Bypass valve or stop valve replacements can be overwhelming, especially when considering specialized evaluations and valve expenses. Combined with exotic materials, flush kits, warming lines and controls, these valves can be downright intimidating. However, if your bypass valves are more than a decade old or frequently on the maintenance schedule, it may be time to evaluate your options.

Bypass valves, or stop valves, are the valves that bypass steam from the heat recovery steam generators or boilers into the condenser during unit startup or steam turbine trip event. Until the pressure and temperature reach minimum recommended values provided by the steam turbine manufacturer, these valves help to protect that asset and keep water from damaging your equipment — and keep you generating.

The replacement process begins with a single-source effort to order the valves and the necessary components; however, there is much more to the demolition and installation of this type of valve than a simple swap out. Without an evaluation of the pipe routing to determine valve geometry, inlet and outlet pipe wall thickness, attemperator location, hanger and support design, and overall pipe stress, the new valves may be doomed to fail even before they are installed.

Luckily, utilities can rely on advances in valve technology, operational methods, warming line design and actuator control and feedback to equip facilities with a more flexible valve, less likely to thermally bind and fail.

For example, consider a utility expediting the procurement and installation of five new bypass valves on a combined-cycle unit. Due to existing valve failures and forced outages resulting from valve component failure or binding of the stem and body, the utility elects to replace two high pressure, two intermediate pressure and one low valve in an upcoming outage — 36 weeks from the order placement — to establish a favorable position during its peak operating season the following spring and summer.

During this process, the existing piping and support structure also must be evaluated prior to delivery, preventing unexpected pipe stress and failure. These overlapping aspects of engineering, lead product procurement and installation services would benefit from a complete turnkey package with a single-source contact for small project execution. This integrated project delivery approach, offering a seamless transition from procurement to engineering to construction, could minimize scope gaps, material delivery and communication miscues that might otherwise lead to slips in scope, schedule and costs.

 

Learn more about how an integrated engineer-procure-construct project delivery approach is also shaking up the norms of construction across industries.

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Bryan Durant is a mechanical engineer at Burns & McDonnell with more than 15 years of experience designing power plants. As the mechanical section manager for Burns & McDonnell’s Energy Group, he’s responsible for the staffing and development of technical resources, project leads and engineering managers.