GE’s Frame 7 turns 50
The 7EA Users Group returns to in-person conferencing August 23 – 27 when owner/operators of
GE Frame 7B-EA gas turbines gather at the Marriott St. Louis Grand for the organization’s 2021 conference. Several score users and more than a hundred exhibitors are expected despite federal, state, and local rules tightly controlling the conduct of meetings during the pandemic.
Recall that the 2020 conference, originally planned for October 19 – 22 at the J W Marriott Houston Galleria, was conducted online October 20 – 22. A summary report on that meeting is included this article.
The technical program for the 2021 meeting is directed by an all-volunteer steering committee of industry engineers with deep 7E experience (Sidebar 1). Note that the OEM aggregates the model designations 7A, 7B, 7C, 7E, 7EA (a/k/a 7E.03 in GE lingo) under the 7E banner. Users typically refer to this group of units as 7EA. Puzzled by the naming convention? Industry sources promise clarity before the 2022 meeting.
Golden Anniversary. The first two GE Frame 7 (Model A) package power plants (PPP) were ordered by Long Island Lighting Co in 1970 and installed 50 years ago this summer—one at the utility’s West Babylon plant in July 1971, the other at Lilco’s Shoreham Plant (a/k/a Wading River) in August 1971. The nominal 52-MW, distillate-fired units, still equipped with their original Speedtronic™ Mark I control systems, are in standby service.
From two, many: The OEM reported during the 2020 meeting that now there are nearly 1200 7Es operating at more than 300 plants in over two-dozen countries. In round numbers, 60% of the fleet is located in North America, 25% in Saudi Arabia. Over the last half century the output of this frame has almost doubled to 91 MW. Sales continue, with expectations that about two-dozen 7E.03s will ship from Greenville within the 2020-2022 window.
More facts about the 7E that help characterize the fleet:
Simple-cycle efficiency is now 33.9%.
The 7E.03 is the dominant model with nearly 900 units operating.
That nearly 200 7Bs are still in service testifies to the value of this model. Even more surprising, perhaps, is that the OEM was preparing to ship two new 7B rotors to a customer as 2020 drew to a close. Those were the first new 7B rotors made by GE in 45 years.
In round numbers, the fleet includes 150 cogen units, 100 in LNG production, 200 hours-based generating units, and more than 700 starts-based engines. Total fleet operating hours are north of 70 million.
Ambient temperatures at sites with units in service range from about -40F (above the Arctic Circle) to 130F (some desert regions in Saudi Arabia).
One of the highlights of the 7E’s history is that this frame hosted the company’s first DLN combustion system. Today, 45% of the fleet is equipped with DLN1 and DLN1+ systems. Other fleet firsts include axial fuel staging and sub-5-ppm NOx.
Steering committee, 2021
Dale Anderson, East Kentucky Power Co-op
Joshua Coots, Duke Energy
Tracy Dreymala, EthosEnergy Group, San Jacinto Peakers
Jeff Hansen, Old Dominion Electric Co-op
Guy LeBlanc, IHI Power Services Corp
Tony Ostlund, Puget Sound Energy
Mike Vonallmen, Clarksdale Public Utilities
Lane Watson, FM Global Chemical Operations
2020 Virtual meeting synopsis
The 7EA Users Group’s 2020 conference was conducted online October 20 – 22. The program arrangement for the first two days was the same: Mornings (9 a.m. to 1 p.m.) were reserved for 15-min one-on-one meetings with vendors. Appointments were made by the users at their convenience, using the virtual scheduling pages prepared for each of the sponsoring service providers.
Two presentations by owner/operators were made during the 1:15 to 2:15 session, followed by four 30-min live vendor presentations. A virtual vendor fair with chat rooms followed from 4 to 5 for service providers presenting earlier that day.
Thursday, October 22, was GE Day. It also started with one-on-one meetings from 9 a.m. to 1 p.m. with OEM experts, followed by 20-min presentations by GE subject matter experts until 3. Then a series of half-hour interactive breakout sessions began, running until end of day.
The eight live vendor presentations made during the first two days of the meeting (list below) were recorded and can be accessed on the Power Users website. Messages from other conference sponsors were pre-recorded and also are available on demand at www.powerusers.org. Most of the pre-recorded presentations also can be viewed at www.ccj-online.com/onscreen.
The GE presentations are available at https://mydashboard.gepower.com.
7EA Stage 3 bucket shingling
An owner/operator with a fleet of more than 30 7EAs, all but one starts-based, was surprised by the damage to third-stage buckets on one of its machines found during an annual borescope inspection (access the presentation to see the photos). Bucket shingling was such that there would be a high risk of catastrophic damage were the machine—call it No. 1—to continue operating.
TIL 1313-2R2 (October 2003) states, “Bucket pairs with shroud overlap should be replaced at first opportunity. During replacement, buckets with less than 0.050-in. engagement should also be replaced.” An outage was taken and the third-stage buckets were removed and sent for repair. The spec required 90 mils of engagement. However, Covid restrictions limited shop visits and the vendor determined engagement by calculation, not fixture fit. The old adage “trust but verify” is appropriate here.
S3B condition fleet-wide was assessed and a sister unit—call it No. 2—which had been serviced by the same repair vendor and outage team as No. 1, was found to have 10 buckets actively shingling, plus some with low engagement.
Plan was to replace No. 2’s buckets with the repaired buckets from No. 1. Upon examination, the final repair report contained only three pictures, there were no NDE results, welds had porosity, the engagement requirement was met in some cases by weld build-up, some contact faces were not parallel. A flawed plan, obviously. Another set of buckets repaired by another vendor were installed in No. 2.
Lessons learned—some relearned—included the following:
- A capable witness would have identified concerns with welds before parts left the shop.
- Engagement by calculation is not adequate.
- When making similar repairs, require a fixture fit.
- Require engagement readings during installation.
- Having an owner’s advocate during outages is important.
Generator breaker failure to open
This presentation focuses on the troubleshooting of a failed generator breaker and steps taken to repair the device and quickly return it to service.
The 15-kV GE Magne-Blast breaker supplied with a four-decades-old Frame 7E gas turbine/generator had become unreliable and was retrofitted economically with a new breaker from National Breaker Services mounted in an old Magne-Blast frame. About six months later, at approximately 290 operations, one of the generator poles didn’t open when required and the incident cascaded to a unit trip.
NBS was notified immediately and an RCA (root cause analysis) was initiated. A loose part was found to have caused over-stress and failure. The breaker was repaired with an upgraded part, plus Q/C improvements were made in assembly. The unit was returned to service by a satisfied customer without incident.
Lube-oil system vacuum, post major maintenance
Oil sprayed from the mist eliminator vent piping for a 25-yr-old 7EA during the unit’s first start following a major inspection that included installation of a life-extended rotor. Prior to the outage no issues had been reported with the mist eliminator or with oil bypassing it.
The speaker describes the instrumentation used to collect the data required for problem analysis and the inspection and troubleshooting associated with the bearings and mist eliminator. System vacuum was re-established after replacing the degraded butterfly valve on the mist eliminator and bearing oil seals, plus the addition of a fourth mist-eliminator filter to increase system throughput from 1500 to 2000 cfm. Bearing split lines also were resealed with a more effective product.
Covid-19 and what we do about it
With yet another strain of coronavirus to deal with today, some of the rules established to mitigate the effects of Covid-19 and later relaxed, are being re-enforced. While it might not have made much sense to dig into the details of this presentation a month or two ago, it likely does now. It reviews the steps taken by a major power producer to keep personnel safe during normal plant operations and outages.
Live vendor presentations
AGT Services. 7EA-driven generators: Stator rewind preparedness
The service lives of generators driven by 7EAs are becoming more difficult in many cases—that is, increased stops/starts, faster ramp rates, etc. Since the average design life of any generator typically is from 20 to 30 years, having a plan in place for stator rewinds may be critical to the success of your plant. It can save months of outage time.
Several owners with a large number of these units in their fleets mitigate risk by having a set of replacement windings “on the shelf.” This presentation highlights the key drivers for performing stator rewinds—including discussion of birth defects that may prevent some of these units from achieving their design lifetimes.
Allied Power Group. Rotor repair and life management: What has and has not changed
GTC Control Solutions. (1) Two single-point of failure case studies; (2) Implementation of TILs 1524 and 1275—what you need to know; (3) Control hardware field updates
Key takeaways for users include the following:
A better understanding of the factors that determine a “single point of failure” and how to identify them, plus the not-so-evident aspects of Technical Information Letters (TILs) that can be learned only by implementation.
Mark VI: Attendees learned about previously unknown/undisclosed failure modes, how to determine if their Mark VI is potentially susceptible to it, and what their opinions are for avoiding future occurrences.
Mark V: Become familiar with two new critical cards from GTC capable of extending Mark V panel lives.
Liburdi. 7EA nozzle repair: Proven LMP® technology for cycling units
Key takeaways for users are these:
Liburdi Powder Metallurgy, LMP®, a patented high-strength metal replacement process used in both the manufacture and repair of gas-turbine superalloy components, is a practical alternative to weld and braze techniques, which may not achieve expectations.
LMP repairs maintain dimensional fidelity, allowing swift and accurate reassembly. Plus they exhibit excellent durability in service.
ORR Protection Systems. Improving the life safety of CO2 fire extinguishing systems
PSM. Targeted upgrades using digital logic and combustor hardware solutions to improve flexibility and reliability
Presentation covers combustor and digital solutions—from small investments to large—that help owner/operators maximize asset life. Example: LEC-NextGen, drop-in compatible with the OEM’s DLN1 combustor, is said to offer increased hardware reliability, fuel flexibility, and even lower emissions. In many cases, structured upgrades can be used in combination with the DLN system in place without having to invest in total hardware or control replacements to benefit from the upgraded features.
Shell Lubricants. Choosing and maintaining lubricants
What you’ll learn from this presentation:
- Mitigating varnish is not a one size fits all.
- Basic understanding of the various options—including filtration units, cleaning/high-velocity flushing, and the top-tier chemical treatments and the short/long-term solutions they provide.
- Replacement fluids.
- Chemical makeup, solvency, and benefits of different base stocks.
- Fluid maintenance.
- A better understanding of what’s possible based on actual customer results.
Trinity Turbine Technology. Upgrading original transition pieces to newly designed Barnes aft mounting
AP+M. Outage in a box
AP+M. Turbotect 2020
Braden Filtration. Functionalization of filter cartridges for air inlet systems
Reviews historical pulse-filter performance for air inlet systems that use self-cleaning pulse cartridges. Learn about nanofiber processes that have allowed for a greater variety and application of varying nanofiber sizes. The customized lamination and adaption of these fibers can be used more efficiently to solve difficult atmospheric and operating conditions.
Cemtek KVB-Enertec. TDL for NO3 compliance
Certrec. Winning strategies for managing NERC regulatory requirements
Chevron. Case studies in varnish removal
See “Chevron VARTECH industrial cleaner helps restore gas turbine to maximum power,” p 87.
JASC. Pitfalls to avoid for enhanced liquid-fuel-system reliability
Gas-turbine fuel-delivery reliability depends on three systems performing equally: liquid fuel, purge air, and water injection. Each system has unique operational characteristics and challenges.
The presentation provides an overview of the various components and the design features developed for each. You’ll come away with a roadmap for achieving fuel-system reliability which provides an ROI in 16 months or less.
Mee Industries. Inlet fogging
Moog. PGO servo valve release
National Electric Coil. A comprehensive approach to 7A6 generator O&M
Whether you have a fleet of 7A6 generators (the model typically married to the 7EA gas turbine) or just one, this presentation is of value to asset managers, maintenance planners, and plant engineers alike. Lifecycle management issues can impact budgets as well as outage planning and execution. Awareness of the specific issues and related failure modes discussed in the presentation can help guide preventive maintenance activities and long-term outage planning.
Parker, Energy Div. Jet-pipe servo valves
Parker, GT Div. Gas-turbine filtration solutions
SVI Industrial/SVI Dynamics. Defining and implementing SCR emission system improvements for GT exhaust
Presentation offers actionable strategies for detailed evaluation of existing SCR systems, low-cost methods for evaluation NH3/NO distribution, CFD modeling, and fast-track retrofit capabilities.