BRONKHORST IN-FLOW, Instruction Manual

Page: 16 / 38

BRONKHORST
®
page 16 9.17.022
1.4.3 Maximum pressure drop
For (pilot) solenoid operated control valves with small orifices the maximum allowable pressure drop for
gases is according to the table.
Diameter [mm] K
v
Normally closed

p max. [bard]
Normally opened

p max. [bard]
0,05
0,07
0,10
0,14
0,20
0,30
0,37
0,50
0,70
1,00
1,30
1,50
1,70
2,00 4,33 x 10
-5
8,48 x 10
-5
1,73 x 10
-4
3,39 x 10
-4
6,93 x 10
-4
1,56 x 10
-3
2,37 x 10
-3
4,33 x 10
-3
8,48 x 10
-3
1,73 x 10
-2
2,93 x 10
-2
3,90 x 10
-2
5,00 x 10
-2
6,63 x 10
-2
40
30
30
30
30
30
30
30
24
12
8
6
5
3,6
30
20
20
20
20
20
20
20
15
8
5
n.a.
n.a.
n.a.
For pilot operated valves the maximum pressure drop is limited to 20 bard. If the the pressure drop during
start-up is higher, it is prefered to install a bypass valve. During start-up this valve should be opened. Also
the minimum pressure drop is limited. For exact figures consult factory or proceed according to the technical
data and/or additional instructions given by the sales office or department.
1.5 Sensors and laminar flow devices
Flow devices are used to determine the total flow rate of a gas flow meter or controller.
Mind that liquid flow sensors, CTA-based sensors and pressure sensors do not require a flow device.
Depending on the application the flow sensors have different removable capillaries, requiring a different
laminar flow device.
Furthermore for flow rates higher than 1250 l
n
/min the main laminar flow device is used in combination with a
capillary / flow device arrangement in order to compensate for the non ideal transfer function of the main
flow device.
In general 3 types of capillary tubes are available:
- Small bore (C-type)
The following notes apply to this type of sensor:
- These sensors have a pressure drop of approx. 35 mbar
- The laminar flow device consists of a stack of discs with precision etched flow channels.
Each flow channel represents approx. 10 ml
n
/min airflow at 35 mbar delta-P.
- In all instruments with a pressure rating above 100 bar (M-type) the sensor is fitted with metal
seals.
- In general instruments with these sensors may be mounted horizontal, as well as in a vertical
position, at low operating pressures. At high pressures (>10 bar) the instruments should be
mounted in a horizontal position.
- The EL-Flow, EL-press metal seal series are fitted with a metal sealed sensor.
- Large bore (D-type)
To this type of sensor the following remarks apply:
- These sensors are preferably used for reactive gases and at low pressure applications.
- The pressure drop is less than 0.5 mbar.
- The laminar flow device forms together with the main channel an annular channel. The dimensions
of this annular channel determine the flow capacity of the instrument.
- The instrument must always be mounted in a horizontal position.
- Medium bore (E-type)
This sensor is used in the “EL-FLOW series” and is used for increasing the flowrange of the “low deltaP
series”. The same remarks as the D-type apply to this sensor, only:
-The pressure drop is approx. 2.5 mbar.