2011

Clash Rules
Using ignore clash rules reduce the number of clash results by ignoring certain combinations of clashing items.
The Clash Detective tool includes both the default clash rules and clash rule templates that can be used to create
custom clash rules.
Default Clash Rules
The following ignore clash rules are built-in:
■ Items in Same Layer - any items found clashing that are in the same layer are not reported in the results.
■ Items in Same Group/Block/Cell - any items found clashing that are in the same group (or inserted block)
are not reported in the results.
■ Items in Same File - any items found clashing that are in the same file (either externally referenced or appended)
are not reported in the results.
■ Items in Same Composite Object - any items found clashing that are part of the same composite object (an
item composed of multiple parts of geometry) are not reported in the results.
■ Items in Previously Found Pair of Composite Objects - any items found clashing that are part of composite
objects (items composed of multiple parts of geometry) that have previously been reported in the test are
not reported in the results.
■ Items with Coincident Snap Points - any items found clashing that have snap points that coincide are not
reported in the results. This can be particularly useful for pipe runs made from cylinders.
Rule Templates
You can also create your own ignore rules. The following rule templates are available (in addition to the default
clash rules):
■ Insulation Thickness - any items found clashing that have the clearance value greater than the specified
insulation thickness are not reported in the results. This rule should be used with a
Clearance test.
If you have a pipe requiring a specific thickness of insulation, then you may want to carry out a clearance
test on that pipe, setting the clearance tolerance to the required insulation thickness. This would identify
any areas where there is not enough clearance around the pipe to install the insulation.
If you have various pipes, all requiring different thicknesses of insulation then rather than setting up a separate
clearance test for each thickness, you can set up one test with the greatest necessary tolerance, that is, assume
all pipes require the maximum thickness of insulation. This rule can then be applied to ignore any clashes
that are falsely identified, as their actual insulation thickness is less than the maximum clearance used.
See the diagram below for an example of where this ignore rule would be applied:
Pipe 1 has insulation thickness t and C is the maximum clearance (thickest insulation) required anywhere
in the current model. Any items (2) that come within the range of t to C will not be reported in the results.
440 | Chapter 16 Locate and Manage Interferences