Power Plant Outage Mechanical Repairs at Jackson Generation in Elwood, IL

The client needed one mechanical contractor capable of managing a varied list of outage repairs across both generating units. The work included rotating equipment, heavy lifts, specialty alloy pressure piping welding, nondestructive examination, heat treatment, confined-space entries, instrumentation connections, large-diameter gasket and expansion joint replacements, and leak repairs.

Several activities also depended on outside inspection or support services. The 9-chrome valve replacement required radiographic testing before and after post-weld heat treatment. Drum doors had to be removed, sent out for machining, returned, and reinstalled. Gearbox replacements required crane access and a carefully controlled removal and reassembly sequence.

For the plant team, the main concern was not simply whether each individual task could be completed. The entire scope had to be sequenced so crane work, inspections, confined-space operations, machining, and mechanical repairs did not interfere with one another or jeopardize the end of the outage.

DePue performed the following work during the scheduled shutdown:

• Replaced four ACC gearboxes, with two changeouts on each unit


• Drained and replaced oil in 48 ACC gearboxes


• Removed and reinstalled IP and LP drum doors for machining


• Replaced a 2-inch 9-chrome valve


• Coordinated four radiographic examinations and post-weld heat treatment


• Replaced small-bore socket-weld valves


• Installed a stainless o-let and thermowell on the RO water system


• Replaced a 48-inch condenser strainer gasket


• Replaced a failed Unit 1 IP turbine thermowell


• Installed screens on HP, IP, and LP vessel vortex piping


• Repaired an HRSG drain damaged during cold weather


• Repaired a leaking lube oil accumulator fitting


• Welded 144 tube-abandonment plates from inside 48-inch ACC piping


• Replaced a 24-inch expansion joint


• Installed new mesh and clips inside the Unit 1 and Unit 2 HP drums


• Replaced a 16-inch butterfly valve on the Unit 2 SCR blower

DePue replaced four air-cooled condenser gearboxes, with two gearboxes changed on each unit, as part of a coordinated heavy equipment setting and crane lift scope.

For each replacement, the crew disconnected the approximately 4,200-pound fan assembly and lowered it using a 125-ton crane. The gearbox shaft was uncoupled from the motor, and the approximately 5,200-pound gearbox was then lowered to the deck.

The crew unsweated the fan blade couplings from the existing equipment and re-sweated them onto the replacement gearboxes. The new gearboxes and fan assemblies were then lifted back into position for coupling and reassembly.

This sequence required coordination among the crane operator, rigging personnel, millwrights, and mechanical crews. Lift timing, equipment orientation, access, coupling work, and reassembly all had to be controlled so each gearbox could move through the replacement sequence without delaying the other planned outage work.

While the gearbox changeouts were underway, DePue also drained and refilled the oil in 48 ACC gearboxes. Performing this maintenance in parallel helped the plant use the outage window for both major equipment replacement and broader preventive service.

DePue completed the code-sensitive welding required to cut out and install a new 2-inch 9-chrome valve as part of the outage scope.

The welds were examined through a four-step radiographic testing sequence:

• Two radiographs before post-weld heat treatment


• Post-weld heat treatment


• Two additional radiographs after heat treatment


• Follow-up crack testing after completion of PWHT

The inspection sequence had to be incorporated into the outage schedule so welding, radiography, heat treatment, and final examination could proceed without creating an avoidable critical-path delay.

DePue also replaced a 1/2-inch socket-weld valve in the gas yard and cut out and welded two new 1/2-inch valves on the Unit 1 condenser B strainer vent lines.

Pressure piping and pressure-retaining system welding requires more than field welding alone. Material requirements, qualified procedures, inspection hold points, heat treatment, examination, and documentation all have to be understood before the system is released for return to service.

The outage included several smaller repairs that were individually important to system reliability and inspection readiness.

DePue installed a new 3/4-inch stainless steel o-let and thermowell on the reverse osmosis water system. The crew also replaced a failed thermowell on the Unit 1 intermediate-pressure turbine.

On the Unit 1 condenser strainer, DePue replaced a leaking 48-inch gasket. The size of the connection required controlled disassembly, gasket placement, flange alignment, and reassembly to restore the joint.

These tasks were coordinated alongside the larger gearbox, valve, vessel, and ACC scopes rather than being treated as separate projects.

Multiple portions of the outage required controlled confined-space entries.

DePue entered the Unit 1 and Unit 2 high-pressure, intermediate-pressure, and low-pressure vessels to install screens on the vortex piping. Crews also entered the HP drums on both units to install new mesh and clips.

One of the most labor-intensive portions of the scope took place inside the ACC system. DePue personnel entered a 48-inch pipe and completed the industrial field welding required to install 144 plates and abandon leaking tubes. Crews worked around the clock to advance the internal welding scope within the outage schedule.

Confined-space work during an outage requires careful coordination of entry controls, atmospheric monitoring, ventilation, communications, hot-work requirements, personnel access, material handling, and rescue planning. These controls had to remain in place while the repair crews maintained the production rate required by the schedule.

DePue replaced a drain on the Unit 2 heat recovery steam generator that had split during cold weather.

The crew also repaired a leak at a fitting on the Unit 2 lube oil accumulator and replaced a 24-inch expansion joint on Unit 2.

These repairs addressed different systems, materials, access conditions, and failure modes. Completing them within the same outage required flexible manpower, coordinated industrial maintenance support, and communication with plant personnel responsible for system isolation, access, inspection, and turnover.

DePue removed the existing valve and installed a new 16-inch butterfly valve on the Unit 2 selective catalytic reduction blower system.

The work required handling and positioning a large valve within the available access, aligning the replacement with the existing system, and completing the installation within the outage sequence.

The client established a May 3 through May 17 shutdown window and presented DePue with a multi-trade scope across Units 1 and 2.

The plant needed gearbox replacements, crane work, ACC maintenance, specialty valve welding, radiography, PWHT, confined-space repairs, drum work, instrumentation connections, leak repairs, and large-valve replacements completed within one coordinated outage.

DePue organized the work into parallel shutdown and turnaround work fronts.
Crews replaced four gearboxes with a 125-ton crane while oil service was completed on 48 additional ACC gearboxes. Other teams advanced valve welding, thermowell installations, gasket replacement, drum door work, HRSG repairs, expansion joint replacement, vessel entries, and SCR blower valve replacement.

Radiography and post-weld heat treatment were incorporated into the 9-chrome valve welding sequence. Confined-space teams worked inside vessels, drums, and 48-inch ACC piping, including round-the-clock welding of 144 tube-abandonment plates.

DePue executed the assigned mechanical scope within the scheduled outage window.

Crane operations, rotating-equipment replacement, confined-space entries, valve and piping work, radiographic examination, post-weld heat treatment, machining, and internal ACC repairs were coordinated toward a clean mechanical handoff at the end of the shutdown.

For the plant team, the result was one contractor managing a broad range of mechanical repairs without separating the work into disconnected scopes.

Power plant outages regularly combine planned maintenance, inspection findings, equipment replacement, emergent repairs, code-sensitive welding, confined-space access, and work that cannot begin until systems are isolated.

The mechanical contractor has to understand more than the individual repair procedure. The contractor must also understand the outage schedule, critical-path activities, lift restrictions, inspection hold points, system turnover sequence, simultaneous operations, and the consequences of missing the return-to-service window.

DePue Mechanical supports plant managers, maintenance managers, facility engineers, operations teams, and outage planners with industrial maintenance crews, qualified welding capabilities, rigging coordination, piping work, equipment replacement, and field execution built around actual plant conditions.

power generation services.

This project demonstrates several DePue capabilities used during planned power plant outages and industrial shutdowns:

• Shutdown, Turnaround, and Tie-In Piping


• ASME Code Welding


• Pressure Vessel and Pressure Piping Welding


• Equipment Setting and Heavy Lift Coordination


• Industrial Maintenance Services


• Industrial Welding Services


• Emergency Industrial Welding


• 24/7 Emergency Mechanical Repair Services
  
• Power Generation Services

DePue Mechanical supports power generation facilities and industrial plants with planned outage and shutdown work, equipment replacement, heavy lifts, pressure piping repairs, valve replacement, code-sensitive welding, confined-space repairs, HRSG work, expansion joints, instrumentation connections, and emergency mechanical repairs.

Send DePue your outage schedule, equipment list, inspection findings, drawings, photographs, material requirements, crane constraints, confined-space scope, and expected testing requirements. Our team can help review the work, identify coordination needs, and build an execution plan around the available outage window.

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