5 months ago

MDA Technologies 3/2016

MDA Technologies 3/2016

Description of the

Description of the simulation modules Figure 1 depicts the most relevant components for the simulation. All displayed components are simulated during the lifting process. The drive unit with clutch transfers the power via a transfer gear box to the lower main pump and the upper charge pump. The fluid (red line with arrows indicating flow direction) flows through the proportional valve to the brake-lowering valve module and finally to the hydraulic motor. Inside the brake-lowering module, the brake piston is driven by the load pressure and the multiple disk brake is opened via an integrated brake-discharge unit (2/2 directional valve and pressure reduction valve). The fluid in the hydraulic motor’s return line (blue line with arrows indicating flow direction) flows back via the brake piston towards the proportional valve. Thus, the load in the illustrated control mode remains hydraulically locked by the brake piston during regular operation. In Figure 2, the stop of the diesel engine and the resulting blockage of the hydraulic pumps are simulated by disconnecting the clutch. In this case, the following situations can be observed: n Because of the switched activated proportional valve, the load pressure at the brake-lowering valve remains high and is only slowly reduced through leakage (see measuring point MI-6). n Due to the high pressure, the integrated brake-discharge unit is further charged with pressure and the multiple disk brake stays open. The load is further retained by the brake piston and held on the hydraulic oil column (see measuring point MI-8). n However, by holding the load on the hydraulic oil column, a potential movement cannot be stopped completely. Due to a leakage inside the hydraulic motor, the winch is rotating at a speed that can’t be detected visually. n Without the continuous feeding of hydraulic oil through the feeding pump, the hydraulic motor cannot absorb oil during the creeping rotation and starts to cavitate. This phenomenon can be observed at measuring point MI-9 with the constantly increasing negative pressure and drive speed at the driving wheel. When reaching less than one turn during cavitation, the motor cannot keep holding the load and slips. n Furthermore, the integrated brake-discharge unit needs another 1-3 seconds to activate the multiple disk brakes with the proportional valve in neutral position (ABT connection). In the operational state, “engine stop – pilot valve still electrically operated” a time response of 6 seconds could be measured. Figure 3 shows a realistic comparison between the simulation with Automation Studio and the real measurements at the plant: n Blue line: load pressure to lift the precast element n Turquoise line: absorption of the load by brake pistons with a tendency to slip (cavitation) n Black line: delayed relief of control pressure on multiple disk brakes About Famic Technologies The portfolio of the company Famic Technologies, founded in 1986, includes high-end products and services in the field of software engineering and industrial automation. The well-known software solution Automation Studio was originally developed for training and further education purposes in the field of fluid technology and is used today all through the industry, for systems development and optimization, maintenance, services and training. 01 Simulation of the winch control MEASUREMENT AND CONTROL MDA Technologies 3/2016

02 Engine stop without additional brake-discharge unit 03 Real-time measurement: Engine stop without additional brake-discharge unit 04 Engine stop with additional brake-discharge unit 02 05 Real-time measurement: Engine stop with additional brake-discharge unit 03 04 05 n Green line: under-supply of feeding for the winch motors In order to eliminate critical situations during simulation, an additional brake discharge valve (3/2 directional valve) has been added between the integrated brake discharge valve, the brake-lowering valve unit, and the multiple disk brake. This integration can be seen in figure 4. While disconnecting the engine clutch, the power declines immediately at the valve’s solenoid and the additional brake discharge valve opens the multiple disk brake directly to the tank. Consequently, the lifted load stands still immediately. A reaction time of 50 milliseconds is measured. The simulation illustrates that in spite of the feeding pump’s missing fluid volume (measuring point MI-11) there is no negative pressure at measuring point MI-9. Therefore, the load doesn’t slip and is held safely. The pressure held at measuring point MI-8 between the motor and brake piston resulting from the ascending lifted load is slowly reduced via the leakages before taking effect on the multiple disk brake. Figure 5 shows again a realistic comparison with the real-time measurement. In the operational case “stop by outage of diesel engine”, the multiple disk brakes (black line) are immediately engaged while the load is safely held mechanically and no longer hydraulically held by the piston of the brake-lowering valve. The load and brake pressure is slowly reduced via the leakage. Hence, a safe operation of the winch can be ensured. With Automation Studio, the operational capability of the original design was verified through simulation. Thus, designing a defective set-off without an additional braking valve could be anticipated. Possible injuries to people and property damage could also be prevented. MDA Technologies 3/2016


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