Requirements change, but the Frame 6B adapts to meet expectations

Frame6 LogoJeff Gillis of ExxonMobil Chemical and Sam Moots of Colorado Energy Management got the 2015 meeting of the Frame 6 Users Group off to a quick start at the Doubletree Resort by Hilton Hotel Paradise Valley in Scottsdale, Ariz, June 22 – 25. The duo is well practiced in handling introductions and housekeeping/safety items, having held their leadership positions for several years. As soon as the co-chairs finished, they handed the “keys” to J C Rawls of BASF Geismar, a member of the group’s steering committee and a polished discussion leader, who launched the technical sessions with an open forum on safety.

Over the next two-and-a-half days, attendees would participate in a robust program incorporating the following:

      • Discussion forums of about an hour each on auxiliaries and generators/excitation facilitated by Gillis, Mike Wenschlag of Chevron on I&C, compressors facilitated by Geoff Kret of Total Petroleum, Moots on the combustion section, and turbine section facilitated by Zahi Youwakim of Huntsman Corp.

      • A robust GE Day included formal presentations and a series of 45-min interactive roundtables. The morning was dedicated to presentations by GE’s engineering team, specialists from across the country and France, on turbine cooling and sealing flows, accessory and engine TILs, generator/load-gear sealing air systems, rotor life management, transactional repairs, controls, and engine upgrades. The afternoon was dedicated to roundtables, chaired by members of the steering committee and including OEM participation, on hot gas path and performance, compressor and GT life management, repairs and realignment of the OEM’s North American service shops, accessories and controls, and outage planning/management.

      • Special vendor presentations were made by Andy Pomerantz of Philadelphia Gear on load gears and accessory drives, and by Wayne Greaves of Sulzer Turbo Services Houston on rotor life assessment.

      • A vendor fair for more than five dozen products/services suppliers to the Frame 6 fleet, and reception, on Tuesday evening from 5 to 8:30.

      • An update on the world’s first TurboPhase installation, at Atlantic Power Corp’s Morris Cogen 6B-powered 3 × 1 combined cycle, by O&M Manager Joe Nichols.

      • Presentation of CCJ’s 2015 Best Practice Award to BASF Geismar for the re-engineering and modification of its boiler feedwater system to reduce energy consumption and improve plant availability/reliability.

      • Wickey Elmo Peterson Award

        Wickey Elmo, conference coordinator for the Frame 6 Users Group, receives the 2015 John F D Peterson Award for dedicated service to the industry and the 6B users from Co-chair Jeff Gillis (right) and Peterson (left) for whom the award is named

        Presentation of the Frame 6 Users Group’s 2015 John F D Peterson Award to conference coordinator Wickey Elmo for her years of dedicated service to the industry and the Frame 6 Users (photo). Elmo, who also has managed the CTOTF™ and its semi-annual meetings for more than two decades, retires from that position at the group’s fall meeting in September; she will continue to serve the Frame 6 group at least through the 2016 meeting at the PGA National Resort and Spa, Palm Beach Gardens, Fla, June 13 – 16. Conference and hotel registration information will be posted on the Frame 6 website as it becomes available.

Rawls opened the safety discussion with a slide encouraging the group to provide perspective and ask questions on such topics as incidents, compartment entry/access, fire protection, maintenance issues/concerns/best practices, exciter/ground brush change-outs, fuel issues, heat, overspeed testing, instrumentation failures, and anything else of interest.

The Frame 6 users don’t need much encouragement to talk about their experiences or to offer meaningful opinions. Room size and attendance of 60 to 70 owner/operators are ideal for productive discussion based on the editors’ experience. Plus, about a third of the attendees in any given year have been around Frame 6s for decades and really do know the machine’s idiosyncrasies. Add to the mixture of participants users with several years of direct engine experience and new personnel eager to learn and it’s relatively easy to ignite a discussion.

Interestingly, the safety discussion this year, and at the last couple of meetings, has reflected user concerns with package fire protection systems and entry safety. Regarding the former, it appears relatively little thought had been given to the lifetime of fire protection systems until recently. Sure, plants were conducting the prescribed tests over the years, but system controls and wiring at some installations have seen better days and should be upgraded or replaced. Plus, some facilities are still using Halon, which is associated with environmental issues. Replacement of the remaining Halon systems could be termed a “work in progress.” CO2 and water mist are alternatives. But selecting the former creates raises safety questions regarding package entry when the gas turbine is operating. Regarding the latter, some users express reluctance at putting water into the package.

The first question in the session came from a user who asked how to drain the liquid CO2 tank for inspection. This is a pressure vessel that at his plant hadn’t been inspected for 20 years. It appeared that a few in attendance had not given this inspection much thought previously; others were not sure of the inspection interval. A user cautioned that venting can be hazardous, especially when the tank is located in an enclosed space. If the vessel is outside, use tape to prevent access to the area near the tank prior to venting. Another caution offered was that rapid venting could cause freeze-up of the tank liquid.

You could gauge how far the religion of safety has progressed over the last several years by the long discussion on package entry. Someone mentioned “confined space” and the floodgates opened. An attendee cautioned about calling the package a confined space because that would cause problems during maintenance; even with the doors off, it still would be a confined space, he said. At his plant, the O&M team considered the package a confined space regarding procedures—permit included—without officially categorizing it as a confined space.

Next, compartment temperature was introduced as a discussion topic. A debate ensued on “how hot is too hot?” Consensus view was that anything more than a couple of hundred degrees can be problematic because controls wiring would be affected adversely. Adequate ventilation was stressed as a starting point. Perhaps some re-engineering is in order, a user suggested; there are many viable ventilation arrangements, he said. One to avoid is locating one fan on the side of the engine. Reason: Uneven cooling could cause a unit trip. Another point made during this discussion was that European standards for compartment ventilation differ from US standards. US owner/operators with engines made in Belfort, France, might want to conduct a system review.

If ventilation is adequate and the package temperature still is too high, start looking for leaks. Check exhaust flex seals for cracking, an operator opined. Another recommended inspecting crossfire tubes for leakage. He said this was the cause of high package temperature at his plant.

Upgrading to bellows type crossfire tubes solved that problem.

There are many flanges that might be leaking hot air/gas, an attendee said. How do you identify the one or two that are? Simple, one of the more experienced users offered: Tie a rag on a stick and do it the old-fashioned way—it works. You can’t find a leak when the engine’s not running, he said.

However, this is counter to the thinking of corporate safety personnel, and the OEM, who warn against package entry when the unit is running. People seem to get at loggerheads over this issue. Many suggestions were offered, including the following:

      • Install a thermal monitor to pinpoint a leak. That idea was nixed by someone who had tried it and found that a hot compartment adversely impacts instrument accuracy and repeatability.

      • Disable CO2 or Halon fire protection systems prior to entry. Is this something the plant really wants to do? Would corporate safety personnel and insurance companies support such a procedure?

      • Develop a safety protocol. One possible example: Keep the door wide open while someone is in the package for a defined period of time with one or more others standing by right outside the door in case assistance is required. Control-room personnel would be forewarned, of course.

      • Review the typical reasons for package entry and revise procedures or upgrade equipment accordingly. The experience at one plant revealed package entry was required most often because of issues with water-cooled flame scanners. They were replaced with fiberoptic flame scanners, which have been problem-free. Install windows in the package door and/or sidewalls, as appropriate, to allow visual confirmation of possible issues before a decision is made to shut down the unit or to enter the compartment while it is operating. Provide remote readouts outside the package for all data a roving operator might need to see on rounds, precluding the need for entry.

      • Check bolts/studs/nuts on flanged joints for proper torque during annual inspections. Engine vibration and thermal cycling can loosen fasteners over time. If joints are loose, you might want to replace gaskets before retorquing to help assure proper fit-up.

      • Install acoustic emission sensors to alert when a leak occurs. Mistras Group has exhibited its equipment for flange leak detection in gas-turbine plants at several user group meetings. The editors spoke with one utility that has purchased multiple systems for its plants. A few systems have been installed; installation of the others is planned as outages allow. The utility engineer in charge of the project said it is a relatively inexpensive system for warning when a leak develops, which is all this user wanted it for—the thought being a leak might be a gas leak and they wanted a heads-up before a combustible mixture can develop in the package. Note that this detector cannot differentiate between fuel and air. When asked about leak location, the user said his company’s arrangement of four sensors per package should be able to identify a section of the package where the leak is but it would not be able to pinpoint the location. However, a more robust monitoring system might be able to do this.

Expanded coverage of the 2015 Frame 6 Users Group meeting will appear in the third-quarter issue of COMBINED CYCLE Journal.

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