No rest until the job is done
The steam turbine producing energy at the Pesquería Power Plant has just passed its first inspection, requiring an arduous process of analysis, decision-making and the full-on commitment of a dedicated team. The occasion also provided the opportunity to carry out maintenance at the Water Treatment Plant.
It was a great moment for the Steam Turbine (ST) at the Pesquería Power Plant as it passed its first major maintenance stoppage with flying colors, completing the first sequence in the Major Maintenance process for the operational areas. The power generation plant, in operation since 2016 to supply energy to both Ternium and TenarisTamsa plants in Mexico, is now in optimal technical conditions to continue functioning efficiently, supported by all the corresponding guarantees—and with a zero accident record.
"This was the first major inspection of the steam turbine, and it was held to ensure the mechanical integrity of the turbine, generator, controls and protection systems, as part of a process to make the machine more reliable. Another benefit we were seeking was to avoid the possibility of incurring in greater expenses if it broke down as a result of lack of maintenance," points out Arturo González Morales, Energy Efficiency Engineering Manager at CEP.
The plant is running three Gas Turbines (GTs) that underwent their major maintenance in September 2021 (GT1), in April 2022 (GT2), and in November 2022 (GT3). However, the steam turbine is a little different. Unlike a gas one, which requires some 28 days of downtime, the inspection process for a steam turbine takes 35 days, as it’s a more robust machine, and has larger areas where inspections and tests are needed.
“Another difference is that although replacing parts for the steam turbine is not on the agenda (as it’s mostly inspections and non-destructive testing that are carried out on the equipment), the plan does contemplate this option so that we can avoid any delays involved in getting hold of parts at the last minute if a need arises,” explains González Morales. The reason is that the machine receives steam at 567 degrees Celsius, generated by external combustion, and this temperature does not have a harsh effect on the parts.
Gas turbines, however, are exposed to the heat of internal natural gas combustion processes of over 1,000 degrees Celsius. “This has a direct impact on the entire hot zone of the turbine and means that parts have to be changed out every 24,000 hours. That’s the overriding difference,” explains the engineer.
Inside the turbine
In major maintenance procedures, the entire machine is dismantled. “We inspect every single screw, blade and ball bearing! We carry out all kinds of measurements and tests and, although we aren’t scheduled to replace parts, in some cases we do find some damage from foreign materials that can’t be repaired onsite,” explains Odón Acosta Hernández, Maintenance & Engineering Manager at CEP.
A major shutdown process is a race against time, as each day that passes, the plant produces two-thirds of its capacity at full load. “To avoid delays, we plan each major shutdown up to a year in advance, because it involves so many activities which are extremely complex. Also because some parts and specialized services are not so easy to come by or are simply unavailable at short notice,” adds Acosta Hernández.
Despite all the planning and preparation, some unexpected technical challenges delayed the return to full operation until December 18 (which had originally been scheduled eight days earlier), requiring an extraordinary effort from an incredibly dedicated team that didn't pause to draw breath until the job was done.
The CEP has a Water Treatment Plant (WTP), which receives gray water from a municipal wastewater pretreatment plant. The WTP is equipped with the equipment necessary to treat and clean the water to the quality standard required to supply the gas and steam turbines and generate electricity. Water is mostly supplied to the systems associated with the operation of the ST (such as the Cooling Tower and the HRSG boilers), as well as other processes (such as the Evaporative Coolers and Fire Fighting System for instance) to a lesser extent.
"As the steam turbine was undergoing maintenance, water consumption was reduced to a minimum, which meant that we could work in conjunction with operational maneuvers to plan a major maintenance exercise on the WTP," explains Alma Rivera, Operations Specialist at the CEP. She adds that at no point did the task affect electricity generation produced by the three gas turbines and other auxiliary services.
"This maintenance was our first experience of Major Maintenance for the WTP, which involved the development of methodologies and strategies to follow up what was planned and made sure we achieved the objectives, which were to ensure water reserves and guarantee the completion of activities prior to the start of the ST plant,” Rivera added.
Priority: safe work
Safety has been a central issue throughout the entire process, and many of the plant's staff are dedicated to this area, particularly with the extended hours and exceptional demand involved. “If we comply with the maintenance frequency and can ensure the quality of the work, we are also complying with personnel safety, electricity availability and energy efficiency,” summarizes Arturo González Morales.
To ensure the highest safety standards, the shutdown is organized using integrated quality management software, which helps to detect training needs in each sector. “We also have a weekly Safe Hour held on Fridays where we talk about safety issues, as well as the Learning from experience program, where staff share what they have learned over time. We also comply with Tecpetrol's HSE Integrated Control feature, including the stop cards, the stop meetings and the management inspections,” lists Odón Acosta Hernández.
"For this major WTP maintenance process, we ended up setting a new HSE record for major maintenance regarding areas such as Zero Disabling Accidents, Zero Accidents with material damage and Zero Incidents, Zero positive cases of alcohol and drugs detected, and highlighting the exceptional quality of leadership for the STOP observations," explains Edgar Cobos, HSE Sr. Supervisor at CEP.
This achievement was possible thanks to strategies such as the designation of new roles and responsibilities. "Among them, the Dynamics of Set Objectives (HSE, Productivity, Family), the Lean Manufacturing Methodology used to plan Major Shutdowns, prioritizing activities in accordance with the Critical Path, taking into account HSE topics, the agile Scrum and Kanban activity monitoring methodologies and HSE feedback,” adds Edgar.
As a sense of mission accomplished pervades the air after over a month of non-stop work for different shifts around the clock, the turbine is back in operation. Odon reflects that, “When people are truly committed, we do great things.”