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Temperature control is a big deal in Pittsburg, Texas, where summer afternoons average in the mid-90s and frequently top 100. At AEP/ SWEPCO’s J. Robert Welsh Power Plant, however, the problem didn’t lie in the outside temperature, but in controlling the reheat temperature. The pneumatic actuators on the attemperator valves couldn’t smoothly control the valves at low levels, slamming back and forth between 10 percent open and fully closed.

The cascading bypass system is perhaps the most common design for managing high-pressure steam in a combined-cycle plant. It is the hot reheat (HRH) bypass valve actuator that defines the valve’s ability to respond to system demands.

Looking back with nostalgia on early driving days as a teenager and young adult in the 1970s and 1980s, the first cars were generally used cars and relatively inexpensive. As such, they required a lot of maintenance. It was not uncommon in those days to see drivers and their broken-down cars on the side of the road in need of rescue.

Driven by both economics and regulations, power plant operators are continually looking for new ways to improve the uptime and reliability of their units. It is a multi–front battle, and now more units are designed for combined-cycle or co-gen applications to recover heat that would be wasted otherwise.

Power plants are designed to operate for decades, provided they undergo regular repair, upgrade and improvement. Much of the time, those maintenance actions are minor. But plant managers expect a few big-ticket expenditures. Public Service Electric & Gas Co. (PSEG), for instance, spent $1.3 billion and more than 7 million hours of labor during the 2008 to 2010 period upgrading emissions controls at its Hudson and Mercer, N.J. coal-fired plants

Operating a boiler is a careful balancing act, matching the fuel, airflow and draft pressure throughout a wide range of load conditions. As plants are being called on to operate differently than in years past, the range of load conditions has increased even more. If response times are too slow, the system can trip, losing production and increasing emissions. The thermal stress lowers equipment life and leads to unplanned maintenance.

Oil and water don’t mix. Neither do oil leaks and EPA regulations. At Florida’s City of Cocoa Claude H. Dyal Water Treatment Facility, this posed a problem. The accumulator system used for the hydraulic actuators contained more than 100 gallons of hydraulic fluid which frequently leaked. “We had a common hydraulic tank that we utilized to actuate those four ball valves on our high service pumps,” said Jeff Childers, the Dyal plant’s Assistant Superintendent.

A modular approach to the assembly of valves and actuators for industrial uses enables Koso America to shorten lead times. Additionally, improvements in training and lean manufacturing methods have enabled the company to double its throughput in the same space. “We supply equipment to the process controls industries,” President and CEO Sam Lalos explains.

At the corporate level of operating a plant a standard business model is to reduce costs and increase revenue. Achieving these high-level business objectives starts with execution at the plant level. Typical areas for improvement include increasing yield and throughput while reducing downtime, energy usage and maintenance costs – all while keeping an eye on improving safety

Combined cycle plants give greater output for the same amount of energy and emissions. But this comes at a cost—increased complexity of design and operations. Optimizing a combined cycle plant requires tuning the gas turbine not just for its own efficiency but also to maximize the stability and efficiency of the heat recovery steam generator (HRSG). The best place to start is right at the beginning: controlling the inlet guide vanes (IGVs) for the combustion turbine in order to regulate the exhaust temperature leading into the HRSG boiler.