Benjamin F.Siple;426 McGee Ave.;Monessen;died Wednesday;November 15;1978 in the Mon Valley Hospital;Carroll Twp.;following a lengthy illness.  He was 79.    Born in Connellsville;he was the son of the late Samuel S.and Ida Gallie Siple.  Mr.Siple had been employed as a pyrometer repairman;with the Page Division;American Chain & Cable Company (ACCO);Monessen;retiring in 1964.  He was a member of the United Methodist Church of Monessen;and the Valley of New Castle Consistory.  He was a 50 year member of the Monessen Lodge 638 F&AM.  Mr.Siple is survived by his widow;Ida Gray Siple;two sons;Robert A.Siple of Chesterton;Ind.;and Barry G.Siple of Wilmington;Del.;;four grandchildren;and two sisters;Mrs.Melvin A.(Jean) Johnston of the Sweeney Plan;Belle Vernon;and Mrs.Thelma J.Mackey of Monessen.  Friends will be received in the Rhome Funeral Home Inc.;1209 Grand Blvd.;Monessen;from 7 to 9 p.m.Thursday and from 2 to 4 and 7 to 9 p.m.Friday.  Services will be held Saturday at 10 a.m.in the chapel of the funeral home;with the Rev.Joseph C.Rial;pastor of the United Methodist Church of Monongahela;officiating.  Interment will be in Belle Vernon Cemetery.  Rhome Funeral Directors;in charge of arrangements.