There is limited literature available when it comes to fault finding of oil operated control valves associated with power plants. This limitation is further aggravated due to lack of Original Equipment Manufacturer (OEM) support in remote settings. This paper provides a detailed study on the learnings captured from the functional failure of oil operated trip and throttle valve (OOTTV) installed at the extraction steam line of steam turbine at a petrochemical plant in Pakistan. Engro Polymer and Chemicals (EPCL), a Chlor Vinyl complex has a captive power plant consisting of one combined cycle power plant (CCPP), having two gas turbines (make: Hitachi) each having 22.5 MW capacity and one extraction condensing steam turbine having 15 MW capacity (make: HTC). Besides, one 6.75 MW SGT-200 1S gas turbine (make: Alstom) is also available. In this paper, first an explanation on schematics and operation & maintenance regime of steam turbine and associated circuit at EPCL is discussed. Then failure event and approach involved in identification of root cause is presented followed by constraints tackled, findings gathered and rectification of the valve. Lastly, gaps in operation and maintenance (O & M) regime have been identified and revised plan has been developed after benchmarking which will increase reliability of the unit.