BRONKHORST®
Page 36
EL-FLOW
Base
Series Mass Flow Controllers
9.17.061
4.2 Using other gasses than specified
Each instrument has been calibrated and adjusted for customer process conditions.
Controllers or valves may not operate correctly, if process conditions vary too much, because of the
restriction of the orifice in the valve.
For flowmeters performance and accuracy may be affected tremendously if physical fluid properties
such as heat capacity and viscosity change due to changing process conditions.
Check chapter 1.7, “Operating Principles”, for detailed information about the sensor principle.
4.2.1 Software for conversion factor calculation
Bronkhorst® gathered the physical properties of over 600 fluids in a database called FLUIDAT.
Application software, such as FLOW CALCULATIONS, enables the user to calculate accurate conversion
factors, not only at 20°C/1 atm but at any temperature/pressure combination, both for gases and for
liquids.
Apply to your distributor for more details of this software.
Check FLUIDAT® on http://www.fluidat.com
FLUIDAT® is a collection of routines to calculate physical properties of gases and liquids. These routines
are made available at the FLUIDAT® on the Net website.
4.2.2 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
4,50
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
3,50 x 10
-1
40
30
30
30
30
30
30
30
24
12
8
6
5
3,6
5
30
20
20
20
20
20
20
20
15
8
5
n.a.
n.a.
n.a
n.a..
For pilot operated valves the maximum pressure drop is limited to 20 bard. If the pressure drop during
start-up is higher, it is preferred 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.
