification of piping components (e.g. valves, reducers, flanges, anchors, etc.).

3. Where soil properties change.

4. Where the maximum spacing (between the internally generated soil points) defined for the current soil identifier is to bechanged.

 The first and second items in this list are straight forward. Thus, the following discussion concentrates on the piping points required fordefining the critical points related to the soil. Different soil types are often encountered along the length of a buried piping system. Apiping point must be defined at the intersection of the pipeline and the plane which divides dissimilar soils. This allows a set of soilproperties to be linked with a specific range of piping (between the specified piping points). Where a new soil type is encountered, asoil identifier and its set of properties must be defined and applied from that point on in the system. In addition, if a buried pipe has avertical orientation new soil properties must also be defined. This is because the orientation of transverse horizontal, up, and down arerelative to the local coordinate system for a straight pipe element (refer to Soil Restraint Properties). However, if only the maximumspacing is to be changed a new soil identifier is not required. Simply modify the spacing value to be associated with the marked portionof the buried pipeline (within the region defined for that soil identifier).

A piping point must also be defined at each location where the maximum spacing of a soil is to be changed. First, the lengths Lb and

Lm

 must be calculated by hand for each buried bend (or tee). Then, the locations of the required piping points can be identified by

applying rational guidelines for the spacing of soil points in the three zones. Since AutoPI PE does not have the ability to specify alinearization of spacings in the transition zone (Zone 2), guidelines are required in addition to those provided in Section D.1. The Figurebelow shows one approach for modeling spacings in the three zones.

Figure D-4

Note that only point A02 is required by the geometry of the system. Points A01 and A03 are defined at a distance of L b from the bendin order to mark the bearing span region in each direction. Point A06 is defined and rigidly anchored at a distance of L a (= 1.5 Lm)since pipe-soil interaction beyond this point (Zone 3) is minimal. Points A04 and A05 are each placed at distances away from the bendso that soil point spacings can be specified by marking the applicable range of piping points. The dimensions at the bottom of Figure D-4 (above) represent the maximum spacing (expressed as multiples of the pipe diameter) to be specified between each set of pipingpoints.

 The maximum spacing defined on the ’Soil’ dialog is used by AutoPIPE as an increment for determining the number of soil points thatwill be generated between any two adjacent piping points, regardless of what spans those points (e.g. a run, bend, valve, etc.). Wherethe distance between adjacent piping points does not equal a whole number of max. spacings, AutoPIPE calculates a smaller spacingvalue based on the total number of spacings it finds between the piping points.

Figure D-5, below, shows a run of buried pipe where the distance from A05 to A06 is L. I f "L" is not wholly divisible by the specifiedmaximum spacing (S), the last spacing interval length will be less than "S" (it will be the length c  S, where "c" is a constant in therange 0 < c < 1).

Figure D-5 

AutoPIPE compares the length of the last spacing interval (number 6 in Figure D-5) with the specified max. spacing value. I f the length

 AutoPIPE Reference Information

Page 1 of 2Defining Soil Points in AutoPIPE

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8/18/2019 Defining Soil corrosion Points in AutoPIPE

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of the last interval is less than the max. spacing value, the soil point spacing is recalculated per the following equation:

(D-7)

where:

On the other hand, if the specified spacing value (S) is greater than the distance between adjacent piping points (L), only a single soilpoint will be generated halfway between the piping points. Again, this is regardless of what connects those points.

AutoPIPE calculates the soil point spacings, and generates the actual soil points whenever the Global Consistency Check is executed. Itshould also be noted that the soil point spacings used by AutoPIPE (S) do not replace the maximum spacing values specified for each

defined soil identifier.

 The user should be aware that soil points are transparent (automatically generated) in AutoPIPE. Each defined soil point adds to theoverall size of the system model. Thus, more disk space is consumed and analyses require more time to complete a run. Therefore,short spacings over long lengths between piping points should be avoided, or else a large number of soil points will be created.

Analysis results are produced for soil points in the same manner as piping (and framing) points are listed. The naming convention forsoil points is the same for every interval between piping points. An example of this convention is shown in Figure D-6.

Figure D-6

For every span between adjacent piping points, generated soil points are named "+1", "+2", "+3", and so on. Soil point numbersincrease in the forward direction of each piping segment. Numeric results for soil points are organized such that the soil point data isinserted between the piping point listings which surround them.

Note: Refer to the Pipe Soil Example in the AutoPIPE Workbook for a detailed example of the development of a buried pipingsystem.

S = Actual spacing length used by AutoPIPE for generating soilpoints (L).

L = Length between adjacent piping points (L).

n = Total number of soil point spacing intervals, based on themaximum spacing "S" (dimensionless).

Page 2 of 2Defining Soil Points in AutoPIPE

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