Siemens 7ML5431 - Orientation in a Vessel with Obstructions; Mounting on a Stillpipe or Bypass Pipe

Installing/mounting
4.3 Proper mounting
SITRANS LR250 with mA/HART
32 Operating Instructions, 10/2019, A5E32220602-AG
4.3.3 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 33).
①
Polarization axis
②
Polarization reference point
③
Display
4.3.4 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 175)
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 (Page 189),
Raised-Face Flange per EN 1092-1 (Page 224), Flanged encapsulated dimensions
(Page 198)or Hygienic encapsulated dimensions (Page 202).
● One continuous length of metallic pipe is preferred, without joints.
● Any false reflections created by joints/welds/imperfections will lead to inaccuracies of the
measurement.
● Joints (if unavoidable) must be machined to ± 0.25 mm (± 0.010") and must have welded
connecting sleeve on the outside.
● If using any hygienic process connections in conjunction with a stillpipe/bypass, please
ensure that the antenna/lens are cleanable in accordance with the applicable approval.
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")
Hygienic 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.