In an Emerson webinar, Optimizing Efficiency of Power Production with Valves, Actuators, and Regulators, Shaik Mohammad Ali and Balakrishnan B. examined how valve selection, design, and verified testing influence efficiency, reliability, and safety in power generation.

Ali focused on pressure relief valves across boiler and balance-of-plant service, while Bala addressed the blowdown valves engineered for high-pressure, high-temperature steam systems.

Why It Matters

In high-pressure, high-temperature service, small deviations in valve performance translate into measurable efficiency losses and safety risk. Code-compliant selection, proven design features, and factory-verified testing help operators avoid unplanned outages, extend maintenance intervals, and protect critical assets.

Key Takeaways

• ASME (American Society of Mechanical Engineers) Section 1 governs boiler island valves, while Section 8 covers balance-of-plant applications with less stringent requirements.
• ASME Code Case 2446 allows pilot-operated pressure relief valves across Section 1 boiler applications, including economizer, drum, superheater, and reheater service.
• The Crosby H series Isoflex seating design enables operation up to 94% of set pressure while limiting seat leakage near the set point.
• Yarway Blowdown Valves built to ASME B31.1 are slow-opening to prevent water hammer in 1500 to 2500 PSI service.
• Inline repairable construction with a solid Stellite plug and vacuum-brazed seat extends valve life in cavitating blowdown service.

Pressure Relief Across Boiler and Balance-of-Plant Service

Ali explained that a power plant has four major sections: the boiler island, turbine island, condenser, and boiler feed water system. Valves on the boiler island fall under ASME Section 1, while the remaining applications fall under ASME Section 8. Section 1 carries the most stringent code requirements: the valve must pop open within 3% of accumulation, blow down within 4%, hold set-pressure tolerances within plus or minus 1%, and pass a seat leakage test at approximately 93% of the set point.

To meet these requirements, every Emerson pressure relief valve is steam-tested in an in-house steam lab before shipment. It arrives with a functional test report documenting the set pressure, blowdown, and seat tightness. Ali noted that economizer service can present hot water, steam, or multiphase fluid at high pressure, so the relief valve must handle any of these conditions. On the Section 8 side, the pressure relief valve next to the boiler feed pump must withstand very high-pressure water that behaves like a jet. Emerson’s Crosby and Anderson Greenwood brands have served these applications for more than 150 years.

Isoflex Seating and Remote Monitoring

For higher-pressure service, Ali described the Crosby H series Isoflex seating technology, developed over 20 years through field experience, lab testing, CFD (computational fluid dynamics), and FEA (finite element analysis). The heel-and-toe geometry keeps the disc heel seated against the nozzle at lower inlet pressures. As pressure approaches the set point, the heel lifts while the toe remains in contact with the nozzle. This allows operation up to 94% of the set pressure without the typical seat leakage seen as a conventional valve approaches its crack point.

Because pressure relief valves are often installed 10 or 15 stories above grade, operators cannot easily observe whether a valve has lifted. Ali noted that the Crosby H series can be supplied with limit switches. Hence, DCSs, such as the DeltaV Distributed Control System, record when a valve opens, providing maintenance teams with the data needed for diagnostics and preventive action.

Blowdown Valves for High-Pressure Steam Service

Bala explained that boiler blowdown removes soluble and non-soluble particles and drains close to atmospheric pressure, creating a large pressure drop. Standard gate, ball, or globe patterns are unsuitable because dams and pockets trap debris, concentrate heat, and accelerate wear. Emerson’s Yarway Blowdown Valves follow ASME B31.1, which calls for slow opening and closing to prevent water hammer in 1500-2500 PSI service.

Bala also emphasized that continuous and intermittent blowdown require different valves. Continuous blowdown handles soluble particles and unavoidable cavitation, while intermittent blowdown handles non-soluble particles that can clog the valve. For intermittent service, the unit tandem design places two valves in a single body, eliminating thermal damage during long periods of closure and reducing welding and costs.

The valves are inline repairable. Crews remove the handwheel and stem assembly from the top to replace the plug or recut the seat, often in about 30 minutes, without cutting the valve out of the pipeline. The plug is solid Stellite rather than Stellite-welded, and the seat is solid Stellite vacuum-brazed to the body. Both choices resist the erosion caused by cavitating blowdown service.

Watch the Full Discussion

Hear Ali and Bala walk through the code requirements, design features, and field examples that shape valve selection for power plant service. Register for the on-demand webinar.