Why when I model my guide gaps as 10 do I then get lateral displacements at this guide of more than 10mm when I go into my displacement report?

I have seen an article somewhere a while back that explained this but can't find it.

Having just posted the send button, I have now remembered why this happens. The displacement is of the node point relative to its starting point.

Plotting the displacements and guide gaps to scale shows what's going on.

Because you are looking at the "Expansion" load case. The EXP case is a difference case, that is why you see it represented as L1 - L2. This means subtract the results of load case 2 from load case 1.

Now, if the results from load case 1 were +9, and the results from load case 2 were -9, then L1 - L2 is 9 -(-9) = 18. The pipe didn't move outside your gap. Remember, the allowed range of movement at a gap is twice the gap size.

We only have one thermal load in the case (ie cold to T1), so we were looking at an operating case, and because we had big axial displacements (over 100mm) when we plot the start and finish locations of the node we can see the pipe is stopping at the support gap as expected (but then rotating, resulting in a larger lateral displacement than the support gap at the end destination of the node.

But Good point about the thermal loadcases.