CHP and digitalisation |
The CMMS know the number of hours equipment, components and systems have run and sends alerts when it is time for inspection. All rotating equipment oils are sampled and analysed quarterly to make sure they are free of impurities.
HRSG operation and maintenance
The HardHat system aids operators in monitoring all aspects of running and maintaining two HRSGs from Rentech Boiler Systems. It keeps track of a great many parameters to ensure everything is running smoothly. For example, the high-fired waterwall, O-type HRSGs should provide up to 225 kilo-pounds per hour (KPPH) of 200 PSIG saturated steam, which is vital to Ford operations. In addition, another up to 90 KPPH can be consumed in the steam turbine as part of combined cycle power generation. “Advanced pattern management and 3D modeling enable operators to keep a close eye on the maintenance of HRSG steam production as well as hot water and high-pressure steam metrics,” said Siess.
Operators can view each HRSG in the 3D model and drill down into systems and components as needed. The CMMS push out maintenance actions coming due. Parts are flagged that need to be maintained or replaced, based on usage.
Take the case of a temperature transmitter in the HRSG’s feedwater header. The operator can click on the part to review documentation, part numbers, past maintenance records, examine any required safety checks, view instrument and sensor readouts and review work orders (a flashing feed control valve on the screen would indicate an active work order). At the end of a shift, the new operator can open the system to see any work orders opened and resolved that day, which reduces the need for lengthy turnover of duties.
Above: Digital rendition of Rentech HRSG stacks and Solar gas turbines
A recent incident involved power loss to the HRSG. The system automatically generated alerts. Investigation detected a power supply drop off to the PLC, which then tripped the HRSG. “We picked up this problem in the HRSG and resolved it within 90 minutes,” said Siess. “As the asset database in HardHat has information on all part numbers, vendors and specs, it saves us a lot of time in routine maintenance.” The Rentech HRSGs include supplemental firing. By raising the gas turbine exhaust temperature via supplemental firing, steam production can be increased by approximately 300%. Operators control supplemental firing from the booth and can keep a close eye on temperature, pressure and steam output numbers to ensure everything is operating as intended.
“The key is to not to waste time and resources in looking for information or engaging in unnecessary activities – everything is prioritised and at the operator’s fingertips,” said Siess. “This kind of automation is increasingly needed as the power generation labour pool is rapidly shrinking.”
Building confidence in automation A system like this isn’t going to go in one day and hey presto, perfect operation from there on out. Siess laid out the trajectory of steady improvement the facility has undergone: nine unit trips in 2020; five in 2021; and two in 2022. Hours of unplanned downtime fell from 50 hours in 2020 to only four in 2022.
The facility schedules a spring and autumn outage to take care of major maintenance actions and inspections. During those windows, Solar Turbines comes on site as part of a long-term service agreement.
Each gas turbine and HRSG is taken down for two to three days. While one unit is being serviced, the other continues to operate to ensure the flow of steam to Ford is never interrupted. Features built into the Rentech HRSG provide further assurance of steam flow. A fresh- air-firing capability utilises a forced draft fan so the HRSG can be operated when the gas turbine is offline. The fan draws in ambient air and the duct burner provides heat to generate 80 KPPH of steam. A louvre-type diverter valve installed between the HRSG and the turbine facilitates steam/electricity switching. If there is no current steam demand, flue gas from the turbine can be diverted up a bypass stack and not through the HRSG to generate only electricity and not steam.
Above: Digital twin image of Rentech HRSG and duct burners 18 | October 2023|
www.modernpowersystems.com
Siess added that automation enables DTE to untether the operator from the chair to go on maintenance rounds for 45 minutes or more without anyone in the control room. Data on plant operation is available via mobile device, which brings the control room into the field. Alerts are issued if anything needs attention. “The right technology gives people enough confidence in automation so they can walk away,” said Siess. “Our operations staff are now comfortably performing 80% of all maintenance activities.”
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