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Hydraulic Circuit Quiries and Pressure Sensors

Good day everybody.

I have a 4 x 4 Mercedes tractor rigged with a Hiab 100AWV loader crane & a Rotzler hydraulic winch. It was professionally built in Sweden to be used in the powerline construction industry. With an estimated weight of 6 to 7 tons and a crane reach of about 11 meters

It has a twin pump that runs from the tractor PTO, one pump feeds the loader crane circuit and the other feeds the winch and outrigger circuit.

The crane, winch and outriggers all function.

The winch/outrigger circuit has a mechanical over pressure valve between the feed and return, located directly after the inline high pressure filter. The return discharges directly into the tank.

The crane circuit has two pipes going back to the tank. One from the crane valve block discharging through a magnetic filter mounted on the tank (like a 'normal' return circuit). The other, is a T off from the pressure side directly after the inline high pressure filter discharging through a solenoid valve fitted to the tank.

Each of the four outriggers is fitted with a XMJ-A160 pressure sensor. Each sensor (each with 2 wires) is wired back to a common junction box.

Other connections going into this common junction box are;
Power in from dashboard (fused)
Power out to winch control
Power out to solenoid valve mounted on tank

Within the junction box are block connectors and a contact switch and a small inline resistor and an earth connection.
Some wires are cut and some are disconnected. Also there is evidence of insect infestation.

Can anybody help me with the following questions;

Why is there a T off on the pressure feed side of the crane circuit going directly to the solenoid valve on the tank?

What action/fault would trigger the mechanical pressure valve on the winch/outrigger circuit?

What is the function of the pressure sensors on each of the out riggers? Where are they sending a signal and why?

If the outrigger sensors are sending a signal to the solenoid valve on the tank how would I rewire the junction box? (The solenoid valve being the only thing I can think of that may be related to their function!)

Any advise would be much appreciated.

Thank You

I have posted a link to a hydraulic circuit sketch I did but not sure if it works.

Parents
  • Thanks for reaching out. I consulted one of our engineers and he recommends for the correct and official answers for the system design that you should address the questions to the company that rebuilt your system or to HIAB directly, however he hadsome answers to the questions you ask that reflect commonly used solutions. 

    1. Why is there a T off on the pressure feed side of the crane circuit going directly to the solenoid valve on the tank?
      => Generally a solenoid operated manifold between Pump and Tank are used as a Bypass valve as a secondary override for system safety function.
    2. What action/fault would trigger the mechanical pressure valve on the winch/outrigger circuit?
      => I will assume that the mechanical pressure valve will protect the maximum pressure as well as the maximum torque on the pump shaft to the Tractor PTO (Power Take Off).
    3. What is the function of the pressure sensors on each of the out riggers? Where are they sending a signal and why?
      => I will assume that the pressure sensor are attached to the main Boom cylinder, and will act as an overload protection for your vehicle. (prevent a tip over) High pressure will open the by-pass valve.
Reply
  • Thanks for reaching out. I consulted one of our engineers and he recommends for the correct and official answers for the system design that you should address the questions to the company that rebuilt your system or to HIAB directly, however he hadsome answers to the questions you ask that reflect commonly used solutions. 

    1. Why is there a T off on the pressure feed side of the crane circuit going directly to the solenoid valve on the tank?
      => Generally a solenoid operated manifold between Pump and Tank are used as a Bypass valve as a secondary override for system safety function.
    2. What action/fault would trigger the mechanical pressure valve on the winch/outrigger circuit?
      => I will assume that the mechanical pressure valve will protect the maximum pressure as well as the maximum torque on the pump shaft to the Tractor PTO (Power Take Off).
    3. What is the function of the pressure sensors on each of the out riggers? Where are they sending a signal and why?
      => I will assume that the pressure sensor are attached to the main Boom cylinder, and will act as an overload protection for your vehicle. (prevent a tip over) High pressure will open the by-pass valve.
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