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BASICS OF INDUSTRIAL VALVES

ACTUATION

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FUNDAMENTAL TECHNIQUES

An actuator is a device that allows the operation of a valve (open/close/set). All valves function under the operating conditions proper to a process. It is important that the actuation is adequately sized and adapted to the environment in which it will be used (size constraints, energy available on site,etc.).

The sizing of an actuator must primarily take into account the forces required to:

• Ensure the sealing contact pressure for tight shut-off of the valve

• Overcome frictional forces of the gland packing

• Overcome the pressure difference between upstream and downstream of the valve (ΔP)

MANUAL ACTUATION

A manually operated valve is equipped with a hand wheel or a crank lever. For quarter turn valves, (see “Technology” chapter), a lever allows the device to be operated quickly.

Multi-turn operated valves are equipped with a hand wheel, or a crank handle that allows them to be operated faster. Among the multi-turn manual actuation mechanisms, two types of systems can be distinguished :

• The “Turning, non-rising” system : while turning the hand wheel, a threaded nut (yoke nut/adjusting nut) drives the actuation stem thread. The hand wheel is fixed and the stem is rising through the center of the hand wheel.

• The “Rising hand wheel” system : the hand wheel is fixed on the actuation stem, acting directly on it. During operation, the stem turns at the same time as the hand wheel. The hand wheel moves linearly with the stem.

Manual actuation is adapted to equipment that is easily accessible and operated infrequently. This system is inexpensive, but requires the intervention of an operator. As an option, emergency hand wheels can be installed to override the motor controls, allowing operation of the valve in case of failure of the main actuator or of the power supply to the actuator.

Options :

• Bevel gear• Offset hand wheel• Gear reducer (multiplication of forces, suitable for high operating

torques)• Hand wheel locking system (cover, lock, padlock, chain, etc.)• Extension to control from a distance• Dead man handle (valve closes automatically without intervention of operator)• Chain wheels (fit for valves high up or difficult to access)• ISO base for future adaptation of motorization

n Lever for quarter-turn operation

n “Rising hand wheel”

n Hand wheel “Turning non-rising”

n Bevel / Reducer

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PNEUMATIC ACTUATION

Options :

• Offset actuator• Custom design (Guichon Valves range of cylinders)• Anti-operating safety mechanism (non-return valve, locking

device, etc.)• Assembled with different pneumatic accessories (solenoid valve,

spool valve, etc.) for automated operation• Possibility of emergency hand wheel after the pneumatic actuator• Dampers (to brake actuator as it approaches closure)• Rotary actuator (rack and pinion) for quarter turn valves

n Piston actuator

SINGLE AND DOUBLE ACTING LINEAR PNEUMATIC ACTUATORS

Linear pneumatic actuators can be piston type or diaphragm type. A single acting will return automatically

to its initial position (spring return), while a double acting remains in the same position if there is no effort .

Diaphragm actuators are known for their easy maintenance (rapid change of the membrane) and their attractive price. Nevertheless, they are not well adapted for a high frequency of operation or a long stroke.

Piston actuators are more costly but will have a longer life span than a diaphragm actuator and are not limited by the stroke length. In function of the effort required to operate the valve, the size can quickly become very significant. In this case, it is possible to opt for a two-stage cylinder design.

Double acting piston actuator : Supply 1 + air vent 2 = Shaft moving outwardAir vent 1 + supply 2 = Shaft moving inward

Single acting actuator :Supply 1 + air vent 2 = Shaft moving outwardAir vent 1 + air vent 2 = Shaft moving inward (spring return)

n Single acting piston actuator

n Diaphragm actuator

Return Spring Piston

ACTUATION

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FUNDAMENTAL TECHNIQUES

VANE TYPE AIR MOTORS

Pneumatic air motors are composed of a housing and a rotor. The cylindrical rotor is equipped with radial slots in which the vanes slide freely. It is eccentric in a larger diameter cylinder (housing). When the rotor turns, the vanes move outward and press up against the housing due to centrifugal force. Because of the air pressure on the vanes, the eccentricity generates a torque that drives the motor. This construction (principal a fair motor with vanes) allows the inversion of the direction of rotation, simply by reversing the intake and exhaust air.

Air motors have numerous advantages. Given their small size, it is possible to mount them in installations where space is limited. Installing an air motor is simple and doesn’t require any electrical accreditation.

It is the same for maintenance operations. Given that the motor is only supplied with air, there are no sparks, which allows its use in explosive environments. On the other hand, the operating time is much longer than a pneumatic actuator, operating torques are limited and the air consumption of the motor is particularly high.

n Air motor

Options :

• Custom design• Anti-operating safety mechanism (non-return valve, locking device,

etc.)• Assembled with different pneumatic accessories (solenoid valve, spool

valve, etc.) for automated operation• Torque limiter• Possibility of emergency hand wheel after the pneumatic actuator• Air supply via auxiliary air tank + regulator in case of emergency (be

careful with the significant consumption of air for this type of actuator)

Inlet/outlet ports

Vane

Rotor

Motor body/

housing

Air Motor

Reducer /Bevel

Air motor

Emergency hand wheel

Reducer

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HYDRAULIC ACTUATION

ELECTRIC ACTUATORS

Hydraulic cylinders have the particularity of being able to generate a significant operating force with a reduced size (supply pressure can reach 350 bar). Simple or double acting, these actuators are quiet while operating, but require the use of a hydraulic center to supply them. They will therefore be selected for valves wich combine elevated pressure and large nominal diameter.

Electric actuators have a good ratio equipment / price. They are regularly equipped with an emergency hand wheel and means of detection integrated directly into the motor. This technology remains nevertheless relatively cumbersome and requires electrical certification for an on-site installation. Depending on the electric actuator technology used, electric actuators have an exemplary reliability and require very little maintenance.

For a short stroke length and a very reduced operation time, the electromechanical actuators are perfectly adapted.Electric actuators are also known for their precision and repeatability. The ball screw system present in linear electric actuators allows for a reduced ssize and makes them high performance actuators for control. Nevertheless, electrical installations for operating linear actuators can be complex and substantial.

Options :

• Offset operation• Anti-operating safety mechanism (non-return valve,

locking device, etc.)• Assembled with different hydraulic accessories

(distributors, etc.) for automated operation• Possibility of emergency hand wheel after the hydraulic actuator• ATEX design• Rotating hydraulic actuator (for quarter turn valves)

Options :

• Bevel / Reducer• Anti-operating safety mechanism (lock, pad lock, etc.)• Torque limiter• Possibility of emergency hand wheel after the electrical

actuator• ATEX, ADF design, or others (see “Standards” chapter)• Position feedback• Positioner• Remote control

n Multiturn electrical actuator

n Linear electrical actuator

ACTUATION

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FUNDAMENTAL TECHNIQUES

SELECTION CRITERIA : GENERAL GUIDANCE CHART

Manual Pneumatic Hydraulic Electric

Linear 1/4 turnCylinder(linear)

Motor(multiturn)

Cylinder (linear)

Motor(multiturn)

Cylinder(linear)

Motor(multiturn)

Quick operating speed

Reduced size

Easy maintenance

Significant operating torque

Operating frequency

Adapted for control

ATEX design

Moderate price

Well adapted Moderately adapted Not suitable

Actuation Type

Criteria