Preventive measures for project schedule control of combined cycle gas turbine power plant

Abstract

The objectives of this research are to analyse the construction critical paths of the combined cycle gas turbine power plant projects and to determine the delay preventive measures for project schedule control. First, the planned and actual construction schedules of the combined cycle gas turbine power plants have been studied and analysed to see their critical paths and also the near-critical path which could potentially become critical. Construction schedules of four power plants constructed in Thailand have been obtained and analysed. Their capacities and main equipment arrangement are summarized in Chapter 5.1. The common work breakdown structures have been set up amongst all the four projects to categorize various activities in different projects schedules under the same group for further analysis.

The analysis results found that all the projects initially share the common critical paths on the notice to proceed issuance. Three out of four projects are subsequently found with critical paths on the turbines’ procurement (either gas turbines or steam turbines) and erections of those while another project is found with the critical path on the pilings, foundations works and then the electrical balance of plant erections. After that, all the projects in this research are found with the common critical paths on the cold and hot commissioning works of turbines particularly when considering the steam turbine first steam afterward, subsequent common critical paths are the overall combined cycle commissioning works, performance test and commercial operation at the end of the projects. In consideration of different project sizes of Project D from others, it is noted that the erection and commissioning works of the main equipment (i.e. gas turbines and steam turbines) consume durations at the same range. The key difference contributing to the overall construction schedule is found on the time used during the main equipment procurement, starting from issuance of purchase order until the equipment arrival on site. Moreover, it is observed that the delay projects (Project B and Project C) are found with too many planned near-critical paths unnecessarily compared to Project A and Project D which were on time, also, their sequences of actual construction are found very confusing.

The possible preventive measures to control those critical paths are discussed including: i) expediting the procurement of main equipment to commence before the notice to proceed issuance. This however requires support from contractual languages agreed by all related parties which has to consider comprehensively from all aspects including legal and financial obligations; ii) ensure that the quality assurance and quality control (QA/QC) are well applied in all fabrication and erection activities to alleviate the problem of individual equipment functioning during the test run and commissioning. Opinions on the analysed results and preventive mitigation measures from two experts in this area have been obtained through interviews. Their experiences on critical paths are found align with the results of this research with some comments and recommendations for further studies provided.

Analysis results of the construction critical paths and near-critical paths together with the recommended preventive mitigation measures to control project schedule in this research are hopefully beneficial to those who will develop, construct or participate in the combined cycle gas turbine power plant projects in the near future.