1. Technical Bulletin Bulletin No PRO 01 06 Effective Date 2 23 81 Cancels PRO 01 06 dated 1 7 77 Page 1 of 1 Subject Piston Ring Configuration Tu Flo 501 Compressor The purpose of this bulletin is to update information provided in Bulletin PRO 01 06 dated 1 7 77 which should be discarded and replaced by this bulletin In late 1978 improved production techniques and the solution of some trouble prone Tu Flo 501 Compressor installations were finalized It became evident that the original 3 0 piston ring design configuration 3 rings located above the pin provided satisfactory oil control Beginning in early 1979 a changeover to the 3 0 piston design began on a running change basis The changeover was completed by the end of 1979 The one exception to the change was compressors built for Caterpillar Caterpillar compressors continue to be built with a 2 1 ring configuration 2 rings above pin 1 below However Caterpillar has recently requested a change to the 3 0 configuration and this change will be made in the near future Service replacement parts ring sets and piston pin sets are listed on Catalog Page 01 X 1