Formal presentations focus on inlet filters, inspection findings, repair technology

There were three formal user/vendor presentations at the 30th anniversary meeting of the Frame 6 Users Group, in addition to those delivered by the OEM’s team on GE Day:

      • Inlet-house air filters, based on the collaborative work between AAF International and a Gulf Coast user.

      • Emergent 6B compressor findings, compiled by Florida-based Advanced Turbine Support LLC.

      • Six steps to successful repair of Frame 6B components, based on the experience of Hans van Esch, founder, TE Services, Houston.

The first and third presentations are available on the user group’s website.

Air filters. It seems like no meeting of gas-turbine users is complete without an air-filter session. The engineer presenting for the owner/operator opened with a slide that outlined his game plan for filtration success. It was based on answers to these questions:

      • How do we select the correct filter for our site?

      • What do we need to do to keep the compressor clean?

      • What is the frequency of filter replacement?

      • What information is required to make the proper decision—including cost of replacement filters, operating profile, ambient conditions, filter-house design, velocity of air through the filter house, etc.

Goal was to retrofit a filtration system that would ensure at least a three-year interval between replacements of AAF’s E-12 HEPA-grade filter. Coalescer filters and pre-filters were tested and selected to support this objective. Here’s what was decided:

      • Install Merv-9 coalescers and replace them quarterly. Existing coalescers were Merv 6 and replaced every other month.

      • Install Merv-15 prefilters and replace at 18-month intervals. Existing pre-filters were Merv 8 and replaced annually.

The first of the plant’s two gas turbines was equipped with the new filters after the fall 2015 outage, which included a thorough cleaning of the compressor. Average power increase over the ambient temperature range of interest (45F to 80F) was 2.4 MW—significant for a nominal 35-MW machine. The second engine received new filters after the spring 2016. Plan is to run three years and then replot data to see how well the filters do over time. Information will be shared with 6B user-group participants at a future meeting.

The speaker mentioned that horizontal cylindrical/conical filters may sag over time because of weight and suggested that manufacturing tolerances for tripods might have to be upgraded to prevent filter bypass caused by the sag. This is important: A 1-mm (40 mils) gap between the filter frame and the inlet-house structure holding the filters in place causes a Merv 15 to perform as a Merv 14.

6B compressor findings. President Rod Shidler of Advanced Turbine Support conducted a rapid-fire luncheon workshop on recurring problems the company’s technicians are finding during their inspections. Although the 6B is considered a dependable workhorse with relatively few compressor issues, he began, recent findings suggest semiannual—or at least annual—borescope inspections should be conducted to maintain high availability. In the process world, that’s particularly important.

Shidler said the company’s inspectors have identified mid-chord cracking in first-stage vanes in the lower half of a 6B compressor and stator Row 17/EGV1 liberations in three other machines. While TIL 1352-2R2 (original release in 2003) discusses aft-compressor damage, he continued, the S1 vane cracking is a “first.” The cracks and the reasons for the cracking are not yet addressed by a Technical Information Letter and appear to be identical in nature to the cracks found in 7EA compressors both with and without clashing (TIL 1884-R1).

Component repairs. Van Esch, one of the industry’s leading experts on inspection and repair of hot parts for industrial gas turbines (IGT), conducts a well-respected three-day training course on Metallurgical Aspects of IGT Component Refurbishment twice annually. He developed a primer from this material, “Six steps to successful repair of GT components,” which was published in consecutive issues of CCJ between 2Q/2005 and 1Q/2006. He updated that work for publication in 3Q/2014.

Van Esch boiled down and tweaked his material for a one-hour presentation focused on the needs of 6B users. Here’s an outline of the subject matter presented:

      • Assessing the condition of GT parts onsite.

      • Preparing meaningful component repair specs.

      • Selecting the appropriate vendor to refurbish turbine parts.

      • Key stages in the repair process.

      • Verifications during the refurbishment process.

      • Verifying final inspection.

GE Day. It seems like hardly a week goes by without an announcement from one of the OEMs on the sale of an advanced machine (late-model F-class, plus G, H, and J series engines), commissioning of a new combined cycle, efficiency gains—sometimes down to relatively few Btu—touting gas-turbine model X as the world’s most efficient, etc.

How much of this blather means anything to someone with O&M responsibility at an operating plant? Very little. What’s important is how your plant is performing today. If your 6B is not meeting expectations—efficiency, availability, reliability, etc—what can you do to turn the tide? Looking ahead, what does the future hold for your equipment? If you’re planning to run “forever,” are you considering life extension, boosting output, improving performance, etc? User group meetings provide the background and contacts to help you navigate the alternatives available to make your plant the best it can be.

From the editor’s perch, GE’s participation in the 2016 Frame 6 Users Group meeting reflected the notion that true collaboration between OEM and end user was the goal and progress was being made in this regard. Everyone knows you catch more flies with honey than vinegar and the sales person concerned with your plant’s success will sell more product. That’s called win/win if you’re an astute buyer.

Frame 6 meetings are all about the Clydesdales that keep industry humming, the engines that can take a beating and keep on running—at the lowest cost possible. GE’s “A” team for this frame, which spent a productive day with the owner/operators (all work, no play), was sensitive to this need.

But, at the same time, these engineers offered a view of the industry’s digital future (fact not fiction), and the proven advancements from the larger frames available for 6B application to meet tomorrow’s demands. Checkbook required? Yes. Expensive in the minds of those typically responsible for managing the finances for a Gulf Coast refinery or chemical plant? Yes. But given the level of experience with the lineup of improvements presented, the benefits and payback period seem quantifiable with a relatively low risk profile.

If you missed the meeting, catch up on what the GE 6B team had to say by accessing the presentation outlines.

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