Electric Actuated Butterfly Valve

What is an electric actuated butterfly valve? 

This is a butterfly valve that is operated using an electric actuator. It is a quarter-turn valve that uses a rotary disc to start, throttle or stop fluid flow through a piping system. The rotational disc is mounted on the fluid passageway. This disc is controlled by the electric actuator via a shaft component attached to it. Electric actuated butterfly valve manufacturers produce various types of these valves which are rated in temperature levels, pressure, and fluid flow rates. These valves are capable of working in gases, liquids, and slurries. Electric actuated butterfly valve manufacturers design these valves for use in different media depending on the construction material used to make the valve. Some of these valves are meant for use in non-corrosive while others are used in very corrosive fluids. The valve has to be used according to the electric actuated butterfly valve manufacturer’s instructions to make it economical for use as well as use it for long period. 

Figure: Electric actuated butterfly valve.

Components of an electric actuated butterfly valve 

Valve body 

This is the part of an electric actuated butterfly valve used to cover the internal components. The body is also the component that contains the valve inlet and outlet ports. The body is made of strong materials like stainless steel, nickel alloy, and carbon steel. 

Electric actuator 

This is the component that provides energy to operate the electric actuated butterfly valve. It converts electrical energy to mechanical energy which then produces torque used to start or stop the valve. 

Stem 

This is a shaft component that connects the actuator to the valve disc. The function of the stem is to transmit mechanical energy from the actuator to the disc. 

Disc 

This is the main component of an electric actuated butterfly valve which is used to start, throttle, or stop fluid flow through the valve. The disc is powered by the actuator via the stem. 

Seats

This are components placed inside the valve body and which forms the resting surface for the disc once the valve is closed. Seats are very important components as they determine where the valve can be used in terms of temperature. The seats can be soft or metallic. The soft seats are used in low temperatures while the metallic ones are meant for high temperatures. 

Gasket 

This component is placed between the pipe and valve mating surfaces. The gasket helps to enhance a bubble-tight seal between the pipe and valve. 

Figure: Components of an electric actuated butterfly valve.

How does an electric actuated butterfly valve work? 

An electric actuated butterfly is very fast in operation because it only needs a quarter turn of the disc to open or close as necessary. To start fluid flow, the electric actuator turns on. This then turns on an electric motor which converts electrical energy to mechanical energy in terms of torque. This torque is transmitted by the valve stem to the disc. This then forces the valve disc to make a quarter turn angle that is a 90^o degree turn. The disc then becomes parallel to the flow passage leaving the valve open for fluid flow. To stop the valve, the actuator reverses the direction of rotation of the motor and which then forces the stem to rotate in the opposite direction (clockwise). As such, the disc becomes co-planar to the pipe and fluid flow where it blocks any fluid attempting to flow through the valve. Electric actuated butterfly valves are also used for throttling flow applications. When used for throttling, the disc opens slightly. This then allows some slight amount of fluid through the valve. 

Figure: Working of an electric actuated butterfly valve.

Types of electric actuated butterfly valves 

Zero offset electric actuated butterfly valve 

This is an electric actuated butterfly valve in which the stem is collinear to the disc centerline. The disc is centered on the seat. The disc, stem, and seat are centered inside the body. When the valve is closed, the seat, body, and disc lie in a concentric position. This design allows for rotation on the central axis. When the valve is fully open, the fluid flow becomes divided into two portions on each side of the disc. Electric actuated butterfly valve manufacturers design this valve to make the seat cover the body to prevent fluid from coming into contact. These valves are made of soft seats which helps them to rely on the deformation and flexibility of the seats to create a tight seal. However, the edges of the disc slide into the seat resulting in full friction between them when the valve is in operation. As such, the service life of the valve reduces. Because the seat is made of rubber or plastic material, electric actuated concentric butterfly valve manufacturers recommend the use of this valve is low temperature and pressure ratings. 

Figure: Concentric electric actuated butterfly valve.

Double offset electric actuated butterfly valve 

This is an electric actuated butterfly valve in which the stem does not pass through the centerline of the valve disc. The stem is offset from the seat centerline and body centerline. The stem is also offset from the valve’s vertical centerline. This design results in two offsets. The seat lifts from the seat when the disc is opened. This helps to reduce friction when the valve opens and closes during the first and last ten degrees of the disc closure. The design results in an electric actuated butterfly valve that is smooth in operation and of good sealing. It also gives the valve a long service life compared to the zero offset type. Electric actuated butterfly valve manufacturers design this valve with soft seats. As such, this valve is recommended for use where there is low temperature and moderate pressure. Applications of this valve include water supply, HVAC, and firefighting among others. 

Figure: Double offset electric actuated butterfly valve and illustrations of the offsets (right side).

Triple offset electric butterfly valve 

This is an electric actuated butterfly valve that has three offsets. The first two are the same as that of the double offset butterfly valve type. The third offset is in the body sealing cone axis. The addition of the third offset helps to get rid of disc and seat contact when the valve is opening or closing. This then helps to eliminate friction. Contact is only possible when the valve closes fully and this then helps to create a mechanical stop which prevents further rotation of the disc. Electric actuated butterfly valve manufacturers make the seat from metallic materials to make it applicable in high-pressure and high-temperature applications. A metallic seat is more rigid and tough compared to the soft seats and thus the valve can withstand abrasive wear. Also, this design of an triple offset butterfly valve enhances the service life compared to other butterfly valves. Applications of this valve include superheated steam in steam power plants, high-temperature fluids, corrosive chemicals, oil and gas, offshore pipelines, paper, and pulp among others. 

Figure: Triple offset electric actuated butterfly valve and illustration of the three offsets (right side).

Double-flanged electric actuated butterfly valve 

This is an electric actuated butterfly valve that has flat flanged ends on the inlet and outlet ports. These flanged ends have holes used to hold bolts that connect the valve and pipe. The pipe also has a flat flanged end with holes so that it can mate perfectly with the valve. Electric actuated butterfly valve manufacturers produce this valve for use in harsh applications involving slurries and sludge as well as corrosive media to make them economical in their use. The cost of these valves is higher compared to other butterfly valves. These valves can withstand high temperatures and high pressure. 

Figure: Double-flanged electric actuated butterfly valve.

Butt-weld electric actuated butterfly valve 

This is a valve that is connected to the pipe through welding. The Inlet and outlet ports of the valve are welded to the piping system. Electric actuated butterfly valve manufacturers design such valves for use in applications involving hazardous fluids like corrosives and flammables. The use of a welded end valve in such applications guarantees safety not only to the environment due to leakage but also to the valve personnel. The disadvantage of this valve is that it cannot be repaired or cleaned while it is connected to the pipeline. The weld has to be removed before any repair is performed. 

Figure: Butt-weld electric actuated butterfly valve.

 Applications of Electric-actuated butterfly valves

• Mining industries. 
• Production of pharmaceutical products. 
• Water supply and wastewater treatment. 
• Processing of foods and beverages. 
• Manufacturing of paper and pulp products. 
• Control steam and water flow in steam power plants. 
• Refinery of petroleum products. 
• Rransfer of oil and gas products. 

Advantages of electric-actuated butterfly valves 

• They are automated.
• They operate very fast. 
• Simple and compact design. 
• They are used in a wide range of industrial applications. 
• They are of lightweight relative to gate valve or globe valve. 
• They are suitable for installation where there is limited space. 
• Resistant to corrosion and abrasion wear. 
• They can tolerate slurries and sludge. 

Disadvantages of electric-actuated butterfly valves 

• Cause some pressure drop because once the valve opens the disc remains in the passage of the fluid flow. 
• They are prone to choking and cavitation. 
• Poor sealing features, especially at high pressure. 

Troubleshooting electric actuated butterfly valve 

The valve does not open or close 

• There is no power. Check the power supply and ensure frequency and voltage are as recommended by the electric actuated butterfly valve manufacturer.

The electric actuator is not working 

• Loose wires, switch or other leads are disconnected. Check the wires, switch, and other leads in the actuator and reconnect where necessary. 
• Loose capacitor or wrong connection. Check the wiring diagram for the proper connection as instructed by the electric actuated butterfly valve manufacturer. 
• The motor is damaged. Replace the electric motor. 
• Terminal block wires are loose or disconnected. Connect the terminal wires as necessary.

The power is on but the valve is not working 

• The capacitor is damaged. Replace the capacitor. 
• The valve needs more torque. Check for foreign materials obstructing the valve disc.

Internal fluid leakage 

• The seats are worn out. Replace the seats. 
• O-rings are worn out. Replace the O-rings. 
• Dirt in the valve. Open the valve and clean the dirt. 

External fluid leakage 

• The gasket is damaged or worn out. Replace the gasket. 
• Loose connection between pipe and valve. Tighten the connecting bolts to the torque values indicated by the electric actuated butterfly valve manufacturer. 
• O-rings are worn out. Replace the O-rings. 

Summary 

An electric actuated butterfly valve is a valve that is operated using an electric actuator. This valve works by using an electric motor to convert electric energy to mechanical energy. This mechanical energy is in terms of torque used to turn the valve disc to allow or block fluid flow. These valves are very fast in operation as the valve disc only needs to rotate for 90^o degrees to attain full closure or to be fully opened.

Electric actuated butterfly valves are used in various applications such as water supply, mining operations, processing foods and beverages, petroleum refinery, paper and pulp, steam power plants, and HVAC systems among others.