Real-time maintenance

With its corporate entity Corus Special Strip, Hille & Müller in Düsseldorf has been specialising on cold-rolled steelstrip with nickel-plated, technical or highly-reflective surfaces for years. Unrefined cold-rolled strip is taken as the basis for the refined products. The products HILUMIN, HILAN or HIBRITE are for example processed to become battery cans in the battery industry, fuel pipes in the automotive industry or deion plates for protective switches in the electrical industry.

CMS and RTM initiative
Maintenance is an operational process that has considerably gained importance over the past years. It is becoming an increasingly decisive competitive factor. High machine and plant uptime is expected from the persons in charge. Maintenance decisively contributes to value retention and increase in value of plants and infrastructure. It considerably influences the plant uptime and productivity and effectively increases the operating result.
In view of the constantly increasing interconnectedness of maintenance within the company, with machine and plant builders as well as with external service providers, knowledge and information management as well as the management of interfaces and partners are becoming more and more important. Downtime is to be minimised, strict cost management to be implemented and product quality to be ensured.
The company looked into these approaches before the start of the project, searching for a holistic approach for monitoring of the most important machine components and aggregates and for signalling of unplanned failures or maintenance requirement in due time.

Project approach and application examples
By means of an optimisation concept, the maintenance strategy was subdivided into reactive, preventive and condition-based measures based on the failure characteristics of the respective machines and equipment. After the general overhaul of the skin pass mill WD 68 this system was chosen as pilot project. The selection of the below components was carried out based on certain evaluation criteria taking into account risks and potentials.

Diagnostic electronics used
By means of the diagnostic electronics VSE001 it is possible to continuously and simultaneously analyse and evaluate the measured signals of up to 4 vibration sensors with the octavis technology. Pre-alarm and alarm are electrically signalled via switching outputs. The trend can be electrically signalled via the analogue output. The diagnostic electronics save 2000 values. Using the Ethernet interface the decentralised diagnosis can also be integrated into higher-level systems. Due to the compatibility of the data (OPC) the diagnostic values can be easily integrated into all usual visualisation environments and can be made accessible to remote diagnosis within the framework of teleservice concepts.
The accelerometer VSA001 serves for measured data acquisition for the octavis diagnostic electronics type VSE001. The special analogue output ensures the correct transmission of high-frequency vibration signals over distances of up to 30 m. The compact and robust design provides good long-term stability even under adverse environmental conditions. Due to the use of silicon technology the sensor is both long-term stable and temperature independent.

Project approach and application examples
In the first project stage the possibilities of octavis for the monitoring of rotating parts were quickly identified, and so the stripping roller component in the reducing mill WR63 was integrated into the concept. A component which frequently fails, due to the permanent influence of emulsions. In case of a failure, the rolling characteristics of the rollers as regards the rolling material are no longer ensured. Result: a blocking stripping roller which causes stress marks on the material surface. This leads to a reduced quality and consequently to the reject of an entire coil.

Condition monitoring system
The lifetime of the component is about 3 to 4 weeks. Currently, the maintenance activity is a preparatory action with the possibility of replacing the stripping roller componentin about 20-30 min. during a coil replacement. Due to the continuous monitoring with octavis connected to the RTM system, the maintenance message is sent by e-mail in due time, about 2 hours before the unplanned production interruption.

Real-time maintenance
RTM operates in real time. Sensors and controllers constantly monitor the physical measured variables that depend on the degree of wear, such as vibration, temperature, pressure, tightening torque or volumetric flow. When a limit value is exceeded, pre-alarm or main alarm as well as a corresponding maintenance rule are triggered.
The maintenance rules are individually adapted to the equipment. When a limit value is exceeded, maintenance messages / orders are triggered accordingly. The messages are transmitted to the maintenance staff by e-mail. The corresponding workflow can be specifically adapted to the company's requirements.
With these positive findings, measured values from data blocks of S7 controllers, such as for example current, rotational speed and position as well as the data of a laser for controlling the material surface were integrated as significant measured variables in a next step. Here as well, already existing important data are transmitted into the RTM via the OPC server as an open data interface and are stored there with limit values.
For the maintenance staff at Hille & Müller it was important to reach a planning stage so that the maintenance measure could be carried out in due time with the right material, the appropriate staff and at the right time.

Real-time maintenance - online& remote
The project, with the aspect of quality assurance by means of the early detection of wear to rolling element bearings and the early signalling by the RTM system to the maintenance staff, amortiseditself within one year. The RTM is configured so that further components, facilities such as fans, pumps etc. can be independently integrated by the own maintenance staff in the future, allowing further savings.