F-class Best Practices: SAFETY

Switchyard cable trench repairs

The 230-kV switchyard at Monroe Power uses trench boxes to route low-voltage cables to various yard components for control and feedback. The trench covers were designed as walkways and are used by technicians to perform daily logs, check transformer bushing levels and winding temps, etc.

A technician was walking down the trench covers while completing a set of daily logs when a cover gave way causing him to fall in the trench. The cover had slid off, causing the right side of the box to collapse inward from lack of support. The tech hit his shin on the next cover in line resulting in a severe laceration.

The trenches consist of approximately 100 separate 4-ft-long boxes. Over the years, the soil surrounding the boxes compacted and pushed in the sides of the boxes, causing the lids to shift out of position. Fig 1 shows the lip on the bottom of the lid no longer fit securely inside of the box causing the lid to shift to the side.

Further inspections of the trench revealed five of the boxes were broken beyond repair and needed replacement. As for the rest of the boxes, their sides had been pushed together about 3 in. on average, causing the improper cover fit-up.

Another problem with the Monroe trench boxes: Concrete lids are heavy and could have caused damage to the cables if they fell in. The worst-case scenario, other than personal injury: A broken wire or a short could have tripped the yard, interrupting power supply to the grid.

Plant personnel concluded the boxes had to be spread back to their original positions and locked down in a way to prevent future accidents or cable damage. They brainstormed and came up with several ideas to accomplish this goal. The idea selected was to use Unistrut and threaded rod to build a spreader that could be left in place but easily removed if necessary.

Trench box Fig

First step was to dig alongside the trenches to allow the sides of the boxes to be spread apart. Holes then were drilled in the sides of each box so the threaded rod could pass through, preventing the support from falling to the bottom of the trench. A 4-in. piece of Unistrut was installed on the threaded rod along with jam nuts to prevent loosening of the support (Fig 2). Two spreader bars were installed in each box. If for some reason the cover did slide over, it would rest on the support and not fall in. The project was designed and completed by plant technicians for $1,536.

Benefits of the modification include: (1) straighter, more-even walking surfaces to reduce trip hazards, (2) lids are unable to fall inside the boxes, thereby preventing personnel injury and or cable damage, and (3) ease of support removal, if necessary.

Minimizing errors during LOTO evolutions improves safety

When the dust settles after commissioning, plant employees often find the drawings provided by contractors are difficult to read, short on information, and/or lacking in clarity. Fremont Energy Center personnel, for example, found they were left an accurate, but cumbersome, set of one-line diagrams for the in-plant electric distribution system.

Staff experienced challenges matching individual pieces of equipment with the specific electrical sources feeding them. This had the potential for causing mistakes while performing lock-out/tag-out (LOTO) evolutions. Plant management decided the clarity of electrical drawings had to be improved and that better labeling was required for the motor control center (MCC) and low-voltage panelboard line-ups.

Staff, assisted by a summer intern, created a set of MCC and panelboard drawings that more clearly identified what auxiliary loads were fed from which line-ups, specified in which cubicle each load’s breaker or starter was located, and presented this information in an easy-to-read format.

The project expanded from just creating new drawings to adding color-coded labeling to the MCC and panelboard line-ups and listing which upstream circuit breakers each line-up was fed from. Finally, a searchable, master spreadsheet was developed; it listed all of the site’s electrical loads in an easy-to-navigate format.

Benefits provided by the new drawings and upgraded equipment labeling included the following:

      • The LOTO process was streamlined. Operators use the new drawings to more quickly populate LOTO permits and to create standardized LOTO forms.

      • The new labeling on the MCCs and panelboards, along with drawings posted on the doors, has reduced the time taken to find electrical feeds when hanging locks for LOTO operations.

      • Color coding of the different MCCs has helped reduce potential errors when identifying loads on redundant MCCs—for example, HRSG 1 versus HRSG 2, GT1 versus GT2.

      • The speed and accuracy of preparation and execution activities for LOTOs have been improved.

Dedicated emergency phone line enhances safety

When numerous contractors were onsite, the plant had no sure way for individuals to notify the control room in the event of an emergency. The facility had a limited number of two-way radios and would routinely issue them to the supervisor of the individual contracting groups. This would require a worker to find his supervisor to contact the control room and report an emergency. In the event of a serious emergency, site management believed the time to complete this effort was excessive and had to be reduced.

Klamath Cogeneration’s safety committee reviewed several options—including purchasing more two-way radios and installing emergency phone booths. The radios proved too expensive and accountability too difficult as the facility may have as many as 150 contract personnel onsite during a large outage. The remote phone booths were an acceptable option but they also were too expensive.

In today’s world, almost everyone carries a cell phone. The committee decided Klamath would install a special communications line and connect it to a dedicated phone in the control room. This phone was located on the opposite side of the control desk, away from the other phones—its ring an obvious indicator of a problem. Operators are trained to drop whatever they are doing and respond to an incoming call on this line.

Contractor indoctrination training now includes instruction on how this program works. At the completion of the training, each worker receives a hardhat sticker and business card with the emergency number. They are also encouraged to program the number directly into their phone at this time. Additionally, signs with the number have been posted throughout the plant for easy access.

This was a simple remedy for a lingering problem. Using this dedicated line, a worker can call in an emergency from the top of the cooling tower or inside the HRSG without the need to find his supervisor. Although Klamath has not experienced a major emergency, the program has received a warm welcome from contractors. The additional expense of another phone line is minuscule compared to the reduced response time in the event of a real emergency.

GT exhaust-door redesign

Gas-turbine exhaust-stack access originally was provided via a bolt-on hatch which poses a significant personnel safety risk during removal and installation because of its excessive weight and awkward lifting position (photo left). Access to the exhaust stack is necessary to perform routine and emergent maintenance activities.

Plant personnel brainstormed ideas and decided on a redesign and replacement of the existing bolt-on exhaust stack access hatch with a pivoting stainless-steel door that does not require removal or lifting by personnel (photo right).

GT access door Fig

Results have included dramatic reduction in personnel injury risk during door removal. An additional benefit obtained was a reduction in door removal man-hours from four to only 15 minutes for one unit. The project leveraged across the fleet has realized 100 man-hours saved annually.

Rail and lanyard solution protects against enclosure fall hazards (link)

Comprehensive gas-line preventive maintenance program (link) 

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