If the diesel engine of a hydraulic vehicle is defective, it usually has to be towed (www.servi.no) . This could cause problems, explains IHA coach Robert Becker: “During the towing process, the traction motor becomes the pump. This has the consequence that oil is conveyed from the low-pressure side to the high-pressure side. The pump stops, it does not turn. That means we have to go somewhere with the oil. “
If users do not meet this problem, “you have very high pressure on the side where the engine feeds in,” says Robert Becker. “The engine has a very high moment, so the vehicle would not move at all. You could not tow it off. The wheels would lock, “explains the IHA test engineer.
Although there are usually high-pressure valves in a closed circuit. “But we do not want to use them like that,” Becker points to concerns and continues: “The valves have another function, a bypass function. This can be used by turning the valves out a bit (https://www.servi.no/produkter/hydraulikk/) . The valves have three functions: First, the overpressure function, where we limit the maximum pressure with the valves at a peak load. The second function is the feed function that allows the feed pump to deliver low pressure through the valves. And then I can also use these valves to generate a bypass by turning the valves out three turns, so please both, so we have a short circuit to both terminals A and B. And if the valves are turned out three turns, then we can tow the vehicle.
With the bypass, the oil can be pumped with relatively little back pressure from the high-pressure side to the low-pressure side. There are only two things to consider, Becker: “Not with a particularly high speed, because we have here concern no feed pressure. The feed pump is not running. And please not for a long time (https://www.servi.no/produkter/pneumatikk-og-vakuum/) . Towing is a difficult term. I would rather say that we pull the vehicle from the road or the field on a low loader and then drive with a low loader to the workshop. If you do this for a long time, the engine sees too much negative pressure, it kavitiert and then it can break. “