Specialized valve trims, designs, and materials are just a few metrics needed to ensure performance, safety, and reliability in harsh conditions.
By Bob Donnelly- Vice President of Business Development – Flo-Tite Valves & Controls
Severe service type valves operate in extreme pressures, high temperatures, and in environments where abrasive materials and harsh chemicals can break down standard valves. They have specific design characteristics, specialized trims, and are made of advanced materials. These attributes ensure they sustain the performance and reliability that is demanded under harsh conditions.
Industries requiring precise control under extreme conditions include power generation, chemical processing, pulp & paper, and oil & gas. Using the wrong valve configurations typically results in rapid corrosion, cavitation, noise, flashing, and erosion — all of which lead to reduced efficiency, safety risks, and costly downtime, compromising valve performance and reliability.
Abrasive substances and corrosive chemicals can easily erode valve surfaces, which occurs from particulates in the media scraping against the valve. It’s also caused by a variety of chemical reactions.
Cavitation results when rapid pressure drops in high-velocity flows and causes hazardous vapor bubbles that erode valve surfaces. This leads to pitting on metal surfaces, structural weakening, and eventual valve failure.
Turbulence within the valve generates noise at high velocities. When this noise exceeds unacceptable decibel levels, it can impact safety levels for plant workers. It also accelerates wear, which could cause premature failure. These valves control any noise that contributes to system processing efficiency and operational safety.
When there are fluid changes, usually from liquid to gas as it flows through a valve, “flashing” happens. Unlike cavitation, vapor bubbles do not collapse. However, they do carry abrasive particulates downstream and can erode seats, valve trims, and often piping. This can result in all kinds of damage.
Problem Solving Features of Severe Service Valves
Advanced materials like titanium, Monel, and Hastelloy provide resistance to erosion and corrosion. Additionally, the CVD-5B hardening process infuses boron into the metal surfaces of these valves. This creates a wear-resistant layer that can withstand temperatures up to 1200°F.
The ST-5 Venturi valve seats used in severe service valves redirect erosive elements away from critical components. This ensures longer and more productive process control operations.
By having custom-designed specialized trims, severe service valves can regulate flow and moderate noise, erosion, and cavitation. They also allow for precise control and contribute to longer lifecycles.
These features can minimize maintenance issues, as well as provide the controls necessary for managing extreme conditions that are common in severe service applications. Customizing severe service valves allows for:
- Reduced downtime
- Precise flow control
- Greater durability in processes during critical operations.
Materials, MSS Standards, and Actuators
When considering control valves for specific severe service applications, the materials must also achieve a tight shutoff, which is critical.
It’s pertinent that process control engineers understand the unique features of each application to specify the right materials and related components. Definitions set by the Manufacturers Standardization Society (MSS) have created benchmark standards for what qualifies as a severe service valve.
Severe service applications have to be carefully monitored to avoid costly failures. Experienced maintenance engineers and plant managers have rigorous inspection protocols and tiered maintenance strategies, which vary in scope and frequency.
These maintenance strategies can be enhanced and integrated with intelligent asset management systems. Advanced algorithms collect data on a variety of parameters that can be analyzed to assess conditions in severe service applications, preventing failures, safety incidents, and process shutdowns. As more applications become electrified, these intelligent asset management systems become more prevalent.
Actuator selection is another important consideration to ensure precise control for long term productivity.
Electric actuators in these applications are equipped with data loggers. New network protocols continuously monitor operations and provide critical data such as flow rate, pressure, temperature, and valve position. Intelligent electric actuators enhance efficiency, safety, and environmental performance.
In conclusion, the severe service segment of the valve industry is the most complex in terms of requirements, extreme operating conditions, and the costly implications associated with failures.