Staff Reporter
SAHIWAL
On 1 November, 2025 Unit-1 of the 1320 MW Sahiwal Coal-Fired Power Plant was taken offline for its scheduled, month-long planned maintenance program, a vital operation that ensures the station’s long-term reliability and sustained efficiency. The outage, slated for completion by the last week of November, brings together every technical and operational discipline on site, from Instrumentation & Control (I&C) and Electrical to Turbine, Boiler, Metal Testing, HSE, and Operations.
Although this is a routine activity within the plant’s maintenance calendar, its impact is anything but ordinary. The exercise aims to restore peak performance margins, validate compliance with all operating and safety limits, and capture incremental efficiency improvements that together sustain Sahiwal’s position as a cornerstone of Pakistan’s grid stability. Commissioned as two 660 MW supercritical units, the Sahiwal plant continues to exemplify how disciplined maintenance and advanced technology deliver dependable base-load generation year after year.
The Instrumentation & Control (I&C) class remains the backbone of every outage because precise measurement and automatic regulation form the central nervous system of any supercritical plant. During this Unit-1 shutdown, the I&C engineers are conducting complete calibration and functional testing across key sensors and transmitters that govern boiler pressure, main steam temperature, turbine speed, and combustion control loops. Transmitters are being carefully removed for bench calibration, while technicians verify thermowell integrity, clean and test solenoid valves, and validate Distributed Control System (DCS) logic sequences for safe start-up, shutdown, and trip scenarios. Outdated or drifting field instruments are being replaced, and loop tuning is performed to re-establish optimum control response. These steps ensure that when Unit-1 returns to service, its automation precision minimizes transients and mechanical stress, improving both reliability and heat-rate performance.
The Electrical class is working in parallel across all voltage levels, from low-voltage distribution to high-voltage generator and transformer systems. Their scope includes relay testing, breaker mechanism inspection, busbar cleaning, and tightness verification on all major switchboards. Detailed insulation resistance and polarization index testing of generator windings is being conducted, paired with rotor and stator examinations to detect early signs of degradation. Thermography data collected prior to the shutdown has guided focused inspections on potential hotspots. Where elevated temperatures were observed, corrective measures are being implemented to prevent recurring faults. The switchyard and auxiliary distribution systems are also undergoing scheduled maintenance, ensuring the integrity of protective coordination and redundant power supplies. This comprehensive electrical work guarantees that once synchronization occurs at the end of the month, Unit-1 will deliver stable and distortion-free power to the grid.
In this maintenance campaign, the Turbine class is once again handling some of the most intricate and high-stakes work in the plant. Select turbine sections, bearings, and couplings have been dismantled for inspection and overhaul. Teams are verifying shaft alignment, bearing clearance, and coupling integrity, as well as checking lubrication systems and thrust bearing performance. Turbine blades and rotors are being inspected following vibration analyses conducted during pre-outage operation. Where required, dynamic balancing and valve reconditioning are being performed to maintain smooth rotational performance and optimal steam flow control. The team is also renewing actuator linkages, replacing gland packings, and calibrating control valves to ensure precise regulation of steam admission. The meticulous attention to turbine health not only reduces the probability of unscheduled trips but also enhances thermal efficiency, an essential factor in maintaining cost-effective electricity generation.
The Boiler class has undertaken an extensive set of inspections and restorative tasks because the boiler remains the heart of energy conversion. Unit-1’s massive furnace and heat-exchange surfaces are being thoroughly inspected, covering superheater, reheater, and economizer tubing, furnace walls, and sootblower systems. Detailed tube-thickness gauging and dimensional surveys are being carried out to identify any metal loss, while tube replacements are scheduled wherever wall thinning approaches engineering limits. Meanwhile, teams are optimizing the coal-feed, pulverizer, and primary air systems to maintain uniform fuel distribution and efficient combustion. Burner tuning exercises are ongoing to perfect fuel-to-air ratios, which directly reduce localized overheating and improve emission quality. The flue-gas cleaning equipment, including electrostatic precipitators (ESPs) and gas ducts, are being cleaned and verified to maintain low particulate emissions. All boiler safety valves, interlocks, and pressure-relief mechanisms are tested to ensure the unit’s full compliance with operational and safety certifications.
The Metal Testing class plays a diagnostic role that informs nearly every major maintenance decision. Their engineers are conducting a wide array of nondestructive tests (NDT), such as ultrasonic thickness measurement, magnetic particle inspection, dye-penetrant testing, and radiographic examination. These tests allow the team to quantify material degradation without dismantling entire assemblies. When anomalies or weld irregularities are found, samples are extracted for metallurgical and chemical analysis, providing conclusive guidance on whether components can be safely reused or must be replaced. Hardness tests and microstructure studies further validate material integrity. The insights from Metal Testing ensure that every decision, whether to repair, reinforce, or replace, is grounded in data, maintaining a balance between safety, cost, and time efficiency.
Throughout the Unit-1 maintenance, the Health, Safety & Environment (HSE) department remains the overarching guardian of the entire operation. The team prepared extensive risk assessments and hazard control plans ahead of the outage, ensuring that all activities comply with plant safety protocols. Permit-to-Work (PTW) systems are strictly implemented, including confined-space entries, hot-work permits, and lockout-tagout (LOTO) enforcement across all departments. HSE specialists are supervising respiratory protection in areas with dust exposure, fall-protection systems around high scaffolds, and daily toolbox talks that reinforce awareness of evolving site hazards. Environmental oversight continues uninterrupted. Stack emission sampling, wastewater quality checks, and dust suppression measures are monitored daily to ensure the plant remains compliant with EPA and other environmental authority standards even while offline. The department’s vigilance ensures that safety and environmental discipline are as integral to maintenance as the mechanical work itself.
The Operations team provides the operational backbone that makes maintenance safe, sequenced, and coordinated. Their responsibilities began before shutdown with the controlled cooldown and isolation of all major systems. During the outage, operators oversee the functioning of auxiliaries, manage drainage and ventilation systems, and facilitate inter-departmental coordination. Operations staff also supervise spares logistics, track contractor activities, and maintain direct communication with the control room. As the outage nears completion, the department will lead commissioning tests, start-up synchronization, load rejection trials, and efficiency verification runs. This tight integration between Operations and Maintenance ensures not only safe handover but also a smooth ramp-up when Unit-1 re-enters service.
Supporting all technical activities are the planning, scheduling, and logistics teams whose structured coordination transforms a complex outage into a synchronized operation. Detailed work packages, Gantt charts, and 3D isometric diagrams enable multiple teams to work simultaneously without interference. Material staging, crane operations, and scaffold management are timed precisely so that turbine, boiler, and electrical crews can proceed without bottlenecks. Regular coordination meetings and a centralized digital outage log keep every department aligned to schedule. The logistics staff ensure that critical spare parts, consumables, and test instruments are available on demand, eliminating downtime from waiting or rework. This disciplined approach helps the plant maintain its reputation for on-time completion of major maintenance projects.
This Unit-1 maintenance campaign is another chapter in Sahiwal’s continuous reliability program. The plant has consistently conducted C-level inspections and major overhauls at regular intervals, ensuring that both 660 MW units operate within their design parameters. Past maintenance campaigns have demonstrated Sahiwal’s commitment to best practices in plant reliability, energy efficiency, and environmental stewardship, a commitment that aligns closely with the standards of its parent group, China Huaneng, and Pakistan’s national regulatory framework.
When Unit-1 completes its maintenance cycle and resumes generation in late November, several tangible outcomes are expected: certified safety of pressure-holding systems, restored sensor and control accuracy, reduced vibration levels, improved insulation margins, and optimized fuel-to-power conversion efficiency. Incremental gains in turbine heat rate, auxiliary power reduction, and generator stability will translate directly into lower operational costs and improved grid performance.
Ultimately, this outage is more than a technical milestone; it is a demonstration of discipline, teamwork, and shared responsibility. Each class, whether I&C, Electrical, Turbine, Boiler, Metal Testing, HSE, or Operations, plays a specialized but interdependent role in returning Unit-1 to service. The plant’s unified approach, honed over years of experience, ensures that decisions are fact-based, execution is precise, and safety remains uncompromised. As the end of November approaches, attention will turn to final commissioning, performance trials, and synchronization. For the national grid, a timely restart is crucial; for the plant, it is a reaffirmation of engineering excellence; and for the people who execute it day and night, it is a reflection of their professionalism, discipline, and pride. The coming days will once again showcase how careful planning and cross-class collaboration can bring a powerhouse like Sahiwal back online, stronger, safer, and more efficient than before.
