Eliminating secondary containment entry protects personnel
Klamath Cogeneration Plant
500-MW, gas-fired, 2 × 1 combined cycle cogeneration facility located in Klamath Falls, Ore
Plant manager: Ray Martens
Key project participants: Greg Dolezal, maintenance manager Bruce Willard, operations and engineering manager
Plants are often constructed with equipment requiring monitoring and/or service located inside secondary containments. In addition to the hazards posed by chemicals, oil, fuel, etc, within these containments, environmental conditions can fill them with water oreven ice.
It has been our long-term goal to eliminate the need for personnel to enter these areas for scheduled duties. The first containment addressed was the anhydrous ammonia tank. The initial construction had personnel climbing over the containment wall and then climbing a ladder to get to the top of the tank. Any emergency egress would have been nearly impossible.
Plant staff took the stance that all areas within the reach of an ammonia release needed two means of evacuation. Therefore, we added a stairway on the side of the tank that lands outside of the containment (Fig31). The second area of attention was the transformers, which have a nitrogen blanket that requires pressure verification twice a day. On our main transformers, this check can be done from outside of the containment and the surrounding fencing. The auxiliary transformers, used for station service, had the nitrogen bottles inside the containment and out of the operator’s view. At Klamath, transformers are notorious for ice buildup. Deck grating and anchor points were attached to the transformer blast wall. The new location required new tubing runs but allowed us the space to have a spare bottle readily available. We also changed the bottle material from steel to aluminum for ease of handling (Fig 32). Lastly, since wastewater discharge is sent to the city’s treatment facility, the plant is required to neutralize demineralizer regeneration water beforehand. The original design had the pH probe inside the containment near the recirculation pumps. To calibrate this probe, the operator was required to enter the containment area, which at our site, is shared with our sulfuric acid storage tank. Our solution was to change where the pH was sampled, add redundancy to the probe, and design it so the operator does not have to remove the probes for calibration.
As seen in Fig 33, the water enters the building from outside (the containment area), flows upward across redundant probes and is discharged back into the chemical waste sump. The probes were installed in the vertical leg to minimize debris, such as resin beads, from accumulating in the pipe and to ensure the probes stay wet to maintain longevity.
The probes can also be bypassed while doing online calibrations. A funnel at the top of the vertical leg allows for the addition of calibration fluids without the need to remove the probes. It also allows for the calibration of both probes simultaneously. We also installed a low point drain. Not only can we get a grab sample from this drain but it also allows for the removal of any accumulated resin beads (Fig 34).
The task of eliminating all entry to secondary containments is a work in progress. Below are just three outcomes of how we are trying to remove the need for our staff to enter our secondary containments while performing routine tasks.
1. Ammonia tank stairwell:
- Provides for an easier route for O&M personnel to access the top of the tank.
- Provides a second point of egress.
2. Transformer nitrogen relocation:
- Keeps the operator out of the containment during reading and bottle exchanges.
- Allows for a readily available spare bottle.n New aluminum bottles are easier to manage.
3. Neutralization pH probes:
- Allow for redundant probes for accuracy and simultaneous calibration.
- Minimize the opportunity for contact of hazardous solutions.
- Move probes away from atmospheric elements.
- Keep operators out of the sulfuric acid containment.