At first glance, deciding between a gate valve and a butterfly valve for an application is not simple. To avoid costly setbacks in an operation, it is critical to understand the differences between these two valve types. This article outlines the fundamental similarities and differences between a gate valve and a butterfly valve, which can be seen in Figure 1, and looks at their application suitability, advantages, and disadvantages.
Gate and butterfly valves are used to turn on and off the flow, but butterfly valves can also regulate flow via partial disc closure. Butterfly valves belong to the quarter-turn valve family and may be closed considerably faster than gate valves, which are multi-turn valves. For high-pressure systems, gate valves are preferred, but butterfly valves are preferred for bigger port sizes.
How does a Gate Valve work?
A gate valve gets its name from its disc, which acts like a gate by halting or permitting media flow. Its operation is easy in comparison to other control valves, making it one of the most often used valves. Because a gate valve is a full-port valve, with ports the same size as the inner diameter of the connected pipes, there is very little resistance to liquid or gas media flowing directly through it. Therefore, the pressure drop through the valve is relatively low. Read our article on gate valves for a more in-depth explanation.
Operating a Gate Valve
Gate valves are multi-turn valves, meaning the handwheel must turn more than 360° to open or close the valve fully. Turning the handwheel in one direction or another moves the gate up or down via the stem. When the gate is fully raised, the pathway is clear and media can flow. When the gate is closed, the media cannot flow. Because of the nonlinear relationship between gate travel and flow rate, gate valves cannot control or throttle flow. If the gate is partially open, the flow will collide with it while passing through the valve, forcing the flow to move at a faster rate and creating turbulence, resulting in greater wear on the disc and seats.
The three most frequent ways to operate a gate valve are manually, pneumatically, and electrically. To open or close the valve manually, an on-site user must rotate the handwheel. Because gate valves are rarely opened or closed, this method is the most cost-effective. Remote actuation of a gate valve is possible with pneumatic and electric techniques. Pneumatic actuation necessitates the presence of a pneumatic system on-site, whereas electrical actuation necessitates the presence of electrical power on-site.
How does a Butterfly Valve work?
A butterfly valve’s basic action is accomplished by turning its handle 90° or employing a pneumatic or electronic actuator. This rotates the disc by turning the valve’s stem. When fully closed, the disc is perpendicular to the flow; when fully open, the disc is parallel to the flow. The disc can be partially opened or closed to achieve proportionate or throttled flow rates. A butterfly valve can be gear-operated via a gearbox in the case of a giant butterfly valve or a valve used in a liquid application where quick closure could cause a water hammer. The gearbox’s handwheel must be turned more than 90°, which eliminates the butterfly valve’s relatively fast closing speed.
Operating a Butterfly Valve
Operating a butterfly valve is a straightforward process. First, locate the valve within the piping system. Then, check for any visible damage or obstructions. If it’s a manual valve, find the handle attached to the valve stem, and turn it counterclockwise to open the valve or clockwise to close it. Typically, a 90-degree rotation is sufficient to move the valve from fully closed to open or vice versa. If the valve is automated with an actuator, follow the specific procedure for your actuator type, which often involves using a control panel or remote system to open or close the valve. Always exercise caution and follow safety guidelines when operating butterfly valves, especially in industrial settings, to ensure proper fluid or gas flow control.
Gate valves vs. Butterfly valves
§ Cost: Generally, a butterfly valve is less expensive than a gate valve, especially at bigger port diameters.
§ Installation space: Butterfly valves require less installation area than gate valves.
§ Weight: A butterfly valve is lighter than a gate valve, which may require support structures at higher port dimensions.
§ Maintenance: While a butterfly valve is relatively easy to maintain, repair, or install due to its small size and low weight, its center disc makes it unsuitable for systems that use pigging and swabbing for cleaning. A gate valve, on the other hand, is excellent for such maintenance.
§ Operation: A butterfly valve can close faster than a gate valve with a similar port diameter. However, this fact means butterfly valves are more susceptible to water hammer.
§ Flow regulation: A butterfly valve has the ability to modulate or throttle flow, whereas a gate valve can simply be turned on and off.
§ Flow resistance: Compared with butterfly valves, gate valves have less flow resistance and therefore less pressure drop..
§ Pressure: Gate valves are more pressure-resistant than butterfly valves.
When to use Gate Valve?
§ Full Open or Full Closed Situations: Gate valves are ideal for applications where the valve must be fully open or closed without intermediate positions. They provide minimal resistance to flow when fully open and a tight seal when fully closed.
§ Isolation and Shutoff: Gate valves excel at isolating sections of a pipeline or system. They are often used for on/off control where the fluid flow needs to be completely shut off for maintenance, repairs, or emergencies.
§ High-Pressure Systems: Gate valves are suitable for high-pressure systems, as they can withstand substantial pressure without significant loss of efficiency.
§ Low-Flow Resistance: In applications where minimal flow resistance is essential, gate valves are preferred because they offer a straight-through path when fully open.
§ Non-Throttling Services: Gate valves are not designed for flow control or throttling applications, so they are best suited for services where flow adjustments are not required.
§ Clean and Non-Abrasive Fluids: Gate valves work well with clean fluids that do not contain abrasive particles that can damage the sealing surfaces.
§ Steam Systems: Gate valves are commonly used in steam systems to control the flow of high-temperature steam.
§ Fire Protection Systems: They are frequently employed in fire protection systems, where quick and reliable shutoff is crucial in case of a fire event.
When to use Butterfly Valve?
§ Flow Regulation: Butterfly valves are suitable for applications requiring moderate flow control, where throttling is necessary but could be more precise. They can be used to modulate the flow rate when needed.
§ Cost-Efficiency: Butterfly valves are often more cost-effective than other valve types, making them a preferred choice when budget constraints concern them.
§ Quick On/Off Control: Butterfly valves offer rapid open-close capabilities, making them useful for quick shutoff or flow diversion.
§ Space Constraints: Butterfly valves are compact and require less space than other valve types. This makes them valuable in installations with limited space.
§ Low-Pressure Applications: They are suitable for low to moderate-pressure systems, such as those found in HVAC systems and water treatment plants.
§ High-Flow Applications: Butterfly valves are effective for handling high-flow applications, as they have minimal flow resistance when fully open.
§ Bi-Directional Flow: Butterfly valves are often bi-directional, which can be installed to allow flow in either direction, making them versatile for various pipeline configurations.
§ Corrosive Environments: In some cases, butterfly valves made from corrosion-resistant materials can be used in applications with corrosive fluids.
§ Bulk Handling: They are commonly used in food processing, pharmaceuticals, and chemicals for handling dry bulk materials like grains and powders.
§ Low Maintenance: Butterfly valves are relatively easy to maintain due to their simple design, making them suitable for applications requiring frequent maintenance.
The choice between a gate valve and a butterfly valve depends on your specific needs. Gate valves excel at providing a tight shutoff in high-pressure, on/off applications, especially for clean fluids with minimal flow resistance when fully open. In contrast, butterfly valves offer more versatility, being effective in moderate flow control, quick open/close scenarios, and cost-effective installations. The decision should be based on factors like your system’s pressure, flow control requirements, budget, and whether precise throttling control is necessary. Consulting with a valve specialist or engineer is often the best approach to determine which valve is better suited for your particular application.