Rotary unions are critical sealing components between fixed plumbing and machinery that constantly rotates. But the union's inner cartridge, which contains the seal and bearing, must be periodically replaced. The cartridge's threaded lock nut called for a special wrench for removal. To simplify maintenance, Rotor Clip Co., Somerset, N.J. (, and Duff Norton, a major manufacturer of rotary unions located in Charlotte, N.C. (, have redesigned the rotary union. Their version is held together by a retaining ring in a simple machined groove rather than threads. This reduces costs and streamlines maintenance.