BEST PRACTICES: MEAG WANSLEY UNIT 9

Simple solution to prevent air accumulation in LO pump discharge line

Best Practices - MEAG Wansley

Challenge. MEAG Wansley had to implement GE Technical Information Letters 1919 (Gas turbine lube- and seal-oil pump discharge check-valve modification) and 1903-R1 (Steam turbine lube-oil system emergency standby pump outlet check-valve modification) without pulling the pumps or drilling holes in the check valves as suggested by the OEM to remove air that could accumulate in the pump casings and discharge lines and impede operation—while still meeting the design intent of the recommended mods.

Access to the lube-oil pumps is limited at Wansley by an air-cooled heat exchanger located directly behind the accessory module. Removing the pumps to perform this mod would require a crane to lift them over the heat-exchanger module. The cost of implementing this TIL by removing the pumps and drilling holes in the check valves was estimated at about 100 man-hours plus $2500 crane rental.

Solution. Plant personnel opted to use the existing tap on the pump just upstream of the check valve to remove any air trapped inside pump discharge line (Fig 1 left). This tap was installed as a sensing line for pressure instruments.

MEAG BP Fig 1

Without removing the pump, plant personnel accessed the existing tap and sensing line through the explosion relief door on the side of the lube-oil reservoir. They then installed a tee in this line and connected the open port of the tee to an excess-flow valve that discharges below the lube-oil level but above the level of the pump casing (Fig 1 right).

Note that an excess-flow valve is basically a self-resetting circuit breaker for a fluid line. It will allow a certain amount of flow, but once that amount is reached, the valve closes. After the system shuts down and the pressure equalizes, the valve reopens.

The excess-flow valve allows air to escape from the pump while not running—thereby preventing the pump from becoming air-bound—but closes when the pump starts, restoring the normal function of the sensing line.

Results. Staff was able to install the modification through the explosion-relief door on the side of the accessory module/lube-oil skid. The pump was started and stopped several times to verify proper operation of the sensing-line instruments and excess-flow valve.

Personnel are confident the pump will not become air-bound while on standby.

Using this approach, the entire job from start to finish took approximately four man-hours and cost less than $300 in parts—a saving of 96 man-hours and $2200 over the alternative solution using the crane.

Project participants: Matt Engelbert and James Jensen

Larger mixed-bed bottles reduce ergonomic risks

Challenge. MEAG Wansley’s water treatment system, as designed, incorporated sixteen 3.6-ft³ mixed-bed bottles, which typically required offsite regeneration every two months. The 50-in.-high × 14-in.-diam cylinders, located inside a stationary truck trailer, were difficult to handle safely. Employees were exposed to multiple ergonomic risks—including strains, slips, trips, and pinch points.

The physical arrangement (Fig 2) required plant personnel to disconnect the 270-lb bottles and move them manually 10 to 15 ft for forklift access. From this point, operators would boom the forklift over piping to lift the bottles to ground level. The procedure was reversed to install regenerated bottles—essentially doubling the work time and hazards.

MEAG BP Figs 2, 3

Solution. Staff research suggested a switch to 34-ft³ mixed-bed tanks. Two such tanks provide the same capacity as the 16 original mixed-bed bottles. Plus, installation of the larger tanks in an adjacent building removed the hazards associated with lifting the bottles from the trailer (Fig 3). Inexpensive PVC piping connects the two locations; an array of valves and quick-connect hoses facilitate installing the tanks for service.

Results. The new mixed-bed tanks are accessed by way of a roll-up garage door. This allows forklift access for replacement, thereby removing ergonomic risks associated with the manual handling of mixed-bed bottles.

A large saving in man-hours was also realized; the new mixed bed tanks can be exchanged by one employee in 30 minutes. Previously, two employees required six hours to exchange the 16 bottles. Technicians appreciate the reduced exposure to ergonomic and safety hazards. System capacity and regeneration cost remained the same.

Project participants: Dana French, Ryan Haas, Dennis Flecker, and Matt Engelbert 

Measuring emergency eye wash and shower pressure

ChallMEAG BP Fig 4enge. All industrial facilities are required to conduct weekly inspections of eye wash and shower stations in accordance with OSHA 29 CFR 1910.15 and ANSI Z358.1. Does your equipment meet the standards established by these regulations? Is the flow at least 20 gpm at 30-90 psig? Can this pressure/flow be sustained for 15 minutes with both the eye wash and shower operating simultaneously?

Like many multi-tenant facilities, MEAG shares with others a common utility service, potable water supply, etc. During a recent inspection, a local operator noted that the pressure “appeared” to be low after approximately one minute of run time. Testing confirmed that suspicion. On a side note, the site routinely loses potable water when repairs are underway or a power failure occurs.

Solution. A simple but reliable method was devised to test the flow rate. Four 55-gal drums were secured to a pallet for ease of movement, and a lightweight aluminum sheet was used to direct the flow of water into the drums. Using a stopwatch and tape measure, depth in the barrel was measured at the end of each minute over the duration of the 15-min test.

Dimensions of the container and simple calculations provided total gallons-per-inch and flow rate. Tests were conducted at multiple stations around the site, and the results were surprising. Flow was less than 9 gpm (half the requirement), and water pressure at the inlet point dropped from 113 to 19 psig when the shower/eye wash station was activated.

Results. When appropriate notifications were made to the host facility’s engineering department, a follow-up investigation revealed a similar problem at another combined-cycle unit immediately adjacent to the MEAG site. Piping repairs restored full pressure and flow of potable water, but this alone does not guarantee availability of water during maintenance or power outages.

Because of this, the site’s chemical unloading procedure was also updated, instructing site personnel to verify proper flow and operation of the eye wash and shower before any work involving hazardous or caustic chemicals commences.

Lessons learned indicate that when testing emergency equipment, subjective procedures should be reviewed and checked periodically—not only to assure compliance but to protect personnel.

Project participants:

Danny Fowler, EHS manager
Matt Engelbert, plant engineer
Ryan Haas, operator

Plant lighting upgrades

Challenge. Plant lighting usually is taken for granted, except by the individuals who have to service the fixtures. Some are located in hard-to-reach places that require a ladder or man-lift. Repair of high-pressure sodium (HPS) fixtures in difficult locations can expose technicians to multiple hazards—elevated work height, weight of the component, risk of electrical shock, among others.

The hinged cover for one of MEAG Wansley’s original HPS fixtures weighed 29 lb and had to be raised vertically to access internal components for repair. Since no support was provided for the raised cover, the technician had to remove it completely to perform repairs. Staff decided to investigate ways to minimize safety and ergonomic hazards and, at the same time, increase reliability and cost-effectiveness of plant lighting.

Solution. Research identified outdoor LED lighting as a promising solution. The LED fixture that best satisfied plant needs weighed less than 15 lb and featured a horizontally hinged cover requiring no support when open.

Not only would this eliminate lifting and holding a 29-lb hinged cover, but the LED fixture considered reportedly would outlast the HPS lights by more than 2:1—50,000 service hours versus 20,000—and consume 85% less power for equivalent output.

Results. Technicians appreciate the reduced exposure to ergonomic and safety hazards afforded by the new LED fixtures. In addition, their longer lifetime, lower power consumption, and less frequent maintenance requirement offset the cost of replacing the fixtures in the near term and reduce annual operating costs for the remainder of the plant’s service life.

Project participants: Tim Williams and Bert Wright

MEAG Wansley Unit 9

Owned by Municipal Electric Authority of Georgia

Operated by NAES Corp

503-MW, gas-fired, 2 × 1 combined cycle located in Franklin, Ga

Plant manager: Tim Williams