Safety. The opening presentation/discussion topic was safety and that held everyone’s interest for more than an hour. When safety discussions began to gain significant traction at user group meetings about five or six years ago, a facilitator from the steering committee generally polled attendees for their safety best practices—snippets of information if you will. Those interested would write them down and bring the ideas back to their plants for implementation.
The G safety presentations Tuesday were far more robust. The first on on how company with many plants handles safety on a fleet basis was particularly informative. The speaker walked his colleagues through various elements of the program, including the following:
- A comprehensive contractor safety orientation program, in both English and Spanish. It’s important for all workers onsite clearly understand what your safety rules are, he said.
- The importance of maintaining a positive safety culture. He stressed the need for plant personnel and contractors to review the day’s work and its safety challenges at an all-hands stand-up meeting at 7 am. And then follow up with a safety critique of the day’s activities at another stand-up meeting at 5 pm.
- A JSA (job safety analysis) review that includes a tailboard for the analysis of job hazards associated with tasks assigned for the next shift.
- Satellite LOTO (lock out/tag out) boxes that are brought to specific job sites—such as a generator overhaul—to facilitate the administration of safe work areas.
- STOP (safety training observation program) cards that allow all workers to participate in the safety decision-making process, if they so choose. The idea behind the STOP cards is to encourage workers to contribute their thoughts—by writing a few sentences on a card—regarding good or bad safety practices. The names of any offenders are not associated with poor safety practices. Contributed ideas are analyzed weekly and incorporated into the safety program. A chart summarizing one week’s submittals revealed that slip and trip hazards were foremost in the minds of site personnel. This was called to the attention of supervisors and deficiencies were corrected.
- The use of financial incentives to promote a safety culture.
The speaker noted that improved safety practices often are contributed by workers doing a particular job for the first time. They tend to question why a task is done in a particular way rather than accept “that’s the way we do it here.” He recalled one good idea that came about as a result of an accident.
The compressor cover was open and all but the first row of blades remained in the machine when an experienced and normally very careful worker walked across the unbladed portion of the unit to get to the other side of the casing. As he hopped down to the split-line he turned his body to avoid a guide pin protruding upward from the flange. His leg got hooked on the sharp corner of a first-stage blade; the resulting gash required hospitalization. That unfortunate incident prompted the design and fabrication of aluminum blade covers for use when the top casing is off the unit and the blades remain in the machine.
That safety is serious business today was underscored by the fact that the speaker’s CEO has a monthly call to plant managers to review safety incidents and near misses throughout the fleet. Managers are asked to explain what happened and what’s being done to prevent a recurrence.
The ensuing discussion raised the point that the impact of an accident such as that described above has several negative effects. First, work stops immediately. Second, workers blame themselves for not seeing and reporting job hazards. Third, it’s tough for employees to get back to work after an accident, and the loss of concentration on the job at hand creates hazards of its own.
The next speaker observed that all plants may approach safety initiatives differently but they’re all working toward the same goal. This plant manager said he hires safety professionals to backstop his team during outages. Staffs are so thin these days, he added, they might not be able to manage both the technical and safety aspects of a job concurrently and to the degree necessary.
The PM discussed the capabilities of several firms that can help plan safety into the outage, perform onsite safety audits, serve as a watchdog, and provide professional help if someone gets in trouble. The remote locations of many plants add to the safety risk, he continued. Safety professionals trained in confined-space rescue and emergency medical response can be valuable members of your outage team.
Generator inspection got some air time by an attendee who discussed his plant’s efforts to meet the intent of an OEM advisory suggesting the need to determine the modal frequencies of generator end-winding components—this to assure they were sufficiently above or below 60 and 120 Hz (a typical goal is 137 Hz and above) to avoid damaging vibration. Stiffening was required to bring each of the plant’s three generators within frequency specs.
Another user noted that an inexperienced borescope technician reported generator field windings in relatively good condition. When the fields were pulled on two of his generators he learned that more than three-quarters of the bars at the top of the unit showed the effects of spark erosion; the other unit, 90%. Some partial discharged was identified in both units.
Rotor lifts. Representatives of two plants stressed the need to have extra slings available for critical lifts—such as rotor removal. Chafing or other damage to wire rope can shut down your lifting operation until you get replacements. Sling damage cost one plant two days on its outage schedule. Attendees also were advised to be sure the certifications on their rotor lifting beams are current.
Steam-turbine stop and control valve seats can suffer severe wear and tear in cycling and fast-ramp service. The plant engineer for one 501G owner said significant valve work was expected in his plant’s two steamers, so a significant number of spare parts were ordered prior to the outage—enough spares to replace one of the four Inconel valves with Stellite seats (two control, two stop). First stop valve opened revealed a seat with a 360-deg crack; the control valve had a 300-deg crack.
The cracks, which extended down through the seats and into the base material of the valve, was machined out using portable tooling. Next, Inconel weld material was deposited and that was machined to final tolerances. The refurbished valves were restored to service.
Inlet struts that cracked on one unit were redesigned and replacements installed. The experienced user suggested that if his colleagues were to perform the same mod, they should consider removing and replacing one strut at a time to maintain the desired configuration of the inlet house and ducting. The danger of inlet struts self-destructing is that liberated parts could carry into the compressor.
Igniters. Failed starts following a modified HGP inspection had plant personnel stumped for a while. Going into the outage the gas turbine had a history of successful starts, no problems. After the outage, the unit suffered a series of failed starts on high blade-path spread. All the usual suspects were investigated, including: fuel-flow imbalance, igniter and cable problems, etc. In the end, good old-fashioned trial-and-error troubleshooting revealed that four igniters were out of spec. Once they were replaced, the unit worked perfectly.
