Extraordinary may be the best word to describe the value of user presentations

D5 D5AUser group meetings without meaningful presentations by owner/operators may not be providing a program of maximum value to attendees. Sure, users learn from the OEM, consultants, and third-party equipment and services providers, but there’s nothing like a presentation by an owner/operator on a subject of interest to the fleet to lay out the cold, hard facts and help others avoid having to relearn lessons already paid for. 

There were several valuable user presentations at the 501D5-D5A Users’ 19th annual meeting in Tucson, June 2-4. Several suggested that the work of vendor personnel be very carefully scrutinized by plant staff or an owner’s independent expert during controls-upgrade projects. The takeaway from these experiences, which involved the migration from legacy control systems to T3000, reinforces the notion that at least some programmers could benefit from collaboration with station personnel regarding the possibility of operational idiosyncrasies before making critical decisions. 

Ray Martens, plant manager of Klamath Cogeneration and vice chair of the 501F Users Group, warned of some of the same problems experienced by these 501D5-D5A users six years ago. Sometimes owner/operators must speak in unison to get the attention necessary for issue resolution. User groups provide the necessary platform.

What follows are some of the editors’ notes from the presentations/discussions on control-system migration in the closed user-only sessions during the three-day D5-D5A event. A planned 10-day conversion from WEStation to Siemens T3000 for a 1 × 1 combined cycle went into Day 19. One issue was that the speed probes on the steam turbine were passive and required converters for the new DCS. The unit was unable to get beyond 2200 rpm until active probes were installed. Another issue was that controls engineering had not been completed on the steamer and logic was being modified during installation.

Onsite leadership was weak, the speaker said, and communication with plant personnel inaccurate at best. Loop checks were disorganized, he continued; preliminary engineering appeared incomplete or, at times, not done at all. The user’s conclusion: The vendor was not prepared for the installation. Trending and logs were very challenging, the speaker added, citing automatic reporting as a fleet issue. Another user described similar challenges at his plant.

Long-term participants in 501D5-D5A meetings may recall discussion of T3000 migration issues a couple of years ago. Referring to notes, the editors recall a user describing the conversion from TXP to T3000 as turning out quite well despite conflicting logic and control settings in the Siemens database versus what the plant had onsite. He strongly recommended that plants transitioning to new control systems verify all settings, conversions, etc.

The obvious takeaway is user groups are addressing the information needs of owner/operators on a continual basis, whether in face-to-face or online meetings, or via conference calls and forums. Chances are good that an issue confronting you has been experienced by others—especially in mature fleets—like the D5 and D5A. Use the network to full advantage.

D5 User 1

Blending of D5A R1 compressor blade. A routine inlet inspection revealed foreign object damage to one Row 1 compressor blade (Fig 1). A liberated icicle during the winter run is believed the cause. The unit had experienced as many as 70 starts and operated for about 500 hours with the damaged blade; Siemens engineering recommended blending the airfoil (Fig 2). This case history illustrates the ability of gas turbines to “ride through” minor damage and accommodate repairs you might not have thought allowable. 

D5 User 2

D5A gas leak. Operations personnel noted gas leakage when B- and C-stage (premix) fuel valves opened. This simple-cycle D5A is equipped with the OEM’s four-stage DLN combustion system. Leakage increased over time. Detectors inside the enclosure registered 23 ppm at one point. Vent fans were turned on during operation to reduce gas concentration.

Troubleshooting activities located gas leaks around several support-housing hex-head screws. Eroded washers were replaced but the enclosure gas concentration remained about the same. A technical advisory issued by the OEM 10 years ago suggested Siemens involvement, and its field-service technicians verified spec flange-face flatness on combustor-portal sealing surfaces with some light stoning.

The speaker noted that the OEM offers a “no-gas-leak guarantee,” provided you buy a spare- parts kit and contract required repairs and any additional field service work through Siemens. He then went to discuss some of the finer points associated with locating and eliminating gas leaks on this specific equipment.

Example: The majority of the washers are machined on one side and care is required during installation to be sure they are not resting on the support-housing fillet (Fig 3). If fit-up is not precise, the screws will “torque out” before washers are seated properly and gas leaks will occur. Also, each support housing has one position that requires a washer machined on two sides to accommodate a fit between the C-stage piping and the flashback thermocouple (Fig 4).

 D5 User 3 D5 User 4 

The vendor performance critique incorporated into most user presentations was critical as most are; perfection is a user expectation. A couple of the comments made: Siemens did a great job once its personnel were onsite, but getting there was quite painful. Another: Parts did not meet specs in all cases, plus some were late arriving. The field engineer would have benefitted from more support in the corporate office. Most users probably would agree nothing mentioned by this speaker was anything different from what they have experienced, no matter what vendor is involved.

Exhaust-cylinder replacement. Lessons learned during an exhaust-cylinder replacement received a lot of interest from the group. To gain some perspective on the magnitude of this undertaking, refer to the Klamath Cogen experience detailed in the article referenced earlier. Here are some of the suggestions made by the D5A owner to attendees:

      • It’s critical to assign someone the responsibility of controlling hardware. Done correctly, this can be a full-time job. Bolts should be color-coded, cleaned up, and locked in bins to prevent loss.

      • Weld in support rods to hold the downstream exhaust manifold in place before unbolting the exhaust cylinder.

      • Remove the spigot fit on the torque tube to avoid having to remove the turbine cylinder during casing alignment. Make a tool to move the torque tube and ream new dowel holes once the final position of the torque tube is determined.

      • Remove about 1/8 in. on the spigot fit to allow proper fit-up of the exhaust cylinder.

      • Scribe a mark inside the exhaust bearing area when the top is in place, otherwise you will have no reference point to show the maximum position of the anti-rotation pin—thereby preventing installation of the exhaust cylinder.

      • Replace the expansion joint when replacing the exhaust cylinder.

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