I just noticed this today; some textures for Redpower are actually outdated/broken.
The once I've noticed are the Accelerator, Magtube, Blueletric alloy furnace, fluid pipes, restriction tubes, Thermopile, grates, igniters, assembler, ejector, relay, and the pump.
(They're in respective order in the picture)
I did a quick little texture fix for you, updated the files c:
http://tinyurl.com/dysoj44