501F, 501G owner/operators share best practices

One of the biggest challenges facing owners and operators of generating assets in deregulated markets is the need to continually improve the performance of their facilities—to increase revenues and decrease expenses. One component of this goal of “continual improvement” is best practices. These are the methods and procedures plants rely on to assure top performance on a predictable and repeatable basis.

Below are best practices shared by five combined-cycle facilities equipped with 501F and 501G engines that were recognized by CCJ’s Best Practices Awards program in 2016. Gain recognition for your plant and colleagues by participating in the 2017 program; deadline for submissions is coming up fast.

Fremont Energy Center, operated and maintained by NAES Corp, was built with fuel-gas solenoid valves installed inside the gas-turbine compartment at a location where temperatures, as indicated by thermal imaging, can reach 300F. Such high temperatures caused multiple solenoid-valve failures. On average, maintenance technicians were replacing one solenoid valve for each machine monthly, at an average cost of $800 each. Historical data revealed the plant had spent more than $40,000 for replacement valves since COD in January 2012.

The maintenance team, plant engineer, and O&M manager decided to move the solenoids outside of the compartment. Using the existing taps, plant personnel ran tubing directly out of the compartment and down to a mount secured to the structure. The power source for the solenoids was routed similarly.

Since moving the solenoid valves, there have been no failures.

AMP Fremont Energy Center, managed by Craig Bonesteel, is a 703-MW, gas-fired, 2 × 1 combined cycle located in Fremont, Ohio.

Lea Power Partners’ combined cycle was designed with dozens of air-operated valves (AOVs) to enable reliable remote operation; two 100%-capacity compressors provide instrument air to the valves. The compressors were susceptible to shut down on high temperature in summer, interrupting air flow to the AOVs and potentially tripping the plant.

The CAMS (Consolidated Asset Management Services) staff improved reliability by purchasing and installing radiators for the air compressors, tapping into the existing plant chilled-water system for cooling. Fans were installed in front of the radiators and shrouds were fabricated to maximize air flow across them. Result: Chilled water flowing through the radiators has reduced the summertime operating temperature of the compressors and eliminated trips.

Cybersecurity safeguards. Attacks on powerplant computers and PLCs by hackers have been increasing each year. Flash drives, DVDs, and CDs used by plant personnel and contractors are bypassing firewalls set up to protect the computer servers used for the plant’s DCS and/or for systems recording operational data and storing files.

These portable devices may be carrying malware capable of disabling plant systems or allowing hackers to control them. Additionally, the design of the stick flash drive is such that it could be filled with a bank of capacitors which could be charged when inserted into a USB port. Were this to happen and allow a large capacitance discharge to occur, it could destroy a server’s hard drive.

Contractors must be allowed to access the plant’s servers for collection of data during testing. Data collected on portable media could be sensitive and must be protected should a flash drive be lost with encryption and password protection.

To protect the plant’s vulnerable digital systems from being manipulated by hackers, a variety of safeguards have been implemented at Lea—including the following:

      • Allow use onsite of only one specific kind of flash drive.

      • Train all contractors and site personnel on the use and design of this specific flash drive, so they can identify it by sight and prevent another type of flash drive from being used.

      • Train all personnel on the encryption of files stored on the designated flash drive to protect data in case a flash drive is lost.

      • Set up kiosks to verify that the flash drives, DVDs, or CDs that will be used on the plant’s servers are malware-free before using them.

GT upgrade yields operational improvements. During a scheduled major inspection (MI), Lea engaged OEM Mitsubishi Hitachi Power Systems Americas to install the company’s F4 upgrade on the plant’s two 501F gas turbines. The upgrade includes an advanced thermal barrier coating and a new cooling design for Row 1 and R2 turbine blades and vanes to increase power output.

R1 compressor blades also were replaced during the scheduled MI, upgrading the existing double-circular-arc airfoil design with the latest multi-circular-arc design.

Here are the results of the F4 upgrade:

      • Improved simple-cycle output by an average of 7%.

      • Improved simple-cycle heat rate by an average of 1.5%.

      • Improved combined-cycle output by 3.25%.

      • Improved combined-cycle efficiency by reducing net plant heat rate 2%.

Lea Power Partners LLC, managed by Roger Schnabel, is a 604-MW, gas-fired, 2 × 1 combined cycle located in Hobbs, NM.

Granite Ridge Energy’s (GRE) cooling-tower system relies on treated city wastewater (grey water) for makeup. It contains significant levels of ammonia, phosphate, and total suspended solids—including bio-solids. To control bacteria and algae in the recirculating system, GRE added significant quantities of bleach, activated bromine, two different non-oxidizing biocides (also considered algaecides), and a bio-detergent.

The challenge to NAES Corp personnel responsible for GRE’s O&M until recently (Calpine Corp bought the plant and operates it today) was to find a safe and environmentally sustainable way to disinfect bacteria and control algae throughout the cooling-tower system—one that would significantly reduce or eliminate the substantial quantity of chemicals required for “complete control.”

Staff based its search for a solution on the following information:

      • Bacteria in the bulk water are mostly aerobic—pseudomonas, coliform, and legionella—with some anaerobic sulfate-reducing bacteria. SRB are most prevalent beneath biofilms and sludge; if abundant they can also exist in the aerobic conditions of the bulk tower recirculating water. Bacterial colonies found in the bulk recirculating water are also known as planktonic colonies and can be associated with health concerns.

      • Bacteria attach to system surfaces—piping, heat exchangers, tower fill, etc—where they produce slime to protect the colony and proliferate. Bacterial slime tends to degrade equipment performance and reduce the lifecycle of wooden cooling-tower structures.

      • Algae attach to cooling-tower components—such as structural beams, water-dispersing fill media, drift control media, internal walkways, and fan shroud areas. They negatively impact cooling-tower performance, wooden structures, and safety.

GRE worked with a water-treatment consultant to develop a safer, more environmentally sustainable approach to reducing disinfection and algae control chemistry. After investigating several options, staff selected Purate™, a safe, proven process for producing chlorine dioxide (ClO2) to minimize the use of chemicals.

Using the ClO2 generator, plant achieved complete control of bacteria and algae throughout the cooling-tower system. Bottom-line results include substantial reductions of bulk-water bacteria, bacterial slime and biofilm, and algae; plus, zero presence of legionella in the bulk water. Other benefits included the following:

      • A 1.5-deg-F reduction in differential temperature across the cooling tower, attributed to better cleaning of fill and drift-eliminating media.

      • Reduced sulfate in wastewater discharge because of decreased use of sulfuric acid.

      • Ability to maintain a higher pH in the cooling tower, because ClO2 is not pH-dependent. Operating at higher pH reduced corrosion in the system.

Granite Ridge Energy LLC, managed by William Vogel, is a 730-MW, gas-fired, two-unit, 1 × 1 combined cycle located in Londonderry, NH.

Millennium Power personnel, who operate and maintain their combined cycle under the NAES Corp banner, believed a better approach to electrical-protection training was needed. Typical documentation consists of one-line drawings designed by engineers to implement plant protective equipment. One-lines are not designed for ease of troubleshooting: they lack description of the faults, and they do not contain corrective actions or guidance should a fault occur.

In most electrical events, the fault location is not readily apparent, and not every event results in obvious equipment damage. Plant staff must work backwards from the relay information to locate and remediate faults. The information on the one-lines could be presented in a format more suited to troubleshooting.

Millennium one-lines consisted of approximately 10 different protection drawings prepared by several different engineering firms. All the drawings followed general IEEE convention but used nomenclature specific to the OEMs and EPCs. They were made by engineers to be read by engineers. In addition, they were developed in the context of how to protect the equipment rather than how to locate a fault.

Plant personnel developed a documentation package that flows from the relay observations to the fault. It contains guidance on faults, instructions for recommended testing, and remediation required to return equipment to service. The package also provides training on equipment specific to the plant and includes a series of expected relay and damage observations for common electrical faults. Each operator receives a bound set of reference materials containing electrical trip guidance and examples of causality responses.

The reference materials give operators the tools, knowledge, and guidance to make well-informed decisions and set in place appropriate courses of action. Sometimes, the right answer is to stop and call for help; however, knowing when to do that is key.

Millennium Power, managed by Mark Winne, is a 360-MW, gas-fired, 1 × 1 combined cycle located in Charlton, Mass.

New Harquahala Generating Co. Powerplants have numerous reporting guidelines and protocols when it comes to safety, environmental, and emergent situations. NHGC is no different in that regard. However, locating the documents and making sure everyone knows where all of the necessary procedures, guidelines, and flowcharts are located can be challenging.

This is especially true when new employees are involved and/or the process is not often used. It is critical when the facility is in the midst of a developing situation when you need clarity as to the process necessary and location of appropriate guidelines.

Having defined locations and quick access to the necessary materials makes serious events much easier to manage correctly, particularly when they occur at times with minimal staff available.

A binder containing guidelines for necessary actions at this NAES Corp-operated plant includes the following:

      • Contact information for NAES, owners, plant personnel, sabotage or bomb threat, EMS, fire, and spill response organizations.

      • Emergency response call form and event log.

      • Bomb threat checklist and procedure.

      • Spill response procedure.

      • Fire response procedure.

      • Injury response procedure.

      • Plant-specific incident flowchart.

The binder is specific to the plant and identified by color coding to differentiate from other materials. Copies of the binder are located throughout the facility at all phone locations and updated as necessary and reviewed annually for edits.

The binders have been used for hands-on training during plant drills and exercises, proving valuable for clarifying necessary actions to be taken during specific emergencies.

New Harquahala Generating Co, managed by Andy Duncan, is an 1080-MW, gas-fired, three-unit, 1 × 1 combined cycle located in Tonopah, Ariz.

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