Over the past several years, there’s been a substantial shift in the DCS market from conventional, fixed functionality input/output (I/O) modules to the fully configurable kind, such as the Universal I/O offered by Schneider Electric. The savings on labor and materials may seem obvious, but engineering firm Bechtel decided to prove out the benefits before recommending to its clients that they standardize on ready-made intelligent enclosures with configurable I/O.
Indeed, an internal study of the improved approach revealed 15-30% savings in instrumentation and automation-related costs on a benchmark Bechtel LNG project.
“We get to see a lot of new technologies,” said Robert Resendez, control and automation team manager, Bechtel Oil and Gas, who spoke about his company’s change in philosophy at Schneider Electric Innovation Days, this week in Austin, Texas. “We get to follow a lot of new technologies, and we get to implement many of them.”
In 2013, Bechtel had just come off of seven LNG projects. “One of the biggest challenges was during design development,” explained Resendez. “We were at the factory acceptance test (FAT) for eight to 12 months on all of them because of all the late changes. What could we do to fix this problem? Universal I/O was a no-brainer.”
The obvious savings due to improved system flexibility were immediately apparent, but Bechtel wanted to know the overall impact on costs. The new approached increased certain costs, but the net effect soon became evident.
Running the numbers
“We started vetting the systems and looking at them from an engineering standpoint,” continued Resendez. “In the conventional system, we had an I/O cabinet and then each I/O point had to be hardwired to a marshaling cabinet, then out to intermediate junction boxes, and then out to the instruments. This was the standard.”
With remote, universal I/O, the intermediate junction boxes were replaced with intelligent enclosures. “All the I/O is now moved out to the field,” explained Resendez. “The connection back to the control room is now fiberoptic cable, so we’ve reduced the cable size and the structure by eliminating the copper cable. And the marshaling cabinets have all but gone away.”
Bechtel took a project it had just completed with 2,253 I/O signals going to four buildings. “We had an I/O rack room, a utility substation, compressor substation and propane condenser substation,” said Resendez. “We replaced the junction boxes with the smart enclosures. Eighty field junction boxes were replaced with 39 mart I/O boxes.” The majority of homerun cabling was eliminated, reducing 195 homerun cables to just 16.
“We eliminated 21,000 homerun cable terminations,” said Resendez. “We eliminated almost two million linear feet of cable. We eliminated all 23 marshaling cabinets, and DCS cabinets went from eight to five. Because we eliminated cabinets, we reduced the footprint from 864 sq.ft. to 234 sq.ft. In some other projects, we’ve eliminated a whole building.”
Despite all of the reductions, Bechtel need to increase other components to accommodate the new technology. With nine clusters of smart junction boxes, Bechtel had to have redundant power and redundant communications. “We added to our electrical budget for fiberoptic communications and power,” added Resendez. “Because of the reduction in junction boxes, the distance from the boxes to the instruments has increased and so the fan-out cabling has increased. But we’re getting better at reducing the fan-out cable by improving design now. Also, the increased fiberoptics means fiberoptic terminations have increased slightly. And, because we need redundant power, we added fuse panels.”
When Bechtel took all the cost of the material and labor, the savings were still substantial. So much so that on every new project the company now recommends the approach.