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Thirty years in the life of an instrument designer

03 September 2009

Tim Chettle rounds off our special 30th Anniversary issue with his reminiscences as an engineering designer in the field of process instrumentation. It's all a matter of keeping up with change - in the technologies and the people!

Like this magazine, I've been in and associated with design engineering for 30 years - although I don't think I've aged quite as well! I've always been involved with process instruments, and have seen them become much more sophisticated - with customers following suit. But what's changed even more is the life of the designer.

I joined Mobrey as a draughtsman, and my design tools were a drawing board, pencil, ruler and calculator - not a computer in sight. Now we have CAD systems and desktop computers with stress and design calculations built in, so much of the number crunching is done for us.
While this has speeded up the design process, it's created new challenges.  Customers expect products tailored to their exact needs, so we need to produce a wide range of variants for each product, using modular designs capable of mass customisation in flexible factories that can manufacture smaller batches.

The growth of manufacturing systems such as ORACLE and SAP means the designer now spends almost as much time feeding data to these systems as actually designing new products!
Process instrumentation has also changed dramatically. When I started out it was largely electromechanical, but we were soon designing electronic alternatives to create systems with more than just a simple on/off switch. Then came the move from 1-5V analogue and pneumatic devices to smaller, lighter 4-20mA devices. With the North Sea oil industry booming, weight was an important factor.

The microchip enabled the move to digital, and process electronics benefited from developments in consumer electronics. The first digital communications used HART (Highway Addressable Remote Transducer), an open protocol which became the de facto fieldbus standard. It enabled the user to obtain more information from a device and communicate with it remotely, significantly reducing commissioning time and the maintenance required. It also meant multiple instruments could be installed on a single twisted pair, reducing cabling costs.

Today, other fieldbus protocols give users more choice but designers a greater challenge as they strive to develop common or platform designs capable of integration into any of the fieldbus loops.
Customer needs have driven this demand for intelligence and information availability. Following years of de-manning, many process sites are run by small teams, who need 'fit and forget' instruments that can be set up quickly, provide two-way communication and require minimum maintenance. These enable users to avoid costly plant shutdowns - but designers must remember that customers also want to minimise equipment costs.

Hence the new design imperative, alongside customer satisfaction, is shareholder value - meaning designers need to understand the financial implications of their design decisions. They also need to create products for a global market, which often means multiple variants to suit different standards.

Designers must beware of becoming increasingly desk-bound, dominated by computers and email. I've been fortunate enough to see our products in use at customer sites all over the world. But health and safety regulations and requirements for extensive safety training before going on site mean many designers never see the conditions under which their products operate.

Site visits remind designers that smaller is not always better. Fingers remain a finite size, and space must be allowed for tools and connectors. An instrument designed for oilfield use may end up in the frozen north or the heat of the desert. Whether temperatures exceed -50C or + 50C, the user needs a product that will not only work reliably in and survive the conditions but can be installed and commissioned in the minimum time before surface temperatures and ambient conditions become unbearable.

I'd encourage all today's designers to get out on site whenever they can, and to put themselves in the user's shoes - their work and their products will benefit.

The life of a designer is very different now from 30 years ago, but it's still one of the most challenging and satisfying jobs around, which is why I love my continued involvement.

Tim Chettle is business & marketing manager at Emerson Process Management

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