Is there a limit to the amount of items a pipe can carry at once, or, a limit on the number of items within a chunk?

I've setup my own Tekkit 3.1.3 server which I'm playing on with a couple of friends. We setup 3 quarries in fairly close proximity. Each quarry's output is piped to a main transport pipe which pipes a long distance back to our main hub. Everything is running fine except that we keep finding random piles of overflow items by the pipe. These aren't as a result of a chest being full. Rather, they are along the length of the actual pipe. The problem disappears if we only run one quarry at a time.

So is there a limit to the number of items the pipes can transport at a time or is this something to do with an item limit per chunk? If so, is there a way to increase this limit?