Creating value added with Condition-based maintenance

Creating value added with Condition-based maintenance

April 2012

By Josef Schindler, Siemens Industry

A change in maintenance solution trends results in significant value added increases in production. Condition-based maintenance makes a sustained contribution to boosting productivity through increased plant availability. This is based on innovative diagnostics mechanisms that continuously update plant-wide centralized information hubs with diagnostics data, so you can carry out the right maintenance measure at precisely the right time – a leap forward in boosting maintenance efficiency in automated production plants.

Value added through maintenance
The production systems of the western industrial nations were leaned down on a massive scale in the 1990s. Productivity differences of up to 40% became apparent between Japan – where the Toyota production system with the KAIZEN  Philosophy started back in 1950 – and Europe/US [1]. Value added chains were then consistently examined for activities that did not create value (waste), inventories were reduced, throughput times shortened, and response capability increased. System solutions for a detailed overview of the entire supply chain became necessary. Just-in-time production and lean thinking [2] were the buzzwords on everyone's lips.

Waste in value added chains

  • Repairs / faults
  • Inventories
  • Waiting times
  • Transport
  • Over-production
  • Journey times
  • Space / area

For technological reasons, maintenance technology in automated plants was unable to keep pace. Sensors for the necessary device diagnostics were not available or were too expensive for widespread use. Diagnostics standards, too, have only in the last few years reached the necessary maturity for plant-wide, vendor-independent overall concepts. Regular preventive maintenance and extensive spare parts management were therefore the mantra for minimizing plant downtimes as much as possible.

Preventive maintenance increases availability
Both fault-correcting and preventive strategies are much in use today. They increase the availability of an automated plant and thus make a contribution to higher value added. The important thing is to remove occurring faults quickly and efficiently, and to minimize future fault potential so that the production process is only interrupted as briefly as possible. However, if it is possible through preventive measures to stop a fault happening in the first place, the economic damage is significantly less since a standstill does not occur.

Maintenance work carried out at regular intervals helps in the following cases, for example:

  • Oil loss
  • Loose screws
  • Dirty machinery
  • Defective tools
  • Vibration
  • Swarf waste/transport
  • Unsuitable workholders
  • Maintenance faults
  • Wear limits exceeded
  • Overheated motors
  • Motor noise
  • Overflowing oil tanks
  • and many more

Figure 1. Reduces costs and increases plant availability: Just-in-time maintenance

Just-in-time maintenance reduces costs by up to 20%
The trend towards condition-based maintenance was only made possible by improved diagnostics options and integration of the diagnostics into the overall systems. Automated systems that enable plant-wide status diagnostics have only become available recently. Condition-based, predictive maintenance avoids downtimes, offers the fastest possible response options, and thus boosts plant availability. This also increases the value added in production systems since plant downtimes are reduced and wasteful preventive maintenance activities (often up to 20% of maintenance costs) become obsolete. Just-in-time maintenance is thus created.

The right maintenance solution makes the difference

The status of the entire automated plant as well as each individual component must be visible at a central information hub. Instead of waiting for a fault to occur, preventive measures can be initiated from there as soon as atypical behaviour, such as wear and tear, is detected. This holistic system optimally supports reactive, preventive and condition-based maintenance strategies for each individual plant and each case, and must comply with cross-vendor standards. Universal data availability from the field level to the enterprise asset management system is also a necessity. Both the central HMI at this information hub and the direct proximity to the plant make it possible to take suitable measures at the right time while keeping overhead as low as possible.

Figure 2. Increased productivity thanks to centralized information hub for maintenance
The discrete world has learned from process automation
Plant Asset Management (PAM) is the jargon for the functionality of supporting maintenance processes at the SCADA level. Some manufacturers already offer solutions for this, especially in classic process automation sectors. Oil & gas, refineries, and the chemical industry are in the lead here with more than 50% of global PAM sales. The solutions here are by no means restricted to the core process or to the process automation system alone. Incoming goods logistics, material preparation and pre-processing, and the outbound areas of filling, packaging, etc., are just as relevant for maintenance, and they are, of course, operated by discrete systems. Why shouldn't discrete manufacturing processes profit from this productivity boost, too? The discrete world has learned from process automation here. In widely used bus systems like Profibus and Profinet, diagnostics mechanisms are already standardized so that status monitoring and maintenance-relevant information are available in more heterogeneous environments. In addition, discrete automation components increasingly possess diagnostics capabilities.

Increase value added with the Simatic Maintenance Station
With the Simatic Maintenance Station, Siemens offers a maintenance system needed to cover requirements both for continuous and discrete productions processes. The Simatic Maintenance Station, based optionally on the established process visualization system Simatic WinCC or the Simatic PCS7 process control system, is the central information hub for plant-level diagnostics and maintenance.

Figure 3. Maintenance at the right time, and fast response to faults thanks to centralized diagnostics and maintenance information in the Simatic Maintenance Station.
It can be used to carry out centrally managed, condition-based diagnostics and maintenance and use existing plant projects without additional configuring overhead. The solution not only enables increased value added, it can also be conveniently integrated into existing systems.

Advantages of the Simatic Maintenance Stations at a glance:
  • Support for condition-based maintenance through plant-wide diagnostics
  • Use of existing project data, no additional engineering overhead
  • Support for vendor-independent standards and integration across all Siemens automation components (e.g. Ethernet, Profinet, Profibus, AS-i, HART, etc.)
  • One central solution for continuous and discrete automated production processes
  • Unique identification and status display of all connected devices ensures short response times
  • Operating and monitoring integrated into one system

In automated plants, the migration from cyclic preventive maintenance to just-in-time servicing with the help of condition-based maintenance systems is in full swing. Similar to energy-saving light bulbs, investments in diagnostics-enabled components pay off within a very short time. The components are easy to integrate into the Simatic Maintenance Station.