In most cases, valves regulate the flow of liquids or gases in a system. However, steam valve design is more complex because steam valves regulate both the temperature and pressure of the liquid or gas.
The pressure of steam, liquid, or gas affects its temperature. Therefore, maintaining the required pressure for water, compounds, or steam is crucial. Steam valves are essential in maintaining pressure because they help balance load disturbances caused by pressure fluctuations.
So, let’s take a look at several types of steam valves.
In steam systems, pressure and temperature control is crucial. Globe Valves precisely shut off steam flow, preventing it from flowing when it’s not needed, thus avoiding system overpressure and overtemperature, reducing the likelihood of safety incidents and protecting equipment and personnel. By precisely controlling the flow and direction of steam, Globe Valves ensure optimal steam utilization within the system and reduce steam waste.
In many steam-dependent industrial processes, such as food processing, pharmaceuticals, and chemicals, a stable steam supply is crucial for ensuring product quality. Globe Valves can accurately control the on/off and flow of steam according to production process requirements, ensuring stability and consistency in the production process, thereby guaranteeing product quality.
Gate valves can only be fully opened or closed and cannot regulate flow. Therefore, they primarily serve as “isolating valves” in steam pipelines, used for maintenance, sectionalizing, or emergency shutoff. When fully open, the passage is nearly straight, minimizing fluid resistance, reducing steam pressure drop, and improving system efficiency. The medium can flow in any direction, making it suitable for complex piping arrangements.
Steam systems often operate at temperatures between -29°C and 570°C and pressures between 1.6 and 16.0 MPa. Gate valves utilize WCB/stainless steel/chrome-molybdenum steel bodies and metal seals for long-term, stable operation. The sealing surfaces are welded with Stellite or stainless steel, and the self-tightening structure meets the zero-tolerance steam leakage safety requirements of power plants, petrochemicals, and other industries. Compared to globe valves, gate valves experience less erosion on the sealing surface when fully open, extending maintenance cycles and reducing downtime costs.
With their three key characteristics of reliable isolation, low flow resistance, and resistance to harsh operating conditions, gate valves are the cornerstone of safe and efficient steam system operation.
A check valve only allows steam to flow in a fixed direction. When steam flows in the opposite direction, the valve disc automatically closes, preventing backflow. For example, installing a check valve in a steam pipeline can prevent backflow during shutdowns or pressure fluctuations, ensuring the normal operation of the steam system.
In steam systems, water hammer can cause serious damage to pipes and equipment. Water hammer occurs when steam suddenly stops or reverses flow. A check valve closes promptly, preventing the reverse flow of steam and water, reducing the risk of water hammer and protecting pipes and equipment from impact.
In steam systems, pumps and drive motors can reverse and be damaged by reverse flow of steam or water. A check valve prevents backflow, protecting the pump and drive motor, and extending their service life.
There are many other valves used in the steam industry, such as industrial ball valves and butterfly valves. We won’t go into detail here. With so many valves to choose from, how can we choose the best valve? Let’s take a look.
Operating Parameters
First, confirm the steam temperature, pressure, flow rate, and corrosiveness. The nominal valve pressure must be ≥ the system design pressure. Materials should be selected based on the temperature-pressure curve, including carbon steel (WCB), stainless steel, or alloy steel; avoid ordinary cast iron.
Functional Requirements
- Isolation/Isolation: Choose a bellows-sealed globe valve or gate valve for reliable sealing and zero leakage.
- Regulation: Use a V-shaped ball valve or specialized regulating valve with equal percentage flow characteristics and erosion resistance.
- Steam Drainage: Choose a float-type or thermodynamic steam trap, calculated based on the condensate volume and pressure differential.
- Backflow Prevention: Choose a lift-type or swing-type check valve.
Structure and Sealing
- Stem Seal: A bellows + graphite packing combination, high-temperature resistant, fireproof, and maintenance-free.
- Seat Sealing Surface: Stainless steel + carbide (Stellite) for erosion resistance and long service life.
- Connection: Flange or butt-weld, ensuring compliance with pipeline standards. Brands and Services
Prioritize brands with a proven track record in nuclear power, petrochemical, or power plant operations, such as Neway, CNNC Su Valve, Shentong, and Qizhong. These brands possess international certifications such as ASME, ISO, and API, and offer 48-hour global emergency response or 72-hour spare parts delivery.
Installation and Maintenance
- Ensure the direction of the valve body arrow aligns with the flow direction of the medium, allowing ample clearance for valve stem operation.
- Choose valves with self-relieving upper seals to allow for packing replacement while the system is under pressure.
- Brands with short lead times, ample spare parts inventory, and on-site commissioning and training offer peace of mind.
Valve selection is a complex issue. If you’re considering purchasing a valve, please contact us. Newton will meet your expectations.
