WORKSHOP: Having looked previously at adding a load-sensing system to a tractor with a closed-centre hydraulics (profi 09/2024), we now turn our attention to open-centre fixed gear pump tractors.
Some five years ago, Cornelius Effing wanted to solve a problem when the family farm needed to use a slurry tanker fitted with a load sensing control with tractors with fixed gear pump open-centre hydraulics. As a Master Fitter with German hydraulic and mechanical engineering company WHM Wesseler, he was perhaps better placed than most to come up with a solution. Now farm proven, the system he came up with is being offered as a plug in kit. It is possible to come up with a simple solution for some fixed gear pump hydraulic tractors. Simply switch a load sensing spool to a constant oil flow by removing the load sensing LS line. The problem with this simple dodge is that there is a risk of generating too much heat in the hydraulic system, with potential losses in power and efficiency.
To get around the problem, Cornelius Effing, with the support of mechanical engineer Martin Mekes and company owner Guido Wesseler, developed a ‘plug and play’ adapter chest that simulates a load-sensing closed centre system.
How it works
A tractor with load-sensing hydraulics will typically operate with a standby pressure of around 20 bar. This pressure in the P (pressure) line is needed to enable a speedy response for a request for oil as a spool is operated. Inside the load-sensing (LS) block of the kit, this requisite standby pressure is built up through a logic valve so the system is ‘primed’ and ready. To minimise energy consumption, the LS chest is set to a standby pressure of 11 bar, surplus flow from the tractors fixed gear pump remaining free to return to the oil reservoir via the low pressure return line.
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