Technical information

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Technical Information 7

Radar Tank Gauge

Note! The behaviour in case of the measuring range being

exceeded can be freely set: the default setting is a current of

22 mA and the generation of a digital warning (E681).

Tank Installation

Tank Installations

The Radar Tank Gaugeis equipped with functions to

suppress interference echoes. The user can activate

these functions. They ensure that interference echoes

(i.e. from edges and weld seams) are not interpreted as

level echo.

• Avoid any installations (1), like limit switches,

temperature sensors, etc., inside the signal beam.

• It is essential that HiHi alarm is below the blocking

distance (BD) and the safety distance (SD).

• Symmetrical installations (2), e.g. vacuum rings,

heating coils, baffles, etc., can also interfere with the

measurement.

Gauge orientation

• Recommended distance (1) wall - outer edge of

nozzle:: ~1/6 of tank diameter.

• Not in the centre (3), interference can cause signal

loss.

• Not above the fill stream (4).

• It is recommended to use a weather protection cover

(2) in order to protect the transmitter from direct sun

or rain. Assembly and disassembly is simply done by

means of a tension clamp.

Optimisation options

• Antenna size: the bigger the antenna, the smaller

the beam angle, the less interference echoes.

• Mapping: the measurement can be optimized by

means of electronic suppression of interference

echoes.

• Antenna alignment.

• Stilling well: a stilling well can always be used to

avoid interference. The 7532 RTG with planar

antenna is recommended for stilling wells with a

diameter DN150 (6”) and larger.

• Metallic screens (3) mounted at a slope spread the

radar signals and can, therefore, reduce interference

echoes.

Please contact Varec for further information.

Note! The 7500 Series Radar Tank Gauge 7532 RTG is

designed for level measurement in stilling wells only!

Caution! Make sure that only one tank wall (not two tank

walls) is directly hit by the radar beam!

Mounting in manway

The parabolic antenna can be mounted on a manway

cover. The manway cover must have an opening with a

diameter D1 or D2 for mounting of the antenna. It has

to be possible to remove the cover in order to mount the

antenna. Please consider the maximum height of the

nozzle (H max. = 200 mm/8") for the diameter of the

basis.

Mounting in a stilling well

• The stilling well should be constructed from metal

(no enamel coating, plastic on request) with a

constant diameter.

• When using a 7532 RTG, an increase of the pipe

diameter from DN150 to DN200 / DN200 to DN250

/ DN250 to DN300 is acceptable. A larger step-

width for the increase of the pipe diameter (e.g.

DN150 to DN300) is possible if the upper part of the

pipe has a suitable length. The length of the stilling

well enlargement must be kept. In this case, the

upper end of the pipe must have a minimum length

of 0.5 m (20“) before the diameter increases. If the

length is less than L, please contact Varec in order to

determine a suitable antenna adapter (separable

antenna horn). Ideally, a sample hatch is used.

• Any rectangular increase of the pipe diameter has to

be avoided.

• Welding seam as smooth as possible and on the

same axis as the slots.

• Slots offset 180° (not 90°).

• Slot width respectively diameter of holes max. 1/10

of pipe diameter, de-burred. Length and number do

not have any influence on the measurement.

• Maximum gap allowed between the antenna/horn

and the inside of the stilling well is 5 mm (3/16").

• At any transition (e.g. when using a ball valve or

mending pipe segments), no gap may be created

exceeding 1 mm (0.04").

• The stilling well must be smooth on the inside

(average roughness Rz ≤ 6.3 μm). Use extruded or

parallel welded stainless steel pipe. An extension of

the pipe is possible with welded flanges or pipe

sleeves. Flange and pipe have to be properly aligned

at the inside.