Feature Sensors & Sensing Systems Effective management reduces costs
Analysis conducted by Volker Erbe, sensors product manager at Bürkert Fluid Control Systems, has investigated the whole life costs associated with field devices such as sensors, transducers and the control platform to which they are connected
T
he first areas that instinctively spring to mind when a process professional is challenged to reduce process control costs are usually purchase cost and installation - and why not? They are the obvious ones and they are the easiest to define and list. When viewed as part of a system however, purchase cost plays only a small part - managing the mul- tiple signals from sensors and trans- ducers differently can radically affect the total cost of ownership for that process system. Erbe’s analysis has revealed there could be far larger savings to be had from making changes to product selection at the initial stage of a pro- ject - changes that can have huge cost repercussions that occur during the less obvious operational phase - those such as training, start-up, process operator time, service, repairs and documentation. Erbe carried out the research to help define costs more accurately for Bürkert process field devices. He then identified where costs lie within a whole life process application and quantified the results of making better decisions early on in a project (see table below).
sensor-based measurement devices and up to 75% of the TCO are costs in the operational phase which is estimated at 15 years usage time.”
Overall process control costs and the possible cost reduction potential is of course dependent on variables within individual plant set-up, including the size in terms of I/O, building size, dis- tances and the kind and complexity of processes and sub-processes involved. Environmental conditions such as high temperatures, high pressures, etc. and the kind of medium, for example aggressive, dangerous or difficult fluids or gasses of any kind, plus other special conditions such as process security demands, standardisation and norms, plus certificates all play a part. In addi- tion, there are often key local priorities, conditions and resources such as edu- cation and the level of redundancy required that need to be considered. In each of the different areas of cost however, there is a potential for cost reduction. Bürkert concentrated on the effects in relation to a control loop, linking sensors and transducers (flow, temperature, level, pH etc.) in a mea- surement and control (e.g. PID) loop with positioners and valves. Bürkert ran several simulations and also drew
around 17% of the initial cost - less than the cost of training when dealing with new equipment.
Other items Bürkert took into consid- eration included support from both internal and external sources and installation - both mechanical and elec- trical, including wiring of all external hardware for comms and power, plus commissioning and start-up costs, including all necessary documentation for plant, instruments and wiring.
Analysis of initial costs
It is not until you reach this level of analysis that you start to see a pattern forming in the peripheral activities, and then start to appreciate the hidden costs. Only then do you begin looking to specify a solution that reduces indi- rect costs, knowing that the saving can be significant when compared to the initial purchase cost of the devices themselves (see chart above).
Operational Costs
Bürkert defined operational costs as recurring activities, including ongoing hardware and software management (replacement, updates, upgrades, extensions) production monitoring and control, maintenance, service and repair, any enhancement carried out during the life of the product, addi- tional documentation (online produc- tion data, quality, changes) and then finally, decommissioning including recycling costs (one time costs only).
The initial question Erbe started with was what part do field devices play and what proportion of the cost associated with them can be saved? The quantity of field devices in process applications is increasing almost exponentially, based on a higher level of automation in today’s processes. Bürkert’s figures show that in a typical process application in food, pharma or general industry, about 20% of the overall investment costs are for
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data from a range of real applications in order to reach trustworthy medians in terms of cost.
Initial costs
Planning is a cost which almost always justifies the investment, as does any time taken to specify instruments and equipment. Purchasing has an adminis- trative cost associated with it and Bürkert found that remarkably the equipment itself only accounted for
Analysis of operational costs To be totally accurate you have to analyse your own plant to have a base- line which gives you information about the share of operating costs using your plant figures, identifying which area is of interest for achieving the best results in cost reductions. You can however use Bürkert’s broad analysis to draw some obvious conclu- sions (see chart on page 16).
Article continued on page 18 APRIL 2013 Automation
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