Etesia HYDRO 124D, Technical Training Manual

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Application to the Hydro 124D
A flow limiter is placed in the grassbox function control valve block. It is placed on the on the
grassbox lifting ram circuit in parallel with a by-pass.
Working on the principle that the oil takes the easiest route (the one that offers the least
resistance), when we direct the flow towards the "large chambers" of the rams, all the flow
(Q
4cc
) passes via the by-pass. On the other hand, when the flow is directed towards the "small
chambers" of the rams, the fluid discharged by the "large chambers" is obliged to pass through
the flow limiter. The flow is then limited to 3.5 l/min. The aim of limiting the flow is to equalise
the time taken to lift and lower the grassbox, but also to prevent it dropping too suddenly.
2.2.4) The safety valves or parachute valves.
Function
This component is used as a safety device on lifting equipment (for example : pods). It detects
sudden increases in flow following, for example, the rupture of a hose. In this case, the flow is
limited and the element comes down slowly. It is mounted on the side of the ram where the oil
is subjected to pressure when the element is lifted. In our case, it is mounted in the filler inlet of
the "large chamber" of the grassbox lifting ram.