Siemens SITRANS P DS III - Page 22

SITRANS P DS III/P410 (7MF4.33.. 7MF4.34.. 7MF4.35..)
20 A5E03434626-04, 05/2015
When taking measurements in a closed container with strong condensate formation, you must fill the negative pressure line
(mostly with the condensate of the measured medium) and install a condensate pot. You can cut off the device using the
dual pneumatic block 7MF9001-2.
Measurement assembly on a closed container (strong condensate formation)
Formula:
Start
-of-scale value:
Δp
MA
= g · (h
U
· ρ- h
V
· ρ')
Full
-scale value:
Δp
MA
= g · (h
O
· ρ- h
V
· ρ')
h
U
Lower filling level
Δp
MA
Start of scale value
h
O
Upper filling level
Δp
ME
Full-scale value
h
V
Gland distance
ρ
Density of the measured medium in the container
p
Pressure
ρ
'
Density of fluid in the negative pressure line
corresponds to the prevailing temperature there
g
Acceleration due to gravity
The process connection on the negative side is a female thread
1
/
4
-18 NPT or an oval flange.
Lay the line for the negative pressure using a seamless steel tube 12 mm x 1.5 mm.
4
Connecting
4.1
Basic safety instructions
WARNING
Unsuitable cables and/or cable glands
Danger of explosion in hazardous areas.
• Only use suitable cables and cable glands complying with the requirements specified in Chapter "Technical data
(Page 36)".
• Tighten the cable glands in accordance with the torques specified in Chapter "Technical data (Page 36)".
• When replacing cable glands use only cable glands of the same type.
•
After installation check that the cables are seated firmly.
WARNING
Hazardous contact voltage in versions with 4-conductor extension
Danger of electrocution in case of incorrect connection.
•
Observe the instructions in the 4-conductor extension operating manual for the electrical connection.