Gen3 - Installation - Generic Main Pressure Sensor Installation
The hydraulic pressure sensors are used to measure the lifting load of the telehandler.
There are two main pressure sensors that need to be mounted to measure the pressure in the
main lift cylinder - Main Head and Main Rod.
Main Head Pressure
The main head pressure sensor measures the pressure in the base of the cylinder. This is the
pressure that is holding the load.
The main lift cylinder has a counterbalance valve attached to the cylinder. The
counterbalance valve is responsible for holding the pressure in the head of the cylinder
so that the boom does not fall when the machine is turned off (and pressure from the
hydraulic motor is no longer applied).
The main head pressure sensor must measure the pressure between the counterbalance
valve and the base of the cylinder, as shown in the hydraulic diagram below. It can not
be placed on the head inlet port of the counterbalance valve.
If hydraulic pressure in the head of the cylinder is lost or escapes the boom will fall,
which is why telehandler designers make it difficult to access the pressure between the
counterbalance valve and head of the cylinder. However there are a number of options
available.
Some counterbalance valves bolt directly onto the cylinder and have ports installed
which have been blanked off. If the counterbalance valve has a port which is connected
to the head of the cylinder, the head pressure sensor can be installed directly into the
counterbalance valve (if thread of the port is G 1/4 matching the thread of the pressure
sensor). If the threads do not match an adapter can be used.
If there are no ports available on the bolt on counterbalance valve, then a hydraulic
manifold block may be able to be installed between the cylinder and the counterbalance
valve. We have a range of manifold blocks that suit common types of the Oil Control
counterbalance valves or one can be manufactured by a machining company.
If the counterbalance valve is welded to the boom or a manifold block, it will not fit between
the cylinder and the counterbalance valve. A port may be able to be drilled into the
counterbalance valve. Before drilling obtain a mechanical drawing of the counterbalance
valve to determine the correct location to drill to ensure the pressure is being measured
on the head of the cylinder. When drilling into the counterbalance valve you want to
avoid the swarf flowing into the hydraulic lines as this can damaged the hydraulic hoses.
After installing the manifold block move the boom through it's
angular range of motion and ensure the pressure sensors or
the counterbalance valve to not get damaged.
Main Rod Pressure
The main rod pressure sensor measures the pressure in the rod or piston side of the cylinder.
This is the pressure acting against the head pressure in the cylinder.
Since the rod pressure does not get locked behind the counterbalance valve, the rod
pressure sensor can be placed anywhere between the hydraulic spool valves and rod of
the cylinder, as shown in the hydraulic diagram below.
This makes it easier to install the rod pressure sensor. If a manifold block was used for
the head pressure sensor it can probably be used for the rod pressure sensor as well.
Otherwise hydraulic tee joints can be supplied which can be installed on the rod inlet on
the counterbalance valve, we have a range of hydraulic tee joints which may fit the thread specification (or a hydraulic supply company could supply the right connection).
Once the pressure sensors are installed connect the supplied 4 pin 4 metre cable to the
M12 screw lock connector at the rear of each pressure sensor.
Finally, the pressure sensor cables will be connected into the CPIM.
An EQSS Gen 3 system also uses another two hydraulic sensors - Compensation Head and Compensation Rod, but these are not discussed in this article.
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