1、Control Valve TerminologyApproved 17 February 2005ANSI/ISA75.05.012000 (R2005)AMERICAN NATIONAL STANDARDISA The Instrumentation,Systems, andAutomation Society TMANSI/ISA-75.05.01-2000 (R2005) Control Valve Terminology ISBN: 1-55617-741-0 Copyright 2005 by ISA The Instrumentation, Systems, and Automa
2、tion Society. All rights reserved. Not for resale. Printed in the United States of America. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means (electronic mechanical, photocopying, recording, or otherwise), without the prior writte
3、n permission of the Publisher. ISA 67 Alexander Drive P.O. Box 12277 Research Triangle Park, North Carolina 27709 -3- ANSI/ISA-75.05.01-2000 (R2005) Preface This preface, as well as all footnotes and annexes, is included for information purposes and is not part of ANSI/ISA-75.05.01-2000 (R2005). Thi
4、s document has been prepared as part of the service of ISAThe Instrumentation, Systems, and Automation Societytoward a goal of uniformity in the field of instrumentation. To be of real value, this document should not be static but should be subject to periodic review. Toward this end, the Society we
5、lcomes all comments and criticisms and asks that they be addressed to the Secretary, Standards and Practices Board; ISA; 67 Alexander Drive; P. O. Box 12277; Research Triangle Park, NC 27709; Telephone (919) 549-8411; Fax (919) 549-8288; E-mail: standardsisa.org. The ISA Standards and Practices Depa
6、rtment is aware of the growing need for attention to the metric system of units in general, and the International System of Units (SI) in particular, in the preparation of instrumentation standards. The Department is further aware of the benefits to USA users of ISA standards of incorporating suitab
7、le references to the SI (and the metric system) in their business and professional dealings with other countries. Toward this end, this Department will endeavor to introduce SI-acceptable metric units in all new and revised standards, recommended practices, and technical reports to the greatest exte
8、nt possible. Standard for Use of the International System of Units (SI): The Modern Metric System, published by the American Society for Testing the second stage is the collapse or implosion of these cavities back into an all-liquid state as the fluid decelerates and static pressure is recovered. 3.
9、30 characterized cam: a component in a valve positioner used to relate the closure member position to the control signal. 3.31 characterized trim: control valve trim that provides defined flow characteristics, such as equal percentage, linear or quick opening, usually stated in terms of CVor KVversu
10、s travel. 3.32 choked flow: a condition wherein the flow rate through a restriction does not increase when the downstream pressure is decreased at a fixed inlet pressure. ANSI/ISA-75.05.01-2000 (R2005) -18- 3.33 class: a convenient round number used to designate allowable pressure/temperature rating
11、s for valves and pipe fittings using arbitrary class numbers from tables developed by ASME and ISO for a variety of materials. 3.34 clearance flow: that flow below the minimum controllable flow with the closure member not seated. 3.35 closure member: the movable part of the valve that is positioned
12、in the flow path to modulate the rate of flow through the valve. 3.36 closure member configurations: 3.36.1 characterized: closure member with contoured surface, such as the “vee plug,“ to provide desired flow characteristics. 3.36.2 cylindrical: a cylindrical closure member with a flow passage thro
13、ugh it (or a partial cylinder). 3.36.3 eccentric rotary plug: closure member face of a rotary motion valve that is not concentric with the shaft centerline and moves into seat when closing. 3.36.4 eccentric spherical disk: the disk is a spherical segment in a rotary motion valve that is not concentr
14、ic with the disk shaft and moves into the seat when closing. 3.36.5 linear: a closure member that moves in a line perpendicular to the seating plane. 3.36.6 rotary: a closure member that is rotated into or away from a seat to modulate flow. 3.36.7 tapered: closure member is tapered and may be lifted
15、 from seating surface before rotating to close or open. 3.37 cold working pressure: the maximum pressure rating of a valve or fitting coincident with ambient temperature, generally in the range from -29 C to +38 C (-20 F to +100 F). 3.38 compressor: the device, in a weir-type or sleeve (pinch) valve
16、, that the valve stem forces against the backside of the diaphragm or sleeve to cause the diaphragm or sleeve to move and seal against the internal flow passageway of the valve body. 3.39 control signal override device: a device that overrides the control signal to the valve actuator, e.g., solenoid
17、 valves, lock-up valves, bypass valves, etc. 3.40 control valve: a power actuated device that modifies the fluid flow rate in a process control system. It consists of a valve connected to an actuator mechanism (including all related accessories) that is capable of changing the position of a closure
18、member in the valve in response to a signal from the controlling system. 19 ANSI/ISA-75.05.01-2000 (R2005) 3.41 control valve gain: the change in the flow rate as a function of the change in valve travel. It is the slope of the installed flow characteristic curve. 3.42 cracked flow: a nonstandard te
19、rm. See “clearance flow.“ 3.43 cycling life: a number of cycles over which a device will operate without changing its performance beyond tolerance. 3.44 CWP: see “cold working pressure.” 3.45 dashpot: a less preferred term. See “snubber.“ 3.46 data plate: a less preferred term. See “nameplate.“ 3.47
20、 dead band, control valve: the range through which a control valves input signal may be varied, upon reversal of direction, without initiating an observable change in the position of the closure member. 3.48 dead end shut off: a nonstandard term used to refer to control valve leakage. Refer to ANSI/
21、FCI 70-2 for specification of leakage classifications. 3.49 diaphragm valve: see “weir-type body.“ 3.50 direct acting valve: a valve that travels to the closed position when the signal increases. 3.51 disk: a circular shaped closure member used to modify the flow rate with either linear or rotary mo
22、tion. 3.52 disk valve: a valve with a closure member consisting of a disk that moves with a rotary or linear motion against a stationary disk, each disk having flow passages through it. 3.53 downstream seating: seating assisted by pressure differential across the closure member in the closed positio
23、n, moving the closure member slightly downstream into tighter contact with the seat ring seal that is supported by the body. 3.54 drift: an undesired change in the output/input relationship over a period of time. 3.55 drip tight: a nonstandard term used to refer to control valve leakage. Refer to AN
24、SI/FCI 70-2 for specification of leakage classifications. 3.56 drop tight: a nonstandard term used to refer to control valve leakage. Refer to ANSI/FCI 70-2 for specification of leakage classifications. ANSI/ISA-75.05.01-2000 (R2005) -20- 3.57 dual sealing valve: a valve that uses a resilient seatin
25、g material for the primary seal and a metal-to-metal seat for a secondary seal. 3.58 dynamic unbalance: the net force/torque produced on the valve stem/shaft by fluid pressure acting on the closure member and stem/shaft at stated travel and flowing conditions. 3.59 end connection: the configuration
26、provided to make a connection with the pipe. 3.59.1 flanged: valve end connections incorporating flanges that mate with corresponding flanges on the piping. 3.59.2 split clamp: valve end connections of various proprietary designs using split clamps to apply gasket or mating surface loading. 3.59.3 t
27、hreaded: valve end connections incorporating threads, either male or female. 3.59.4 welded: valve end connections that have been prepared for welding to the line pipe or other fittings. May be butt weld (BWE), or socket weld (SWE). 3.60 end-to-end dimension: a nonstandard control valve term. See “fa
28、ce-to-face dimension.“ 3.61 environment: ambient conditions (including temperature, pressure, humidity, radioactivity, and corrosiveness of the atmosphere) surrounding the valve and actuator. Also, the mechanical and seismic vibration transmitted through the piping or heat radiated toward the actuat
29、or from the valve body. 3.62 erosion-resistant trim: valve trim that has been designed with special surface materials or geometry to resist the erosive effects of the fluid flow. 3.63 extension bonnet: a bonnet with a packing box that is extended above the usual height so as to maintain the temperat
30、ure of the packing within its operating limits. 3.64 face-to-face dimension: the dimension from the face of the inlet opening to the face of the outlet opening of a valve. 3.65 flange facing: the finish on the end connection that mates with gasket surfaces. 3.66 failure mode: the position to which t
31、he valve closure member moves when the actuating energy source fails. 3.66.1 fail-closed: a condition wherein the valve closure member moves to a closed position when the actuating energy source fails. 21 ANSI/ISA-75.05.01-2000 (R2005) 3.66.2 fail-in-place: a condition wherein the valve closure memb
32、er stays in its last position when the actuating energy source fails. 3.66.3 fail-open: a condition wherein the valve closure member moves to an open position when the actuating energy source fails. 3.66.4 fail-safe: a characteristic of a particular valve and its actuator that upon loss of actuating
33、 energy supply will cause a valve closure member to be fully closed, fully open, or remain in the last position, whichever position is defined as necessary to protect the process. Fail-safe action may involve the use of auxiliary controls connected to the actuator. 3.67 flangeless control valve: a v
34、alve without integral line flanges, that is installed by bolting between companion flanges, with a set of bolts or studs, generally extending through the companion flanges. 3.68 flow characteristic: an indefinite term. (See below “inherent flow“ and “installed flow.“) 3.68.1 equal percentage charact
35、eristic: an inherent flow characteristic that, for equal increments of rated travel, will ideally give equal percentage changes of the flow coefficient (Cvor Kv). 3.68.2 inherent flow characteristic: the relationship between the flow rate and the closure member travel as it is moved from the closed
36、position to rated travel with constant pressure drop across the valve. 3.68.3 installed flow characteristic: the relationship between the flow rate and the closure member travel as it is moved from the closed position to rated travel as the pressure drop across the valve is influenced by the varying
37、 process conditions. 3.68.4 linear characteristic: an inherent flow characteristic that can be represented by a straight line on a rectangular plot of flow coefficient (Cvor Kv) versus rated travel. Therefore, equal increments of travel provide equal increments of flow coefficient (Cvor Kv). 3.68.5
38、modified parabolic characteristic: an inherent flow characteristic that provides equal percent characteristic at low closure member travel and approximately a linear characteristic for upper portions of closure member travel. 3.68.6 quick opening characteristic: an inherent flow characteristic in wh
39、ich a maximum flow coefficient is achieved with minimal closure member travel. 3.69 flow coefficient (CV& KV): a constant related to the geometry of a valve, for a given valve travel, that establishes flow capacity. 3.70 globe valve: a valve with a linear motion closure member whose seal is perpendi
40、cular to the stem motion, one or more ports, and a body distinguished by a globular shaped cavity around the port region. (See Figure 4a.) ANSI/ISA-75.05.01-2000 (R2005) -22- 3.71 guides, closure member: the means by which the closure member is aligned with the seat and held stable throughout its tr
41、avel. The guide is held rigidly in the body, bonnet, and/or bottom flange. 3.72 hand jack: a manual hydraulic or mechanical override device, using a lever, to stroke a valve or to limit its travel. 3.73 handwheel: a mechanical manual override device, using a rotary wheel, to stroke a valve or to lim
42、it its travel. 3.74 hard facing: a material applied to valve internals to resist fluid erosion and/or to reduce the chance of galling between moving parts, particularly at high temperatures. 3.75 hard plating: a thin metal deposit, sometimes electroplated, used to provide a surface coating. Hard pla
43、ting is many orders of magnitude thinner than hard facing. 3.76 hysteresis: the maximum difference in output value for any single input value during a calibration cycle, excluding errors due to dead band. This difference is sometimes called hysteretic error. See ANSI/ISA-51.1-1979 (R1993), Process I
44、nstrumentation Terminology. 3.77 hysteresis plus dead band: the maximum difference for the same input between the upscale and downscale output values during a full range traverse in each direction. This is the summation of hysteresis and dead band. 3.78 identification plate: a less preferred term. S
45、ee “nameplate.“ 3.79 in-line valve: a valve having a closure member that moves to seat axially in the direction of the flow path. In-line valves are normally operated by a fluid energy source but may be operated mechanically. 3.80 integral seat: a flow control orifice and seat that is an integral pa
46、rt of the body. 3.81 integral stem/shaft: a design in which the stem/shaft is an integral part of the closure member. 3.82 jacketed valve: a valve body cast with a double wall or provided with a double wall by welding material around the body so as to form a passage for a heating or cooling medium.
47、Also refers to valves that are enclosed in split metal jackets having internal heat passageways or electric heaters. May be referred to as “steam jacketed“ or “vacuum jacketed.“ In a vacuum-jacketed valve, a vacuum is created in the space between the body and secondary outer wall to reduce the trans
48、fer of heat by convection from the atmosphere to the internal process fluid, usually cryogenic. 3.83 lantern ring: a rigid spacer assembled in the packing box with packing normally above and below it and designed to allow lubrication of the packing or access for a leak-off connection. 3.84 lapping:
49、a process of mating contact surfaces by grinding and/or polishing. 23 ANSI/ISA-75.05.01-2000 (R2005) 3.85 leakage class: classifications established by ANSI/FCI 70-2 to categorize seat leakage allowances for different needs of seat tightness. 3.86 leak-off gland: a packing box with packing above and below the lantern ring so as to provide a collection point for fluid leaking past the primary seal (lower packing). 3.87 lift: a nonstandard term. See “travel.“ 3.88 limit switch: a nonstandard term. See “position switch.“ 3.89 linearity: the closeness to which a curve re
