Excessive Load Limitation System
Excessive Load Limitation System (ELLS) Testing
Excessive Load Limit System (ELLS) used on the IMT Telescoping Crane models ensures the
system is currently operable and will not allow the crane to be excessively overloaded.
The purpose of the ELLS is to prohibit the excessive overloading of the crane. It does this by
disarming the functions that make it possible for the operator to apply greater than allowable
stress to the crane structure and components.
The load rating of the crane is determined by the pressure induced in the lower boom cylinder.
The ELLS senses the pressure in the base end of the lower boom cylinder with a normally
closed pressure switch located on the valve block on the top of the cylinder. When the pressure
in the base end of the cylinder exceeds the setting of the pressure switch for that particular
crane, the pressure switch opens and breaks the ground connection for the solenoids that shift
the valve spool on the appropriate functions. Once the ground connection is disengaged, the
solenoids that shift the valve spools for the appropriate functions can not be activated using the
remote control handle. Only those functions that will not increase the load moment of the crane
structure and components will be operable (i.e.- winch down, extension in, lower boom up,
rotation). The operator is able to use “WINCH DOWN” to set the weight down to relieve the
crane and “EXTENSION IN” to bring the load in for a shorter load radius. Either of these two
functions will decrease the load moment of the crane structure and components, thus
decreasing the pressure in the main cylinder.
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