Steam is used to generate electricity and for processing food, chemicals, and other products. Additionally, it can be used to clean, heat, and humidify. Therefore, steam control valves are essential in most applications that require control. Usually, steam control valves are installed to reduce the inlet steam pressure. Steam valves can also control the temperature in addition to pressure.
Steam is used frequently at lower pressures in industrial processes. The temperature is controlled through steam pressure since steam at low pressure has higher latent heat. Steam pressure and temperature are related. The lower steam pressure will also improve plant safety. Using steam for process heating provides multiple benefits such as high efficiency, reliability, and simplicity of the system, making steam a popular choice for modern process designers. A state-of-the-art automated valve helps maximize delivery and process efficiencies by regulating steam pressure and flow.
STEAM VALVES
The most popular industrial steam valves are shown below.
ANGLE VALVES
Angle seat valves are pneumatically operated piston valves that provide linear actuation to lift the seal from its seat. The flow is slightly hampered in the open position because the seat is placed under a corner. This would result in excellent flow and low-pressure drop. The industrial angle valves regulate the flow of gases, vacuum, steam, and even aggressive fluids. They can also operate with high viscosity fluids and high temperatures, even at zero differential pressures. The rugged design of angle seat valves makes them a popular choice for heavy-duty applications, and their service life is very long. Therefore, they are excellent and durable. These valves can also be an alternative to solenoid valves, especially with viscous and contaminated fluids where typical solenoid valves fail. Angle valves can be operated using a single or double-acting configuration, affecting their pressure rating.
ADVANTAGES
- A high flow rate is obtained with low-pressure drops.
- Water hammer elimination and backflow resistance
- Provides longer service life than ball valves
DISADVANTAGES
- Since it retains the single seat valve structure, the larger the channel, the smaller the allowable differential pressure.
APPLICATIONS
The angle valves can deliver millions of operation cycles in demanding applications such as steam, water, and aggressive media. Ideal for vacuum applications and can be used in fast-acting applications up to 1000 cycles per hour with an expected life of over 10 million. They are mainly used in chemicals, water, sewage, food and beverage, oil and gas, etc.
BALL VALVES
The flow of a liquid or gas is controlled by a ball valve that uses a drilled rotating ball. Fluid can flow out or be blocked by rotating the sphere 90 degrees around its axis. Even when the valve is not in use for a long time, they are characterized by a long service life and offer reliable sealing over the life span. And that’s why they are more popular as shutoff valves than gate valves. The ball valves, in exceptional cases, are used as control valves. However, this application is less common due to the relatively limited rate control accuracy.
ADVANTAGES
- Quick to open and close
- Lighter and smaller than a gate valve
- Provides bubble-tight service.
- Different ball valve designs provide flexibility in the selection and can be used for slurry and clean purposes.
- The multiport design provides versatility and reduces the number of valves needed. In addition, the force required to actuate the valve is smaller than that needed for the gate/globe valve.
- Reliable service in high-pressure and high-temperature applications is provided with high-quality ball valves.
DISADVANTAGES
- Not suitable for extended throttling applications
- Airborne particles can settle and become trapped in body cavities in slurries or other applications, causing valve leakage, wear, or failure.
APPLICATIONS
Some typical applications for ball valves are low point exhausts and high point vents in liquid, gas, and other fluid services. Cooling water and water supply systems, steam service, air, liquid, and gas applications requiring bubble-tight service, and instrument root valves.
BUTTERFLY VALVES
The operating mechanism of butterfly valves is very similar to that of ball valves. However, the butterfly is nothing but a disk connected to a rod. The valve closes when the stem rotates the disc a quarter turn to a perpendicular position in the direction of flow, and when the valve opens, the disc is rotated back to allow flow. Thanks to their lightweight, low cost, small installation footprint, high availability, and fast operation, butterfly valves are used for on-off or modulating services. We can operate these valves with a handle, gear or automatic actuator.
APPLICATION
Among diverse industries and applications, the butterfly valves are widespread in food, pharmaceutical, chemicals, and petroleum products, sewage treatment, water supply, gas supply, fuel management, and fire protection. These valves are available in large sizes and are suitable for handling liquids and slurries containing relatively large amounts of solids at low pressure.
ADVANTAGES
- Butterfly valves are small and, when actuated,
- Open and close very quickly.
- Compared to the ball valve, the disc is lighter, and the valve requires smaller structural support of comparable diameter.
- As the butterfly valves are very accurate, they are advantageous in industrial applications.
- They require very little maintenance and are pretty reliable.
DISADVANTAGES
Part of the disc is exposed to the flow even when fully open.
Regardless of the setting, the throttle always drives a pressure switch through the valve.
The thicker liquids may stop the movement of the disc.
GLOBE VALVES
Globe valves are linear motion shutoff valves in which the shutoff element is moved vertically in and out of the seat. Often, the closing member is referred to as a disc, regardless of its shape.. Seat opening varies in direct proportion to disc travel. This proportional relationship between valve opening and disc travel is ideally suited for duties involving the regulation of flow rate. Globe valves are best suited for regulating and controlling fluid flow and are typically used in small pipelines.
APPLICATIONS
Globe valves are widely used for different purposes. Some practical applications are in high point vents, low point drains where leak tightness and flow control are of utmost concern, and in the lube oil reservoir, feedwater, or chemical containers where pressure drop is not an issue. Globe valve is also used in power and process plants, wastewater, and steam lines. And buildings require upstream fluid flow such as water heaters and other equipment.
ADVANTAGES
- Precise throttling and control.
- High-pressure limits.
- It can be fast acting.
DISADVANTAGES
- High head loss.
- Large opening for disc assembly.
- Heavier than other valves.
- Cantilevered mounting of the disc to the stem.
- Low coefficient of flow.
- Not suitable for clean or sterile applications.
GATE VALVE
Gate valves are linear motion valves in which a flat closure element slides into the flow stream to provide shutoff. Gate valves are generally divided into two types: parallel and wedge. Similar gate valves use a flat disc gate between two parallel seats (upstream and downstream). The main advantage of a gate valve is the straight passage without obstacles, which induces a minimum pressure drop on the valve. The free bore of a gate valve also allows for a pig’s passage in cleaning pipe procedures. However, gate valves are slower than quarter-turn valves and should only be used in the fully open or closed position, not to regulate flow.
APPLICATION
Gate valves are used in many industrial applications, including oil and gas, pharmaceuticals, manufacturing, automotive, and marine. Non-rising stem gate valves are very popular on ships, underground applications, or where vertical space is limited because they don’t take up extra space. Gate valves can be used in harsh environments such as high-temperature and high-pressure environments. They are often found in power plants, water treatment, mining and offshore applications.
ADVANTAGES
- Small flow resistance.
- The opening and closing torque are low.
- You can use it in the medium to flow in two directions of the ring network pipeline.
- There is no restriction on the direction of flow of the medium.
- When fully open, the working medium’s sealing surface is less eroded.
- The body structure is simple. As a result, the manufacturing process is better.
- The structural length is relatively short.
DISADVANTAGES
- Pressure limitations.
- Lack of cleanliness.
- Low shutoff.
- The overall size and opening height are more significant, and the space for installation is also larger.
- During opening and closing, the friction and abrasion of the sealing surface are more significant.
- It has two sealing surfaces, which increase processing, grinding, and maintenance difficulties.
- It takes a longer time to open and close.
DIAPHRAGM VALVES
Diaphragm valves use a ‘pinch’ method that utilises a flexible diaphragm to stop the flow of the valve. One of the significant advantages of using diaphragm valves is that the valve components can be isolated from the process fluid, making them ideal for sanitary applications. However, diaphragm valves are limited to a maximum temperature of 450° F.
APPLICATION
- Wastewater and water
- Paper and pulp
- Power
- Cement
- Chemical
- Minerals and mining
- Bioprocessing and Pharmaceutical
ADVANTAGES
- Leak-proof seal.
- Ease of maintenance.
- Repair in this type of valve is made without interruption in the pipeline.
- Tight shutoff.
- It reduces the leakage into the environment.
DISADVANTAGES
- You can use it for only moderate pressure of approximately 300 psi.
- You can use it for moderate temperatures of around -60 to 450 F.
- You cannot use them for multi-turn operations.
- Their body should be corrosion-resistant material.
