Rangeability
Rangeability is not clearly defined in regard to PICVs as PICVs hold a pre-setting element as well as a pressure independent element. The pre-setting element is often identical to the regulation element.
Controllability in control valves is related to the pre-setting and regulation element only as the control curves are created under constant differential pressure providing below mathematical reasoning:
Both the FlowCon Essentia, FlowCon Green, FlowCon GreEQ and FlowCon SM ranges hold a 100% linear pre-setting and regulation unit and are – according to IEC 60534 standard – considered holding high control range giving a control range of 1:1000.
Another definition of rangeability, which is more suitable to PICVs as it includes the pressure regulating element, is to consider the rangeability as being the ratio between the highest to the lowest flow that the valve can control without exceeding the specified limits. These limits are defined as a total tolerance, which includes both the mechanical tolerances as well as the valve’s pressure independency and hysteresis and their tolerances.
Removing the pressure related tolerances, by reviewing the valve at a specific ΔP, significantly improves the tolerances. The tolerances based on mechanical tolerances alone are defined as 5% of the minimum adjusted flow rate for the FlowCon Essentia, FlowCon Green and FlowCon GreEQ valves and 2% for the FlowCon SM range.
Another parameter to consider, upon discussing minimum controllable flow, is the actuator resolution as this defines how accurate the valve can be controlled by the actuator. The actuators used for the proposed valves hold a resolution of 1:100 for FN / FNP, FH and FNR actuators used for FlowCon Essentia, FlowCon Green and FlowCon GreEQ ranges and 1:1000 for SM actuators used for FlowCon SM range when using a 0-10V signal.
Note 1: The minimum flow rate is defined as being the smallest flow the valve can control without exceeding the specified limits. For FlowCon SM valves and FlowCon Essentia.0 valves, this value is defined by the mechanical tolerances and not the minimum flow the actuator can modulate to. For FlowCon Essentia.1/.2, FlowCon Green and FlowCon GreEQ, the lowest value is defined by the actuator and not the machanical tolerance.
Model |
Highest Settable Max. Flow |
Lowest Settable Max. Flow |
Minimum Controlled Flow |
Mechanical Tolerance at Lowest Setting |
Rangeability (note 2) |
[l/hr] | [l/hr] | [l/hr] | [l/hr] | [lx:1] | |
FlowCon Essentia.0 | 465 | 35 | 30 | 2 | 15 |
FlowCon Essentia.1 | 1.000 | 105 | 10 | 5 | 100 |
FlowCon Essentia.2 | 1.700 | 150 | 17 | 7 | 100 |
FlowCon Green.0 | 575 | 37 | 6 | 2 | 100 |
FlowCon Green.1 | 1.110 | 64 | 11 | 3 | 100 |
FlowCon Green.1HF | 2.650 | 620 | 27 | 31 | 100 |
FlowCon Green.2 | 4.630 | 865 | 46 | 43 | 100 |
FlowCon Green.3 | 13.647 | 1.900 | 136 | 95 | 100 |
FlowCon GreEQ.0 | 454 | 17 | 5 | 1 | 100 |
FlowCon GreEQ.1 | 805 | 27 | 8 | 1 | 100 |
FlowCon GreEQ.2 | 2.160 | 850 | 22 | 43 | 100 |
FlowCon SM.1.1 | 2.470 | 633 | 3 | 13 | 190 |
FlowCon SM.2.1 | 8.420 | 1.850 | 9 | 37 | 228 |
FlowCon SM.3.0 | 15.000 | 5.310 | 15 | 106 | 141 |
FlowCon SM.3.1 | 27.500 | 9.240 | 28 | 185 | 149 |
FlowCon SM.3.2 | 35.600 | 12.800 | 36 | 256 | 139 |
FlowCon SM.4.1 | 33.800 | 12.600 | 34 | 252 | 134 |
FlowCon SM.4.2 | 51.000 | 17.000 | 51 | 340 | 150 |
FlowCon SM.4.3 | 72.700 | 13.300 | 73 | 266 | 273 |
FlowCon SM.5.1 | 83.800 | 23.300 | 84 | 466 | 180 |
FlowCon SM.5.2 | 106.000 | 25.600 | 106 | 512 | 207 |
FlowCon SM.6.0 | 277.000 | 33.100 | 277 | 662 | 418 |
Turn Down Ratio
Turn down ratio is used to describe the ratio between the maximum and minimum controllable flow in a given system. A product holding a spindle height limitation will result in limitation to its available resources and therefore have a lower turn down ratio than rangeability. E.g. a valve holding a 100:1 rangeability and sized for a specific system to utilize only 40% of its capacity, results in a 40:1 turn down ratio.
The FlowCon Essentia, FlowCon Green and FlowCon GreEQ valves – unlike most other PICVs – do not have any stroke limitation regardless of setpoint as these valves always utilize 100% of its capacity. The turn down ratio is therefore 100:1.
The FlowCon SM range is controlled by rotary actuator motion and holds a very high rangeability. When calculating the FlowCon SM’s turn down ratio, actual degree rotation is divided by the maximum degree rotation. As an example, FlowCon SM.3.1 has a rotation limitation to 1.080° when selected for a max. flow of 11.600 l/hr compared to 2.160° in highest maximum flow settings. This effectively means that the valve’s turn down ratio is 50%3 of its specified rangeability or full capacity or in other words 50:1 for this selected lower flow setting. If lower flow rates are required, it is recommended to select a SM.3.0 instead in order to keep turn down ratio up.
Note 3: 1.080°/2.160° = 50%
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Importance of Control Curves in PICVs
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Rangeability and Turn Down Ratio - Update
Definition and use of Rangebility, Resolution and Turn Down Ratio in FlowCon PICVs
Leakage Classification IEC60534-4 - Update
Article is updated to include FlowCon Essentia. All actuated FlowCon valves are classified according to Int. Standard IEC60534-4, Class IV and V