Fireloop(tm) - UL Listed Flexible Expansion Loop (fire sprinkler applications):

All sprinkler pipe passing through or crossing building seismic joints, shall contain a flexible expansion loop, designed for seismic movement. Flexible loops shall impart no thrust loads to building structure. 
Loops shall be located at, or near, the building seismic joint. Seismic bracing shall not pass through building seismic joint and shall not connect or tie together different sides or parts of building structure. Flexible loops shall be capable of movement in the ±X, ±Y, ±Z planes. Movement requirements and location, relative to seismic separation, shall be determined by system design engineer. Flexible loops may be installed to accommodate thermal expansion, seismic movement, and building settlement. Unless specified otherwise by system design engineer or governing codes, all flexible loop connections to sprinkler piping shall be installed, inspected, and tested 
in accordance with current NFPA-13 standards. 

Flexible loops shall consist of two flexible sections of hose and braid, two 
90 degree elbows, and 180 degree return. Loops shall include a factory supplied, center support nut located at the bottom of the 180 degree return, and a drain/air release plug. Materials of construction and end fitting type shall be consistent with pipe material and equipment/pipe connection fittings. Flexible expansion/seismic loops to be "Metraloop(r) Fireloop(tm) as manufactured by The Metraflex Company, Chicago(r), IL.