1、BRITISH STANDARD BS ISO 12238:2001 Pneumatic fluid power Directional control valves Measurement of shifting time ICS 23.100.50 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBS ISO 12238:2001 This British Standard, having been prepared under the direction of the Engineering Se
2、ctor Committee, was published under the authority of the Standards Committee and comes into effect on 15 September 2001 BSI 08-2001 ISBN 0 580 37769 5 National foreword This British Standard reproduces verbatim ISO 12238:2001 and implements it as the UK national standard. The UK participation in its
3、 preparation was entrusted to Technical Committee MCE/18, Fluid power systems and components, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or Eu
4、ropean publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the ne
5、cessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee
6、any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page pages ii to v, a
7、blank page, pages 1 to 12, an inside back cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsINTERNATIONAL STANDARD ISO 12238 First edition 2001-07-15 Reference number ISO 12
8、238:2001(E) Pneumatic fluid power Directional control valves Measurement of shifting time Transmissions pneumatiques Distributeurs de commande directionnels Mesure du temps de commutationii ISO 12238:2001(E) iii Contents Page 1 Scope . 1 2 Normative references . 1 3 Terms and definitions 1 4 Symbols
9、 and units 2 5 Test equipment . 2 6 Test accuracy 7 7 Test procedure 7 8 Data calculations 8 9 Reporting of test data . 8 10 Identification statement (reference to this International Standard) . 8 Annexes A Terms and definitions on switching characteristics taken from other international, regional a
10、nd national standards 9 A.1 From ISO 5598:1985 . 9 A.2 From CETOP RP111P - 1989-11-01 9 A.3 From JIS B8375-1981 . 10 A.4 From ANSI/(NFPA) T3.21.8-1990 . 10 B Example of generated test data and values to be reported 11 Bibliography. 12ISO 12238:2001(E) iv Foreword ISO (the International Organization
11、for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has t
12、he right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Interna
13、tional Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the memb
14、er bodies casting a vote. Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. International Standard ISO 12238 was prepared by Technical Co
15、mmittee ISO/TC 131, Fluid power systems, Subcommittee SC 5, Control products and components. Annexes A and B of this International Standard are for information only.ISO 12238:2001(E) v Introduction In pneumatic fluid power systems, power is transmitted and controlled through a gas under pressure cir
16、culating within a circuit. In some applications, the designer of a fluid power system needs to know the time required to cause the valving elements in a pneumatic directional control valve to move and to generate an output signal.INTERNATIONAL STANDARD ISO 12238:2001(E) 1 Pneumatic fluid power Direc
17、tional control valves Measurement of shifting time 1 Scope This International Standard specifies test procedures for measuring the shifting times of electrically- or pneumatically-operated directional control valves and moving-part logic elements, establishes a definition for shifting time, and is i
18、ntended to improve the application of pneumatic fluid power by providing users and manufacturers of pneumatic valves with a standardized test procedure for measuring the shifting time it defines. 2 Normative references The following normative documents contain provisions which, through reference in
19、this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the
20、most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 1000, SI units and recommendations for the use of their
21、 multiples and of certain other units. ISO 1219-1:1991, Fluid power systems and components Graphic symbols and circuit diagrams Part 1: Graphic symbols. ISO 5598:1985, Fluid power systems and components Vocabulary. ISO 6358:1989, Pneumatic fluid power Components using compressible fluids Determinati
22、on of flow-rate characteristics. 3 Terms and definitions For the purposes of this International Standard, the terms and definitions given in ISO 5598 and the following apply. 3.1 shifting time time lapse measured from a change in the control signal (electrical or pneumatic) until the time at which t
23、he pressure in the associated outlet port changes by between specified pressure levels, with only a pressure transducer connected to the outlet NOTE This definition is very similar to that of “dead time” in ISO 5598:1985, 4.0.7.1.1 and 4.0.7.1.2. The only difference between the two definitions is th
24、e specification of the outlet pressure change. Many national standards, as well as ISO 5598, give additional (and sometimes conflicting) definitions for other terms related to the shifting characteristics of valves. A number of these are given in annex A. 10 %ISO 12238:2001(E) 2 3.2 shifting on-time
25、 shifting time when the control signal is applied 3.3 shifting off-time shifting time when the control signal is removed 4 Symbols and units 4.1 The symbols and units for parameters used in this International Standard shall be as given in Table 1. 4.2 Graphic symbols used in this International Stand
26、ard conform to the requirements of ISO 1219-1. 5 Test equipment 5.1 Basic test equipment The basic test equipment shall be as shown in Figures 1 and 2. 5.2 Pressure measuring tubes 5.2.1 A straight pressure measuring tube shall be made to thread into the valve inlet port, as well as into the valve p
27、ilot port when applicable, and shall be made in accordance with 5.5 of ISO 6358:1989. 5.2.2 Select and attach pressure measuring tubes to the test valve whose threads correspond to each port size of the valve flow path, and to the valve pilot port when applicable. Table 1 Symbols and units Symbol Pa
28、rameter Unit (in accordance with ISO 1000) Inside diameter of pressure measuring tube Supply reservoir pressure ( ) a Control pressure () Base for time measurement Exhaust shifting time Fill shifting time Supply reservoir temperature a ;. d mm p 1 kPa bar p 3 kPa bar t o ms t E ms t F ms 1 C 1 bar =
29、 10 5 Pa = 100 kPa = 0,1 MPa 1 Pa = 1N/m 2ISO 12238:2001(E) 3 Key 1 Control signal 2 Pressure transducers 3 Output recording device(s) 4 Valve under test 5 Pressure measuring tube in accordance with ISO 6358 6 Shut-off valve (optional) 7 Thermometer 8 Supply reservoir Figure 1 Test equipment for ele
30、ctrically-operated valvesISO 12238:2001(E) 4 Key 1 Control valve 2 Control pressure transducer 3 Pressure transducers 4 Output recording device(s) 5 Valve under test 6 Pressure measuring tube in accordance with ISO 6358 7 Shut-off valve (optional) 8 Thermometer 9 Supply reservoir Figure 2 Test equip
31、ment for pneumatically-operated valvesISO 12238:2001(E) 5 5.3 Pressure transducers 5.3.1 Install a pressure transducer directly into each outlet port to be tested, as well as into the inlet pressure measuring tube. 5.3.2 When a pneumatically-operated valve is tested, mount the control pressure trans
32、ducer into the pilot pressure measuring tube. 5.3.3 Use pressure transducers, amplifiers and recording devices that together have a system frequency response of within at and a reference time to a known base resolvable to less than . 5.3.4 Changes in the shifting time caused by limitation of the neg
33、ative voltage peaks due to the test equipment should not exceed . 5.4 Supply reservoir 5.4.1 Use a supply reservoir of sufficient capacity so that the pressure drop in the flow tube during the test does not exceed of the supply pressure. A larger pressure drop is permissible but will increase the sh
34、ifting time and result in a less favourable rating for the product under test. Connections from the supply reservoir should be several times larger than the pressure measuring tube and as short as possible, to minimize the pressure drop. 5.4.2 Use a supply reservoir that provides for measuring of th
35、e internal air temperature of the reservoir. 5.4.3 Locate the optional shut-off valve, and the control valve when applicable, as close as possible to the reservoir outlet. Use a valve whose flow area is larger than that of the pressure measuring tube, because a smaller valve can restrict flow and in
36、crease shifting time. 5.5 Control signal 5.5.1 For solenoid pilot-operated valves (see Figure 1), maintain pilot supply pressure at either the pressure supplied to the valve or the maximum rated pilot supply pressure, whichever is less. 5.5.2 For a.c. solenoid-operated valves, generate the control s
37、ignal with a trigger device set to trigger at the zero voltage crossover point. Maintain voltage to within of the rated voltage. 5.5.3 For d.c. solenoid-operated valves, maintain steady-state voltage to within of the rated voltage. 5.5.4 For pneumatically-operated valves (see Figure 2), maintain the
38、 pilot pressure at the same pressure as in the supply reservoir or at the maximum permitted pilot pressure, whichever is less. 5.6 Data recording system During a test run, record the pressure variations with time for all transducers in the system. Figure 3 gives examples of how data from an analogue
39、 recorder would appear. Other data recording techniques, including digital methods, whi chdon otp ro du ced atainth i sf o rm ,m a yb eus ed . 3,0 dB 2 000 Hz 0,1 ms 0,1 ms 3% 5% 5%ISO 12238:2001(E) 6 Key 1 Control d.c. solenoid (V) 2 Control a.c. solenoid (V) 3 Control Pressure pilot ( ) 4 Control
40、Vented pilot ( ) 5 Percent of supply pressure a b maximum recommended drop c Fill test d Exhaust test e Time Figure 3 Typical data record generated from an analog recorder kPa bar kPa bar p 1 3% (ms)ISO 12238:2001(E) 7 6 Test accuracy Test conditions shall be maintained and data obtained within the
41、accuracy limits given in Table 2. 7 Test procedure 7.1 Set up the test circuit as shown in Figure 1 or, when appropriate, Figure 2, with components as specified in clause 5. 7.2 The fill and exhaust test time for each outlet port shall be measured based on the operation capabilities of the valve, ei
42、ther shifting on-time or shifting off-time. The following data shall be recorded: the fill time from inlet to each outlet port, and the exhaust time from each outlet to exhaust port. Additional data on other possible flow paths through the valve (for example, two inlets for dual pressure valves) may
43、 also be recorded. 7.3 The fill test time shall be determined as follows. 7.3.1 Maintain supply reservoir pressure at a gauge pressure of ( ) or at the maximum rated pressure, whichever is less. 7.3.2 Vent the outlet port under test to atmosphere. 7.3.3 Maintain the supply reservoir temperature betw
44、een and . 7.3.4 Perform several preliminary valve shifts by energizing or de-energizing the solenoid on electrically-operated valves, or by operating the control valve to pressurize or depressurize the pilot control mechanism on pneumatically- operated valves. 7.3.5 Perform three test runs for each
45、flow path, venting the outlet port each time and waiting at least before performing the next test run, to ensure temperature stabilization. 7.4 The exhaust test time shall be determined as follows. 7.4.1 Charge the outlet port under test to a gauge pressure of ( ) or to the maximum rated pressure, w
46、hichever is less. 7.4.2 Maintain the supply reservoir temperature between and . 7.4.3 Perform several preliminary valve shifts by energizing or de-energizing the solenoid on electrically-operated valves, or by operating the control valve to pressurize or depressurize the pilot control mechanism on p
47、neumatically- operated valves. 7.4.4 Perform three test runs for each flow path, pressurizing the outlet port each time and waiting at least before performing the next test run, to ensure temperature stabilization. 7.5 Testing to measure exhaust and fill testing may be combined to run in sequence. T
48、able 2 Test accuracy parameters Parameter of measuring instrument Permissible systematic error Pressure ( ) Temperature Time 10 kPa 0,1 bar 2 C 0,4 ms 630 kPa 6,3 bar 18 C3 0 C 1 min 630 kPa 6,3 bar 18 C3 0 C 1 minISO 12238:2001(E) 8 8 Data calculations 8.1 For electrically-operated valves, establis
49、h the time base ( ) as the point at which a definite change in the voltage is noted (see Figure 3). 8.2 For pneumatically-operated valves, establish the time base ( ) as the point at which a change in pilot pressure is noted (see Figure 3). 8.3 Measure the time to fill from to the point at which the pressure reaches of its supply reservoir pressure value for each test run of an outlet port. Determine the average of the data from the several test runs for each outlet port; this is the fill shifting tim
