Over time, wear phenomena occur in every system. However, this normally happens so slowly that it remains unnoticed for a long time. Influencing factors such as operating errors or overloads can cause additional rapid acceleration of the wear process.
To prevent pump damage, and ultimately machine failure, it is necessary to detect the wear as early as possible. Only then is it possible to arrange for the components concerned to be replaced and to avert an unplanned machine stoppage.
Thanks to the monitoring functions, all wear conditions of the hydraulic pump can be detected, which are associated with a change in pump leakage. Pump leakage is a minor leak within the pump. This is also called pump volumetric loss or pump slip (also pump slippage).
The leak exists in every pump, but the degree to which it is pronounced differs from pump to pump. This leads to the fact that at high pressures, part of the pumped flow rate flows back through the pump and therefore reduces efficiency. I.e. the speed increases while the pressure remains the same. In case of continuously high loading of the pump, the leak also increases with time.
With the help of the pump protection functions integrated directly in the converter, the slip speed is determined and adjusted automatically. Here the determined leak in the drive is readjusted until a warning limit is reached and a warning is output. The operating company is informed automatically, that a pump exchange is necessary. The function therefore increases the availability of the pump, prevents stoppage times and increases process quality.
Sensor drift: Inaccuracy of the pressure sensor
A further wear phenomenon occurs at the pressure sensor. The aging is determined as a result of the increasing sensor drift, i.e. an inaccuracy of the sensor. This is due to an offset in the sensor signal, which grows with the age of the sensor and so increasingly distorts the sensor signal.
Like the pump leak, here too, the sensor drift is monitored by a regular comparison routine. The sensor values are then optimized initially. With increasing inaccuracy and exceeding of a limit value, the wear is detected and necessary sensor exchange is indicated.
With the help of the IoT interface, a servo-hydraulics dashboard can be created, which provides real-time information about different states and the capacity utilization of the machine. Data such as motor and oil temperature, speed and pressure, as well as the pump capacity utilization are displayed. The values each correspond to the respective actual variable values.
For example, dry running of the pump is detective due to the lack of a pressure rise when the pump starts up. In addition, the pump protection function detects cable breaks or defective sensors on the basis of the pressure signal and therefore protects the system from overloads in case of failure.
Several protection functions also have the task of not allowing conditions to become critical in the first place. For example, there is an acceleration limit, which protects the pump from speed changes that occur too quickly. The speed set value curves are flattened automatically, before they are implemented by the controller.
The Idle function provides further preventive protection. During pauses, the set values are optimized to achieve pressureless oil circulation and to protect the pump from frequent starts.
The thermal pump protection is particularly interesting. Thermal overload is particularly likely in case of long dwell times during the machine cycle. This increases wear and can lead to premature pump failure. A temperature model is therefore used to calculate the pump’s thermal capacity utilization. If a threshold value is reached, hydraulic bypasses are connected to relieve the pump. The pump is flushed and damage due to overheating is prevented.
In addition, the integrated protection functions also detect massive faults and switch off the drive in an emergency, in order to protect the hydraulic system.
Commissioning made easy
No special knowledge is required to start up the servo-pump. It is only necessary for the pump and volume set value to be preset by the machine control.
A so-called wizard guides the user quickly and easily through the individual steps of the startup process. Detailed specialist servo-pump knowledge is not necessary for the basic startup. Access to a motor and converter database makes the input of individual parameters superfluous. It is only necessary to select a specific motor/converter combination. The step-by-step guide through the program makes it impossible to forget an input.
With the Wizard, the startup can be accelerated and possible errors or faults can be eliminated. That saves time and money.
