A gate valve is a shut-off valve that is used to control or completely shut off the flow in piping systems. In industrial water and wastewater treatment, the gate valve is often used to regulate the volume flow of liquids such as water, chemicals or wastewater. It is characterized by a simple design and high reliability and is mainly used in applications where low pressure loss and complete shut-off are required.
Table of contents
Technical background
A gate valve works by vertically moving a slide or wedge that plunges into the flow medium and completely closes or opens the pipe cross-section. The gate valve moves perpendicular to the flow direction of the medium. When the gate valve is fully open, it lies outside the flow path, resulting in minimal pressure loss and allowing unimpeded flow. Gate valves are primarily designed for on/off operation (fully open or closed) and are less suitable for throttling the flow.
Gate valves are available in various designs, depending on the requirements of the system. Typical materials are cast iron, steel, stainless steel or plastics, depending on the medium to be transported and the operating conditions such as pressure, temperature and susceptibility to corrosion.
Structure and mode of operation
A gate valve consists of the following main components:
- Housing: The housing surrounds the gate valve and the mechanics and must be pressure and corrosion resistant. It is integrated directly into the piping system.
- Slide valve (wedge): The gate valve blocks the flow when it is moved to the closed position. There are different types of gate valves, such as parallel gate valves or wedge gate valves, depending on the required tightness and application.
- Spindle: The spindle is a screw spindle that moves the slider up and down. It can be operated manually via a handwheel or automatically via an electric, pneumatic or hydraulic drive.
- Seals: Seals are crucial to ensure a leak-free shut-off. They prevent the medium from flowing through the gate valve when it is closed.
Types of gate valves
Parallel gate valve: With this type of gate valve, a flat, parallel plate moves between two sealing surfaces in the body. This design is particularly suitable for media with low to medium pressures and ensures good tightness.
Wedge gate valve: The wedge gate valve has a wedge-shaped plate that is pressed into the sealing surfaces, resulting in a higher sealing force. Wedge gate valves are particularly advantageous at high pressures and in corrosive environments, as they provide a more robust seal.
Metal-seated gate valves: These gate valves use metal-to-metal seals and are used in applications where high temperatures or abrasive media are present. They are particularly resistant, but are more susceptible to abrasion and require regular maintenance.
Soft-seated gate valves: These gate valves have seals made of rubber or other elastic materials that provide a reliable seal at lower temperatures and pressures. They are often used in water distribution networks and waste water systems.
Application of gate valves in water and wastewater treatment
Gate valves are one of the most frequently used fittings in industrial water and wastewater technology. They are particularly suitable for:
Water treatment systems: In water treatment, gate valves are used to control water flows in filters, reverse osmosis systems (such as our ALMA OSMO reverse osmosis systems) and pumping stations. They serve as main shut-off valves that can quickly and safely interrupt the flow during maintenance work or emergencies.
Wastewater treatment plants: Gate valves are used in wastewater treatment plants to control sludge flows and wastewater flows. In the various stages of mechanical, biological and chemical treatment, they ensure that the flows of raw and treated wastewater can be regulated as required.
Industrial cooling water systems: Gate valves are used in cooling circuits to route or shut off large quantities of cooling water through the systems. As high flow rates are often required here, the ability of the gate valve to keep the pressure loss low is of particular importance.
Chemical industry: In the chemical industry, where aggressive and corrosive liquids are transported through pipelines, chemical-resistant gate valves made of materials such as stainless steel or plastic are used. These ensure that the medium is safely shut off and no leaks occur.
Advantages of the gate valve
- Low pressure loss: As the gate valve is completely removed from the flow path when fully open, there is minimal pressure loss, making the gate valve particularly suitable for high-flow applications.
- Robust sealing: Gate valves offer reliable shut-off, even at high pressures and under demanding operating conditions. Wedge gate valves in particular can build up a very high sealing force at high pressures.
- Easy maintenance: Gate valves have a relatively simple design, which simplifies their maintenance. They are durable and only require occasional checks and maintenance of the seals.
Challenges
- Slow closing process: The mechanical process of closing a gate valve can be relatively slow, especially with large pipelines, which can be a disadvantage in emergency situations.
- Not suitable for throttling: Gate valves are not suitable for use as throttle valves, as the partial opening can lead to turbulence and erosion, which damages the gate valve and impairs the sealing ability.
- Abrasive media: With highly abrasive media, the valve can wear out quickly, which can lead to more frequent maintenance intervals.
Conclusion
The gate valve is a versatile and robust shut-off valve used in many industrial applications, especially in water and wastewater treatment. Thanks to its low pressure loss and reliable shut-off performance, it is ideal for use in pipelines where complete opening and closing is required. The selection of the right gate valve, whether as a wedge gate valve or parallel gate valve, depends on the operating conditions and the specific requirements of the medium.
