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API Specification 6D Twenty-second Edition - Introduction

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6.10 Handwheels and wrenches (levers)

Wrenches for valves shall either be of an integral design or consist of a head which fits on the stem and is designed to take an extended handle. The head design shall allow permanent attachment of the extended section if specified by the purchaser.
The maximum force required at the handwheel or wrench to apply the breakaway torque or thrust shall not exceed 360 N.
Wrenches shall not be longer than twice the face-to-face or end-to-end dimension of the valve.
Handwheel diameter(s) shall not exceed the face-to-face or end-to-end length of the valve or 1 000 mm, whichever is the smaller, unless otherwise agreed. Except for valve sizes DN 40 (NPS 11/2) and smaller, spokes shall not extend beyond the perimeter of the handwheel unless otherwise agreed.
When specified by the purchaser, the handwheel of the gearbox input shaft shall be provided with a torque-limiting device, such as a shear pin, to prevent damage to the drive train.

6.11 Locking devices
Valves shall be supplied with locking devices if specified by the purchaser. Locking devices for check valves shall be designed to lock the valve in the open position only.
Locking devices for other types of valve shall be designed to lock the valve in the open and/or closed position.

6.12 Position indicators
Valves fitted with manual or powered actuators shall be furnished with a visible indicator to show the open and the closed position of the obturator.
For plug and ball valves, the wrench and/or the position indicator shall be in line with the pipeline when the valve is open and transverse when the valve is closed. The design shall be such that the component(s) of the indicator and/or wrench cannot be assembled to falsely indicate the valve position.
Valves without position stops shall have provision for the verification of open and close alignment with the operator/actuator removed.

Contents
1Scope…………………………………………………………………………………………………………………….1
2 Normative references……………………………………………………………………………………………….. 1

3 Terms and definitions…………………………………………………………………………………………….. 3
4 Symbols and abbreviations……………………………………………………………………………………. 6
4.1Symbols………………………………………………………………………………………………….. 6
4.2 Abbreviations………………………………………………………………………………………………………. 6
5 Valve types and configurations……………………………………………………………….. 7
5.1 Valve types…………………………………………………………………………………. 7
5.2 Valve configurations……………………………………………………………………. 7
6 Design…………………………………………………………………………………………………… 19
6.1 Pressure and temperature rating……………………………………………………………. 19
6.2 Sizes……………………………………………………………………………………….. 20
6.3 Face-to-face and end-to-end dimensions…………………………….. 20
6.4 Minimum-bore full-opening valves………………………………………………………………… 33
6.5 Valve operation……………………………………………………………………………… 33
6.6 Pigging……………………………………………………………………………………. 33
6.7 Valve ends………………………………………………………………. 34
6.8 Pressure relief…………………………………………………………………………………. 34
6.9 Bypass, drain and vent connections………………………………………………………………. 34
6.10 Hand wheels and wrenches (levers)………………………………………… 35
6.11 Locking devices…………………………………………………………. 35

6.12 Position indicators…………………………………………………………. 35
6.13 Operators and stem extensions…………………………………………………….. 36
6.14 Sealant injection……………………………………………………………….. 36
6.15 Lifting lugs …………………………………………………………………………………… 36
6.16 Actuators……………………………………………………………………….. 36
6.17 Drive trains…………………………………………………………………………….. 36
6.18 Stem retention ……………………………………………………………………… 37
6.19 Fire safety……………………………………………………………………………. 37
6.20 Anti-static device……………………………………………………………………………………….. 37
6.21 Design documents ………………………………………………………………………………………. 37
6.22 Design document review……………………………………………………………………………. 37
7 Materials……………………………………………………………………………………………………….. 37
7.1 Material specification………………………………………………………………………………………… 37
7.2 Service compatibility ……………………………………………………………………… 37
7.3 Forged parts ……………………………………………………………………………………………………. 38
7.4 Welding ends……………………………………………………………………………………………… 38
7.5 Toughness test requirements………………………………………………………………… 38
7.6 Bolting …………………………………………………………………………………………………………. 39
7.7 Sour service……………………………………………………………………………………………………….. 39
8 Welding ……………………………………………………………………………………………. 39
8.1 Qualifications…………………………………………………………………………………………. 39
8.2 Impact testing………………………………………………………………………………………………… 39
8.3 Hardness testing ……………………………………………………………………………….. 40
9 Quality control ………………………………………………………………………………………… 41
9.1 General ……………………………………………………………………………………………. 41
9.2 Measuring and test equipment ……………………………………………………………………….. 42
9.3 Qualification of inspection and test personnel ………………………………………………………… 42
9.4 NDE of repair welding…………………………………………………………………….. 42
10 Pressure testing ……………………………………………………………………………. 43
10.1 General ……………………………………………………………………………………… 43

10.2 Stem backseat test……………………………………………………………………………. 43
10.3 Hydrostatic shell test ……………………………………………………………………………… 44
10.4 Hydrostatic seat test …………………………………………………………………………………. 44
10.5 Draining………………………………………………………………………………………………… 46
11 Marking…………………………………………………………………………………………………… 46
11.1 Requirements………………………………………………………………………………………………… 46
11.2 Marking example ……………………………………………………………………………………………… 49
12 Storage and shipping……………………………………………………………………………………………… 50
12.1 Painting …………………………………………………………………………………………………… 50
12.2 Corrosion prevention……………………………………………………………………………………….. 50
12.3 Openings……………………………………………………………………………………………. 50
13 Documentation …………………………………………………………………………………… 50
Annex A (informative) Purchasing guidelines…………………………………………………………. 51
Annex B (normative) Supplementary NDE requirements ………………………………………….. 53
Annex C (normative) Supplementary test requirements ………………………………………………. 57
Annex D (normative) Supplementary documentation requirements……………………………….. 61
Annex E (informative) API Monogram………………………………………………………………………………………………………

HTML clipboardAngle Valve: A valve design in which one port is co-linear with the valve stem or actuator, and the other port is at a right angle to the valve stem. (See also Globe Valve.) Bellows Seal Bonnet: A bonnet that uses a bellows for sealing against leakage around the closure member stem (figure 1–6). Bonnet: The portion of the valve that contains the packing box and stem seal and can guide the stem. It provides the principal opening to the body cavity for assembly of internal parts or it can be an integral part of the valve body. It can also provide for the attachment of the actuator to the valve body.

Typical bonnets are bolted, threaded, welded, pressureseals, or integral with the body. (This term is often used in referring to the bonnet and its included packing parts. More properly, this group of component parts should be called the bonnet assembly.) Bonnet Assembly: (Commonly Bonnet, more properly Bonnet Assembly): An assembly including the part through which a valve stem moves and a means for sealing against leakage along the stem. It usually provides a means for mounting the actuator and loading the packing assembly. Bottom Flange: A part that closes a valve body opening opposite the bonnet opening. It can include a guide bushing and/or serve to allow reversal of the valve action. Bushing: A device that supports and/ or guides moving parts such as valve stems.

Cage: A part of a valve trim that surrounds the closure member and can provide flow characterization and/or a seating surface. It also provides stability, guiding, balance, and alignment, and facilitates assembly of other parts of the valve trim. The walls of the cage contain openings that usually determine the flow characteristic of Chapter 1. Introduction to Control Valves 10 Figure 1-8. Characterized Cages for Globe-Style Valve Bodies W0958/IL W0959/IL W0957/IL   
 
 the control valve. Various cage styles are shown in figure 1-8. Closure Member: The movable part of the valve that is positioned in the flow path to modify the rate of flow through the valve. Closure Member Guide: That portion of a closure member that aligns its movement in either a cage, seat ring, bonnet, bottom flange, or any two of these. Cylinder: The chamber of a piston actuator in which the piston moves (figure 1-7). Cylinder Closure Seal: The sealing element at the connection of the piston actuator cylinder to the yoke. Diaphragm: A flexible, pressure responsive element that transmits force to the diaphragm plate and actuator stem. Diaphragm Actuator: A fluid powered device in which the fluid acts upon a flexible component, the diaphragm. Diaphragm Case: A housing, consisting of top and bottom section, used for supporting a diaphragm and establishing one or two pressure chambers. Diaphragm Plate: A plate concentric with the diaphragm for transmitting force to the actuator stem. Direct Actuator: A diaphragm actuator in which the actuator stem extends with increasing diaphragm pressure. Extension Bonnet: A bonnet with greater dimension between the packing box and bonnet flange for hot or cold service. Globe Valve: A valve with a linear motion closure member, one or more ports, and a body distinguished by a globular shaped cavity around the port region. Globe valves can be further classified as: two-way single-ported; two-way double-ported (figure 1-9); angle-style (figure 1-10); three-way (figure 1-11); unbalanced cage-guided (figure 1-3); and balance cage-guided (figure 1-12). Lower Valve Body: A half housing for internal valve parts having one flow connection. The seat ring is normally clamped between the upper valve body and the lower valve body in split valve constructions.

Offset Valve: A valve construction having inlet and outlet line connections on different planes but 180 degrees opposite each other. Packing Box (Assembly): The part of the bonnet assembly used to seal against leakage around the closure Chapter 1. Introduction to Control Valves 11 Figure 1-9. Reverse Double-Ported Globe-Style Valve Body W0467/IL Figure 1-10. Flanged Angle-Style Control Valve Body W0971/IL member stem. Included in the complete packing box assembly are various combinations of some or all of the following component parts: packing, packing follower, packing nut, lantern ring, packing spring, packing flange, packing flange studs or bolts, packing flange nuts, packing ring, packing wiper ring, felt wiper ring, belleville springs, anti-extrusion ring. Individual Figure 1-11. Three-Way Valve with Balanced Valve Plug W0665/IL Figure 1-12. Valve Body with Cage-Style Trim, Balanced Valve Plug, and Soft Seat W0992/IL packing parts are shown in figure 1-13. Piston: A movable pressure responsive element that transmits force to the piston actuator stem (figure 1-7). Piston Type Actuator: A fluid powered device in which the fluid acts upon a movable piston to provide motion to the actuator stem. Piston type actuators (figure 1-7) are classified as either double-acting, so that full power Chapter 1. Introduction to Control Valves 12 Figure 1-13. Comprehensive Packing Material Arrangements for Globe-Style Valve Bodies B2565 / IL LOCATION OF SACRIFICIAL ZINC WASHER, IF USED. 
  

 14A1849-E 1 12A7837-A 
  
 13A9775-E can be developed in either direction, or as spring-fail so that upon loss of supply power, the actuator moves the valve in the required direction of travel. Plug: A term frequently used to refer to the closure member. Port: The flow control orifice of a control valve. Retaining Ring: A split ring that is used to retain a separable flange on a valve body. Reverse Actuator: A diaphragm actuator in which the actuator stem retracts with increasing diaphragm pressure. Reverse actuators have a seal bushing (figure 1-4) installed in the upper end of the yoke to prevent leakage of the diaphragm pressure along the actuator stem. Rubber Boot: A protective device to prevent entrance of damaging foreign material into the piston actuator seal bushing. Seal Bushing: Top and bottom bushings that provide a means of sealing the piston actuator cylinder against leakage. Synthetic rubber O-rings are used in the bushings to seal the cylinder, the actuator stem, and the actuator stem extension (figure 1-7). Seat: The area of contact between the closure member and its mating surface that establishes valve shut-off. Seat Load: The net contact force between the closure member and seat with stated static conditions. In practice, the selection of an actuator for a given control valve will be based on how much force is required to overcome static, stem, and dynamic unbalance with an allowance made for seat load. Seat Ring: A part of the valve body assembly that provides a seating surface for the closure member and can provide part of the flow control orifice. Separable Flange: A flange that fits over a valve body flow connection. It is generally held in place by means of a retaining ring. Spring Adjustor: A fitting, usually threaded on the actuator stem or into

Chapter 1. Introduction to Control Valves 13 the yoke, to adjust the spring compression. Spring Seat: A plate to hold the spring in position and to provide a flat surface for the spring adjustor to contact. Static Unbalance: The net force produced on the valve stem by the fluid pressure acting on the closure member and stem with the fluid at rest and with stated pressure conditions. Stem Connector: The device that connects the actuator stem to the valve stem. Trim: The internal components of a valve that modulate the flow of the controlled fluid. In a globe valve body, trim would typically include closure member, seat ring, cage, stem, and stem pin. Trim, Soft-Seated: Valve trim with an elastomeric, plastic or other readily deformable material used either in the closure component or seat ring to provide tight shutoff with minimal actuator forces. Upper Valve Body: A half housing for internal valve parts and having one flow connection. It usually includes a means for sealing against leakage along the stem and provides a means for mounting the actuator on the split valve body. Valve Body: The main pressure boundary of the valve that also provides the pipe connecting ends, the fluid flow passageway, and supports the seating surfaces and the valve closure member. Among the most common valve body constructions are: a) single-ported valve bodies having one port and one valve plug; b) double-ported valve bodies having two ports and one valve plug; c) twoway valve bodies having two flow connections, one inlet and one outlet; d) three-way valve bodies having three flow connections, two of which can be inlets with one outlet (for converging or mixing flows), or one inlet and two outlets (for diverging or diverting flows). The term valve body, or even just body, frequently is used in referring to the valve body together with its bonnet assembly and included trim parts. More properly, this group of components should be called the valve body assembly. Valve Body Assembly (Commonly Valve Body or Valve, more properly Valve Body Assembly): An assembly of a valve, bonnet assembly, bottom flange (if used), and trim elements. The trim includes the closure member, which opens, closes, or partially obstructs one or more ports. Valve Plug: A term frequently interchanged with plug in reference to the closure member. Valve Stem: In a linear motion valve, the part that connects the actuator stem with the closure member. Yoke: The structure that rigidly connects the actuator power unit to the valve.

HTML clipboardLinear Characteristic*: An inherent flow characteristic that can be repreChapter 1. Introduction to Control Valves 5 sented by a straight line on a rectangular plot of flow coefficient (Cv) versus rated travel. Therefore equal increments of travel provide equal increments of flow coefficient, Cv (figure 1-2). Loop: (See Closed Loop.) Loop Gain: The combined gain of all the components in the loop when viewed in series around the loop. Sometimes referred to as open-loop gain. It must be clearly specified whether referring to the static loop gain or the dynamic loop gain at some frequency.

Manual Control: (See Open Loop.) Open Loop: The condition where the interconnection of process control components is interrupted such that information from the process variable is no longer fed back to the controller set point so that corrections to the process variable are no longer provided. This is typically accomplished by placing the controller in the manual operating position. Packing: A part of the valve assembly used to seal against leakage around the valve disk or stem. Positioner*: A position controller (servomechanism) that is mechanically connected to a moving part of a final control element or its actuator and that automatically adjusts its output to the actuator to maintain a desired position in proportion to the input signal. Process: All the combined elements in the control loop, except the controller. The process typically includes the control valve assembly, the pressure vessel or heat exchanger that is being controlled, as well as sensors, pumps, and transmitters.

Process Gain: The ratio of the change in the controlled process variable to a corresponding change in the output of the controller. Process Variability: A precise statistical measure of how tightly the process is being controlled about the set point. Process variability is defined in percent as typically (2s/m), where m is the set point or mean value of the measured process variable and s is the standard deviation of the process variable. Quick Opening Characteristic*:

An inherent flow characteristic in which a maximum flow coefficient is achieved with minimal closure member travel (figure 1-2). Relay: A device that acts as a power amplifier. It takes an electrical, pneumatic, or mechanical input signal and produces an output of a large volume flow of air or hydraulic fluid to the actuator. The relay can be an internal component of the positioner or a separate valve accessory. Resolution: The minimum possible change in input required to produce a detectable change in the output when no reversal of the input takes place.

Resolution is typically expressed as a percent of the input span. Response Time: Usually measured by a parameter that includes both dead time and time constant. (See T63, Dead Time, and Time Constant.) When applied to the valve, it includes the entire valve assembly. Second-Order: A term that refers to the dynamic relationship between the input and output of a device. A second- order system or device is one that has two energy storage devices that can transfer kinetic and potential energy back and forth between themselves, thus introducing the possibility of oscillatory behavior and overshoot. Sensor: A device that senses the value of the process variable and provides a corresponding output signal to a transmitter. The sensor can be an integral part of the transmitter, or it may be a separate component. Chapter 1. Introduction to Control Valves 6 Set Point: A reference value representing the desired value of the process variable being controlled. Shaft

Wind-Up: A phenomenon where one end of a valve shaft turns and the other does not. This typically occurs in rotary style valves where the actuator is connected to the valve closure member by a relatively long shaft. While seal friction in the valve holds one end of the shaft in place, rotation of the shaft at the actuator end is absorbed by twisting of the shaft until the actuator input transmits enough force to overcome the friction. Sizing (Valve): A systematic procedure designed to ensure the correct valve capacity for a set of specified process conditions. Stiction: (See Friction.) T63 (Tee-63): A measure of device response. It is measured by applying a small (usually 1-5%) step input to the system. T63 is measured from the time the step input is initiated to the time when the system output reaches 63% of the final steady-state value. It is the combined total of the system Dead Time (Td) and the system Time Constant (t). (See Dead Time and Time Constant.) Time Constant: A time parameter that normally applies to a first-order element. It is the time interval measured from the first detectable response of the system to a small (usually 0.25% - 5%) step input until the system output reaches 63% of its final steady-state value. (See T63.) When applied to an open-loop process, the time constant is usually designated as
(Tau). When applied to a closed-loop system, the time constant is usually designated as λ (Lambda). Transmitter: A device that senses the value of the process variable and transmits a corresponding output signal to the controller for comparison with the set point. Travel*: The movement of the closure member from the closed position to an intermediate or rated full open position. Travel Indicator: A pointer and scale used to externally show the position of the closure member typically with units of opening percent of travel or degrees of rotation. Trim*: The internal components of a valve that modulate the flow of the controlled fluid.

Valve: (See Control Valve Assembly.) Volume Booster: A stand-alone relay is often referred to as a volume booster or simply booster because it boosts, or amplifies, the volume of air supplied to the actuator. (See Relay.) Sliding-Stem Control Valve Terminology The following terminology applies to the physical and operating characteristics of standard sliding-stem control valves with diaphragm or piston actuators. Some of the terms, particularly those pertaining to actuators, are also appropriate for rotary-shaft control valves. Many of the definitions presented are in accordance with ISA S75.05,

Control Valve Terminology, although other popular terms are also included. Additional explanation is provided for some of the more complex terms. Component part names are called out on accompanying figures 1-3 through 1-6. Separate sections follow that define specific rotaryshaft control valve terminology, control valve functions and characteristics terminology, and other process control terminology. Actuator Spring: A spring, or group of springs, enclosed in the yoke or actuator casing that moves the actuator stem in a direction opposite to that created by diaphragm pressure.

HTML clipboardThe controller output (CO) is the input to the valve assembly and the process variable (PV) is the output as shown in figure 1-1. When the term Dead Band is used, it is essential that both the input and output variables are identified, and that any tests to measure dead band be under fully loaded conditions. Dead band is typically expressed as a percent of the input span. Dead Time: The time interval (Td) in which no response of the system is detected following a small (usually 0.25% - 5%) step input.

It is measured from the time the step input is initiated to the first detectable response of the system being tested. Dead Time can apply to a valve assembly or to the entire process. (See T63.) Disk: A valve trim element used to modulate the flow rate with either linear or rotary motion. Can also be referred to as a valve plug or closure member.

Equal Percentage Characteristic*: An inherent flow characteristic that, for equal increments of rated travel, will ideally give equal percentage changes of the flow coefficient (Cv) (figure 1-2). Final Control Element: The device that implements the control strategy determined by the output of the controller. While the final control element can be a damper, a variable speed drive pump, or an on-off switching device, the most common final control element in the process control industries is the control valve assembly. The control valve manipulates a flowing fluid, such as gasses, steam, water, or chemical compounds, to compensate for the load disturbance and keep the regulated process variable as close as possible to the desired set point. First-Order: A term that refers to the dynamic relationship between the input and output of a device. A first-order system or device is one that has only one energy storage device and whose dynamic transient relationship between the input and output is characterized by an exponential behavior. Friction: A force that tends to oppose the relative motion between two surfaces that are in contact with each other. The friction force is a function of the normal force holding these two surfaces together and the characteristic nature of the two surfaces. Friction has two components: static friction and dynamic friction. Static friction is the force that must be overcome before there is any relative motion between the two surfaces. Once relative movement has begun, dynamic friction is the force that must be overcome to maintain the relative motion. Running or sliding friction are colloquial terms that are sometimes used to describe dynamic friction. Stick/slip or “stiction” are colloquial terms that are sometimes used to describe static friction. Static friction is one of the major causes of dead band in a valve assembly. Gain: An all-purpose term that can be used in many situations. In its most general sense, gain is the ratio of the magnitude of the output change of a given system or device to the magnitude of the input change that caused the output change. Gain has two components: static gain and dynamic gain. Static gain is the gain relationship between the input and output and is an indicator of the ease with which the input can initiate a change in the Chapter 1. Introduction to Control Valves 4 Figure 1-2. Inherent Valve Characteristics A3449/IL output when the system or device is in a steady-state condition. Sensitivity is sometimes used to mean static gain. Dynamic gain is the gain relationship between the input and output when the system is in a state of movement or flux. Dynamic gain is a function of frequency or rate of change of the input. Hysteresis*:

The maximum difference in output value for any single input value during a calibration cycle, excluding errors due to dead band. Inherent Characteristic*: The relationship between the flow coefficient and the closure member (disk) travel as it is moved from the closed position to rated travel with constant pressure drop across the valve. Typically these characteristics are plotted on a curve where the horizontal axis is labeled in percent travel and the vertical axis is labeled as percent flow (or Cv) (figure 1-2). Because valve flow is a function of both the valve travel and the pressure drop across the valve, conducting flow characteristic tests at a constant pressure drop provides a systematic way of comparing one valve characteristic design to another. Typical valve characteristics conducted in this manner are named Linear, Equal-Percentage, and Quick Opening (figure 1-2). Inherent Valve Gain: The magnitude ratio of the change in flow through the valve to the change in valve travel under conditions of constant pressure drop. Inherent valve gain is an inherent function of the valve design. It is equal to the slope of the inherent characteristic curve at any travel point and is a function of valve travel. Installed Characteristic*: The relationship between the flow rate and the closure member (disk) travel as it is moved from the closed position to rated travel as the pressure drop across the valve is influenced by the varying process conditions. (See Valve Type and Characterization in Chapter 2 for more details on how the installed characteristic is determined.) Installed Valve Gain: The magnitude ratio of the change in flow through the valve to the change in valve travel under actual process conditions. Installed valve gain is the valve gain relationship that occurs when the valve is installed in a specific system and the pressure drop is allowed to change naturally according to the dictates of the overall system. The installed valve gain is equal to the slope of the installed characteristic curve, and is a function of valve travel.

(See Valve Type and Characterization in Chapter 2 for more details on how the installed gain is determined.) I/P: Shorthand for current-to-pressure (I-to-P). Typically applied to input transducer modules. Linearity*: The closeness to which a curve relating to two variables approximates a straight line. (Linearity also means that the same straight line will apply for both upscale and downscale directions. Thus, dead band as defined above, would typically be considered a non-linearity.)

HTML clipboardWhat Is A Control Valve?

Process plants consist of hundreds, or even thousands, of control loops all networked together to produce a product to be offered for sale. Each of these control loops is designed to keep some important process variable such as pressure, flow, level, temperature, etc. within a required operating range to ensure the quality of the end product. Each of these loops receives and internally creates disturbances that detrimentally affect the process variable, and interaction from other loops in the network provides disturbances that influence the process variable.

To reduce the effect of these load disturbances, sensors and transmitters collect information about the process variable and its relationship to some desired set point. A controller then processes this information and decides what must be done to get the process variable back to where it should be after a load disturbance occurs. When all the measuring, comparing, and calculating are done, some type of final control element must implement the strategy selected by the controller. The most common final control element in the process control industries is the control valve.

The control valve manipulates a flowing fluid, such as gas, steam, water, or chemical compounds, to compensate for the load disturbance and keep the regulated process variable as close as possible to the desired set point. Many people who talk about control valves or valves are really referring to a control valve assembly. The control valve assembly typically consists of the valve body, the internal trim parts, an actuator to provide the motive power to operate the valve, and a variety Chapter 1. Introduction to Control Valves 2 of additional valve accessories, which can include positioners, transducers, supply pressure regulators, manual operators, snubbers, or limit switches. Other chapters of this handbook supply more detail about each of these control valve assembly components. Whether it is called a valve, control valve or a control valve assembly, is not as important as recognizing that the control valve is a critical part of the control loop. It is not accurate to say that the control valve is the most important part of the loop. It is useful to think of a control loop as an instrumentation chain. Like any other chain, the whole chain is only as good as its weakest link. It is important to ensure that the control valve is not the weakest link. Following are definitions for process control, sliding-stem control valve, rotary-shaft control valve, and other control valve functions and characteristics terminology.

NOTE: Definitions with an asterisk (*) are from the ISA Control Valve Terminology draft standard S75.05 dated October, 1996, used with permission. Process Control Terminology Accessory: A device that is mounted on the actuator to complement the actuator’s function and make it a complete operating unit. Examples include positioners, supply pressure regulators, solenoids, and limit switches. Actuator*: A pneumatic, hydraulic, or electrically powered device that supplies force and motion to open or close a valve. Actuator Assembly: An actuator, including all the pertinent accessories that make it a complete operating unit. Backlash: The general name given to a form of dead band that results from a temporary discontinuity between the input and output of a device when the input of the device changes direction. Slack, or looseness of a mechanical connection is a typical example. Capacity* (Valve): The rate of flow through a valve under stated conditions.

Closed Loop: The interconnection of process control components such that information regarding the process variable is continuously fed back to the controller set point to provide continuous, automatic corrections to the process variable. Controller: A device that operates automatically by use of some established algorithm to regulate a controlled variable. The controller input receives information about the status of the process variable and then provides an appropriate output signal to the final control element. Control Loop: (See Closed Loop.) Control Range: The range of valve travel over which a control valve can maintain the installed valve gain between the normalized values of 0.5 and 2.0. Control Valve: (See Control Valve Assembly.) Control Valve Assembly: Includes all components normally mounted on the valve: the valve body assembly, actuator, positioner, air sets, transducers, limit switches, etc. Dead Band: The range through which an input signal can be varied, upon reversal of direction, without initiating an observable change in the output signal. Dead band is the name given to a general phenomenon that can apply to any device. For the valve

Where process applications require control valves which are able to withstand the effects of highly corrosive media Badger RC250 barstock valves are the ideal choice.

The Badger range of valves is available in the UK through liquids handling specialists Pump Engineering, and includes a wide range of options, such as the RC250 model.

The valves are available in a range of materials including, stainless steel, Hastelloy, Monel and titanium and will handle flows from 100 lit/hour up to 8000 lit/hour, at pressures up to 9 Bar. RC250 valves feature; Linear or equal % trims, Hastelloy C and Tantalum trims, Kynar trim Cv’s from 6.0 to 0.05 and metallic trim CV’s from 6.0 to 0.0000018. The valve is available in sizes ¼”, ½”, ¾” and 1” with NPT or wafer style connections and a  choice of Teflon CV rings or REK packing is available. Control options include pneumatic and electric actuators.

The RC250 (807) barstock model is also available in PVDF and  will therefore withstand a wide range of corrosive media occurring in water treatment, chemical feed, pH control, semiconductor and pulp & paper applications. These type of applications could involve aggressive fluids such as; sodium hypochlorite, chlorine dioxide, sulphuric acid, sodium chlorate, ammonium fluoride and hydrochloric acid, all of which can be safely handled by the RC250 PVDF valve

Emerson Process Management announces the release of the Fisher GX 3-way control valve and actuator system.  The new GX 3-way has the ability to accurately control the temperature of water, oils, steam, and other industrial fluids.  Applications include heat exchangers and lubricating skids.

The flow cavity of the GX 3-Way valve body has been engineered to provide stable flow and reduce process variability.  This linear stability is perfectly suited for temperature and pH control applications.  The GX 3-way valve is multi-faceted in its ability to cover both flow mixing (converging) and flow splitting (diverging) applications with no extra parts needed.  Unlike other 3-way valves, it features both side-port and bottom-port common trim.

The GX 3-way valve package addresses the space limitations of the OEM industry.  It meets the requirements of both EN and ASME standards.  In addition, it is available with a complete accessory package, including the FIELDVUE DVC2000 integrated digital valve controller.  The GX 3-way is rugged, reliable, and easy to select.  Internal valve trim is designed to ensure long service life and avoid unnecessary maintenance.