Several points:

1. ASME B31.3-2006, Para 319.4.3: "The significance of all parts of the line and of all restraints introduced for the purpose of reducing moments and forces on equipment or small branch lines, and also the restraint induced by support friction, shall be recognized."

2. Friction is a very tricky thing. A force vs. displacement curve can be thought of as a sawtooth sort of curve, where the pitch of the peaks depends on many incalculable things. In general, it is NOT correct to reason that "the displacement here is X, and that is enough to relieve the friction." Once the displacement becomes sufficient to cause the line to move, the load also does not go to zero, the friction force merely drops from the static friction value (0.4 for steel to steel) to the sliding friction value (usually less than half of the static friction value). So the amplitude of the sawtooth curve is not 100% of the static friction force value, but somewhat less.

3. If you rely on friction to help you, you will be disappointed. If you ignore friction, you will also be disappointed.

4. If you install an intermediate anchor between loops, your analysis will show that the friction forces on opposite sides cancelling each other out to some extent. This is a very dicey assumption - each suppport near the intermediate anchor has a separate sawtooth curve, and in general the pitch of the individual sawtooth curves will not be the same. So, even if the supports are spaced very regularly, the first support on one side of the anchor may be at the peak of one of the sawteeth (movement is just about to occur) while the first support on the other side may well have just moved and be at the valley of its curve.

5. One can make a good argument that friction is only relevant for the first N supports near a piece of equipment or intermediate anchor. The reasoning is that the force on the (N+1)th support acts on the Nth support, but the deflection that it causes is small and thus the force from the (N+1)th support has no mechanism to pass itself through to the (N-1)th support other than the infinitesimal compression of the pipe as predicted by Young's modulus. Despite this, it is common practice on a pipe rack to design anchor towers for friction loads calculated from the weight of the pipe between anchors. This sounds huge, but unless you are in a seismically inactive part of the world, it's still way below what one would normally include for seismic loads. And then there is wind... (Don't ask me how to calculate N. I have no idea.)

NozzleTwister's suggestion is a good one, though - break out friction, wind, seismic, and other design loads separately for your structural guys. They so love to do arithmetic. :-) Seriously, the building Code they are using may require, or at least allow, them to treat the various categories of loads differently. And they may have some leeway to use less than the direct sum of the individual loads for their effective design load.