Bladder accumulators - like diaphragm, piston or spring accumulators- are hydraulic accumulators. In a hydraulic system, a bladder accumulator ensures volume compensation and energy storage and dampens pulsations.
moneo RTM ensures easy monitoring of bladder accumulators in hydraulic systems. Potential bladder failures or ruptures can be detected early and sudden downtimes of the hydraulic system can be prevented.
Currently, the function of the bladder accumulator is not monitored. Maintenance activities are performed based on a set time interval. No information is available regarding the fatigue life of the bladder. The data of the existing pressure and temperature sensors is not analysed or monitored further.
This is why failures of the accumulator bladder are detected too late or aren’t detected at all. Damage to other system components can occur as a result. If volume compensation through the bladder accumulator is no longer ensured, the hydraulic pump will be subjected to an increased load, which means that it may no longer be possible to guarantee sufficient pressure energy.
The condition monitoring method patented by ifm for this application helps to optimise maintenance and detect impending bladder failures at an early stage.
To detect a bladder failure in time, key parameters of the bladder accumulator must be monitored, such as the number of filling and draining operations. An alarm is to be triggered when a set threshold is exceeded.
The current condition of the bladder can also be detected by permanently measuring the surface temperature at various positions of the bladder accumulator, enabling early detection of a potential bladder failure/rupture.
To achieve condition monitoring of the bladder accumulator, the existing sensors are used and the data and thresholds are visualised and managed in moneoRTM. Additional temperature bolt-on sensors are installed without having to intervene in the system. moneoRTM is installed on an internal server. Using an IO-Link master, all sensor values are transmitted to the internal VLAN and to moneo.
With the help of moneo, it was able to implement condition-based maintenance and ensure the process capability of the hydraulic system. moneoRTM
The visualisation dashboard provides users with a clear view of all relevant bladder accumulator data.
Static thresholds are monitored by two calculated values (for details see section Calculated values).
On the one hand, the number of load changes determined via a calculated value is monitored. The threshold for this can be taken from the manufacturer’s data sheet.
On the other hand, a condition consisting of two measured values is checked using calculated values:
AND
Only if both conditions are true, a bladder rupture is likely and an alarm will be triggered.
Dynamic thresholds (SmartLimitWatcher) provide information about the status of the bladder function. For this, the system pressure is monitored as a target variable. To calculate the dynamic thresholds, the following auxiliary parameters are used:
This function can be used to easily define what should happen after a warning or alarm has been triggered, e.g.:
For applications where regular refilling is necessary, it is advisable to optimise the replenishment process, for example by sending an email notification to a defined group of recipients responsible for the production supply as soon as the specified level in a tank is not reached any more, so as to trigger the refilling process.
Using calculated values, additional information can be generated from measured values.
In the following flow diagram, two measured values are compared. Only if the condition for both measured values is met 1 is output, otherwise 0 is output.
In the following flow diagram, the load changes of a bladder are counted. They are an indicator of bladder wear. The system pressure is monitored and compared to minimum and maximum values. If the maximum pressure is exceeded, the counter is incremented and further incrementing is blocked until the system pressure is below the minimum pressure once.