IEC 60534-2-4 pdf download – Industrial-process control valves – Part 2-4: Flow capacity – Inherent flow characteristics and rangeability

IEC 60534-2-4 pdf download – Industrial-process control valves – Part 2-4: Flow capacity – Inherent flow characteristics and rangeability
1 Scope
This part of IEC 60534 applies to all types of industrial-process control valves. It defines how to state typical control valve inherent flow characteristics and inherent rangeabilities. It also defines how to establish criteria for adherence to manufacturer-stated flow characteristics.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition or the referenced document (including any amendments) applies.
IEC 60534-1 :2005, Industrial-process control valves – Part 1: Control valve terminology and general considerations
IEC 60534-2-3, Industrial-process control valves – Part 2-3: Flow capacity – Test procedures
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60534-1 and the
following apply.
3.1
flow coefficient
(see IEC 60534-1 , 4.6)
3.2
rated flow coefficient
(see IEC 60534-1 , 4.6.3)
3.3
relative flow coefficient ( Φ )
Φ 0 is the relative flow coefficient at 0 % relative travel
[IEC 60534-1 , 4.9 modified]
3.4
travel
(see IEC 60534-1 , 4.5.2)
3.5
rated travel
(see IEC 60534-1 , 4.5.3)
3.6
relative travel (h)
(see IEC 60534-1 , 4.5.4)
3.7
nominal slope
slope of the best fit line
for an ideal inherent linear flow characteristic, the nominal slope is: m
with m=”
-Po
for an ideal inherent equal percentage flow characteristic, the nominal slope is: n
with n = log
3.8
inherent flow characteristic(see lEC 60534-1，4.9)
3.8.1
ideal inherent linear flow characteristic(see lEC 60534-1，4.9.1)
3.8.2
ideal inherent equal percentage flow characteristic(see lEC 60534-1,4.9.2)
3.9
inherent rangeability
ratio of the largest flow coefficient(max) to the smallest flow coefficient ( min) within whichthe deviation from the stated inherent flow characteristic does not exceed the allowable
deviation stated in Clause 7
[IEC60534-1,4.11 modified]
4Symbols
Table 1 gives an overview of the symbols used in this standard.
5 Typical inherent flow characteristics
The typical inherent flow characteristics and the values of n, m and for a specific size, typeand trim configuration of a control valve shall be stated by the manufacturer either graphicallyor in tabular form.
When tabulated, specific flow coefficients shall be stated for the following travel positions: at5%，10 %，20 %， and every subsequent 10 % of rated travel up to and including 100 % (seeFigures 1 and 2).
The manufacturer may publish flow coefficients in addition to those at the above stated travelpositions.
ln addition，the manufacturer is encouraged to specify the generic name of a specific flowcharacteristic,such as “linear” or “equal percentage”, if applicable，following the terms anddefinitions of IEC 60534-1.
The manufacturer shall state the largest flow coefficient that meets the criteria of Clause 7, ifit is less than the rated flow coefficient (see Figures 1 and 2).