Dump Truck Hydraulic Wet Line Kit Schematics
Engineering diagrams for Petra 2-Line and 3-Line wet line systems — hydraulic piping plus the pneumatic air-shift control circuit. Colour-coded routing, numbered component callouts, and a print-ready PDF.
4-page PDF · hydraulic 2-line, 3-line, pneumatic control, comparison · US Letter landscape · vector, prints clean in black & white
Side-by-Side System Comparison
Both configurations drawn to the same scale, with the difference table below. The only physical change is at the pump return port — everything downstream follows from it.
2-Line Wet Line Kit
Standard configuration for dedicated dump trailers running intermittent raise and lower cycles. The pump return port is plugged and only two hoses are run.
Plugged return port
The return port on the dump pump is sealed with a hex plug — no third hose is run.
Two hoses total
One suction hose (reservoir to pump) plus one pressure hose (pump to cylinder base).
Operating precaution
Disengage the PTO once the body is down. Held oil builds heat if the pump keeps turning.
3-Line Wet Line Kit
Heavy-duty configuration with a dedicated low-pressure return line back to the reservoir, allowing extended operation and longer pump life.
Continuous recirculation
Oil returns to the reservoir whenever the control valve sits in neutral, so the PTO can stay engaged.
Cooler running
Circulating oil back to the reservoir sheds heat instead of trapping it in the pump, supporting extended operation.
3-line sleeve insert
A sleeve fits the pump inlet/return junction to isolate return flow from the suction feed.
Air Control Circuit
How the cab controls reach the hardware: wet tank supply through a pressure protection valve, a cab toggle to the PTO air-shift cylinder, and a 3-position lever to the pump's raise and lower air fittings.
Pressure protection valve
Tees off the wet tank and isolates the wet kit, so an air leak downstream cannot bleed the brake supply.
Two cab valves
A 2-position valve engages the PTO; a separate 3-position valve drives the pump spool for raise, hold, and lower.
Spring-centred to HOLD
The hoist control returns to the centre HOLD position when released, blocking both pump air ports.
Technical Feature Comparison
Specification differences between the two wet line kit configurations.
| Feature / Specification | 2-Line Wet Line Kit | 3-Line Wet Line Kit (Petra Rec.) |
|---|---|---|
| Return line connection | Plugged at the pump body | Un-plugged, 3-line sleeve insert |
| Return flow path | Internal bypass / hold | Direct low-pressure return to reservoir |
| Extended operation | Limited — risk of pump heat | Suited to extended operation |
Need help with your installation?
Petra technicians can help you select the exact PTO, pump, reservoir, and hose assembly for your specific truck chassis.