Ooh, look what you made me do
Look what you made me do
Look what you just made me do
Look what you just made me do

("Look What You Made Me Do," by Taylor Swift et. all, 2017)

Salutations to Rameez!

 

VALVE ACTUATORS OPEN AND CLOSE VALVES AUTOMATICALLY 

As was mentioned in PTOA Segment #257, the blowdown tasks performed by Blowdown Valves do not necessarily have to be performed by human beings called Process Operators.

A plethora of tasks are performed in processing industries by Valves that are automatically actuated to perform the task of opening and closing. Valves are also automatically actuated to control Process Variables (Flowrate, Pressure, Temperature, and Level).

No Process Operator is involved with the day-in and day-out tasks these Valves perform. However, the Outside Operator will monitor the Valve's condition, and the Instrumentation Technician will perform maintenance when necessary. 

The four technologies used to actuate Valves fall into three categories:

• 

  From Left to Right: Pnuematic Actuated Control Valve, Electrically Actuated Solenoid Valve, Electrically Actuated Inching and On/Off Motor Operated Valves (MOVs).

  Electric Valve Actuators:

  • Solenoids (Electro-magnetic Operated On-Off Valves).
  • Motorized Operated Valves (uses a Motor for On-Off Control and slow "Inching" Control).
• Hydraulic Actuator Valves (uses hydraulic oil for heavy duty, high PV Pressure process service).

 

The above technologies are predominantly used for On-Off Control of the PV Flowrate, albeit the MOV can be modified for more gradual control of the PV Pressure.

A not-at-all exhaustive list of applications for Actuated Valves includes oil and gas exploration, production, and pipeline conveyance, fuel gas safety, water treatment, water deluge systems, and HVAC.

The popular third technology used for Valve Actuation is:

• Pneumatic Actuator Valves (uses "Instrument Air" supplied between 3-15 psi for continuous analog control of all Process Variables).

Pnuematic Actuator Valves are commonly referred to as "Control Valves" and will be featured in the next PTOA Segment.

 

The Pnuematic Actuator can cheaply and continuously control all four Process Variables (Flowrate, Pressure, Temperature, and Level) at a Set Point value that lies somewhere between a maximum and minimum.

Otherwise stated, the popular Pnuematic Actuator "Control Valve" is not just for On-Off Control.

 

ELECTRIC VALVE ACTUATORS:
SOLENOIDS AND MOVs

Electric Valve Actuators have advantages over Hydraulic Valve Actuators.

These advantages include better precision, higher efficiency, less maintenance, and better environmental performance compared to the valve actuating technology that requires the use of hydraulic fluids.

Solenoid Valves are Valve Actuators which are powered by an electric current creating a magnetic field.

Otherwise stated, the Solenoid Valve is an example of applied "Electromagnetism" (Electromagnetism was featured in PTOA Segment #187). 

Motor Operated Valves (MOVs) are exactly as advertised ... the assembly that actuates the Valve includes a Motor. A Motor coordinates phases of electromagnetism to create rotational motion. Induction Motors were featured in PTOA Segment #188.

 

Form and Function of Solenoid Valves
(aka: On-Off Actuation of Valves via Electro-Magnetism) 

Solenoids are electromagnetic Valve Actuators that are used to rapidly actuate shutting off flow.

A Solenoid Valve is a rapid shutoff Valve.

Coordinating the task of stopping flow ... and then rapidly starting flow again in a timed sequence ... can be used as a strategy to release, distribute and mix fluids.

The components of a Solenoid Valve are:

• A doughnut-shaped Coil of wire.
• A magnetic Frame onto which the Coil is mounted.
• A Plunger ... which is an iron bar placed inside the Coil of wire.
• A Spring (optional, but common)

 

The function of a Solenoid Valve is as follows:

When an applied current energizes the Coil, a magnetic field is created. This magnetic field attracts the Plunger.

The force of the Plunger's movement depends upon the number of turns in the Coil and the magnitude of the current energizing the coil.

When the Solenoid is de-energized by stopping the applied current, the Spring will return the Plunger to its original position.

The nearby Solenoid Valve gifs and schematics do not emphasize that a Solenoid Valve is a solid-state unit ...  meaning that it is not attached to a Valve. The position of the Plunger determines when the Valve is "Open" or "Closed."

The electromagnetic force impacting the Plunger performs the on-off action of a Solenoid Valve!

The nearby gif illustrates how a Fail Close Solenoid Valve works. With a little tweaking, the Solenoid Valve can be designed to be a Fail Open Solenoid Valve.

Solenoid Valves can be designed to be Fail Open or Fail Closed Valves. "Failing Open" means the fluid will continue to flow through the Valve in the event of a power outage. "Failing Closed" means the fluid flow will abruptly stop in the event of a power outage.

The Solenoid Valve in the gif is a "2-Way Solenoid Valve." This type of Solenoid Valve has a single flow inlet and a single flow outlet and is either open or closed. When open, fluid flows through it. When closed fluid cannot flow through it.

The "3-Way Solenoid Valve" has three ports and is capable of diverting fluid through different ports.

A "4-Way Solenoid Valve" functions like a double-acting cylinder. The 4-Way Solenoid Valve has several connectors that determine the synchronized function of two exhaust ports, two-cylinder ports, and a pressure sensing port.

Solenoid Valves can also be used to control the Pneumatically Actuated Ball Valves featured in the next PTOA Segment. In this type of process service, the Solenoid Valve will divert compressed air to the designated port on the Pnuematic Actuator.

 

Form and Function of Motor Operated Valves (MOVs)
(aka:  Actuation of Valves Requiring 480 V, 3 Phase Power in the USA)  

Brilliant PTOA Readers and Students already read the PTOA Focus Study on Motors (PTOA Segments #187 through #190) and thus are aware that a Motor coordinates three phases of electromagnetism to create Torque, aka the motion that imparts rotational mechanical energy (Torque was featured in PTOA Segment #186).

The MOV non-Valve components are:

• A Motor
• A Gearbox
• A Control Unit

 

 

These MOV components are attached to a Valve which directly controls the flowing fluid's PV Flowrate and direction. The Valve attached to the MOV components could be one that PTOA Readers recently learned about in PTOA Segments #252 through #254.

Unlike the Solenoid Valve, the Valve that is attached to an MOV must have additional design attention if the Valve must fail in a safe position.

Furthermore,MOVs must have electrical limit switches that shut the motor off when it has turned the Valve as far as it can go. Additional switches are needed to protect the motor's coils from burning out in the event the excitation current remains live while the Valve's action is unexpectedly impeded.

The Motor in a MOV is more resistant to voltage shock than a Solenoid Valve.

However, unlike a Solenoid Valve...The MOV must be reset when power is restored (a Solenoid Valve can be reset in the midst of a power outage).

The reduction gears within the Gearbox of the MOV can convert the rotational motion of the Motor into these operational modalities:

• 

  LEFT: A Linear Motion MOV would start or stop flow. The Gate Valve could be MOV actuated to open and close. Flow could alternate between either direction. MIDDLE: A Rotary Motion MOV could rotate the Flapper Valve on the Check Valve. RIGHT: The Quarter Turn MOV on a Ball Valve would open/close the Ball Valve with a quarter of a turn.

  Linear MOVs provide a linear motion for Gate Valves, Globe Valves, or Diaphragm Valves to Open and Close.

• Rotary MOVs provide a rotating motion that rotates Ball Valves, Butterfly Valves, and Plug Valves.
• Quarter-Turn MOVs actuate valves that require a 90-degree rotation to open or close Ball Valves, Butterfly Valves, and Plug Valves.

 

The Control Unit of the MOV receives input signals from a (not shown) Controller.

The Control Unit might be a manual switch, but nowadays is probably a computer program, or a remote-control system. The Control Unit quickly converts the input from the (not shown) Controller into the desired activation orders for positioning the MOV.

 

Process Service Selection for Solenoid Valve versus MOV Actuated Valve

The process service application of a Solenoid Valve versus a MOV-actuated Ball Valve requires evaluation:

• 

  Left: MOV Right: Solenoid

  Size limitations: Solenoid Valves are more compact and lightweight; their process service application is limited to port sizes of 2 inches or smaller. Some process applications require greater flow capacity which is in the wheelhouse of the MOV-Ball Valve.

• Materials of Fabrication Limitation: Solenoid Valves are typically fabricated from stainless steel and bronze. The Ball Valve being actuated by an MOV can be made of other types of metal or even plastic, which may work better in the process application.
• Operating Pressure Limitation: MOV actuated Ball Valves can withstand much higher operating Pressures than Solenoids can.
• 

  Solenoids wear out faster than MOVs. Particulate matter gets stuck in the Solenoid Plunger but gets wiped free in an MOV Actuated Ball Valve.

  Fluid Particulates: Particulates get stuck in Solenoid Valves but not in MOV-actuated Ball Valves.

• Speed and Cycle Life: Solenoid Valves open and close significantly faster than MOV-actuated Ball Valves. But the MOV-operated Ball Valve has a significantly longer cycle life.
• Optimizing Investment versus Operating Costs: The initial investment cost of installing Solenoid Valves is cheaper than the installation costs for an MOV-actuated Ball Valve, which requires higher voltage power supply. Furthermore, modifying a Ball Valve to fail safe adds additional investment expense. Since the Solenoid Valve opens and closes faster than an MOV-actuated Ball Valve, the selection of a Solenoid Valve might appear to be a no-brainer in 2 inch or less pipe size. However, the rapid frequency of actuation results in more Solenoid wear and tear ...  ergo, Solenoid Valves require more maintenance expense compared to MOVs.
• 

  The rotary motion of an MOV can be employed in a Check Valve or modified for Linear Flow and "inching Control."

  Service Application Versatility: MOVs are multi-functional; MOVs can perform more than just the shutoff task of Solenoid Valves. MOVs can be used for regulating the PV Flowrate, not just switching it on or off as a Solenoid does. MOVs can control the PV Flowrate in the Half-Open / Half-Closed Position (or other flow magnitudes between totally Open and totally Closed).

 

HYDRAULICALLY OPERATED VALVES

Brilliant PTOA Readers and Students ... meaning those who are reading the PTOA Segments in the intended sequential order ... already know that a contained liquid ... for example, a container of hydraulic oil ... exerts significant Pressure on the walls and bottom of the container.

 

The Force component of the Pressure created by a container of hydraulic oil can be used to open and close large diameter Valves.  The fundamentals of hydraulic Pressure were featured in PTOA Segments #145 to #147.

A Valve that is hydraulically activated uses hydraulic oil to forcefully Open and Close Valves in heavy duty, high PV Pressure process services.

Think about it, Fred!

Maintaining a reservoir of hydraulic oil would only be preferable in process services where there is no available and reliable instrument air or electrical utility ... or when the process service is so heavy duty and high PV Pressure that the other Valve Actuation technologies cannot be used.

Hydraulic Actuated Valves are found in oil and gas extraction and marine applications.

Hydraulic Actuator Valves are also used to move heavy machinery or lift large loads.

 

TAKE HOME MESSAGES: Valves can be automatically actuated electrically, hydraulically, and pneumatically (i.e. with Instrument Air). This PTOA Segment featured electric and hydraulic valve actuation technologies. Pneumatic Actuated Valves are featured in the next PTOA Segment.

Electric Valve Actuation Technologies:

Solenoid Valves use applied electromagnetism to rapidly shut off a Valve. The position of the Solenoid's Plunger determines if the Valve is open or closed. Solenoids are easy to design Fail Open or Fail Closed. The Solenoid Valve is less expensive to install and takes less footprint yet requires more maintenance than the MOV.

Motorized Operated Valves (MOVs) have a Control Box, Motor, and Gearbox that are attached to a Valve. The torque created by the Motor can be converted in the Gearbox to a variety of flow and pressure control applications, not just a shutoff function. However, the MOV has specific power supply requirements to accommodate the Motor and must have electrical limits switches in the Control Box to protect the Motor's windings. The MOV must be modified to fail in a safe position and must be reset after a power outage. 

Hydraulic Valve Actuation:

Hydraulic Valve Actuators use the Force component of contained hydraulic oil to Open and Close Valves. Like MOVs, Hydraulic Valve Actuators are connected to a Valve. Hydraulic Valve Actuators are used in heavy duty, high PV Pressure applications.

©2025 PTOA Segment 0258

PTOA PV FLOWRATE FOCUS STUDY AREA
PIPING NETWORK HARDWARE

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