Overload Protection - Siemens SIWAREX WL270 Operating Instructions Manual

4.4

Overload protection

CAUTION
Irreparable faults and damage to the load cells
When using load cells with small rated loads, always provide overload protection in order to
protect the cells from becoming damaged. This applies both to the measuring direction and
the transverse direction.
If load cells are used beyond the maximum working load or the maximum transverse load,
this can cause irreparable faults and even fracturing of the load cell or the installation unit.
Overload protection in the measuring direction
Load cells can be protected against vertical overload by limiting the measuring path with
stops.
For load cells with high rated loads, the risk of an unintentional overload is not as great.
Possible additional loads can already be taken into consideration during the dimensioning of
the load cells.
Another method for protecting load cells from an overload is to over-dimension the load cells.
Overload protection in the transverse direction
For the CP-S SA load cells, the weight force is introduced into the load cells via bearing
surfaces. Up to a certain degree, these bearing surfaces allow lateral movement of the load
bearing implement or a change in its length as a result of expansion due to heat. They
generate a restoring force corresponding to the deflection, which re-centers the load bearing
implement. This freedom of movement is desired and necessary for accurate weighing.
If the transverse force is so great that it exceeds the restoring force of the load cell (and thus
the deflection limit), then corresponding protective measures are required. Pendulum limiters
or guide elements are suitable for this, for example.
Pendulum limiters must be constructed or set in such a way that the maximum deflection
cannot be exceeded in any direction. This is shown in two examples in the following figure.
Figure 4-2
CP-S SA
Operating Instructions, 04/2009, A5E02522341B
Pendulum limitation with a maximum deflection of 4 mm as exemplified by two weighing
platforms
Application planning
4.4 Overload protection
15