In late 2013, a Midwestern U.S. hydrogen gas plant was planning an outage that would coincide with a shutdown by a nearby petroleum refinery customer. The refinery provided the hydrogen plant a two-week window in April 2014 to upgrade aging components, conduct safety tests and perform routine maintenance.
The gas plant focused its planned improvements on line two, which was commissioned in 2006 and sends 22 million cubic feet of hydrogen per day to the refinery via a pipeline. With its robust chemical properties and simplicity, pure hydrogen is used by oil refineries to purify several products and fuels.
At this time, hydrogen plant engineers realized an opportunity to replace aging computers and upgrade the plant’s Siemens PCS 7 distributed control system (DCS).
With a tight window, plant management hired Longmont, Colo.-based system integrator Pigler Automation to upgrade the DCS platform from version 6.1 SP1 to version 8. The integrator has a wealth of experience with system upgrades in the process space, along with migrating third-party products to Siemens control systems.
Besides a complete platform upgrade, Pigler replaced legacy computers with Siemens Simatic 547 and Microbox 427 industrial computers that connected to the DCS’s existing processors, input/output hardware and HMI monitors.
Additionally, the system upgrade would now yield diagnostics on mechanical equipment without additional sensors for pumps, motors or valves. This is done by way of the system’s maintenance station, based on Siemens’ plant asset management platform, Comos. The maintenance software recognizes values outside of their thresholds for equipment structure borne noise or acceleration via diagnostic function blocks that have recorded various analog and binary data. Then the system produces stored maintenance messages to operators to alert them of equipment values outside of scope.
Nuisance alarms addressed
As with many process plants, operators experience numerous alarm states, and disruption by non-essential alarms is added distraction to their coveted production time. According to Harry Pigler, president of Pigler Automation, the system upgrade would bring engineers more flexibility with nuisance alarms via a smart alarm hiding tool that would eliminate unwanted alarms.
Helping in the matter was Pigler’s intimate knowledge of alarm system management via the ISA 18.2 committee that developed the ANSI/ISA 18.2 Alarm Systems Management standard for the process industries.
“We worked with engineers at the hydrogen facility to identify alarms and we made sure each alarm rationalization was correct and that it was really necessary,” Pigler says. “What's the operator supposed to do? How much time does he need to respond to a certain event?”
During factory acceptance testing (FAT), software changes were reviewed and plant states were simulated. “Once we defined the plant states, we identified the alarms to be hidden,” Pigler says. “We did this in the Process Object View in bulk and, during the FAT, the plant operators actually saw which alarms were hidden or would be hidden.”
Operators are still able to review hidden alarms, Pigler says. “With this hiding process, we don’t spend a lot of time and money to change the configuration code.”
Focus on compressors and reformer
The system integrator approached smart alarm hiding programming as a pilot project that focused on two gas compressors and one reformer at the hydrogen plant. The smart hiding feature can accommodate up to 32 alarm states per plant area.
The compressors increase the pressure on gas by reducing its volume and the reformer combines the feed gas with steam to produce the synthesized gas that is piped to the petroleum refinery. In this case, the compressors had run and stop states and the reformer had trip and no trip values.
“The compressors had many more states, but they didn’t want alarms tied to compressor motors stopping,” Pigler says. “The reformers had more states as well, but we defined two states so the reformer shutdown is a safety state to shut down the plant. Everything else is the other state that includes startup, the production warm-up and ramping up production.”
Important alarms and events that are not a consequence of a main event are still active. However, if a pump is tripped, there is no need for a low-pressure alarm caused by the stopped pump.
“In the controller, the software allows you to define a new block from the library and assign it to a plant area for smart alarm hiding,” Pigler says. “The controller still sends every alarm to the database of the Simatic PCS 7 HMI system. If you want to adjust which alarm is hidden or displayed, you simply change a check box per alarm and state.”
Under the smart alarm hiding, all events are recorded and visible in the alarm journal. “The alarms are still created in the controller and time-stamped,” Pigler says. “So they are still around and auto acknowledged, even though the operator does not get swamped by them.”
Smart alarm hiding a hit
When it came time to start piping gas again to the refinery, the upgrade was complete and the hydrogen gas supplier was ready well within the two-week window, Pigler says.
“Smart alarm hiding is a really powerful and easy-to-use tool,” he says. “All the expected alarms are hidden. That helps to better judge what to do next to get the plant in production quickly. The customer loved it so much that we are doing other upgrades for similar plants, and they have extended the scope of areas that they want to cover.”