Pepperl+Fuchs Pulscon LTC57, Руководство пользователя, Страница: 23 / 176

Pulscon LTC57 PROFIBUS PA
Mounting
2015
-0
3
23
6.1.3 Notes on the mechanical load of the probe
Tensile load limit of rope probes
Tensile load
Bulk solids exert tensile forces on rope probes whose height increases with:
• the length of the probe, i. e. max. cover
• the bulk density of the product,
• the silo diameter and
• the diameter of the probe rope
Since the tensile forces are also heavily dependent on the viscosity of the product, a higher
safety factor is necessary for highly viscous products and if there is a risk of cornice buildup. In
critical cases it is better to use a 6 mm rope instead of a 4 mm one.
The same forces also act on the silo cover. On a fixed rope, the tensile forces are definitely
greater, but this can not be calculated. Observe the tensile strength of the probes.
Options for reducing the tensile forces:
• Shorten the probe.
• If the maximum tensile load is exceeded, check whether it would be possible to use a non-
contact ultrasonic or level-radar device.
The following diagrams show typical loads for frequently occurring bulk solids as reference
values. The calculation is performed for the following conditions:
• Calculation according to DIN 1055, Part 6 for the cylindrical part of the silo.
• Suspended probe (probe end not fixed at the bottom)
• Free-flowing bulk solid, i. e. mass flow. A calculation for core flow is not possible. In the
event of collapsing cornices, considerably higher loads can occur.
• The specification for tensile forces contains the safety factor 2 (in addition to the safety
factors already taken into account by DIN 1055), which compensates for the normal
fluctuation range in pourable bulk solids.
Feature "Probe" Probe Tensile load limit [kN] Max. rupture load [kN]
a
a
The ceiling of the silo must be designed to withstand this load.
Option 2, 3 Rope 4 mm (1/6 in) 316 12 20
Option M, Q Rope 6 mm (1/4 in) 316 30 42
Option N, S Rope 6 mm (1/4 in)
PA > Steel
12 20
Option R, T Rope 8 mm (1/3 in)
PA > Steel
30 42
Table 6.1