Electronic pressure-independent characterised control valve EPIV

Transcription

1 Electronic pressure-independent characterised control valve Table of contents The electronic characterised control valve () Project planning 4 Selection and dimensioning 5 Constant flow volume V 5 Valve design 5 Verification of the differential pressure 6 Design on missing hydraulic data 6 Flow characteristic curves 6 Dimensional diagram for EV DN Application 8 Media 8 Medium temperature 8 Dimensional diagram for EV DN Application 9 Media 9 Medium temperature 9 P5- en Subject to changes /

2 The electronic characterised control valve () Structure Nominal diameter DN 5-50 Nominal diameter DN Control ball valve (Leakage rate A according to EN 66-) Air bubble-tight sealing control device ensures absolutely sealed shut-off at zero load and thus reliably prevents activation losses. Measuring pipe with volumetric flow sensor Optimally adapted to the requirements of the ultrasonic flow measurement field of application 3. Drive Drive specially optimized for pressure-independent flow control Mode of operation The actuator consists of three components: control ball valve, measuring pipe with volumetric flow sensor and the drive. The set maximum flow (V max) is allocated to the maximum actuation signal (typically V / 0%). The actuator can be either communicative or analogue. The medium is detected by the sensor in the measuring pipe and is applied as the flow value. The measured value is compared with the setpoint (analogous to actuation signal or requirement via bus communication). The drive corrects the deviation by changing the valve position. The angle of rotation α varies according to the differential pressure through the actuation element. V p < p < p3 p3 p V p α Transfer response of the heat exchanger Depending on the construction type, temperature spread, medium and hydraulic circuit, the power Q 'is not proportional to the water volume flow V (Graph ). In classical temperature control, it is attempted to keep the actuation signal Y proportional to the power Q' (Graph ). This is achieved by means of an equal-percentage valve characteristic curve (Graph 3). Q V 3 Y V For applications with linear transfer behaviour (a-value ~) the flow characteristic of the can be changed from equal percentage to linear. / P5- en Subject to changes

3 The electronic control ball valve () (continuation) Control characteristics The velocity of the medium is measured in the measuring component (sensor electronics) and converted to a flow rate signal. The actuation signal Y corresponds to the power Q via the exchanger. The volumetric flow is controlled in the. The actuation signal Y is converted into an equal-percentage volumetric flow characteristic curve and provided with the max value as the new reference variable w. The momentary control deviation forms the actuation signal Y for the drive. The specially configured control parameters in connection with the precise flow rate sensor ensure a stable quality of control. It is however not suitable for rapid control processes, i.e. for domestic water control. U5 displays the measured volumetric flow as voltage (factory setting). As an alternative, U5 can be used for displaying the valve opening angle. Y A ) D A U5 D ) w PP/MP D A DN k V V max Y M P5- en Subject to changes 3 /

4 Project planning Relevant information Dimensions Pipeline clearances -way version Flow direction Water quality Dirt filter Design water system Shut-off devices Definitions The data, information and limit values listed on the electronic pressure independent control ball valves () data sheets are to be taken into account and/or complied with, respectively. EP..R+MP (DN 5 50 with standard drive) EP..R+KMP (DN 5 50 with electrical emergency actuation function) EP..R+MOD (DN 5 50 with modbus drive) P6..W..E-MP (DN with standard drive) P6..W..EV-KBAC (DN with electrical emergency actuation function) P6..W..E-MOD (DN with modbus drive) The dimensions of the drive combination used depend on the design and nominal diameter used. The dimensions are listed on the data sheets. The minimum clearances between the pipelines and the walls and ceilings required for project planning depend not only on the valve dimensions but also on the version. The dimensions can be found on the corresponding data sheet. -way s are throttle devices. The installation in the return flow is recommended. This leads to lower thermal loads on the fitting. The specified flow direction must be observed. The water quality requirements specified in VDI 035 must be adhered to. The is a control device. So that the control task can be taken over in the long term, central dirt filters are recommended in the system. Application is permitted only in closed water circuits. Care must be taken to ensure that sufficient numbers of shut-off devices are installed. V nom is the maximum possible flow. V max is the maximum flow rate which has been set with the greatest actuation signal, for example, V. V max can be set between 30% and 0% of V nom (DN 5 50). V max can be set between 45% and 0% of V nom (DN 65 50). V min 0% cannot be varied. V [m 3 /h] 0% V nom 30% V max 0 Y [V] 0% 4 / P5- en Subject to changes

5 Design and dimensioning A conventional (pressure-dependent) valve is designed based on the kv value. For a given nominal flow, this is dependent on the differential pressure which is present across the valve. In order to obtain a sufficient quality of control, the valve authority Pv must also be taken into account for pressure-dependent valves. For a pressure-independent solution, such as the, the design is greatly simplified. Due to the automatic adjustment of flow deviations, the always provides the required water quantity even with differential pressure fluctuations and during partial load operation. Due to this dynamic adjustment, the valve authority amounts to. Constant flow volume V' Due to the permanent comparison of the measured flow value with the target value and the corresponding automatic readjustment of the valve opening position, a constant, pressureindependent water quantity is ensured over a large differential pressure range. 50 V [l/min] V max = nominal flow V nom (catalogue value) Control requirement 0% (for example V) p [kpa] Pressure-independent flow over a large differential pressure range due to dynamic balancing (Example EP040R+MP) Valve design The valve is determined using the maximum flow rate required V max. A calculation of the kvs value is not required. The required system specific maximum flow V max must lie within the permissible setting range of the DN 5 50: V max = 30 0% of V nom (data sheet value) DN 65 50: V max = 45 0% of V nom (data sheet value) During commissioning, the desired system-specific flow rate value V'max is set on the valve using the ZTH EU actuator device, software PC tool or via bus V [l/min] V max = nominal flow V nom (catalogue value) Control requirement 0% (for example V) V max = 50% V nom (setting) Control requirement 0% (for example V) p [kpa] System specific setting of the maximum flow V max (Example EP040R+MP) Verification of the differential pressure For proper operation, the differential pressure across the valve must lie within a defined range. P5- en Subject to changes 5 /

6 Design and dimensioning (Continued) Minimum differential pressure (minimum pressure drop) The minimum required differential pressure (pressure drop across the valve) to reach the desired volumetric flow V'max can be calculated using the theoretical kvs value (see data sheet) and the formula below. The calculated value is dependent on the required maximum volumetric flow V max. Higher differential pressures are compensated for automatically by the valve. Formula: p min = 0 x V max k vs theor. p min : kpa V max : m 3 /h k vs theor. : m 3 /h Example (DN.5 with the desired maximum flow = 50% V nom ) EP05R+MP kvs theor. = 8.6 m 3 /h V nom = 69 l/min 50% * 69 l/min = 34.5 l/min =.07 m 3 /h p min = 0 x V max k vs theor..07 m = 0 x 3 /h = 6 kpa 8.6 m 3 /h Maximum differential pressure Higher differential pressures across the valve are compensated for automatically by this. A movement of the closing body in the direction of the closing point causes an increase in the pressure drop across the valve. This ensures a constant water quantity The permitted maximum differential pressure is specified on the data sheet. Design on missing hydraulic data Flow characteristics If no hydraulic data are available, then the same valve DN can be selected as the heat exchanger nominal diameter. In the case of an electronic pressure-independent control ball valve, the actuation signal requirement corresponds directly to a flow value. The offers various setting options with which the characteristic curve can be influenced: Characteristics of the characteristic curve equal percentage optimized with a characteristic curve factor n(gl) = 3., in the opening range(*) (factory setting) linear Operating range Y DC... V (factory setting) Starting point DC V / Ending point DC V Adjustable flow rate V max DN5 50: % of V nom DN 65 50: % of V nom Factory setting V`max = 0% of V nom Inverting actuation signal no (factory setting) yes (*) The course is linear in the lower opening range between 0 30% stroke. This ensures outstanding control characteristics, including in the lower partial load range. Flow rate curve (factory setting) 6 / P5- en Subject to changes

7 Design and dimensioning (Continued) V [l/min] V max (= 0% V nom) 0 Y [V] Flow rate curve - settings: V max reduced V [l/min] V max V max (= 70% V nom) 0 Y [V] Flow rate curve - setting: linear characteristic Operating range V V [l/min] V max (= 0% V nom) 0 Y [V] P5- en Subject to changes 7 /

8 Dimensional diagram for DN 5 DN 50 Application Media Medium temperatures This actuator is used in closed cold and hot water systems for continuous water-side control of air handling units and heating systems. Cold and hot water, water with glycol up to max. 50% vol. The permissible medium temperatures can be found in the corresponding data sheets. V 0 [m 3 /h] pv0 [kpa] pv0 [bar] DN 5 DN 0 DN 5 DN 3 DN 40 DN V 0 [l/s] p min Minimum differential pressure required for pressure-independent operation p max Maximum permissible differential pressure for a long service life of the valve p max (low noise) Maximum permissible differential pressure for low noise operation p v0 Differential pressure with ball valve full open. V 0 Nominal flow at p v0 Formula k vs k v = V 0 p v0 0 k vs [m 3 /h] V 0 [m 3 /h] p v0 [kpa] 8 / P5- en Subject to changes

9 Dimensional diagram for DN Application Media Medium temperatures This actuator is used in closed cold and hot water systems for continuous water-side control of air handling units and heating systems. Cold and hot water, water with glycol up to max. 50% vol. The permissible medium temperatures can be found in the corresponding data sheets. V 0 [m 3 /h] pv0 [kpa] pv0 [bar] DN 65 DN 80 DN 0 DN 5 DN 50 V 0 [l/s] p max Minimum differential pressure required for pressure-independent operation p max Maximum permissible differential pressure for a long service life of the valve p v0 Differential pressure with ball valve full open. V 0 Nominal flow at p v0 Formula k vs k v = V 0 p v0 0 k vs [m 3 /h] V 0 [m 3 /h] p v0 [kpa] P5- en Subject to changes 9 /

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