User's Manual

Installing/mounting
4.2 Mounting location
SITRANS LR250 (HART)
20 Operating Instructions, 01/2014, A5E32220602-AB
4.2.3
Orientation in a vessel with obstructions
Polarization reference point
For best results on a vessel with obstructions, or a stillpipe with openings, orient the front or
back of the device toward the obstructions. For an illustration, see Device orientation (Page 21).
①
Polarization axis
②
Polarization reference point
③
Display
4.2.4
Mounting on a Stillpipe or Bypass Pipe
A stillpipe or bypass pipe is used for products with a low dK, or when vortex or extremely
turbulent conditions exist. It can also be used to provide optimum signal conditions on foaming
materials. See Dielectric constant of material measured in Performance (Page 182) for more
information.
● The pipe diameter must be matched with the antenna size. Use the largest antenna size that
will fit the stillpipe/bypass pipe
1)
. See Threaded Horn dimensions or Raised-Face Flange per
EN 1092-1 (Page 208).
● One continuous length of metallic pipe is preferred, without joints. Bad joints create
reflections.
● Joints (if unavoidable) must be machined to ± 0.25 mm (± 0.010") and must have welded
connecting sleeve on the outside.
1)
Mounting in a pipe greater than 100 mm (4") can cause large errors, and therefore is not
recommended.
Suitable pipe diameters:
Horn antenna
40 to 100 mm (1.5 to 4")
PVDF antenna
50 mm (2") only
Flanged encapsulated antenna
50 to 100 mm (2 to 4")
Not recommended:
> 100 mm (4")
Bypass vent:
Required at the upper end of the bypass
1)
1)
To equalize pressure and keep the liquid level in the bypass constant with the liquid level in the
vessel.