Attachment Point Elements

ISODRAFT User Guide

Design Requirements : Attachment Point Elements

ISODRAFT uses attachment point elements in the DESIGN database, known as ATTAs. These are used to allow forces, moments, etc. to be applied to a Branch during pipe stressing, to show the location of support points, and to attach comments, flow arrows, etc. to the pipes on isometric plots.

The different types of ATTA are defined by the setting of the ATTY attribute. The ATTY settings and other information for different types of ATTA are given below.

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Support ATTAs are used to mark the position of a support on the pipe. There are three types of support ATTA:

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ATTY type Unset, is the default type of support ATTA. They are used to mark the position of a support on the pipe. They should be positioned on the centreline of the pipe. If they are not:

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Data consistency checking will generate an error message, unless ATTACHECK OFF is set, in which case no check is made for correct orientation and position of the ATTA.
If the ATTA is within tube, it will be shown at the p-leave of the previous component or at the head of the branch. This can cause the dimensioning of another Support ATTA further down the pipe to be omitted.

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To position the ATTA within the previous component, connect it in list order after the component, then explicitly set its position, or move it BY the required distance along the direction of P-arrive. Note that, in this case, data consistency checking will generate an error message unless ATTACHECK OFF is set.
For elbows and bends, ATTAs can be positioned on projected centrelines, i.e. at the intersection of centrelines.

Note:

Supports on tube are shown with a symbol, but supports on components are not.

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ATTY type Hang ATTAs are used in the Hangers & Supports application to indicate where a hanger type support will be attached to a pipe or component. They operate in exactly the same way as ATTY type Unset ATTAs.

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ATTY type Weld ATTAs are also used in the Hangers & Supports application. This type of ATTA is used to position the plotted ATTA symbol a fixed distance inside the previous component (e.g. at the P0 of an ELBO component), rather than moving the ATTA to that point as the user has to do with ATTY types Unset and Hang.

It is accomplished by the ATTA having a P3 point, which is a set distance in the arrive direction from P1/P2. The distance between P1/P2 and P3 must be set in the catalogue for each ATTA of this type, which is then used with the same component (e.g. ELBO). The symbol for this ATTA is automatically plotted at its P3 point.

Inserting the ATTA directly after the previous component makes sure the ATTA symbol is plotted at the correct point inside that component.

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Comment ATTAs are used to add a drawing note with leader line to a position on a pipe, typically to add a floor penetration note. They have ATTY set to CCCC. If this point is not already dimensioned, for example, if it lies in the tube, additional dimensions to the ATTA position will be output.

Comment ATTAs should lie on the centreline of the pipe.

To position the ATTA within the previous component, connect it in list order after the component, then explicitly set its position, or move it BY the required distance along the direction of p-arrive. Note that, in this case, data consistency checking will generate an error message unless ATTACHECK OFF is set.

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Non-dimensional Comment ATTAs are used to add a drawing note with leader line to a position on a pipe; for example, to add a paint colour note. They have ATTY set to CCNN. This type of ATTA will not be dimensioned.

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Flow ATTAs are used to position inline flow arrows in tube. They have ATTY set to FLOW. The arrow is not dimensioned, but it is positioned on the tube in proportion to its 3D position.

The flow is from head to tail if the FLOW of the branch is the default forwards direction, or tail to head if the FLOW of the branch is backwards.

Note:

The FLOWARROWS INLINE command must be used for flow arrows to be plotted for tube.

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Split ATTAs for a normal isometric are used to set the point at which an isometric should be split onto the next sheet. They have ATTY set to XXXX.

ISODRAFT sometimes repositions split points if a more logical point is close. For example, consider a Tee with a Flange welded to P3, and a Gasket and a Valve connected to the Flange. If a Split ATTA is positioned between the Tee and the Flange, ISODRAFT will split the pipe at the natural break formed by the Flange.

Normal Split ATTAs are ignored for system isometrics and equipment trim isometrics.

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Split ATTAs for system isometrics have ATTY set to SSSS. This type of ATTA is used to set the point at which a system isometric or equipment trim isometric should be split onto the next sheet. The same considerations as for normal isometric split ATTAs apply.

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Insulation symbol ATTAs have ATTY set to INPP (insulation personnel protection). This ATTA type is used to set the start and stop points of insulation on the isometric. The insulation specification note will be shown at the start point of the insulation, but not at the end (to avoid duplicating information).