PIPE6010: Valve Actuators

A solution to the_______ required to operate larger valves is to equip the v/v with a *gear system* which provide a ________.

A solution to the *high torque* required to operate larger valves is to equip the v/v with a ________ which provide a *mechanical advantage.*

Although *Pneumatic actuators* can be used for _____operation, they are typically used for _______.

Although ________ can be used for *on-off* operation, they are typically used for *modulating service.*

Chain & wheel operators are used for v/vs that: a) Req auto v/v positioning using a remote op device b) Can't be operated by 1 person c) Req electro-hydraulic operators& remote op device d) Cannot be located within easy reach

Cannot be located within easy reach

2 types of Pneumatic Operators are:

Diaphragm & Piston

Pneumatic or Hydraulic Piston Actuators are ____ acting meaning ________________.

Double Acting. *Fluid acts on both sides of the piston.*

The air used to operate a pneumatic v/v actuator must be free of: a) oil & water b) water and 02 c) water & C02 c) oil & N02

Oil & water

A solenoid operate v/v can be used to control position of the disc in a globe v/v when the: a) v/v must be fully opened / closed b) v/v plug to be modulated @ intermediate position c) response spd of actuator must be increased d) spring in actuator req extra force to open v/v

v/v must be fully opened / closed (on/off control)

*Solenoid v/vs* are employed in ______ systems where *on and off* operation is required. They are ______ to manufacture and are as *reliable* as their source of power.

________ are employed in *small size* systems where _____ operation is required. They are *inexpensive* to manufacture and are as ____ as their source of power.

*Chain & Wheel* operators are used for v/vs that cannot be ___________. They are the lowest-cost, _____ operating devices and are widely used where _______ v/v positioning is not required.

________ operators are used for v/vs that cannot be *located within easy reach.* They are the _____, *remote operating* devices and are widely used where *automatic* v/v positioning is not required.

Pneumatic Actuators convert _________ into *v/v stem motion* by applying pressure to a _______. The air pressure provides large amounts of *force* to give positive action to the stem and overcome the _____ and *packing friction.*

_________ convert *air signal* into _______by applying pressure to a *diaphragm.* The air pressure provides large amounts of ____ to give positive action to the stem and overcome the *spring action* and _________.

Air loaded diaphragm actuators are _________ and considered _______ to spring loaded types in many applications requiring the use of a valve positioner.

_________ diaphragm actuators are *springless* and considered *superior* to spring loaded types in many applications requiring the use of a valve positioner.

Electric actuators receive an electric signal to position the v/v to the desired setting. These devices may be ______ or ______ operated.

_________ position the v/v to the desired setting. These devices may be *solenoid or electric motor* operated.

*Pneumatic or hydraulic piston* actuators are used when the force required to position a valve or a damper is ____________.

____________ actuators are used when the force required to position a valve or a damper is *higher than that which can be provided by a diaphragm.*

Spring operated pneumatic operators can be adjusted by:

adjusting initial spring tension.

The most common mechanical or manual actuator is the ______.

handwheel

Equipping larger v/vs with a gear system is 1 solution to the ______ required to operate v/v. a) low torque b) high torque c) additional manpower d) handwheel

high torque

A disadvantage of a gear system on a valve operator is

increased friction losses and long valve opening and closing times.

V/v operators, are classified according to the form of ___________.

input signal and output power used.

Air Supply to Pneumatic Actuators require air for all control purposes be as free of _________. Sometimes, the air necessary to operate an actuator comes _______ from the controller. It is usually _____, _____ and _______.

ir Supply to Pneumatic Actuators require air for all control purposes be as free of *moisture, oil, and other contaminants.* Sometimes, the air necessary to operate an actuator comes *directly* from the controller. It is usually *boosted, filtered and regulated.*

In automated processes v/v operators may be powered by what 5 means?

mechanical, electrical, hydraulic, pneumatic, or electro-hydraulic means.

Spring Loaded Diaphragm Actuators operate a

plug and seat

Pneumatic actuators are widely used in the petroleum and chemical industries because they are: a) safe, simple, and reliable. b) most popular for on-off operation c) less expensive than other actuators d) instrument air is readily available

safe, simple, and reliable.

Air loaded diaphragm actuators have __ signal pressures controlling the valve _________. One side of the diaphragm is supplied with a *constant* air pressure, _______, and air pressure from the controller is applied to the _______ side.

*2 air signal pressures* controlling the valve *differentially.* 1 side of the diaphragm is supplied with a _______air pressure, *20-30 kPa (3-4 psi),* and air pressure from the controller is applied to the *opposite* side.

Spring Loaded Diaphragm Actuators can either be *direct acting* (air-to -____________ ) or *reverse acting* (air-to-________ )

*direct acting* (air-to -*close*) or *reverse acting* (air-to-*open*)

Electrical v/v operators are relatively expensive, in both equipment and wiring costs. They have the following advantages:

- operated from several different locations. - Remote indicating devices can be installed to show position at any operating station. - V/v operating speeds (to close) - V/vs can be installed & operated w/o regard to operating levels, access for service, or proximity to other equipment.

With an air loaded diaphragm actuator design: a) spring & unbalanced force on v/v plug, due to press, opposes air press on diaphragm b) Spring action is constant but force provided by spring is erratic @ any deg of compression c) Diff control is achieved by a single air press signal d) 2 air signal press control v/v differentially

2 air signal pressures control the v/v differentially.

Electrical v/v operators have speed ranges to close v/vs of

2 sec for some units, to 4 min.

Typical pressures to the Spring Loaded Diaphragm Actuators are from _________. The maximum pressure is due to __________.

20-100 kPa (3-15 psi) to 40-200 kPa (6-30 psi). The maximum pressure is due to *the limitations of the diaphragm casing.*

When it's desired to position v/v plug of a pneumatic piston actuator at any intermediate position a _____ is required. a) Positioner b) Worm gear c) Solenoid d) mech linkage

A positioner is required

A solution to the high torque required to operate larger v/vs is to equip it with a gear system so that v/v: a) can be closed & opened much quicker b) Easier for operator to open/close c) can be closed much faster d) position can be more precisely regulated

Easier for operator to open/close

For *Pneumatic or Hydraulic actuators* with ______ positioning, the cylinder can be *loaded & unloaded* by a simple _____. However, when it is desired to position the valve plug at any *intermediate* position, a _______ is required

For ___________ with *on-off* positioning, the cylinder can be ____ and _____ by a simple *solenoid valve.* However, when it is desired to position the valve plug at any ______ position, a *positioner* is required

In a *direct-operating v/v,* the _______ is used in place of a *v/v stem & handwheel.* The plunger is connected _____ to the *disc* of a globe v/v.

In a ______, the *solenoid plunger* is used in place of a ___ & ____. The plunger is connected *directly* to the ____ of a globe v/v.

Larger motorized v/vs are equipped with a *high-speed electric motor* & a system of ______to position the v/v. The gear train lowers *the speed,* thus increasing ______ to get *tight closure.* The motors used can be _______ or *unidirectional* types. _______ are provided to *open the motor circuit* at each extreme _____ or when a *predetermined torque* has been developed by the motor.

Larger motorized v/vs are equipped with a _____________ & a system of *reduction gears* to position the v/v. The gear train lowers_____, thus increasing *the torque* to get _______. The motors used can be *reversing *or ______ types. *Limit switches* are provided to _____ the motor circuit at each extreme *travel* or when a _______ has been developed by the motor.

Large motorized valves are equipped with limit switches to: a) open motor electrical circuit at each extreme travel b) open motor electrical circuit when a predetermined torque has been developed by motor c) cause an increase in speed of response to a control signal d) Both a & b

Open motor electrical circuit at each extreme travel *and* at a predetermined torque.

______ actuators are used when force required to position a v/v or damper is higher than can be provided by a diaphragm. a) Pneumatic piston b) Mechanical c) Spring loaded diaphragm d) Solenoid driven

Pneumatic piston

Air loaded diaphragm actuators are referred to as the ______. Rather than a spring there is a

Preloaded types. Large air dome.

What reasons make Pneumatic or Hydraulic Piston Actuators quicker, and have more accurate control?

Since *higher air or hydraulic pressures* can be applied, a *lower volume has to be displaced* to and from the piston, which causes an *increase in speed of response* to a control signal. Piston actuators can provide a *much greater stem movement* than a diaphragm actuator.

A preloaded type actuator has a large air dome on top of the diaphragm which replaces the: a) Coil b) Worm & gear c) Piston d) Spring

Spring

Diaphragm Pneumatic Operators come in 2 types:

Spring Loaded & Air Loaded

The draw back of springs in an actuator?

Spring action can be erratic and the force provided by the spring is almost constant at any degree of compression.

Air loaded diaphragm actuators are considered superior to spring loaded types because: a) diff control is achieved by a singe air signal b) spring & underbalanced force on plug oppose air press on diaphragm c) spring action is constant but force provided by spring is erratic @ any deg. of compression d) spring action can be erratic & force of the spring is constant @ any deg of compression

Spring action can be erratic- the force of the spring is *constant* at any degree of compression.

The solenoid-operated valves are ______ and are used in many *automatic control systems.*

The__________ are *snap acting* and are used in many _________ systems.

The main disadvantage of a electric v/v operator is : a) They are expensive - equip & wiring cost b) v/vs must be installed at right op levels c) only a small range of op speeds attainable d) Can't be operated from several locations

They are relatively expensive - both in equipment & wiring cost