The value proposition of user-only discussion forums

D5 D5AThe open discussion sessions at user group meetings are somewhat like “show and tell” was in grammar school: Listening to what colleagues have to say you get answers to questions you never thought to ask, and finding out about things you never knew existed. Plus, you have the opportunity to put a few photos up on the screen and ask the group, “Does anyone know what caused this?”

Often, the open discussion sessions are what attendees remember best. Everyone is equal and the only dumb question is the one not asked. These user-only forums typically begin with collaboration among owner/operators on topics introduced by the OEM or third-party equipment and services providers earlier. Example: “So and so said this and that improved unit heat rate. Has anyone implemented this solution? What was the result? How difficult was the implementation? Where were the potholes on the road to success?” The only things never discussed are contract terms and costs.

After those questions are exhausted, the discussion leaders dig for the O&M pains plant personnel are suffering, ask for lessons learned, best practices others might find beneficial, etc. Here are some of the things learned on a broad range of topics from the 501D5-D5A users:

Staffing. Discussion on this topic can be endless. Nearly 10 years ago, one of the editors asked attendees at an E-class user group meeting how many employees they had at a 2 × 1 combined cycle. The consensus reply, by show of hands, was 30; today, the number typically is less than 20; tomorrow, perhaps even less. There is nothing being said in the industry today that would suggest staff increases are on the horizon.

One of the D5-D5A users said his company operates four 2 × 1 combined cycles and three peaking plants with a total of nine people to manage O&M for the 2700-MW fleet. While contractor personnel run the combined cycles, each of those facilities has a member of the operations-savvy corporate staff onsite. The more than 600 MW of simple-cycle assets are at unmanned locations until they operate. Then a member of the corporate staff becomes the CRO—the only person at the plant.

The question that remained after everyone had his or her say: At what point does the corporate strategy of “Do more with less” fall apart and wind up costing far more than a few salaries? Consider that the thinner your staffing, the greater the impact of a loss when a person moves on; particularly so, if it’s a highly valued member of your team.

The chance of hiring someone with equivalent capabilities today is slim to none. In case you have been “off the grid” for the past few years, senior people are retiring at an alarming rate (sometimes because staff reductions have added significantly to their unpaid responsibilities); the armed forces have shrunk, dramatically reducing the prospective labor pool; qualified technicians can make more money in other industries, etc.

Plus, the shine is off the contractor apple. Where do the aftermarket services providers get competent people to operate and maintain your plant if you can’t? Erosion of skills and lack of commitment calls for more supervision by owner personnel, not less. To illustrate this point, a user mentioned having a discussion with a vendor regarding “human performance issues” and the need to improve the rigor in factory acceptance tests for control systems. Do you dare allow a contractor onsite without staff supervision? But how can your people “supervise” if they don’t have the requisite experience? Seems like a downward spiral with no good ending.

Mention was made of the deteriorating quality of new parts and of repairs to hot parts. One experienced user said he ordered two sets of turbine blades to get one satisfactory set. New OEM parts sometimes do not meet his company’s QA requirements for repaired blades, he continued, suggesting all owners do rigorous incoming inspections because “minimum criteria” change over time.

Another experienced user said his plant had to reject three new R2 turbine blades during an overhaul. The location of the defect was unusual, he said. The OEM said it had never seen this before. Further investigation of parts in inventory did not reveal any other defects. A casting anomaly was determined to be the cause. The first question that comes to mind: Why wasn’t the defect found earlier given the effort spent on six-sigma work processes and inspection practices?

This fact also was brought to light at the spring 2015 CTOTF™ meeting where a presentation by Aaron Frost Allied Power Group’s technical director revealed the possible negative impacts to owners of cost pressures in the new parts and repair businesses. Caveat emptor: Owners need highly qualified personnel to write repair specs, review quotes, conduct repair-facility audits, and make decisions on contract awards. A low-price decision today can easily compromise expectations.

Cold-weather issues get some air time. Annual verification of adequate heat tracing, steam sparging, preheating of gas-turbine inlet air, and use of dampers or duct balloons to prevent a steady stream of cold air from flowing through the GT during shutdown are among the solutions to consider.

One user told of a low-temperature lock-out on his generator when the ambient temperature dipped below -4F. A colleague shouted, “Me too.” The logic of having such a lockout made no sense to them—or to anyone else in the room—because the temperature in the generator compartment was 25 to 30 deg F higher. The OEM finally agreed, but it still took a year to get the issue resolved.

Liquid fuel. Experience with oil firing was brought to the floor. Interestingly, six or seven years ago some plants with dual-fuel firing removed distillate plumbing to simplify outages. Recently, the (1) dramatic drop in the price of oil, (2) declining quality of gas supplies, and (3) rule by some grid operators to require dual-fuel capability to qualify for capacity payments, have some gas-only plants adding oil firing capability.

Those users asked colleagues burning oil about their experiences. Coking of fuel lines and clean out of liquid-fuel lines on shutdown with water or high-pressure air after burning oil, sludge in oil tanks, controls issues, etc, were all mentioned. Among the possible coking solutions identified were water-cooled liquid-fuel valves from JASC and that company’s ZEE product, which allows plants to exercise and monitor the fuel delivery and flow metering systems to the burners without firing liquid fuel.

Splitter-plate cutback mod. Siemens presented on its solution to mitigate cracking of inlet-manifold splitter plates and struts. Here’s what some of the users had to say:

      • One plant’s fix was to drill the crack and re-weld it. No further cracking issues since this was done several years ago, so the OEM’s fix has not yet been implemented.

      • An offshore plant identified minor cracking of splitter plates on two of its D5As. A conventional weld repair was made; no further action is planned unless it doesn’t hold up.

      • A user reported self-performing, with Siemens’ guidance, the splitter-plate cutback and bolted strut mods on one unit last fall. Splitter-plate cracking was severe and horizontal struts were broken on one of the plant’s two D5As, he reported. Modal testing revealed that the natural frequency of the struts was about 61 Hz. There have been no issues in the 3500 equivalent base-load hours of service since the repairs were completed.

Turning-gear (TG) operation was included in the OEM’s presentations lineup and summarized in an accompanying CCJ ONsite article. Here a few users share their thoughts:

      • Intermittent TG timers were installed by one owner on its D5s and D5As. When a timer is enabled, jacking-oil pumps turn on and the turning gear is operated once a day for two hours; TG operates continuously when the timer is The user said its tests revealed startup vibration is not impacted by such intermittent operation when disc-cavity temperatures are below 100F.

      • Another user said when immediate availability of a generating unit is not required and disc-cavity temperatures are acceptable, the TG is turned off and operated weekly for about a shift. This owner typically receives notification of intent to start two to four hours in advance.

      • Yet another user offered the following TG program:

        1. 1. Run the turning gear 24/7 until the highest disc-cavity temperature drops to 120F.

        2. 2. Discontinue TG operation for 12 hours.

        3. 3. Initiate TG operation for two hours.

        4. 4. Discontinue TG operation for 12 hours.

        5. 5. Repeat steps 3 and 4 until called upon to operate.

If called to operate your gas turbine in the real-time market, immediately initiate TG operation and prepare for GT startup. If called to operate in the day-ahead market, initiate TG operation upon notice of day-ahead dispatch and prepare for GT startup according to plant-approved procedures. After shutting down the GT, start turning gear and proceed with steps 1 through 5.

Extended life hardware is a popular topic at every meeting. One user offered that his base-load units have had 16K combustion parts for many years and have completed several successful 16K runs—one stretched to 17K. Another owner reported working on a nominal 18-month overhaul cycle (13.2K fired hours) which has been pushed out to more than 15K hours when necessary. This operating paradigm has produced satisfactory results using old-style (not 16K) combustion parts.

However, the owner pointed out that its parts are not the industry norm. It specifies upgraded coatings/hard surfacing and tighter repair tolerances than the large majority of users. But the assets discussed traditionally have not run with wet compression. In the last couple of years, the user continued, wet compression has been used more often and more wear and TBC coating loss have been experienced—but not to the point of forcing reduced run times. The additional wear is believed responsible for an increase in combustor noise.

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